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Debugging with DDD

DDD is a graphical front-end for GDB and other command-line debuggers.

This is the First Edition of Debugging with DDD, 15 January, 2004, for DDD Version 3.3.9-test2.

Table of Contents

Copyright © 2004 Universität des Saarlandes
Lehrstuhl Softwaretechnik
Postfach 15 11 50
66041 Saarbrücken
GERMANY

Distributed by
Free Software Foundation, Inc.
59 Temple Place - Suite 330
Boston, MA 02111-1307
USA

DDD and this manual are available via the DDD WWW page.

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.1 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts and no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License"; See Documentation License, for details.

Send questions, comments, suggestions, etc. to ddd@gnu.org.
Send bug reports to bug-ddd@gnu.org.


Node:Summary, Next:, Previous:Top, Up:Top

Summary of DDD

The purpose of a debugger such as DDD is to allow you to see what is going on "inside" another program while it executes--or what another program was doing at the moment it crashed.

DDD can do four main kinds of things (plus other things in support of these) to help you catch bugs in the act:

Technically speaking, DDD is a front-end to a command-line debugger (called inferior debugger, because it lies at the layer beneath DDD). DDD supports the following inferior debuggers:

See Choosing an Inferior Debugger, for choosing the appropriate inferior debugger. See Sample Session, for getting a first impression of DDD.


Node:About this Manual, Next:, Up:Summary

About this Manual

This manual comes in several formats:

The manual itself is written in TeXinfo format; its source code ddd.texi is contained in the DDD source distribution ddd-3.3.9-test2.tar.gz.

The picture sources come in a separate package ddd-3.3.9-test2-pics.tar.gz; you need this package only if you want to re-create the PostScript, HTML, or PDF versions.


Node:Typographic Conventions, Next:, Previous:About this Manual, Up:Summary

Typographic conventions

<Ctrl+A>
The name for a key on the keyboard (or multiple keys pressed simultaneously)
run
A sequence of characters to be typed on the keyboard.
~/.ddd/init
A file.
Help
A graphical control element, such as a button or menu item.
File => Open Program
A sequence of menu items, starting at the top-level menu bar.
argc - 1
Program code or debugger command.
-g
A command-line option.
$
System prompt.
(gdb)
Debugger prompt.
_
Cursor position.
version
A metasyntactic variable; something that stands for another piece of text.
definition
A definition.
caution
Emphasis.
A warning
Strong emphasis.
DDD
An acronym.

Here's an example. break location is a typed command at the (gdb) prompt; the metasyntactic variable location would be replaced by the actual location. _ is the cursor position after entering the command.

     (gdb) break location
     Breakpoint number at location
     (gdb) _
     


Node:Free Software, Next:, Previous:Typographic Conventions, Up:Summary

Free software

DDD is free; this means that everyone is free to use it and free to redistribute it on a free basis. DDD is not in the public domain; it is copyrighted and there are restrictions on its distribution, but these restrictions are designed to permit everything that a good cooperating citizen would want to do. What is not allowed is to try to prevent others from further sharing any version of DDD that they might get from you. The precise conditions are found in the GNU General Public License that comes with DDD; See License, for details.

The easiest way to get a copy of DDD is from someone else who has it. You need not ask for permission to do so, or tell any one else; just copy it.


Node:Getting DDD, Next:, Previous:Free Software, Up:Summary

Getting DDD

If you have access to the Internet, you can get the latest version of DDD from the anonymous FTP server ftp.gnu.org in the directory /gnu/ddd. This should contain the following files:

ddd-version.tar.gz
The DDD source distribution. This should be all you need.
ddd-version-html-manual.tar.gz
The DDD manual in HTML format. You need this only if you want to install a local copy of the DDD manual in HTML format.
ddd-version-pics.tar.gz
Sources of images included in the DDD manual. You need this only if you want to recreate the DDD manual.

DDD can also be found at numerous other archive sites around the world; check the file ANNOUNCE in a DDD distribution for the latest known list.


Node:Contributors, Next:, Previous:Getting DDD, Up:Summary

Contributors to DDD

Dorothea Lütkehaus and Andreas Zeller were the original authors of DDD. Many others have contributed to its development. The files ChangeLog and THANKS in the DDD distribution approximates a blow-by-blow account.


Node:History, Previous:Contributors, Up:Summary

History of DDD

The history of DDD is a story of code recycling. The oldest parts of DDD were written in 1990, when Andreas Zeller designed VSL, a box-based visual structure language for visualizing data and program structures. The VSL interpreter and the Box library became part of Andreas' Diploma Thesis, a graphical syntax editor based on the Programming System Generator PSG.

In 1992, the VSL and Box libraries were recycled for the NORA project. For NORA, an experimental inference-based software development tool set, Andreas wrote a graph editor (based on VSL and the Box libraries) and facilities for inter-process knowledge exchange. Based on these tools, Dorothea Lütkehaus (now Dorothea Krabiell) realized DDD as her Diploma Thesis, 1994.

The original DDD had no source window; this was added by Dorothea during the winter of 1994-1995. In the first quarter of 1995, finally, Andreas completed DDD by adding command and execution windows, extensions for DBX and remote debugging as well as configuration support for several architectures. Since then, Andreas has further maintained and extended DDD, based on the comments and suggestions of several DDD users around the world. See the comments in the DDD source for details.

Major DDD events:

April, 1995
DDD 0.9: First DDD beta release.
May, 1995
DDD 1.0: First public DDD release.
December, 1995
DDD 1.4: Machine-level debugging, glyphs, Emacs integration.
October, 1996
DDD 2.0: Color displays, XDB support, generic DBX support, command tool.
May, 1997
DDD 2.1: Alias detection, button tips, status displays.
November, 1997
DDD 2.2: Sessions, display shortcuts.
June, 1998
DDD 3.0: Icon tool bar, Java support, JDB support.
December, 1998
DDD 3.1: Data plotting, Perl support, Python support, Undo/Redo.
January, 2000
DDD 3.2: New manual, Readline support, Ladebug support.
January, 2001
DDD 3.3: Data themes, JDB 1.2 support, VxWorks support.
November, 2002
DDD 3.3.2: Bash support.
March, 2003
DDD 3.3.3: Better Bash support. Compiles using modern tools thanks to Daniel Schepler.


Node:Sample Session, Next:, Previous:Summary, Up:Top

A Sample DDD Session

You can use this manual at your leisure to read all about DDD. However, a handful of features are enough to get started using the debugger. This chapter illustrates those features.

The sample program sample.c (see Sample Program) exhibits the following bug. Normally, sample should sort and print its arguments numerically, as in the following example:

     $ ./sample 8 7 5 4 1 3
     1 3 4 5 7 8
     $ _
     

However, with certain arguments, this goes wrong:

     $ ./sample 8000 7000 5000 1000 4000
     1000 1913 4000 5000 7000
     $ _
     

Although the output is sorted and contains the right number of arguments, some arguments are missing and replaced by bogus numbers; here, 8000 is missing and replaced by 1913.3

Let us use DDD to see what is going on. First, you must compile sample.c for debugging (see Compiling for Debugging), giving the -g flag while compiling:

     $ gcc -g -o sample sample.c
     $ _
     

Now, you can invoke DDD (see Invocation) on the sample executable:

     $ ddd sample
     

After a few seconds, DDD comes up. The Source Window contains the source of your debugged program; use the Scroll Bar to scroll through the file.

PICS/tut-invoke.jpg

The Debugger Console (at the bottom) contains DDD version information as well as a GDB prompt.4

     GNU DDD Version 3.3.9-test2, by Dorothea Lütkehaus and Andreas Zeller.
     Copyright © 1995-1999 Technische Universität Braunschweig, Germany.
     Copyright © 1999-2001 Universität Passau, Germany.
     Copyright © 2001-2004 Universität des Saarlandes, Germany.
     Reading symbols from sample...done.
     (gdb) _
     

The first thing to do now is to place a Breakpoint (see Breakpoints), making sample stop at a location you are interested in. Click on the blank space left to the initialization of a. The Argument field (): now contains the location (sample.c:31). Now, click on Break to create a breakpoint at the location in (). You see a little red stop sign appear in line 31.

The next thing to do is to actually execute the program, such that you can examine its behavior (see Running). Select Program => Run to execute the program; the Run Program dialog appears.

PICS/tut-run.jpg

In Run with Arguments, you can now enter arguments for the sample program. Enter the arguments resulting in erroneous behavior here--that is, 8000 7000 5000 1000 4000. Click on Run to start execution with the arguments you just entered.

GDB now starts sample. Execution stops after a few moments as the breakpoint is reached. This is reported in the debugger console.

     (gdb) break sample.c:31
     Breakpoint 1 at 0x8048666: file sample.c, line 31.
     (gdb) run 8000 7000 5000 1000 4000
     Starting program: sample 8000 7000 5000 1000 4000
     
     Breakpoint 1, main (argc=6, argv=0xbffff918) at sample.c:31
     (gdb) _
     

The current execution line is indicated by a green arrow.

     => a = (int *)malloc((argc - 1) * sizeof(int));
     

You can now examine the variable values. To examine a simple variable, you can simply move the mouse pointer on its name and leave it there. After a second, a small window with the variable value pops up (see Value Tips). Try this with argc to see its value (6). The local variable a is not yet initialized; you'll probably see 0x0 or some other invalid pointer value.

To execute the current line, click on the Next button on the command tool. The arrow advances to the following line. Now, point again on a to see that the value has changed and that a has actually been initialized.

PICS/tut-value.jpg

To examine the individual values of the a array, enter a[0] in the argument field (you can clear it beforehand by clicking on ():) and then click on the Print button. This prints the current value of () in the debugger console (see Printing Values). In our case, you'll get

     (gdb) print a[0]
     $1 = 0
     (gdb) _
     

or some other value (note that a has only been allocated, but the contents have not yet been initialized).

To see all members of a at once, you must use a special GDB operator. Since a has been allocated dynamically, GDB does not know its size; you must specify it explicitly using the @ operator (see Array Slices). Enter a[0]@(argc - 1) in the argument field and click on the Print button. You get the first argc - 1 elements of a, or

     (gdb) print a[0]@(argc - 1)
     $2 = {0, 0, 0, 0, 0}
     (gdb) _
     

Rather than using Print at each stop to see the current value of a, you can also display a, such that its is automatically displayed. With a[0]@(argc - 1) still being shown in the argument field, click on Display. The contents of a are now shown in a new window, the Data Window. Click on Rotate to rotate the array horizontally.

PICS/tut-display.jpg

Now comes the assignment of a's members:

     =>  for (i = 0; i < argc - 1; i++)
             a[i] = atoi(argv[i + 1]);
     

You can now click on Next and Next again to see how the individual members of a are being assigned. Changed members are highlighted.

To resume execution of the loop, use the Until button. This makes GDB execute the program until a line greater than the current is reached. Click on Until until you end at the call of shell_sort in

     =>  shell_sort(a, argc);
     

At this point, a's contents should be 8000 7000 5000 1000 4000. Click again on Next to step over the call to shell_sort. DDD ends in

     =>  for (i = 0; i < argc - 1; i++)
             printf("%d ", a[i]);
     

and you see that after shell_sort has finished, the contents of a are 1000, 1913, 4000, 5000, 7000--that is, shell_sort has somehow garbled the contents of a.

To find out what has happened, execute the program once again. This time, you do not skip through the initialization, but jump directly into the shell_sort call. Delete the old breakpoint by selecting it and clicking on Clear. Then, create a new breakpoint in line 35 before the call to shell_sort. To execute the program once again, select Program => Run Again.

Once more, DDD ends up before the call to shell_sort:

     =>  shell_sort(a, argc);
     

This time, you want to examine closer what shell_sort is doing. Click on Step to step into the call to shell_sort. This leaves your program in the first executable line, or

     => int h = 1;
     

while the debugger console tells us the function just entered:

     (gdb) step
     shell_sort (a=0x8049878, size=6) at sample.c:9
     (gdb) _
     

This output that shows the function where sample is now suspended (and its arguments) is called a stack frame display. It shows a summary of the stack. You can use Status => Backtrace to see where you are in the stack as a whole; selecting a line (or clicking on Up and Down) will let you move through the stack. Note how the a display disappears when its frame is left.

PICS/tut-backtrace.jpg

Let us now check whether shell_sort's arguments are correct. After returning to the lowest frame, enter a[0]@size in the argument field and click on Print:

     (gdb) print a[0] @ size
     $4 = {8000, 7000, 5000, 1000, 4000, 1913}
     (gdb) _
     

Surprise! Where does this additional value 1913 come from? The answer is simple: The array size as passed in size to shell_sort is too large by one--1913 is a bogus value which happens to reside in memory after a. And this last value is being sorted in as well.

To see whether this is actually the problem cause, you can now assign the correct value to size (see Assignment). Select size in the source code and click on Set. A dialog pops up where you can edit the variable value.

PICS/tut-set.jpg

Change the value of size to 5 and click on OK. Then, click on Finish to resume execution of the shell_sort function:

     (gdb) set variable size = 5
     (gdb) finish
     Run till exit from #0  shell_sort (a=0x8049878, size=5) at sample.c:9
     0x80486ed in main (argc=6, argv=0xbffff918) at sample.c:35
     (gdb) _
     

Success! The a display now contains the correct values 1000, 4000, 5000, 7000, 8000.

PICS/tut-finish.jpg

You can verify that these values are actually printed to standard output by further executing the program. Click on Cont to continue execution.

     (gdb) cont
     1000 4000 5000 7000 8000
     
     Program exited normally.
     (gdb) _
     

The message Program exited normally. is from GDB; it indicates that the sample program has finished executing.

Having found the problem cause, you can now fix the source code. Click on Edit to edit sample.c, and change the line

     shell_sort(a, argc);
     

to the correct invocation

     shell_sort(a, argc - 1);
     

You can now recompile sample

     $ gcc -g -o sample sample.c
     $ _
     

and verify (via Program => Run Again) that sample works fine now.

     (gdb) run
     `sample' has changed; re-reading symbols.
     Reading in symbols...done.
     Starting program: sample 8000 7000 5000 1000 4000
     1000 4000 5000 7000 8000
     
     Program exited normally.
     (gdb) _
     

All is done; the program works fine now. You can end this DDD session with Program => Exit or Ctrl+Q.


Node:Sample Program, Up:Sample Session

Sample Program

Here's the source sample.c of the sample program.

     /* sample.c -- Sample C program to be debugged with DDD */
     
     #include <stdio.h>
     #include <stdlib.h>
     
     static void shell_sort(int a[], int size)
     {
         int i, j;
         int h = 1;
         do {
             h = h * 3 + 1;
         } while (h <= size);
         do {
             h /= 3;
             for (i = h; i < size; i++)
             {
                 int v = a[i];
                 for (j = i; j >= h && a[j - h] > v; j -= h)
                     a[j] = a[j - h];
                 if (i != j)
                     a[j] = v;
             }
         } while (h != 1);
     }
     
     int main(int argc, char *argv[])
     {
         int *a;
         int i;
     
         a = (int *)malloc((argc - 1) * sizeof(int));
         for (i = 0; i < argc - 1; i++)
             a[i] = atoi(argv[i + 1]);
     
         shell_sort(a, argc);
     
         for (i = 0; i < argc - 1; i++)
             printf("%d ", a[i]);
         printf("\n");
     
         free(a);
         return 0;
     }
     


Node:Invocation, Next:, Previous:Sample Session, Up:Top

Getting In and Out of DDD

This chapter discusses how to start DDD, and how to get out of it. The essentials are:


Node:Invoking, Next:, Up:Invocation

Invoking DDD

Normally, you can run DDD by invoking the program ddd.

You can also run DDD with a variety of arguments and options, to specify more of your debugging environment at the outset.

The most usual way to start DDD is with one argument, specifying an executable program:

     ddd program
     

If you use GDB, DBX, Ladebug, or XDB as inferior debuggers, you can also start with both an executable program and a core file specified:

     ddd program core
     

You can, instead, specify a process ID as a second argument, if you want to debug a running process:

     ddd program 1234
     

would attach DDD to process 1234 (unless you also have a file named 1234; DDD does check for a core file first).

You can further control DDD by invoking it with specific options. To get a list of DDD options, invoke DDD as

     ddd --help
     

Most important are the options to specify the inferior debugger (see Choosing an Inferior Debugger), but you can also customize several aspects of DDD upon invocation (see Options).

DDD also understands the usual X options such as -display or -geometry. See X Options, for details.

All arguments and options that are not understood by DDD are passed to the inferior debugger; See Inferior Debugger Options, for a survey. To pass an option to the inferior debugger that conflicts with an X option, or with a DDD option listed here, use the --debugger option (see Options).


Node:Choosing an Inferior Debugger, Next:, Up:Invoking

Choosing an Inferior Debugger

The most frequently required options are those to choose a specific inferior debugger.

Normally, the inferior debugger is determined by the program to analyze:

If you invoke DDD without any of these options, but give a program to analyze, then DDD will automatically determine the inferior debugger:

See Customizing Debugger Interaction, for more details on determining the inferior debugger.


Node:Options, Next:, Previous:Choosing an Inferior Debugger, Up:Invoking

DDD Options

You can further control how DDD starts up using the following options. All options may be abbreviated, as long as they are unambiguous; single dashes - instead of double dashes -- may also be used. Almost all options control a specific DDD resource or resource class (see Customizing).

--attach-windows
Attach the source and data windows to the debugger console, creating one single big DDD window. This is the default setting.

Giving this option is equivalent to setting the DDD Separate resource class to off. See Window Layout, for details.

--attach-source-window
Attach only the source window to the debugger console.

Giving this option is equivalent to setting the DDD separateSourceWindow resource to off. See Window Layout, for details.

--attach-data-window
Attach only the source window to the debugger console.

Giving this option is equivalent to setting the DDD separateDataWindow resource to off. See Window Layout, for details.

--automatic-debugger
Determine the inferior debugger automatically from the given arguments.

Giving this option is equivalent to setting the DDD autoDebugger resource to on. See Customizing Debugger Interaction, for details.

--button-tips
Enable button tips.

Giving this option is equivalent to setting the DDD buttonTips resource to on. See Customizing Help, for details.

--configuration
Print the DDD configuration settings on standard output and exit.

Giving this option is equivalent to setting the DDD showConfiguration resource to on. See Diagnostics, for details.

--check-configuration
Check the DDD environment (in particular, the X configuration), report any possible problem causes and exit.

Giving this option is equivalent to setting the DDD checkConfiguration resource to on. See Diagnostics, for details.

--data-window
Open the data window upon start-up.

Giving this option is equivalent to setting the DDD openDataWindow resource to on. See Toggling Windows, for details.

--dbx
Run DBX as inferior debugger.

Giving this option is equivalent to setting the DDD debugger resource to dbx. See Customizing Debugger Interaction, for details.

--debugger name
Invoke the inferior debugger name. This is useful if you have several debugger versions around, or if the inferior debugger cannot be invoked under its usual name (i.e. gdb, wdb, dbx, xdb, jdb, pydb, or perl).

This option can also be used to pass options to the inferior debugger that would otherwise conflict with DDD options. For instance, to pass the option -d directory to XDB, use:

          ddd --debugger "xdb -d directory"
          

If you use the --debugger option, be sure that the type of inferior debugger is specified as well. That is, use one of the options --gdb, --dbx, --xdb, --jdb, --pydb, or --perl (unless the default setting works fine).

Giving this option is equivalent to setting the DDD debuggerCommand resource to name. See Customizing Debugger Interaction, for details.

--debugger-console
Open the debugger console upon start-up.

Giving this option is equivalent to setting the DDD openDebuggerConsole resource to on. See Toggling Windows, for details.

--disassemble
Disassemble the source code. See also the --no-disassemble option, below.

Giving this option is equivalent to setting the DDD disassemble resource to on. See Customizing Source, for details.

--exec-window
Run the debugged program in a specially created execution window. This is useful for programs that have special terminal requirements not provided by the debugger window, as raw keyboard processing or terminal control sequences. See Using the Execution Window, for details.

Giving this option is equivalent to setting the DDD separateExecWindow resource to on. See Customizing the Execution Window, for details.

--font fontname
-fn fontname
Use fontname as default font.

Giving this option is equivalent to setting the DDD defaultFont resource to fontname. See Customizing Fonts, for details.

--fonts
Show the font definitions used by DDD on standard output.

Giving this option is equivalent to setting the DDD showFonts resource to on. See Diagnostics, for details.

--fontsize size
Set the default font size to size (in 1/10 points). To make DDD use 12-point fonts, say --fontsize 120.

Giving this option is equivalent to setting the DDD FontSize resource class to size. See Customizing Fonts, for details.

--fullname
-f
Enable the TTY interface, taking additional debugger commands from standard input and forwarding debugger output on standard output. Current positions are issued in GDB -fullname format suitable for debugger front-ends. By default, both the debugger console and source window are disabled. See TTY mode, for a discussion.

Giving this option is equivalent to setting the DDD TTYMode resource class to on. See TTY mode, for details.

--gdb
Run GDB as inferior debugger.

Giving this option is equivalent to setting the DDD debugger resource to gdb. See Customizing Debugger Interaction, for details.

--glyphs
Display the current execution position and breakpoints as glyphs. See also the --no-glyphs option, below.

Giving this option is equivalent to setting the DDD displayGlyphs resource to on. See Customizing Source, for details.

--help
-h
-?
Give a list of frequently used options. Show options of the inferior debugger as well.

Giving this option is equivalent to setting the DDD showInvocation resource to on. See Diagnostics, for details.

--host hostname
--host username@hostname
Invoke the inferior debugger directly on the remote host hostname. If username is given and the --login option is not used, use username as remote user name. See Remote Debugger, for details.

Giving this option is equivalent to setting the DDD debuggerHost resource to hostname. See Remote Debugger, for details.

--jdb
Run JDB as inferior debugger.

Giving this option is equivalent to setting the DDD debugger resource to gdb. See Customizing Debugger Interaction, for details.

--ladebug
Run Ladebug as inferior debugger.

Giving this option is equivalent to setting the DDD debugger resource to ladebug. See Customizing Debugger Interaction, for details.

--lesstif-hacks
Equivalent to --lesstif-version 999. Deprecated.

Giving this option is equivalent to setting the DDD lessTifVersion resource to 999. See LessTif, for details.

--lesstif-version version
Enable some hacks to make DDD run properly with LessTif. See LessTif, for a discussion.

Giving this option is equivalent to setting the DDD lessTifVersion resource to version. See LessTif, for details.

--license
Print the DDD license on standard output and exit.

Giving this option is equivalent to setting the DDD showLicense resource to on. See Diagnostics, for details.

--login username
-l username
Use username as remote user name. See Remote Debugger, for details.

Giving this option is equivalent to setting the DDD debuggerHostLogin resource to username. See Remote Debugger, for details.

--maintenance
Enable the top-level Maintenance menu with options for debugging DDD. See Maintenance Menu, for details.

Giving this option is equivalent to setting the DDD maintenance resource to on. See Maintenance Menu, for details.

--manual
Print the DDD manual on standard output and exit.

Giving this option is equivalent to setting the DDD showManual resource to on. See Diagnostics, for details.

--news
Print the DDD news on standard output and exit.

Giving this option is equivalent to setting the DDD showNews resource to on. See Diagnostics, for details.

--no-button-tips
Disable button tips.

Giving this option is equivalent to setting the DDD buttonTips resource to off. See Customizing Help, for details.

--no-data-window
Do not open the data window upon start-up.

Giving this option is equivalent to setting the DDD openDataWindow resource to off. See Toggling Windows, for details.

--no-debugger-console
Do not open the debugger console upon start-up.

Giving this option is equivalent to setting the DDD openDebuggerConsole resource to off. See Toggling Windows, for details.

--no-disassemble
Do not disassemble the source code.

Giving this option is equivalent to setting the DDD disassemble resource to off. See Customizing Source, for details.

--no-exec-window
Do not run the debugged program in a specially created execution window; use the debugger console instead. Useful for programs that have little terminal input/output, or for remote debugging. See Using the Execution Window, for details.

Giving this option is equivalent to setting the DDD separateExecWindow resource to off. See Customizing the Execution Window, for details.

--no-glyphs
Do not use glyphs; display the current execution position and breakpoints as text characters.

Giving this option is equivalent to setting the DDD displayGlyphs resource to off. See Customizing Source, for details.

--no-lesstif-hacks
Equivalent to --lesstif-version 1000. Deprecated.

Giving this option is equivalent to setting the DDD lessTifVersion resource to 1000. See LessTif, for details.

--no-maintenance
Do not enable the top-level Maintenance menu with options for debugging DDD. This is the default. See Maintenance Menu, for details.

Giving this option is equivalent to setting the DDD maintenance resource to off. See Maintenance Menu, for details.

--no-source-window
Do not open the source window upon start-up.

Giving this option is equivalent to setting the DDD openSourceWindow resource to off. See Toggling Windows, for details.

--no-value-tips
Disable value tips.

Giving this option is equivalent to setting the DDD valueTips resource to off. See Value Tips, for details.

--nw
Do not use the X window interface. Start the inferior debugger on the local host.
--perl
Run Perl as inferior debugger.

Giving this option is equivalent to setting the DDD debugger resource to perl. See Customizing Debugger Interaction, for details.

--pydb
Run PYDB as inferior debugger.

Giving this option is equivalent to setting the DDD debugger resource to pydb. See Customizing Debugger Interaction, for details.

--panned-graph-editor
Use an Athena panner to scroll the data window. Most people prefer panners on scroll bars, since panners allow two-dimensional scrolling. However, the panner is off by default, since some M*tif implementations do not work well with Athena widgets. See Display Resources, for details; see also --scrolled-graph-editor, below.

Giving this option is equivalent to setting the DDD pannedGraphEditor resource to on. See Display Resources, for details.

--play-log log-file
Recapitulate a previous DDD session.
          ddd --play-log log-file
          

invokes DDD as inferior debugger, simulating the inferior debugger given in log-file (see below). This is useful for debugging DDD.

Giving this option is equivalent to setting the DDD playLog resource to on. See Customizing Debugger Interaction, for details.

--PLAY log-file
Simulate an inferior debugger. log-file is a ~/.ddd/log file as generated by some previous DDD session (see Logging). When a command is entered, scan log-file for this command and re-issue the logged reply; if the command is not found, do nothing. This is used by the --play option.
--rhost hostname
--rhost username@hostname
Run the inferior debugger interactively on the remote host hostname. If username is given and the --login option is not used, use username as remote user name. See Remote Debugger, for details.

Giving this option is equivalent to setting the DDD debuggerRHost resource to hostname. See Remote Debugger, for details.

--scrolled-graph-editor
Use M*tif scroll bars to scroll the data window. This is the default in most DDD configurations. See Display Resources, for details; see also --panned-graph-editor, above.

Giving this option is equivalent to setting the DDD pannedGraphEditor resource to off. See Display Resources, for details.

--separate-windows
--separate
Separate the console, source and data windows. See also the --attach options, above.

Giving this option is equivalent to setting the DDD Separate resource class to off. See Window Layout, for details.

--session session
Load session upon start-up. See Resuming Sessions, for details.

Giving this option is equivalent to setting the DDD session resource to session. See Resuming Sessions, for details.

--source-window
Open the source window upon start-up.

Giving this option is equivalent to setting the DDD openSourceWindow resource to on. See Toggling Windows, for details.

--status-at-bottom
Place the status line at the bottom of the source window.

Giving this option is equivalent to setting the DDD statusAtBottom resource to on. See Window Layout, for details.

--status-at-top
Place the status line at the top of the source window.

Giving this option is equivalent to setting the DDD statusAtBottom resource to off. See Window Layout, for details.

--sync-debugger
Do not process X events while the debugger is busy. This may result in slightly better performance on single-processor systems.

Giving this option is equivalent to setting the DDD synchronousDebugger resource to on. See Customizing Debugger Interaction, for details.

--toolbars-at-bottom
Place the toolbars at the bottom of the respective window.

Giving this option is equivalent to setting the DDD toolbarsAtBottom resource to on. See Window Layout, for details.

--toolbars-at-top
Place the toolbars at the top of the respective window.

Giving this option is equivalent to setting the DDD toolbarsAtBottom resource to off. See Window Layout, for details.

--trace
Show the interaction between DDD and the inferior debugger on standard error. This is useful for debugging DDD. If --trace is not specified, this information is written into ~/.ddd/log (~ stands for your home directory), such that you can also do a post-mortem debugging. See Logging, for details about logging.

Giving this option is equivalent to setting the DDD trace resource to on. See Diagnostics, for details.

--tty
-t
Enable TTY interface, taking additional debugger commands from standard input and forwarding debugger output on standard output. Current positions are issued in a format readable for humans. By default, the debugger console is disabled.

Giving this option is equivalent to setting the DDD ttyMode resource to on. See TTY mode, for details.

--value-tips
Enable value tips.

Giving this option is equivalent to setting the DDD valueTips resource to on. See Value Tips, for details.

--version
-v
Print the DDD version on standard output and exit.

Giving this option is equivalent to setting the DDD showVersion resource to on. See Diagnostics, for details.

--vsl-library library
Load the VSL library library instead of using the DDD built-in library. This is useful for customizing display shapes and fonts.

Giving this option is equivalent to setting the DDD vslLibrary resource to library. See VSL Resources, for details.

--vsl-path path
Search VSL libraries in path (a colon-separated directory list).

Giving this option is equivalent to setting the DDD vslPath resource to path. See VSL Resources, for details.

--vsl-help
Show a list of further options controlling the VSL interpreter. These options are intended for debugging purposes and are subject to change without further notice.
--wdb
Run WDB as inferior debugger.

Giving this option is equivalent to setting the DDD debugger resource to wdb. See Customizing Debugger Interaction, for details.

--xdb
Run XDB as inferior debugger.

Giving this option is equivalent to setting the DDD debugger resource to xdb. See Customizing Debugger Interaction, for details.


Node:X Options, Next:, Previous:Options, Up:Invoking

X Options

DDD also understands the following X options. Note that these options only take a single dash -.

-display display
Use the X server display. By default, display is taken from the DISPLAY environment variable.
-geometry geometry
Specify the initial size and location of the debugger console.
-iconic
Start DDD iconified.
-name name
Give DDD the name name.
-selectionTimeout timeout
Specify the timeout in milliseconds within which two communicating applications must respond to one another for a selection request.
-title name
Give the DDD window the title name.
-xrm resourcestring
Specify a resource name and value to override any defaults.


Node:Inferior Debugger Options, Next:, Previous:X Options, Up:Invoking

Inferior Debugger Options

All options that DDD does not recognize are passed to the inferior debugger. This section lists the most useful options of the different inferior debuggers supported by DDD. In case these options do not work as expected, please lookup the appropriate reference.


Node:GDB Options, Next:, Up:Inferior Debugger Options
GDB Options

These GDB options are useful when using DDD with GDB as inferior debugger. Single dashes - instead of double dashes -- may also be used.

-b baudrate
Set serial port baud rate used for remote debugging.
--cd dir
Change current directory to dir.
--command file
Execute GDB commands from file.
--core corefile
Analyze the core dump corefile.
--directory dir
-d dir
Add directory to the path to search for source files.
--exec execfile
Use execfile as the executable.
--mapped
Use mapped symbol files if supported on this system.
--nx

-n
Do not read .gdbinit file.
--readnow
Fully read symbol files on first access.
--se file
Use file as symbol file and executable file.
--symbols symfile
Read symbols from symfile.

See Invoking GDB, for further options that can be used with GDB.


Node:DBX and Ladebug Options, Next:, Previous:GDB Options, Up:Inferior Debugger Options
DBX and Ladebug Options

DBX variants differ widely in their options, so we cannot give a list here. Check out the dbx(1) and ladebug(1) manual pages.


Node:XDB Options, Next:, Previous:DBX and Ladebug Options, Up:Inferior Debugger Options
XDB Options

These XDB options are useful when using DDD with XDB as inferior debugger.

-d dir
Specify dir as an alternate directory where source files are located.
-P process-id
Specify the process ID of an existing process the user wants to debug.
-l library
Pre-load information about the shared library library. -l ALL means always pre-load shared library information.
-S num
Set the size of the string cache to num bytes (default is 1024, which is also the minimum).
-s
Enable debugging of shared libraries.

Further options can be found in the xdb(1) manual page.


Node:JDB Options, Next:, Previous:XDB Options, Up:Inferior Debugger Options
JDB Options
JDB as of JDK 1.2

The following JDB options are useful when using DDD with JDB (from JDK 1.2) as inferior debugger.

-attach address
attach to a running virtual machine (VM) at address using standard connector
-listen address
wait for a running VM to connect at address using standard connector
-listenany
wait for a running VM to connect at any available address using standard connector
-launch
launch VM immediately instead of waiting for run command

These JDB options are forwarded to the debuggee:

-verbose[:class|gc|jni]
-v
Turn on verbose mode.
-Dname=value
Set the system property name to value.
-classpath path
List directories in which to look for classes. path is a list of directories separated by colons.
-X option
Non-standard target VM option
JDB as of JDK 1.1

The following JDB options are useful when using DDD with JDB (from JDK 1.1) as inferior debugger.

-host hostname
host machine of interpreter to attach to
-password psswd
password of interpreter to attach to (from -debug)

These JDB options are forwarded to the debuggee:

-verbose
-v
Turn on verbose mode.
-debug
Enable remote Java debugging,
-noasyncgc
Don't allow asynchronous garbage collection.
-verbosegc
Print a message when garbage collection occurs.
-noclassgc
Disable class garbage collection.
-checksource
-cs
Check if source is newer when loading classes.
-ss number
Set the maximum native stack size for any thread.
-oss number
Set the maximum Java stack size for any thread.
-ms number
Set the initial Java heap size.
-mx number
Set the maximum Java heap size.
-Dname=value
Set the system property name to value.
-classpath path
List directories in which to look for classes. path is a list of directories separated by colons.
-prof
-prof:file
Output profiling data to ./java.prof. If file is given, write the data to ./file.
-verify
Verify all classes when read in.
-verifyremote
Verify classes read in over the network (default).
-noverify
Do not verify any class.
-dbgtrace
Print info for debugging JDB.

Further options can be found in the JDB documentation.


Node:PYDB Options, Next:, Previous:JDB Options, Up:Inferior Debugger Options
PYDB Options

For a list of useful PYDB options, check out the PYDB documentation.


Node:Perl Options, Next:, Previous:PYDB Options, Up:Inferior Debugger Options
Perl Options

The most important Perl option to use with DDD is -w; it enables several important warnings. For further options, see the perlrun(1) manual page.


Node:Bash Options, Previous:Perl Options, Up:Inferior Debugger Options
Bash Options

If you have the proper bash installed, the option needed to specify debugging support is --debugger. (If your bash doesn't understand this option you need to pick up a version of bash that does from http://bashdb.sourceforge.net.)


Node:Multiple Instances, Next:, Previous:Inferior Debugger Options, Up:Invoking

Multiple DDD Instances

If you have multiple DDD instances running, they share common preferences and history files. This means that changes applied to one instance may get lost when being overwritten by the other instance. DDD has two means to protect you against unwanted losses. The first means is an automatic reloading of changed options, controlled by the following resource (see Customizing):

checkOptions (class CheckOptions) Resource
Every n seconds, where n is the value of this resource, DDD checks whether the options file has changed. Default is 30, which means that every 30 seconds, DDD checks for the options file. Setting this resource to 0 disables checking for changed option files.

Normally, automatic reloading of options should already suffice. If you need stronger protection, DDD also provides a warning against multiple instances. This warning is disabled by default, If you want to be warned about multiple DDD invocations sharing the same preferences and history files, enable Edit => Preferences => Warn if Multiple DDD Instances are Running.

This setting is tied to the following resource (see Customizing):

warnIfLocked (class WarnIfLocked) Resource
Whether to warn if multiple DDD instances are running (on) or not (off, default).


Node:X Warnings, Previous:Multiple Instances, Up:Invoking

X warnings

If you are bothered by X warnings, you can suppress them by setting Edit => Preferences => General => Suppress X warnings.

This setting is tied to the following resource (see Customizing):

suppressWarnings (class SuppressWarnings) Resource
If on, X warnings are suppressed. This is sometimes useful for executables that were built on a machine with a different X or M*tif configuration. By default, this is off.


Node:Quitting, Next:, Previous:Invoking, Up:Invocation

Quitting DDD

To exit DDD, select File => Exit. You may also type the quit command at the debugger prompt or press <Ctrl+Q>. GDB and XDB also accept the q command or an end-of-file character (usually <Ctrl+D>). Closing the last DDD window will also exit DDD.

An interrupt (<ESC> or Interrupt) does not exit from DDD, but rather terminates the action of any debugger command that is in progress and returns to the debugger command level. It is safe to type the interrupt character at any time because the debugger does not allow it to take effect until a time when it is safe.

In case an ordinary interrupt does not succeed, you can also use an abort (<Ctrl+\> or Abort), which sends a SIGABRT signal to the inferior debugger. Use this in emergencies only; the inferior debugger may be left inconsistent or even exit after a SIGABRT signal.

As a last resort (if DDD hangs, for example), you may also interrupt DDD itself using an interrupt signal (SIGINT). This can be done by typing the interrupt character (usually <Ctrl+C>) in the shell DDD was started from, or by using the UNIX kill command. An interrupt signal interrupts any DDD action; the inferior debugger is interrupted as well. Since this interrupt signal can result in internal inconsistencies, use this as a last resort in emergencies only; save your work as soon as possible and restart DDD.


Node:Sessions, Next:, Previous:Quitting, Up:Invocation

Persistent Sessions

If you want to interrupt your current DDD session, you can save the entire the entire DDD state as session on disk and resume later.


Node:Saving Sessions, Next:, Up:Sessions

Saving Sessions

To save a session, select File => Save Session As. You will be asked for a symbolic session name session.

If your program is running (see Running), or if you have opened a core file (see Opening Core Dumps), DDD can also include a core file in the session such that the debuggee data will be restored when re-opening it. To get a core file, DDD typically must kill the debuggee. This means that you cannot resume program execution after saving a session. Depending on your architecture, other options for getting a core file may also be available.

Including a core dump is necessary for restoring memory contents and the current execution position. To include a core dump, enable Include Core Dump.

PICS/ddd-save-session.jpg

After clicking on Save, the session is saved in ~/.ddd/sessions/session.

Here's a list of the items whose state is saved in a session:

After saving the current state as a session, the session becomes active. This means that DDD state will be saved as session defaults:

To make the current session inactive, open the default session named [None]. See Resuming Sessions, for details on opening sessions.


Node:Resuming Sessions, Next:, Previous:Saving Sessions, Up:Sessions

Resuming Sessions

To resume a previously saved session, select File => Open Session and choose a session name from the list. After clicking on Open, the entire DDD state will be restored from the given session.

The session named [None] is the default session which is active when starting DDD. To save options for default sessions, choose the default session before exiting DDD. See Saving Options, for details.

PICS/ddd-open-session.jpg

If a the restored session includes a core dump, the program being debugged will be in the same state at the time the session was saved; in particular, you can examine the program data. However, you will not be able to resume program execution since the process and its environment (open files, resources, etc.) no longer exist. However, you can restart the program, re-using the restored breakpoints and data displays.

Opening sessions also restores command definitions, buttons, display shortcuts and the source tab width. This way, you can maintain a different set of definitions for each session.

You can also specify a session to open when starting DDD. To invoke DDD with a session session, use

     ddd --session session
     

There is also a shortcut that opens the session session and invokes the inferior debugger on an executable named session (in case session cannot be opened):

     ddd =session
     

There is no need to give further command-line options when restarting a session, as they will be overridden by the options saved in the session.

You can also use an X session manager such as xsm to save and restore DDD sessions.7 When being shut down by a session manager, DDD saves its state under the name specified by the session manager; resuming the X session makes DDD reload its saved state.


Node:Deleting Sessions, Next:, Previous:Resuming Sessions, Up:Sessions

Deleting Sessions

To delete sessions that are no longer needed, select File => Open Session or File => Save Session. Select the sessions you want to delete and click on Delete.

The default session [None] cannot be deleted.


Node:Customizing Sessions, Previous:Deleting Sessions, Up:Sessions

Customizing Sessions

You can change the place where DDD saves its sessions by setting the environment variable DDD_SESSIONS to the name of a directory. Default is ~/.ddd/sessions/.

Where applicable, DDD supports a gcore command to obtain core files of the running program. You can enter its path via Edit => Preferences => Helpers => Get Core File. Leave the value empty if you have no gcore or similar command.

This setting is tied to the following resource (see Customizing):

getCoreCommand (class GetCoreCommand) Resource
A command to get a core dump of a running process (typically, gcore) @FILE@ is replaced by the base name of the file to create; @PID@ is replaced by the process id. The output must be written to @FILE@.@PID@.

Leave the value empty if you have no gcore or similar command.


Node:Remote Debugging, Next:, Previous:Sessions, Up:Invocation

Remote Debugging

You can have each of DDD, the inferior debugger, and the debugged program run on different machines.


Node:Remote Host, Next:, Up:Remote Debugging

Running DDD on a Remote Host

You can run DDD on a remote host, using your current host as X display. On the remote host, invoke DDD as

     ddd -display display
     

where display is the name of the X server to connect to (for instance, hostname:0.0, where hostname is your host).

Instead of specifying -display display, you can also set the DISPLAY environment variable to display.


Node:Remote Debugger, Next:, Previous:Remote Host, Up:Remote Debugging

Using DDD with a Remote Inferior Debugger

In order to run the inferior debugger on a remote host, you need remsh (called rsh on BSD systems) access on the remote host.

To run the debugger on a remote host hostname, invoke DDD as

     ddd --host hostname remote-program
     

If your remote username differs from the local username, use

     ddd --host hostname --login username remote-program
     

or

     ddd --host username@hostname remote-program
     

instead.

There are a few caveats in remote mode:

See Customizing Remote Debugging, for customizing remote mode.


Node:Customizing Remote Debugging, Up:Remote Debugger
Customizing Remote Debugging

When having the inferior debugger run on a remote host (see Remote Debugging), all commands to access the inferior debugger as well as its files must be run remotely. This is controlled by the following resources (see Customizing):

rshCommand (class RshCommand) Resource
The remote shell command to invoke TTY-based commands on remote hosts. Usually, remsh, rsh, ssh, or on.

listCoreCommand (class listCoreCommand) Resource
The command to list all core files on the remote host. The string @MASK@ is replaced by a file filter. The default setting is:
          Ddd*listCoreCommand: \
          file @MASK@ | grep '.*:.*core.*' | cut -d: -f1
          

listDirCommand (class listDirCommand) Resource
The command to list all directories on the remote host. The string @MASK@ is replaced by a file filter. The default setting is:
          Ddd*listDirCommand: \
          file @MASK@ | grep '.*:.*directory.*' | cut -d: -f1
          

listExecCommand (class listExecCommand) Resource
The command to list all executable files on the remote host. The string @MASK@ is replaced by a file filter. The default setting is:
          Ddd*listExecCommand: \
          file @MASK@ | grep '.*:.*exec.*' \
            | grep -v  '.*:.*script.*' \
            | cut -d: -f1 | grep -v '.*\.o$'
          

listSourceCommand (class listSourceCommand) Resource
The command to list all source files on the remote host. The string @MASK@ is replaced by a file filter. The default setting is:
          Ddd*listSourceCommand: \
          file @MASK@ | grep '.*:.*text.*' | cut -d: -f1
          


Node:Remote Program, Previous:Remote Debugger, Up:Remote Debugging

Debugging a Remote Program

The GDB debugger allows you to run the debugged program on a remote machine (called remote target), while GDB runs on the local machine.

See Remote Debugging, for details. Basically, the following steps are required:

The local .gdbinit file is useful for setting up directory search paths, etc.

Of course, you can also combine DDD remote mode and GDB remote mode, running DDD, GDB, and the debugged program each on a different machine.


Node:Customizing Debugger Interaction, Previous:Remote Debugging, Up:Invocation

Customizing Interaction with the Inferior Debugger

These settings control the interaction of DDD with its inferior debugger.


Node:Debugger Invocation, Next:, Up:Customizing Debugger Interaction

Invoking an Inferior Debugger

To choose the default inferior debugger, select Edit => Preferences => Startup => Debugger Type. You can

The following DDD resources control the invocation of the inferior debugger (see Customizing).

autoDebugger (class AutoDebugger) Resource
If this is on (default), DDD will attempt to determine the debugger type from its arguments, possibly overriding the debugger resource (see below). If this is off, DDD will invoke the debugger specified by the debugger resource regardless of DDD arguments.

debugger (class Debugger) Resource
The type of the inferior debugger to invoke (gdb, dbx, ladebug, xdb, jdb, pydb, perl, or bash).

This resource is usually set through the --gdb, --dbx, --ladebug, --xdb, --jdb, --pydb, --perl, and --bash options; See Options, for details.

debuggerCommand (class DebuggerCommand) Resource
The name under which the inferior debugger is to be invoked. If this string is empty (default), the debugger type (debugger resource) is used.

This resource is usually set through the --debugger option; See Options, for details.


Node:Debugger Initialization, Next:, Previous:Debugger Invocation, Up:Customizing Debugger Interaction

Initializing the Inferior Debugger

DDD uses a number of resources to initialize the inferior debugger (see Customizing).


Node:GDB Initialization, Next:, Up:Debugger Initialization
GDB Initialization

gdbInitCommands (class InitCommands) Resource
This string contains a list of newline-separated commands that are initially sent to GDB. As a side-effect, all settings specified in this resource are considered fixed and cannot be changed through the GDB settings panel, unless preceded by white space. By default, the gdbInitCommands resource contains some settings vital to DDD:
            Ddd*gdbInitCommands: \
            set height 0\n\
            set width 0\n\
             set verbose off\n\
            set prompt (gdb) \n
          

While the set height, set width, and set prompt settings are fixed, the set verbose settings can be changed through the GDB settings panel (although being reset upon each new DDD invocation).

Do not use this resource to customize GDB; instead, use a personal ~/.gdbinit file. See your GDB documentation for details.

gdbSettings (class Settings) Resource
This string contains a list of newline-separated commands that are also initially sent to GDB. Its default value is
            Ddd*gdbSettings: \
            set print asm-demangle on\n
          

This resource is used to save and restore the debugger settings.

sourceInitCommands (class SourceInitCommands) Resource
If on (default), DDD writes all GDB initialization commands into a temporary file and makes GDB read this file, rather than sending each initialization command separately. This results in faster startup (especially if you have several user-defined commands). If off, DDD makes GDB process each command separately.


Node:DBX Initialization, Next:, Previous:GDB Initialization, Up:Debugger Initialization
DBX Initialization

dbxInitCommands (class InitCommands) Resource
This string contains a list of newline-separated commands that are initially sent to DBX. By default, it is empty.

Do not use this resource to customize DBX; instead, use a personal ~/.dbxinit or ~/.dbxrc file. See your DBX documentation for details.

dbxSettings (class Settings) Resource
This string contains a list of newline-separated commands that are also initially sent to DBX. By default, it is empty.


Node:XDB Initialization, Next:, Previous:DBX Initialization, Up:Debugger Initialization
XDB Initialization

xdbInitCommands (class InitCommands) Resource
This string contains a list of newline-separated commands that are initially sent to XDB. By default, it is empty.

Do not use this resource to customize DBX; instead, use a personal ~/.xdbrc file. See your XDB documentation for details.

xdbSettings (class Settings) Resource
This string contains a list of newline-separated commands that are also initially sent to XDB. By default, it is empty.


Node:JDB Initialization, Next:, Previous:XDB Initialization, Up:Debugger Initialization
JDB Initialization

jdbInitCommands (class InitCommands) Resource
This string contains a list of newline-separated commands that are initially sent to JDB. This resource may be used to customize JDB. By default, it is empty.

jdbSettings (class Settings) Resource
This string contains a list of newline-separated commands that are also initially sent to JDB. By default, it is empty.

This resource is used by DDD to save and restore JDB settings.


Node:PYDB Initialization, Next:, Previous:JDB Initialization, Up:Debugger Initialization
PYDB Initialization

pydbInitCommands (class InitCommands) Resource
This string contains a list of newline-separated commands that are initially sent to PYDB. By default, it is empty.

This resource may be used to customize PYDB.

pydbSettings (class Settings) Resource
This string contains a list of newline-separated commands that are also initially sent to PYDB. By default, it is empty.

This resource is used by DDD to save and restore PYDB settings.


Node:Perl Initialization, Next:, Previous:PYDB Initialization, Up:Debugger Initialization
Perl Initialization

perlInitCommands (class InitCommands) Resource
This string contains a list of newline-separated commands that are initially sent to the Perl debugger. By default, it is empty.

This resource may be used to customize the Perl debugger.

perlSettings (class Settings) Resource
This string contains a list of newline-separated commands that are also initially sent to the Perl debugger. By default, it is empty.

This resource is used by DDD to save and restore Perl debugger settings.


Node:Bash Initialization, Next:, Previous:Perl Initialization, Up:Debugger Initialization
Bash Initialization

bashInitCommands (class InitCommands) Resource
This string contains a list of newline-separated commands that are initially sent to the Bash debugger. By default, it is empty.

This resource may be used to customize the Bash debugger.

bash (class Settings) Resource
This string contains a list of newline-separated commands that are also initially sent to the Perl debugger. By default, it is empty.

This resource is used by DDD to save and restore Bash debugger settings.


Node:Finding a Place to Start, Next:, Previous:Bash Initialization, Up:Debugger Initialization
Finding a Place to Start

initSymbols (class InitSymbols) Resource
When loading an executable, DDD queries the inferior debugger for the initial source location--typically the main function. If this location is not found, DDD tries other symbols from this newline-separated list. The default value makes DDD look for a variety of main functions (especially FORTRAN main functions):
          main\n\
          MAIN\n\
          main_\n\
          MAIN_\n\
          main__\n\
          MAIN__\n\
          _main\n\
          _MAIN\n\
          __main\n\
          __MAIN
          


Node:Opening the Selection, Previous:Finding a Place to Start, Up:Debugger Initialization
Opening the Selection

openSelection (class OpenSelection) Resource
If this is on, DDD invoked without argument checks whether the current selection or clipboard contains the file name or URL of an executable program. If this is so, DDD will automatically open this program for debugging. If this resource is off (default), DDD invoked without arguments will always start without a debugged program.


Node:Debugger Communication, Previous:Debugger Initialization, Up:Customizing Debugger Interaction

Communication with the Inferior Debugger

The following resources control the communication with the inferior debugger.

blockTTYInput (class BlockTTYInput) Resource
Whether DDD should block when reading data from the inferior debugger via the pseudo-tty interface. Most UNIX systems except GNU/Linux require this; set it to on. On GNU/Linux, set it to off. The value auto (default) will always select the "best" choice (that is, the best choice known to the DDD developers).

bufferGDBOutput (class BufferGDBOutput) Resource
If this is on, all output from the inferior debugger is buffered until a debugger prompt appears. This makes it easier for DDD to parse the output, but has the drawback that interaction with a running debuggee in the debugger console is not possible. If off, output is shown as soon as it arrives, enabling interaction, but making it harder for DDD to parse the output. If auto (default), output is buffered if and only if the execution window is open, which redirects debuggee output and thus enables interaction. See Using the Execution Window, for details.

contInterruptDelay (class InterruptDelay) Resource
The time (in ms) to wait before automatically interrupting a cont command. DDD cannot interrupt a cont command immediately, because this may disturb the status change of the process. Default is 200.

displayTimeout (class DisplayTimeout) Resource
The time (in ms) to wait for the inferior debugger to finish a partial display information. Default is 2000.

positionTimeout (class PositionTimeout) Resource
The time (in ms) to wait for the inferior debugger to finish a partial position information. Default is 500.

questionTimeout (class QuestionTimeout) Resource
The time (in seconds) to wait for the inferior debugger to reply. Default is 10.

runInterruptDelay (class InterruptDelay) Resource
The time (in ms) to wait before automatically interrupting a run command. DDD cannot interrupt a cont command immediately, because this may disturb process creation. Default is 2000.

stopAndContinue (class StopAndContinue) Resource
If on (default), debugger commands interrupt program execution, resuming execution after the command has completed. This only happens if the last debugger command was either a run or a continue command. If off, debugger commands do not interrupt program execution.

synchronousDebugger (class SynchronousDebugger) Resource
If on, X events are not processed while the debugger is busy. This may result in slightly better performance on single-processor systems. See Options, for the --sync-debugger option.

terminateOnEOF (class TerminateOnEOF) Resource
If on, DDD terminates the inferior debugger when DDD detects an EOF condition (that is, as soon as the inferior debugger closes its output channel). This was the default behavior in DDD 2.x and earlier. If off (default), DDD takes no special action.

useTTYCommand (class UseTTYCommand) Resource
If on, use the GDB tty command for redirecting input/output to the separate execution window. If off, use explicit redirection through shell redirection operators < and >. The default is off (explicit redirection), since on some systems, the tty command does not work properly on some GDB versions.


Node:Windows, Next:, Previous:Invocation, Up:Top

The DDD Windows

DDD is composed of three main windows. From top to bottom, we have:


PICS/ddd-all.jpg

Besides these three main windows, there are some other optional windows:


Node:Menu Bar, Next:, Up:Windows

The Menu Bar

The DDD Menu Bar gives you access to all DDD functions.

File
Perform file-related operations such as selecting programs, processes, and sessions, printing graphs, recompiling, as well as exiting DDD.
Edit
Perform standard editing operations, such as cutting, copying, pasting, and killing selected text. Also allows editing DDD options and preferences.
View
Allows accessing the individual DDD windows.
Program
Perform operations related to the program being debugged, such as starting and stopping the program.
Commands
Perform operations related to DDD commands, such as accessing the command history or defining new commands.
Status
Examine the program status, such as the stack traces, registers, or threads.
Source
Perform source-related operations such as looking up items or editing breakpoints.
Data
Perform data-related operations such as editing displays or layouting the display graph.
Maintenance
Perform operations that are useful for debugging DDD. By default, this menu is disabled.
Help
Give help on DDD usage.

There are two ways of selecting an item from a pull-down menu:

The menus can also be torn off (i.e. turned into a persistent window) by selecting the dashed line at the top.

If a command in the pull-down menu is not applicable in a given situation, the command is disabled and its name appears faded. You cannot invoke items that are faded. For example, many commands on the Edit menu appear faded until you select text on which they are to operate; after you select a block of text, edit commands are enabled.


Node:File Menu, Next:, Up:Menu Bar

The File Menu

The File menu contains file-related operations such as selecting programs, processes, and sessions, printing graphs, recompiling, as well as exiting DDD.

Open Program
Open Class
Open a program or class to be debugged (<Ctrl+O>). See Opening Programs, for details.
Open Recent
Re-open a recently opened program to be debugged. See Opening Programs, for details.
Open Core Dump
Open a core dump for the currently debugged program. See Opening Core Dumps, for details.
Open Source
Open a source file of the currently debugged program. See Opening Source Files, for details.
Open Session
Resume a previously saved DDD session (<Ctrl+N>). See Resuming Sessions, for details.
Save Session As
Save the current DDD session such that you can resume it later (<Ctrl+S>). See Saving Sessions, for details.
Attach to Process
Attach to a running process of the debugged program. See Attaching to a Process, for details.
Detach Process
Detach from the running process. See Attaching to a Process, for details.
Print Graph
Print the current graph on a printer. See Printing the Graph, for details.
Change Directory
Change the working directory of your program. See Working Directory, for details.
Make
Run the make program (<Ctrl+M>). See Recompiling, for details.
Close
Close this DDD window (<Ctrl+W>). See Quitting, for details.
Restart
Restart DDD.
Exit
Exit DDD (<Ctrl+Q>). See Quitting, for details.


Node:Edit Menu, Next:, Previous:File Menu, Up:Menu Bar

The Edit Menu

The Edit menu contains standard editing operations, such as cutting, copying, pasting, and killing selected text. Also allows editing DDD options and preferences.

Undo
Undo the most recent action (<Ctrl+Z>). Almost all commands can be undone this way. See Undo and Redo, for details.
Redo
Redo the action most recently undone (<Ctrl+Y>). Every command undone can be redone this way. See Undo and Redo, for details.
Cut
Removes the selected text block from the current text area and makes it the X clipboard selection (<Ctrl+X> or <Shift+Del>; See Customizing the Edit Menu, for details). Before executing this command, you have to select a region in a text area--either with the mouse or with the usual text selection keys.

This item can also be applied to displays (see Deleting Displays).

Copy
Makes a selected text block the X clipboard selection (<Ctrl+C> or <Ctrl+Ins>; See Customizing the Edit Menu, for details). You can select text by selecting a text region with the usual text selection keys or with the mouse. See Customizing the Edit Menu, for changing the default accelerator.

This item can also be applied to displays (see Deleting Displays).

Paste
Inserts the current value of the X clipboard selection in the most recently selected text area (<Ctrl+V> or <Shift+Ins>; See Customizing the Edit Menu, for details). You can paste in text you have placed in the clipboard using Copy or Cut. You can also use Paste to insert text that was pasted into the clipboard from other applications.
Clear
Clears the most recently selected text area (<Ctrl+U>).
Delete
Removes the selected text block from the most recently selected text area, but does not make it the X clipboard selection.

This item can also be applied to displays (see Deleting Displays).

Select All
Selects all characters from the most recently selected text area (<Ctrl+A> or or <Ctrl+Shift+A>; see Customizing the Edit Menu, for details).
Preferences
Allows you to customize DDD interactively. See Customizing, for details.
Debugger Settings
Allows you to customize the inferior debugger. See Debugger Settings, for details.
Save Options
If set, all preferences and settings will be saved for the next DDD invocation. See Saving Options, for details.


Node:View Menu, Next:, Previous:Edit Menu, Up:Menu Bar

The View Menu

The View menu allows accessing the individual DDD windows.

Command Tool
Open and recenter the command tool (<Alt+8>). See Command Tool, for details.
Execution Window
Open the separate execution window (<Alt+9>). See Using the Execution Window, for details.
Debugger Console
Open the debugger console (<Alt+1>). See Commands, for details.
Source Window
Open the source window (<Alt+2>). See Navigating, for details.
Data Window
Open the data window (<Alt+3>). See Displaying Values, for details.
Machine Code Window
Show machine code (<Alt+4>). See Machine Code, for details.


Node:Program Menu, Next:, Previous:View Menu, Up:Menu Bar

The Program Menu

The Program menu performs operations related to the program being debugged, such as starting and stopping the program.

Most of these operations are also found on the command tool (see Command Tool).

Run
Start program execution, prompting for program arguments (<F2>). See Starting Program Execution, for details.
Run Again
Start program execution with the most recently used arguments (<F3>). See Starting Program Execution, for details.
Run in Execution Window
If enabled, start next program execution in separate execution window. See Using the Execution Window, for details.
Step
Continue running your program until control reaches a different source line, then stop it and return control to DDD (<F5>). See Resuming Execution, for details.
Step Instruction
Execute one machine instruction, then stop and return to DDD (<Shift+F5>). See Machine Code Execution, for details.
Next
Continue to the next source line in the current (innermost) stack frame (<F6>). This is similar to Step, but function calls that appear within the line of code are executed without stopping. See Resuming Execution, for details.
Next Instruction
Execute one machine instruction, but if it is a function call, proceed until the function returns (<Shift+F6>). See Machine Code Execution, for details.
Until
Continue running until a source line past the current line, in the current stack frame, is reached (<F7>). See Resuming Execution, for details.
Finish
Continue running until just after function in the selected stack frame returns (<F8>). Print the returned value (if any). See Resuming Execution, for details.
Continue
Resume program execution, at the address where your program last stopped (<F9>); any breakpoints set at that address are bypassed. See Resuming Execution, for details.
Continue Without Signal
Continue execution without giving a signal (<Shift+F9>). This is useful when your program stopped on account of a signal and would ordinary see the signal when resumed with Continue. See Signals, for details.
Kill
Kill the process of the debugged program (<F4>). See Killing the Program, for details.
Interrupt
Interrupt program execution (<Esc> or <Ctrl+C>; see Customizing the Edit Menu, for details). This is equivalent to sending an interrupt signal to the process. See Interrupting, for details.
Abort
Abort program execution (and maybe debugger execution, too; <Ctrl+\>). This is equivalent to sending a SIGABRT signal to the process. See Quitting, for details.


Node:Commands Menu, Next:, Previous:Program Menu, Up:Menu Bar

The Commands Menu

The Commands menu performs operations related to DDD commands, such as accessing the command history or defining new commands.

Most of these items are not meant to be actually executed via the menu; instead, they serve as reminder for the equivalent keyboard commands.

Command History
View the command history. See Command History, for details.
Previous
Show the previous command from the command history (<Up>). See Command History, for details.
Next
Show the next command from the command history (<Down>). See Command History, for details.
Find Backward
Do an incremental search backward through the command history (<Ctrl+B>). See Command History, for details.
Find Forward
Do an incremental search forward through the command history (<Ctrl+F>). See Command History, for details.
Quit Search
Quit incremental search through the command history (<Esc>). See Command History, for details.
Complete
Complete the current command in the debugger console (<Tab>). See Entering Commands, for details.
Apply
Apply the current command in the debugger console (<Apply>). See Entering Commands, for details.
Clear Line
Clear the current command line in the debugger console (<Ctrl+U>). See Entering Commands, for details.
Clear Window
Clear the debugger console (<Shift+Ctrl+U>). See Entering Commands, for details.
Define Command
Define a new debugger command. See Defining Commands, for details.
Edit Buttons
Customize DDD buttons. See Defining Buttons, for details.


Node:Status Menu, Next:, Previous:Commands Menu, Up:Menu Bar

The Status Menu

The Status menu lets you examine the program status, such as the stack traces, registers, or threads.

Backtrace
View the current backtrace. See Backtraces, for a discussion.
Registers
View the current register contents. See Registers, for details.
Threads
View the current threads. See Threads, for details.
Signals
View and edit the current signal handling. See Signals, for details.
Up
Select the stack frame (i.e. the function) that called this one (<Ctrl+Up>). This advances toward the outermost frame, to higher frame numbers, to frames that have existed longer. See Stack, for details.
Down
Select the stack frame (i.e. the function) that was called by this one (<Ctrl+Down>). This advances toward the innermost frame, to lower frame numbers, to frames that were created more recently. See Stack, for details.


Node:Source Menu, Next:, Previous:Status Menu, Up:Menu Bar

The Source Menu

The Source menu performs source-related operations such as looking up items or editing breakpoints.

Breakpoints
Edit all Breakpoints. See Editing all Breakpoints, for details.
Lookup ()
Look up the argument () in the source code (<Ctrl+/>). See Looking up Definitions, for details.
Find >> ()
Look up the next occurrence of the argument () in the current source code (<Ctrl+.>). See Textual Search, for details.
Find << ()
Look up the previous occurrence of the argument () in the current source code (<Ctrl+,>). See Textual Search, for details.
Find Words Only
If enabled, find only complete words (<Alt+W>). See Textual Search, for details.
Find Case Sensitive
If enabled, find is case-sensitive (<Alt+I>). See Textual Search, for details.
Display Line Numbers
If enabled, prefix source lines with their line number (<Alt+N>). See Customizing Source, for details.
Display Machine Code
If enabled, show machine code (<Alt+4>). See Machine Code, for details.
Edit Source
Invoke an editor for the current source file (<Shift+Ctrl+V>). See Editing Source Code, for details.
Reload Source
Reload the current source file (<Shift+Ctrl+L>). See Editing Source Code, for details.


Node:Data Menu, Next:, Previous:Source Menu, Up:Menu Bar

The Data Menu

The Data menu performs data-related operations such as editing displays or layouting the display graph.

Displays
Invoke the Display Editor. See Editing all Displays, for details.
Watchpoints
Edit all Watchpoints. See Editing all Watchpoints, for details.
Memory
View a memory dump. See Examining Memory, for details.
Print ()
Print the value of () in the debugger console (<Ctrl+=>). See Printing Values, for details.
Display ()
Display the value of () in the data window (<Ctrl+->). See Displaying Values, for details.
Detect Aliases
If enabled, detect shared data structures (<Alt+A>). See Shared Structures, for a discussion.
Display Local Variables
Show all local variables in a display (<Alt+L>). See Displaying Local Variables, for details.
Display Arguments
Show all arguments of the current function in a display (<Alt+U>). See Displaying Local Variables, for details.
Status Displays
Show current debugging information in a display. See Displaying Program Status, for details.
Align on Grid
Align all displays on the grid (<Alt+G>). See Aligning Displays, for a discussion.
Rotate Graph
Rotate the graph by 90 degrees (<Alt+R>). See Rotating the Graph, for details.
Layout Graph
Layout the graph (<Alt+Y>). See Layouting the Graph, for details.
Refresh
Update all values in the data window (<Ctrl+L>). See Refreshing the Data Window, for details.


Node:Maintenance Menu, Next:, Previous:Data Menu, Up:Menu Bar

The Maintenance Menu

The Maintenance menu performs operations that are useful for debugging DDD.

By default, this menu is disabled; it is enabled by specifically requesting it at DDD invocation (via the --maintenance option; see Options). It is also enabled when DDD gets a fatal signal.

Debug DDD
Invoke a debugger (typically, GDB) and attach it to this DDD process (<F12>). This is useful only if you are a DDD maintainer.
Dump Core Now
Make this DDD process dump core. This can also be achieved by sending DDD a SIGUSR1 signal.
Tic Tac Toe
Invoke a Tic Tac Toe game. You must try to get three stop signs in a row, while preventing DDD from doing so with its skulls. Click on New Game to restart.
When DDD Crashes
Select what to do when DDD gets a fatal signal.
Debug DDD
Invoke a debugger on the DDD core dump when DDD crashes. This is useful only if you are a DDD maintainer.
Dump Core
Just dump core when DDD crashes; don't invoke a debugger. This is the default setting, as the core dump may contain important information required for debugging DDD.
Do Nothing
Do not dump core or invoke a debugger when DDD crashes.

Remove Menu
Make this menu inaccessible again.


Node:Help Menu, Next:, Previous:Maintenance Menu, Up:Menu Bar

The Help Menu

The Help menu gives help on DDD usage. See Getting Help, for a discussion on how to get help within DDD.

Overview
Explains the most important concepts of DDD help.
On Item
Lets you click on an item to get help on it.
On Window
Gives you help on this DDD window.
What Now?
Gives a hint on what to do next.
Tip of the Day
Shows the current tip of the day.
DDD Reference
Shows the DDD Manual.
DDD News
Shows what's new in this DDD release.
Debugger Reference
Shows the on-line documentation for the inferior debugger.
DDD License
Shows the DDD License (see License).
DDD WWW Page
Invokes a WWW browser for the DDD WWW page.
About DDD
Shows version and copyright information.


Node:Customizing the Menu Bar, Previous:Help Menu, Up:Menu Bar

Customizing the Menu Bar

The Menu Bar can be customized in various ways (see Customizing).


Node:Auto-Raise Menus, Next:, Up:Customizing the Menu Bar
Auto-Raise Menus

You can cause pull-down menus to be raised automatically.

autoRaiseMenu (class AutoRaiseMenu) Resource
If on (default), DDD will always keep the pull down menu on top of the DDD main window. If this setting interferes with your window manager, or if your window manager does not auto-raise windows, set this resource to off.

autoRaiseMenuDelay (class AutoRaiseMenuDelay) Resource
The time (in ms) during which an initial auto-raised window blocks further auto-raises. This is done to prevent two overlapping auto-raised windows from entering an auto-raise loop. Default is 100.


Node:Customizing the Edit Menu, Previous:Auto-Raise Menus, Up:Customizing the Menu Bar
Customizing the Edit Menu

In the Menu Bar, the Edit Menu can be customized in various ways. Use Edit => Preferences => Startup to customize these keys.

The <Ctrl+C> key can be bound to different actions, each in accordance with a specific style guide.

Copy
This setting binds <Ctrl+C> to the Copy operation, as specified by the KDE style guide. In this setting, use <ESC> to interrupt the debuggee.
Interrupt
This (default) setting binds <Ctrl+C> to the Interrupt operation, as used in several UNIX command-line programs. In this setting, use <Ctrl+Ins> to copy text to the clipboard.

The <Ctrl+A> key can be bound to different actions, too.

Select All
This (default) setting binds <Ctrl+A> to the Select All operation, as specified by the KDE style guide. In this setting, use <Home> to move the cursor to the beginning of a line.
Beginning of Line
This setting binds <Ctrl+A> to the Beginning of Line operation, as used in several UNIX text-editing programs. In this setting, use <Ctrl+Shift+A> to select all text.

Here are the related DDD resources:

cutCopyPasteBindings (class BindingStyle) Resource
Controls the key bindings for clipboard operations.
  • If this is Motif (default), Cut/Copy/Paste is on <Shift+Del>/<Ctrl+Ins>/<Shift+Ins>. This is conformant to the M*tif style guide.
  • If this is KDE, Cut/Copy/Paste is on <Ctrl+X>/<Ctrl+C>/<Ctrl+V>. This is conformant to the KDE style guide. Note that this means that <Ctrl+C> no longer interrupts the debuggee; use <ESC> instead.

selectAllBindings (class BindingStyle) Resource
Controls the key bindings for the Select All operation.
  • If this is Motif, Select All is on <Shift+Ctrl+A>.
  • If this is KDE (default), Select All is on <Ctrl+A>. This is conformant to the KDE style guide. Note that this means that <Ctrl+A> no longer moves the cursor to the beginning of a line; use <Home> instead.


Node:Tool Bar, Next:, Previous:Menu Bar, Up:Windows

The Tool Bar

Some DDD commands require an argument. This argument is specified in the argument field, labeled ():. Basically, there are four ways to set arguments:

Using GDB and Perl, the argument field provides a completion mechanism. You can enter the first few characters of an item an press the <TAB> key to complete it. Pressing <TAB> again shows alternative completions.

After having entered an argument, you can select one of the buttons on the right. Most of these buttons also have menus associated with them; this is indicated by a small arrow in the upper right corner. Pressing and holding mouse button 1 on such a button will pop up a menu with further operations.

PICS/ddd-toolbar.jpg

These are the buttons of the tool bar. Note that not all buttons may be inactive, depending on the current state and the capabilities of the inferior debugger.

Lookup

Look up the argument () in the source code. See Looking up Definitions, for details.

Find >>

Look up the next occurrence of the argument () in the current source code. See Textual Search, for details.

Break/Clear

Toggle a breakpoint (see Breakpoints) at the location ().

Break
If there is no breakpoint at (), then this button is labeled Break. Clicking on Break sets a breakpoint at the location (). See Setting Breakpoints, for details.
Clear
If there already is a breakpoint at (), then this button is labeled Clear. Clicking on Clear clears (deletes) the breakpoint at the location (). See Deleting Breakpoints, for details.

Watch/Unwatch

Toggle a watchpoint (see Watchpoints) on the expression ().

Watch
If () is not being watched, then this button is labeled Watch. Clicking on Watch creates a watchpoint on the expression (). See Setting Watchpoints, for details.
Unwatch
If () is being watched, then this button is labeled Unwatch. Clicking on Unwatch clears (deletes) the watchpoint on (). See Deleting Watchpoints, for details.

Print

Print the value of () in the debugger console. See Printing Values, for details.

Display

Display the value of () in the data window. See Displaying Values, for details.

Plot

Plot () in a plot window. See Plotting Values, for details.

Show/Hide

Toggle details of the selected display(s). See Showing and Hiding Details, for a discussion.

Rotate

Rotate the selected display(s). See Rotating Displays, for details.

Set

Set (change) the value of (). See Assignment, for details.

Undisp

Undisplay (delete) the selected display(s). See Deleting Displays, for details.


Node:Customizing the Tool Bar, Up:Tool Bar

Customizing the Tool Bar

The DDD tool bar buttons can appear in a variety of styles, customized via Edit => Preferences => Startup.

Images
This lets each tool bar button show an image illustrating the action.
Captions
This shows the action name below the image.

The default is to have images as well as captions, but you can choose to have only images (saving space) or only captions.

PICS/ddd-toolbars.jpg

If you choose to have neither images nor captions, tool bar buttons are labeled like other buttons, as in DDD 2.x. Note that this implies that in the stacked window configuration, the common tool bar cannot be displayed; it is replaced by two separate tool bars, as in DDD 2.x.

If you enable Flat buttons (default), the border of tool bar buttons will appear only if the mouse pointer is over them. This latest-and-greatest GUI invention can be disabled, such that the button border is always shown.

If you enable Color buttons, tool bar images will be colored when entered. If DDD was built using M*tif 2.0 and later, you can also choose a third setting, where buttons appear in color all the time.

Here are the related resources (see Customizing):

activeButtonColorKey (class ColorKey) Resource
The XPM color key to use for the images of active buttons (entered or armed). c means color, g (default) means grey, and m means monochrome.

buttonCaptions (class ButtonCaptions) Resource
Whether the tool bar buttons should be shown using captions (on, default) or not (off). If neither captions nor images are enabled, tool bar buttons are shown using ordinary labels. See also buttonImages, below.

buttonCaptionGeometry (class ButtonCaptionGeometry) Resource
The geometry of the caption subimage within the button icons. Default is 29x7+0-0.

buttonImages (class ButtonImages) Resource
Whether the tool bar buttons should be shown using images (on, default) or not (off). If neither captions nor images are enabled, tool bar buttons are shown using ordinary labels. See also buttonCaptions, above.

buttonImageGeometry (class ButtonImageGeometry) Resource
The geometry of the image within the button icon. Default is 25x21+2+0.

buttonColorKey (class ColorKey) Resource
The XPM color key to use for the images of inactive buttons (non-entered or insensitive). c means color, g (default) means grey, and m means monochrome.

flatToolbarButtons (class FlatButtons) Resource
If on (default), all tool bar buttons with images or captions are given a `flat' appearance--the 3-D border only shows up when the pointer is over the icon. If off, the 3-D border is shown all the time.

flatDialogButtons (class FlatButtons) Resource
If on (default), all dialog buttons with images or captions are given a `flat' appearance--the 3-D border only shows up when the pointer is over the icon. If off, the 3-D border is shown all the time.


Node:Command Tool, Next:, Previous:Tool Bar, Up:Windows

The Command Tool

The command tool is a small window that gives you access to the most frequently used DDD commands. It can be moved around on top of the DDD windows, but it can also be placed besides them.

By default, the command tool sticks to the DDD source window: Whenever you move the DDD source window, the command tool follows such that the distance between source window and command tool remains the same. By default, the command tool is also auto-raised, such that it stays on top of other DDD windows.

The command tool can be configured to appear as a command tool bar above the source window; see Edit => Preferences => Source => Tool Buttons Location for details.

Whenever you save DDD state, DDD also saves the distance between command tool and source window, such that you can select your own individual command tool placement. To move the command tool to its saved position, use View => Command Tool.

PICS/ddd-tool.jpg

These are the buttons of the command tool. Note that not all buttons may be inactive, depending on the current state and the capabilities of the inferior debugger.

Run
Start program execution. When you click this button, your program will begin to execute immediately. See Starting Program Execution, for details.
Interrupt
Interrupt program execution. This is equivalent to sending an interrupt signal to the process. See Interrupting, for details.
Step
Continue running your program until control reaches a different source line, then stop it and return control to DDD. See Resuming Execution, for details.
Stepi
Execute one machine instruction, then stop and return to DDD. See Machine Code Execution, for details.
Next
Continue to the next source line in the current (innermost) stack frame. This is similar to Step, but function calls that appear within the line of code are executed without stopping. See Resuming Execution, for details.
Nexti
Execute one machine instruction, but if it is a function call, proceed until the function returns. See Machine Code Execution, for details.
Until
Continue running until a source line past the current line, in the current stack frame, is reached. See Resuming Execution, for details.
Finish
Continue running until just after function in the selected stack frame returns. Print the returned value (if any). See Resuming Execution, for details.
Cont
Resume program execution, at the address where your program last stopped; any breakpoints set at that address are bypassed. See Resuming Execution, for details.
Kill
Kill the process of the debugged program. See Killing the Program, for details.
Up
Select the stack frame (i.e. the function) that called this one. This advances toward the outermost frame, to higher frame numbers, to frames that have existed longer. See Stack, for details.
Down
Select the stack frame (i.e. the function) that was called by this one. This advances toward the innermost frame, to lower frame numbers, to frames that were created more recently. See Stack, for details.
Undo
Undo the most recent action. Almost all commands can be undone this way. See Undo and Redo, for details.
Redo
Redo the action most recently undone. Every command undone can be redone this way. See Undo and Redo, for details.
Edit
Invoke an editor for the current source file. See Editing Source Code, for details.
Make
Run the make program with the most recently given arguments. See Recompiling, for details.


Node:Customizing the Command Tool, Next:, Up:Command Tool

Customizing the Command Tool

The Command Tool can be customized in various ways.

See Customizing Buttons, for details on customizing the tool buttons.


Node:Disabling the Command Tool, Up:Customizing the Command Tool
Disabling the Command Tool

You can disable the command tool and show its buttons in a separate row beneath the tool bar. To disable the command tool, set Edit => Preferences => Source => Tool Buttons Location => Source Window.

PICS/ddd-source-prefs.jpg

Here's the related resource:

commandToolBar (class ToolBar) Resource
Whether the tool buttons should be shown in a tool bar above the source window (on) or within the command tool (off, default). Enabling the command tool bar disables the command tool and vice versa.


Node:Customizing Tool Position, Previous:Customizing the Command Tool, Up:Command Tool

Command Tool Position

The following resources control the position of the command tool (see Customizing):

autoRaiseTool (class AutoRaiseTool) Resource
If on (default), DDD will always keep the command tool on top of other DDD windows. If this setting interferes with your window manager, or if your window manager keeps the command tool on top anyway, set this resource to off.

stickyTool (class StickyTool) Resource
If on (default), the command tool automatically follows every movement of the source window. Whenever the source window is moved, the command tool is moved by the same offset such that its position relative to the source window remains unchanged. If off, the command tool does not follow source window movements.

toolRightOffset (class Offset) Resource
The distance between the right border of the command tool and the right border of the source text (in pixels). Default is 8.

toolTopOffset (class Offset) Resource
The distance between the upper border of the command tool and the upper border of the source text (in pixels). Default is 8.


Node:Customizing Tool Decoration, Up:Customizing Tool Position
Customizing Tool Decoration

The following resources control the decoration of the command tool (see Customizing):

decorateTool (class Decorate) Resource
This resource controls the decoration of the command tool.
  • If this is off, the command tool is created as a transient window. Several window managers keep transient windows automatically on top of their parents, which is appropriate for the command tool. However, your window manager may be configured not to decorate transient windows, which means that you cannot easily move the command tool around.
  • If this is on, DDD realizes the command tool as a top-level window. Such windows are always decorated by the window manager. However, top-level windows are not automatically kept on top of other windows, such that you may wish to set the autoRaiseTool resource, too.
  • If this is auto (default), DDD checks whether the window manager decorates transients. If yes, the command tool is realized as a transient window (as in the off setting); if no, the command tool is realized as a top-level window (as in the on setting). Hence, the command tool is always decorated using the "best" method, but the extra check takes some time.


Node:Getting Help, Next:, Previous:Command Tool, Up:Windows

Getting Help

DDD has an extensive on-line help system. Here's how to get help while working with DDD.

All these functions can be customized in various ways (see Customizing Help).

If, after all, you made a mistake, don't worry: almost every DDD command can be undone. See Undo and Redo, for details.


Node:Undo and Redo, Next:, Previous:Getting Help, Up:Windows

Undoing and Redoing Commands

Almost every DDD command can be undone, using Edit => Undo or the Undo button on the command tool.

Likewise, Edit => Redo repeats the command most recently undone.

The Edit menu shows which commands are to be undone and redone next; this is also indicated by the popup help on the Undo and Redo buttons.


Node:Customizing, Previous:Undo and Redo, Up:Windows

Customizing DDD

DDD is controlled by several resources--user-defined variables that take specific values in order to control and customize DDD behavior.

Most DDD resources can be set interactively while DDD is running or when invoking DDD. See Resource Index, for the full list of DDD resources.

We first discuss how customizing works in general; then we turn to customizing parts of DDD introduced so far.


Node:How Customizing Works, Next:, Up:Customizing

How Customizing DDD Works


Node:Resources, Next:, Up:How Customizing Works
Resources

Just like any X program, DDD has a number of places to get resource values from. For DDD, the most important places to specify resources are:

Not every resource has a matching command-line option. Each resource (whether in ~/.ddd/init or Ddd) is specified using a line

     Ddd*resource: value
     

For instance, to set the pollChildStatus resource to off, you would specify in ~/.ddd/init:

     Ddd*pollChildStatus: off
     

For more details on the syntax of resource specifications, see the section RESOURCES in the X(1) manual page.


Node:Changing Resources, Next:, Previous:Resources, Up:How Customizing Works
Changing Resources

You can change DDD resources by three methods:


Node:Saving Options, Previous:Changing Resources, Up:How Customizing Works
Saving Options

You can save the current option settings by setting Edit => Save Options. Options are saved in a file named .ddd/init in your home directory when DDD exits. If a session session is active, options will be saved in ~/.ddd/sessions/session/init instead.

The options are automatically saved when exiting DDD. You can turn off this feature by unsetting Edit => Save Options. This is tied to the following resource:

saveOptionsOnExit (class SaveOnExit) Resource
If on (default), the current option settings are automatically saved when DDD exits.


Node:Customizing Help, Next:, Previous:How Customizing Works, Up:Customizing

Customizing DDD Help

DDD Help can be customized in various ways.


Node:Button tips, Next:, Up:Customizing Help
Button Tips

Button tips are helpful for novices, but may be distracting for experienced users. You can turn off button tips via Edit => Preferences => General => Automatic display of Button Hints => as Popup Tips.

You can also turn off the hint that is displayed in the status line. Just toggle Edit => Preferences => General => Automatic Display of Button Hints => in the Status Line.

PICS/ddd-general-prefs.jpg

These are the related DDD resources (see Customizing):

buttonTips (class Tips) Resource
If on (default), enable button tips.

buttonDocs (class Docs) Resource
If on (default), show button hints in the status line.


Node:Tip of the day, Next:, Previous:Button tips, Up:Customizing Help
Tip of the day

You can turn off the tip of the day by toggling Edit => Preferences => Startup => Startup Windows => Tip of the Day.

Here is the related DDD resource (see Customizing):

startupTips (class StartupTips) Resource
If on (default), show a tip of the day upon DDD startup.

See Options, for options to set this resource upon DDD invocation.

The actual tips are controlled by these resources (see Customizing):

startupTipCount (class StartupTipCount) Resource
The number n of the tip of the day to be shown at startup. See also the tipn resources.

tipn (class Tip) Resource
The tip of the day numbered n (a string).


Node:Help Helpers, Previous:Tip of the day, Up:Customizing Help
Help Helpers

DDD relies on a number of external commands, specified via Edit => Preferences => Helpers.

PICS/ddd-helpers.jpg

To uncompress help texts, you can define a Uncompress command:

uncompressCommand (class UncompressCommand) Resource
The command to uncompress the built-in DDD manual, the DDD license, and the DDD news. Takes a compressed text from standard input and writes the uncompressed text to standard output. The default value is gzip -d -c; typical values include zcat and gunzip -c.

To view WWW pages, you can define a Web Browser command:

wwwCommand (class WWWCommand) Resource
The command to invoke a WWW browser. The string @URL@ is replaced by the URL to open. Default is to try a running Netscape first (trying mozilla, then netscape), then $WWWBROWSER, then to invoke a new Netscape process, then to let a running Emacs or XEmacs do the job (via gnudoit), then to invoke Mosaic, then to invoke Lynx in an xterm.

To specify netscape-6.0 as browser, use the setting:

          Ddd*wwwCommand: \
               netscape-6.0 -remote 'openURL(@URL@)' \
            || netscape-6.0 '@URL@'
          

This command first tries to connect to a running netscape-6.0 browser; if this fails, it starts a new netscape-6.0 process.

This is the default WWW Page shown by Help => DDD WWW Page:

wwwPage (class WWWPage) Resource
The DDD WWW page. Value: http://www.gnu.org/software/ddd/


Node:Customizing Undo, Next:, Previous:Customizing Help, Up:Customizing

Customizing Undo

DDD Undo can be customized in various ways.

To set a maximum size for the undo buffer, set Edit => Preferences => General => Undo Buffer Size.

This is related to the maxUndoSize resource:

maxUndoSize (class MaxUndoSize) Resource
The maximum memory usage (in bytes) of the undo buffer. Useful for limiting DDD memory usage. A negative value means to place no limit. Default is 2000000, or 2000 kBytes.

You can also limit the number of entries in the undo buffer, regardless of size (see Customizing):

maxUndoDepth (class MaxUndoDepth) Resource
The maximum number of entries in the undo buffer. This limits the number of actions that can be undone, and the number of states that can be shown in historic mode. Useful for limiting DDD memory usage. A negative value (default) means to place no limit.

To clear the undo buffer at any time, thus reducing memory usage, use Edit => Preferences => General => Clear Undo Buffer


Node:Customizing Windows, Next:, Previous:Customizing Undo, Up:Customizing

Customizing the DDD Windows

You can customize the DDD Windows in various ways.


Node:Splash Screen, Next:, Up:Customizing Windows
Splash Screen

You can turn off the DDD splash screen shown upon startup. Just select Edit => Preferences => Startup DDD Splash Screen.

PICS/ddd-startup-prefs.jpg

The value applies only to the next DDD invocation.

This setting is related to the following resource:

splashScreen (class SplashScreen) Resource
If on (default), show a DDD splash screen upon start-up.

You can also customize the appearance of the splash screen (see Customizing):

splashScreenColorKey (class ColorKey) Resource
The color key to use for the DDD splash screen. Possible values include:
  • c (default) for a color visual,
  • g for a multi-level greyscale visual,
  • g4 for a 4-level greyscale visual, and
  • m for a dithered monochrome visual.
  • best chooses the best visual available for your display.

Please note: if DDD runs on a monochrome display, or if DDD was compiled without the XPM library, only the monochrome version (m) can be shown.


Node:Window Layout, Next:, Previous:Splash Screen, Up:Customizing Windows
Window Layout

By default, DDD stacks commands, source, and data in one single top-level window. To have separate top-level windows for source, data, and debugger console, set Edit => Preferences => Startup => Window Layout => Separate Windows.

PICS/ddd-separate.jpg

Here are the related DDD resources:

separateDataWindow (class Separate) Resource
If on, the data window and the debugger console are realized in different top-level windows. If off (default), the data window is attached to the debugger console.

separateSourceWindow (class Separate) Resource
If on, the source window and the debugger console are realized in different top-level windows. If off (default), the source window is attached to the debugger console.

By default, the DDD tool bars are located on top of the window. If you prefer the tool bar being located at the bottom, as in DDD 2.x and earlier, set Edit => Preferences => Startup => Tool Bar Appearance => Bottom.

This is related to the toolbarsAtBottom resource:

toolbarsAtBottom (class ToolbarsAtBottom) Resource
Whether source and data tool bars should be placed above source and data, respectively (off, default), or below, as in DDD 2.x (on).

The bottom setting is only supported for separate tool bars--that is, you must either choose separate windows or configure the tool bar to have neither images nor captions (see Customizing the Tool Bar).

If you use stacked windows, you can choose whether there should be one tool bar or two tool bars. By default, DDD uses two tool bars if you use separate windows and disable captions and images, but you can also explicitly change the setting via this resource:

commonToolBar (class ToolBar) Resource
Whether the tool bar buttons should be shown in one common tool bar at the top of the common DDD window (on, default), or whether they should be placed in two separate tool bars, one for data, and one for source operations, as in DDD 2.x (off).

You can also change the location of the status line (see Customizing):

statusAtBottom (class StatusAtBottom) Resource
If on (default), the status line is placed at the bottom of the DDD source window. If off, the status line is placed at the top of the DDD source window (as in DDD 1.x).

See Options, for options to set these resources upon DDD invocation.


Node:Customizing Fonts, Next:, Previous:Window Layout, Up:Customizing Windows
Customizing Fonts

You can configure the basic DDD fonts at run-time. Each font is specified using two members:

To specify fonts, select Edit => Preferences => Fonts.

PICS/ddd-font-prefs.jpg

The Browse button opens a font selection program, where you can select fonts and attributes interactively. Clicking quit or select in the font selector causes all non-default values to be transferred to the DDD font preferences panel.

The following fonts can be set using the preferences panel:

Default Font
The default DDD font to use for labels, menus, and buttons. Default is helvetica-bold.
Variable Width
The variable width DDD font to use for help texts and messages. Default is helvetica-medium.
Fixed Width
The fixed width DDD font to use for source code, the debugger console, text fields, and the execution window. Default is lucidatypewriter-medium.
Data
The DDD font to use for data displays. Default is lucidatypewriter-medium.

Changes in this panel will take effect only in the next DDD session. To make it effective right now, restart DDD (using File => Restart DDD).

After having made changes in the panel, DDD will automatically offer you to restart itself, such that you can see the changes taking effect.

The Reset button restores the most recently saved preferences.

Here are the resources related to font specifications:

defaultFont (class Font) Resource
The default DDD font to use for labels, menus, buttons, etc. The font is specified as an X font spec, where the initial Foundry specification may be omitted, as well as any specification after Family.

Default value is helvetica-bold.

To set the default DDD font to, say, helvetica medium, insert a line

          Ddd*defaultFont: helvetica-medium
          

in your ~/.ddd/init file.

defaultFontSize (class FontSize) Resource
The size of the default DDD font, in 1/10 points. This resource overrides any font size specification in the defaultFont resource (see above). The default value is 120 for a 12.0 point font.

variableWidthFont (class Font) Resource
The variable width DDD font to use for help texts and messages. The font is specified as an X font spec, where the initial Foundry specification may be omitted, as well as any specification after Family.

Default value is helvetica-medium-r.

To set the variable width DDD font family to, say, times, insert a line

          Ddd*fixedWidthFont: times-medium
          

in your ~/.ddd/init file.

variableWidthFontSize (class FontSize) Resource
The size of the variable width DDD font, in 1/10 points. This resource overrides any font size specification in the variableWidthFont resource (see above). The default value is 120 for a 12.0 point font.

fixedWidthFont (class Font) Resource
The fixed width DDD font to use for source code, the debugger console, text fields, and the execution window. The font is specified as an X font spec, where the initial Foundry specification may be omitted, as well as any specification after Family.

Default value is lucidatypewriter-medium.

To set the fixed width DDD font family to, say, courier, insert a line

          Ddd*fixedWidthFont: courier-medium
          

in your ~/.ddd/init file.

fixedWidthFontSize (class FontSize) Resource
The size of the fixed width DDD font, in 1/10 points. This resource overrides any font size specification in the fixedWidthFont resource (see above). The default value is 120 for a 12.0 point font.

dataFont (class Font) Resource
The fixed width DDD font to use data displays. The font is specified as an X font spec, where the initial Foundry specification may be omitted, as well as any specification after Family.

Default value is lucidatypewriter-medium.

To set the DDD data font family to, say, courier, insert a line

          Ddd*dataFont: courier-medium
          

in your ~/.ddd/init file.

dataFontSize (class FontSize) Resource
The size of the DDD data font, in 1/10 points. This resource overrides any font size specification in the dataFont resource (see above). The default value is 120 for a 12.0 point font.

As all font size resources have the same class (and by default the same value), you can easily change the default DDD font size to, say, 9.0 points by inserting a line

     Ddd*FontSize: 90
     

in your ~/.ddd/init file.

Here's how to specify the command to select fonts:

fontSelectCommand (class FontSelectCommand) Resource
A command to select from a list of fonts. The string @FONT@ is replaced by the current DDD default font; the string @TYPE@ is replaced by a symbolic name of the DDD font to edit. The program must either place the name of the selected font in the PRIMARY selection or print the selected font on standard output. A typical value is:
          Ddd*fontSelectCommand: xfontsel -print
          

See Options, for options to set these resources upon DDD invocation.


Node:Toggling Windows, Next:, Previous:Customizing Fonts, Up:Customizing Windows
Toggling Windows

In the default stacked window setting, you can turn the individual DDD windows on and off by toggling the respective items in the View menu (see View Menu). When using separate windows (see Window Layout), you can close the individual windows via File => Close or by closing them via your window manager.

Whether windows are opened or closed when starting DDD is controlled by the following resources, immediately tied to the View menu items:

openDataWindow (class Window) Resource
If off (default), the data window is closed upon start-up.

openDebuggerConsole (class Window) Resource
If off, the debugger console is closed upon start-up.

openSourceWindow (class Window) Resource
If off, the source window is closed upon start-up.

See Options, for options to set these resources upon DDD invocation.


Node:Text Fields, Next:, Previous:Toggling Windows, Up:Customizing Windows
Text Fields

The DDD text fields can be customized using the following resources:

popdownHistorySize (class HistorySize) Resource
The maximum number of items to display in pop-down value histories. A value of 0 (default) means an unlimited number of values.

sortPopdownHistory (class SortPopdownHistory) Resource
If on (default), items in the pop-down value histories are sorted alphabetically. If off, most recently used values will appear at the top.


Node:Icons, Next:, Previous:Text Fields, Up:Customizing Windows
Icons

If you frequently switch between DDD and other multi-window applications, you may like to set Edit => Preferences => General => Iconify all windows at once. This way, all DDD windows are iconified and deiconified as a group.

This is tied to the following resource:

groupIconify (class GroupIconify) Resource
If this is on, (un)iconifying any DDD window causes all other DDD windows to (un)iconify as well. Default is off, meaning that each DDD window can be iconified on its own.

If you want to keep DDD off your desktop during a longer computation, you may like to set Edit => Preferences => General => Uniconify when ready. This way, you can iconify DDD while it is busy on a command (e.g. running a program); DDD will automatically pop up again after becoming ready (e.g. after the debugged program has stopped at a breakpoint). See Program Stop, for a discussion.

Here is the related resource:

uniconifyWhenReady (class UniconifyWhenReady) Resource
If this is on (default), the DDD windows are uniconified automatically whenever GDB becomes ready. This way, you can iconify DDD during some longer operation and have it uniconify itself as soon as the program stops. Setting this to off leaves the DDD windows iconified.


Node:Adding Buttons, Next:, Previous:Icons, Up:Customizing Windows
Adding Buttons

You can extend DDD with new buttons. See Defining Buttons, for details.


Node:More Customizations, Previous:Adding Buttons, Up:Customizing Windows
More Customizations

You can change just about any label, color, keyboard mapping, etc. by changing resources from the Ddd application defaults file which comes with the DDD source distribution. Here's how it works:

See Application Defaults, for details on the application-defaults file.


Node:Debugger Settings, Previous:Customizing Windows, Up:Customizing

Debugger Settings

For most inferior debuggers, you can change their internal settings using Edit => Settings. Using the settings editor, you can determine whether C++ names are to be demangled, how many array elements are to print, and so on.

PICS/ddd-settings.jpg

The capabilities of the settings editor depend on the capabilities of your inferior debugger. Clicking on ? gives an an explanation on the specific item; the GDB documentation gives more details.

Use Edit => Undo to undo changes. Clicking on Reset restores the most recently saved settings.

Some debugger settings are insensitive and cannot be changed, because doing so would endanger DDD operation. See the gdbInitCommands and dbxInitCommands resources for details.

All debugger settings (except source and object paths) are saved with DDD options.


Node:Navigating, Next:, Previous:Windows, Up:Top

Navigating through the Code

This chapter discusses how to access code from within DDD.


Node:Compiling for Debugging, Next:, Up:Navigating

Compiling for Debugging

In order to debug a program effectively, you need to generate debugging information when you compile it. This debugging information is stored in the object file; it describes the data type of each variable or function and the correspondence between source line numbers and addresses in the executable code.9

To request debugging information, specify the -g option when you run the compiler.

Many C compilers are unable to handle the -g and -O options together. Using those compilers, you cannot generate optimized executables containing debugging information.

GCC, the GNU C compiler, supports -g with or without -O, making it possible to debug optimized code. We recommend that you always use -g whenever you compile a program. You may think your program is correct, but there is no sense in pushing your luck.

When you debug a program compiled with -g -O, remember that the optimizer is rearranging your code; the debugger shows you what is really there. Do not be too surprised when the execution path does not exactly match your source file! An extreme example: if you define a variable, but never use it, DDD never sees that variable--because the compiler optimizes it out of existence.


Node:Opening Files, Next:, Previous:Compiling for Debugging, Up:Navigating

Opening Files

If you did not invoke DDD specifying a program to be debugged, you can use the File menu to open programs, core dumps and sources.


Node:Opening Programs, Next:, Up:Opening Files

Opening Programs

To open a program to be debugged, select File => Open Program.10 Click on Open to open the program

In JDB, select File => Open Class instead. This gives you a list of available classes to choose from.

PICS/ddd-open.jpg

To re-open a recently debugged program or class, select File => Open Recent and choose a program or class from the list.

If no sources are found, See Source Path, for specifying source directories.


Node:Opening Core Dumps, Next:, Previous:Opening Programs, Up:Opening Files

Opening Core Dumps

If a previous run of the program has crashed and you want to find out why, you can have DDD examine its core dump.11

To open a core dump for the program, select File => Open Core Dump. Click on Open to open the core dump.

Before Open Core Dump, you should first use File => Open Program to specify the program that generated the core dump and to load its symbol table.


Node:Opening Source Files, Next:, Previous:Opening Core Dumps, Up:Opening Files

Opening Source Files

To open a source file of the debugged program, select File => Open Source.

Click on Open to open the source file. See Source Path, if no sources are found.


Node:Filtering Files, Previous:Opening Source Files, Up:Opening Files

Filtering Files

When presenting files to be opened, DDD by default filters files when opening execution files, core dumps, or source files, such that the selection shows only suitable files. This requires that DDD opens each file, which may take time. See Customizing File Filtering, if you want to turn off this feature.


Node:Looking up Items, Next:, Previous:Opening Files, Up:Navigating

Looking up Items

As soon as the source of the debugged program is available, the source window displays its current source text. (see Source Path, if a source text cannot be found.)

In the source window, you can lookup and examine function and variable definitions as well as search for arbitrary occurrences in the source text.


Node:Looking up Definitions, Next:, Up:Looking up Items

Looking up Definitions

If you wish to lookup a specific function or variable definition whose name is visible in the source text, click with mouse button 1 on the function or variable name. The name is copied to the argument field. Change the name if desired and click on the Lookup button to find its definition.

PICS/ddd-source-popup.jpg

As a faster alternative, you can simply press mouse button 3 on the function name and select the Lookup item from the source popup menu.

As an even faster alternative, you can also double-click on a function call (an identifier followed by a ( character) to lookup the function definition.

If a source file is not found, See Source Path, for specifying source directories.


Node:Textual Search, Next:, Previous:Looking up Definitions, Up:Looking up Items

Textual Search

If the item you wish to search is visible in the source text, click with mouse button 1 on it. The identifier is copied to the argument field. Click on the Find >> button to find following occurrences and on Find >> => Find << () to find previous occurrences.

By default, DDD finds only complete words. To search for arbitrary substrings, change the value of the Source => Find Words Only option.


Node:Looking up Previous Locations, Next:, Previous:Textual Search, Up:Looking up Items

Looking up Previous Locations

After looking up a location, use Edit => Undo (or the Undo button on the command tool) to go back to the original locations. Edit => Redo brings you back again to the location you looked for.

PICS/ddd-source.jpg


Node:Source Path, Previous:Looking up Previous Locations, Up:Looking up Items

Specifying Source Directories

Executable programs sometimes do not record the directories of the source files from which they were compiled, just the names. Even when they do, the directories could be moved between the compilation and your debugging session.

Here's how GDB accesses source files; other inferior debuggers have similar methods.

GDB has a list of directories to search for source files; this is called the source path. Each time GDB wants a source file, it tries all the directories in the list, in the order they are present in the list, until it finds a file with the desired name. Note that the executable search path is not used for this purpose. Neither is the current working directory, unless it happens to be in the source path.

If GDB cannot find a source file in the source path, and the object program records a directory, GDB tries that directory too. If the source path is empty, and there is no record of the compilation directory, GDB looks in the current directory as a last resort.

To specify a source path for your inferior debugger, use Edit => Debugger Settings (see Debugger Settings and search for appropriate entries (in GDB, this is Search path for source files).

If Debugger Settings has no suitable entry, you can also specify a source path for the inferior debugger when invoking DDD. See Inferior Debugger Options, for details.

When using JDB, you can set the CLASSPATH environment variable to specify directories where JDB (and DDD) should search for classes.

If DDD does not find a source file for any reason, check the following issues:


Node:Customizing Source, Previous:Looking up Items, Up:Navigating

Customizing the Source Window

The source window can be customized in a number of ways, most of them accessed via Edit => Preferences => Source.

PICS/ddd-source-prefs.jpg


Node:Customizing Glyphs, Next:, Up:Customizing Source

Customizing Glyphs

In the source text, the current execution position and breakpoints are indicated by symbols (glyphs). As an alternative, DDD can also indicate these positions using text characters. If you wish to disable glyphs, set Edit => Preferences => Source => Show Position and Breakpoints => as Text Characters option. This also makes DDD run slightly faster, especially when scrolling.

This setting is tied to this resource:

displayGlyphs (class DisplayGlyphs) Resource
If this is on, the current execution position and breakpoints are displayed as glyphs; otherwise, they are shown through characters in the text. The default is on. See Options, for the --glyphs and --no-glyphs options.

You can further control glyphs using the following resources:

cacheGlyphImages (class CacheMachineCode) Resource
Whether to cache (share) glyph images (on) or not (off). Caching glyph images requires less X resources, but has been reported to fail with OSF/Motif 2.1 on XFree86 servers. Default is off for OSF/Motif 2.1 or later on GNU/Linux machines, and on otherwise.

glyphUpdateDelay (class GlyphUpdateDelay) Resource
A delay (in ms) that says how much time to wait before updating glyphs while scrolling the source text. A small value results in glyphs being scrolled with the text, a large value disables glyphs while scrolling and makes scrolling faster. Default: 10.

maxGlyphs (class MaxGlyphs) Resource
The maximum number of glyphs to be displayed (default: 10). Raising this value causes more glyphs to be allocated, possibly wasting resources that are never needed.


Node:Customizing Searching, Next:, Previous:Customizing Glyphs, Up:Customizing Source

Customizing Searching

Searching in the source text (see Textual Search) is controlled by these resources, changed via the Source menu:

findCaseSensitive (class FindCaseSensitive) Resource
If this is on (default), the Find commands are case-sensitive. Otherwise, occurrences are found regardless of case.

findWordsOnly (class FindWordsOnly) Resource
If this is on (default), the Find commands find complete words only. Otherwise, arbitrary occurrences are found.


Node:Customizing Source Appearance, Next:, Previous:Customizing Searching, Up:Customizing Source

Customizing Source Appearance

You can have DDD show line numbers within the source window. Use Edit => Preferences => Source => Display Source Line Numbers.

displayLineNumbers (class DisplayLineNumbers) Resource
If this is on, lines in the source text are prefixed with their respective line number. The default is off.

You can instruct DDD to indent the source code, leaving more room for breakpoints and execution glyphs. This is done using the Edit => Preferences => Source => Source indentation slider. The default value is 0 for no indentation at all.

indentSource (class Indent) Resource
The number of columns to indent the source code, such that there is enough place to display breakpoint locations. Default: 0.

By default, DDD uses a minimum indentation for script languages.

indentScript (class Indent) Resource
The minimum indentation for script languages, such as Perl, Python, and Bash. Default: 4.

The maximum width of line numbers is controlled by this resource.

lineNumberWidth (class LineNumberWidth) Resource
The number of columns to use for line numbers (if displaying line numbers is enabled). Line numbers wider than this value extend into the breakpoint space. Default: 4.

If your source code uses a tab width different from 8 (the default), you can set an alternate width using the Edit => Preferences => Source => Tab width slider.

tabWidth (class TabWidth) Resource
The tab width used in the source window (default: 8)


Node:Customizing Source Scrolling, Next:, Previous:Customizing Source Appearance, Up:Customizing Source

Customizing Source Scrolling

These resources control when the source window is scrolled:

linesAboveCursor (class LinesAboveCursor) Resource
The minimum number of lines to show before the current location. Default is 2.

linesBelowCursor (class LinesBelowCursor) Resource
The minimum number of lines to show after the current location. Default is 3.


Node:Customizing Source Lookup, Next:, Previous:Customizing Source Scrolling, Up:Customizing Source

Customizing Source Lookup

Some DBX and XDB variants do not properly handle paths in source file specifications. If you want the inferior debugger to refer to source locations by source base names only, unset the Edit => Preferences => Source => Refer to Program Sources by full path name option.

This is related to the following resource:

useSourcePath (class UseSourcePath) Resource
If this is off (default), the inferior debugger refers to source code locations only by their base names. If this is on (default), DDD uses the full source code paths.

By default, DDD caches source files in memory. This is convenient for remote debugging, since remote file access may be slow. If you want to reduce memory usage, unset the Edit => Preferences => Source => Cache source files option.

This is related to the following resource:

cacheSourceFiles (class CacheSourceFiles) Resource
Whether to cache source files (on, default) or not (off). Caching source files requires more memory, but makes DDD run faster.


Node:Customizing File Filtering, Previous:Customizing Source Lookup, Up:Customizing Source

Customizing File Filtering

You can control whether DDD should filter files to be opened.

filterFiles (class FilterFiles) Resource
If this is on (default), DDD filters files when opening execution files, core dumps, or source files, such that the selection shows only suitable files. This requires that DDD opens each file, which may take time. If this is off, DDD always presents all available files.


Node:Stopping, Next:, Previous:Navigating, Up:Top

Stopping the Program

The principal purposes of using a debugger are so that you can stop your program before it terminates; or so that, if your program runs into trouble, you can investigate and find out why.

Inside DDD, your program may stop for any of several reasons, such as a signal, a breakpoint, or reaching a new line after a DDD command such as Step. You may then examine and change variables, set new breakpoints or remove old ones, and then continue execution.

The inferior debuggers supported by DDD support two mechanisms for stopping a program upon specific events:


Node:Breakpoints, Next:, Up:Stopping

Breakpoints


Node:Setting Breakpoints, Next:, Up:Breakpoints

Setting Breakpoints

You can set breakpoints by location or by name.

Setting Breakpoints by Location

Breakpoints are set at a specific location in the program.

If the source line is visible, click with mouse button 1 on the left of the source line and then on the Break button.

As a faster alternative, you can simply press mouse button 3 on the left of the source line and select the Set Breakpoint item from the line popup menu.

PICS/ddd-line-popup.jpg

As an even faster alternative, you can simply double-click on the left of the source line to set a breakpoint.

As yet another alternative, you can select Source => Breakpoints. Click on the Break button and enter the location.

(If you find this number of alternatives confusing, be aware that DDD users fall into three categories, which must all be supported. Novice users explore DDD and may prefer to use one single mouse button. Advanced users know how to use shortcuts and prefer popup menus. Experienced users prefer the command line interface.)

Breakpoints are indicated by a plain stop sign, or as #n, where n is the breakpoint number. A greyed out stop sign (or _n_) indicates a disabled breakpoint. A stop sign with a question mark (or ?n?) indicates a conditional breakpoint or a breakpoint with an ignore count set.

If you set a breakpoint by mistake, use Edit => Undo to delete it again.

Setting Breakpoints by Name

If the function name is visible, click with mouse button 1 on the function name. The function name is then copied to the argument field. Click on the Break button to set a breakpoint there.

As a shorter alternative, you can simply press mouse button 3 on the function name and select the Break at item from the popup menu.

As yet another alternative, you can click on Break... from the Breakpoint editor (invoked through Source => Breakpoints) and enter the function name.

Setting Regexp Breakpoints

Using GDB, you can also set a breakpoint on all functions that match a given string. Break => Set Breakpoints at Regexp () sets a breakpoint on all functions whose name matches the regular expression given in (). Here are some examples:


Node:Deleting Breakpoints, Next:, Previous:Setting Breakpoints, Up:Breakpoints

Deleting Breakpoints

To delete a visible breakpoint, click with mouse button 1 on the breakpoint. The breakpoint location is copied to the argument field. Click on the Clear button to delete all breakpoints there.

If the function name is visible, click with mouse button 1 on the function name. The function name is copied to the argument field. Click on the Clear button to clear all breakpoints there.

As a faster alternative, you can simply press mouse button 3 on the breakpoint and select the Delete Breakpoint item from the popup menu.

As yet another alternative, you can select the breakpoint and click on Delete in the Breakpoint editor (invoked through Source => Breakpoints).

As an even faster alternative, you can simply double-click on the breakpoint while holding <Ctrl>.


Node:Disabling Breakpoints, Next:, Previous:Deleting Breakpoints, Up:Breakpoints

Disabling Breakpoints

Rather than deleting a breakpoint or watchpoint, you might prefer to disable it. This makes the breakpoint inoperative as if it had been deleted, but remembers the information on the breakpoint so that you can enable it again later.12

To disable a breakpoint, press mouse button 3 on the breakpoint symbol and select the Disable Breakpoint item from the breakpoint popup menu. To enable it again, select Enable Breakpoint.

PICS/ddd-bp-popup.jpg

As an alternative, you can select the breakpoint and click on Disable or Enable in the Breakpoint editor (invoked through Source => Breakpoints.

Disabled breakpoints are indicated by a grey stop sign, or _n_, where n is the breakpoint number.

The Disable Breakpoint item is also accessible via the Clear button. Just press and hold mouse button 1 on the button to get a popup menu.


Node:Temporary Breakpoints, Next:, Previous:Disabling Breakpoints, Up:Breakpoints

Temporary Breakpoints

A temporary breakpoint is immediately deleted as soon as it is reached.13

To set a temporary breakpoint, press mouse button 3 on the left of the source line and select the Set Temporary Breakpoint item from the popup menu.

As a faster alternative, you can simply double-click on the left of the source line while holding <Ctrl>.

Temporary breakpoints are convenient to make the program continue up to a specific location: just set the temporary breakpoint at this location and continue execution.

The Continue Until Here item from the popup menu sets a temporary breakpoint on the left of the source line and immediately continues execution. Execution stops when the temporary breakpoint is reached.

The Set Temporary Breakpoint and Continue Until Here items are also accessible via the Break button. Just press and hold mouse button 1 on the button to get a popup menu.


Node:Editing Breakpoint Properties, Next:, Previous:Temporary Breakpoints, Up:Breakpoints

Editing Breakpoint Properties

You can change all properties of a breakpoint by pressing mouse button 3 on the breakpoint symbol and select Properties from the breakpoint popup menu. This will pop up a dialog showing the current properties of the selected breakpoint.

PICS/ddd-bp-properties.jpg

As an even faster alternative, you can simply double-click on the breakpoint.


Node:Breakpoint Conditions, Next:, Previous:Editing Breakpoint Properties, Up:Breakpoints

Breakpoint Conditions

The simplest sort of breakpoint breaks every time your program reaches a specified place. You can also specify a condition for a breakpoint. A condition is just a Boolean expression in your programming language. A breakpoint with a condition evaluates the expression each time your program reaches it, and your program stops only if the condition is true.

This is the converse of using assertions for program validation; in that situation, you want to stop when the assertion is violated-that is, when the condition is false. In C, if you want to test an assertion expressed by the condition assertion, you should set the condition !assertion on the appropriate breakpoint.

Break conditions can have side effects, and may even call functions in your program. This can be useful, for example, to activate functions that log program progress, or to use your own print functions to format special data structures. The effects are completely predictable unless there is another enabled breakpoint at the same address. (In that case, DDD might see the other breakpoint first and stop your program without checking the condition of this one.)

Note that breakpoint commands are usually more convenient and flexible for the purpose of performing side effects when a breakpoint is reached. See Breakpoint Commands, for details.


Node:Breakpoint Ignore Counts, Next:, Previous:Breakpoint Conditions, Up:Breakpoints

Breakpoint Ignore Counts

A special case of a breakpoint condition is to stop only when the breakpoint has been reached a certain number of times. This is so useful that there is a special way to do it, using the ignore count of the breakpoint. Every breakpoint has an ignore count, which is an integer. Most of the time, the ignore count is zero, and therefore has no effect. But if your program reaches a breakpoint whose ignore count is positive, then instead of stopping, it just decrements the ignore count by one and continues. As a result, if the ignore count value is n, the breakpoint does not stop the next n times your program reaches it.

In the field Ignore Count of the Breakpoint Properties panel, you can specify the breakpoint ignore count.15

If a breakpoint has a positive ignore count and a condition, the condition is not checked. Once the ignore count reaches zero, DDD resumes checking the condition.


Node:Breakpoint Commands, Next:, Previous:Breakpoint Ignore Counts, Up:Breakpoints

Breakpoint Commands

You can give any breakpoint (or watchpoint) a series of DDD commands to execute when your program stops due to that breakpoint. For example, you might want to print the values of certain expressions, or enable other breakpoints.16

Using the Commands buttons of the Breakpoint Properties panel, you can edit commands to be executed when the breakpoint is hit.

To edit breakpoint commands, click on Edit >> and enter the commands in the commands editor. When done with editing, click on Edit << to close the commands editor.

Using GDB, you can also record a command sequence to be executed. To record a command sequence, follow these steps:

  1. Click on Record to begin the recording of the breakpoint commands.
  2. Now interact with DDD. While recording, DDD does not execute commands, but simply records them to be executed when the breakpoint is hit. The recorded debugger commands are shown in the debugger console.
  3. To stop the recording, click on End or enter end at the GDB prompt. To cancel the recording, click on Interrupt or press <ESC>.
  4. You can edit the breakpoint commands just recorded using Edit >>.


Node:Moving and Copying Breakpoints, Next:, Previous:Breakpoint Commands, Up:Breakpoints

Moving and Copying Breakpoints

To move a breakpoint to a different location, press mouse button 1 on the stop sign and drag it to the desired location.17 This is equivalent to deleting the breakpoint at the old location and setting a breakpoint at the new location. The new breakpoint inherits all properties of the old breakpoint, except the breakpoint number.

To copy a breakpoint to a new location, press <Shift> while dragging.


Node:Looking up Breakpoints, Next:, Previous:Moving and Copying Breakpoints, Up:Breakpoints

Looking up Breakpoints

If you wish to lookup a specific breakpoint, select Source => Breakpoints => Lookup. After selecting a breakpoint from the list and clicking the Lookup button, the breakpoint location is displayed.

As an alternative, you can enter #n in the argument field, where n is the breakpoint number, and click on the Lookup button to find its definition.


Node:Editing all Breakpoints, Next:, Previous:Looking up Breakpoints, Up:Breakpoints

Editing all Breakpoints

To view and edit all breakpoints at once, select Source => Breakpoints. This will popup the Breakpoint Editor which displays the state of all breakpoints.

PICS/ddd-edit-breakpoints.jpg

In the breakpoint editor, you can select individual breakpoints by clicking on them. Pressing <Ctrl> while clicking toggles the selection. To edit the properties of all selected breakpoints, click on Props.


Node:Hardware-Assisted Breakpoints, Previous:Editing all Breakpoints, Up:Breakpoints

Hardware-Assisted Breakpoints

Using GDB, a few more commands related to breakpoints can be invoked through the debugger console:

hbreak position
Sets a hardware-assisted breakpoint at position. This command requires hardware support and some target hardware may not have this support. The main purpose of this is EPROM/ROM code debugging, so you can set a breakpoint at an instruction without changing the instruction.
thbreak pos
Set a temporary hardware-assisted breakpoint at pos.

See Setting breakpoints, for details.


Node:Watchpoints, Next:, Previous:Breakpoints, Up:Stopping

Watchpoints

You can make the program stop as soon as some variable value changes, or when some variable is read or written. This is called setting a watchpoint on a variable.18

Watchpoints have much in common with breakpoints: in particular, you can enable and disable them. You can also set conditions, ignore counts, and commands to be executed when a watched variable changes its value.

Please note: on architectures without special watchpoint support, watchpoints currently make the program execute two orders of magnitude more slowly. This is so because the inferior debugger must interrupt the program after each machine instruction in order to examine whether the watched value has changed. However, this delay can be well worth it to catch errors when you have no clue what part of your program is the culprit.


Node:Setting Watchpoints, Next:, Up:Watchpoints

Setting Watchpoints

If the variable name is visible, click with mouse button 1 on the variable name. The variable name is copied to the argument field. Otherwise, enter the variable name in the argument field. Click on the Watch button to set a watchpoint there.

Using GDB and JDB 1.2, you can set different types of watchpoints. Click and hold mouse button 1 on the Watch button to get a menu.


Node:Editing Watchpoint Properties, Next:, Previous:Setting Watchpoints, Up:Watchpoints

Editing Watchpoint Properties

To change the properties of a watchpoint, enter the name of the watched variable in the argument field. Click and hold mouse button 1 on the Watch button and select Watchpoint Properties.

The Watchpoint Properties panel has the same functionality as the Breakpoint Properties panel (see Editing Breakpoint Properties). As an additional feature, you can click on Print to see the current value of a watched variable.


Node:Editing all Watchpoints, Next:, Previous:Editing Watchpoint Properties, Up:Watchpoints

Editing all Watchpoints

To view and edit all watchpoints at once, select Data => Watchpoints. This will popup the Watchpoint Editor which displays the state of all watchpoints.

The Watchpoint Editor has the same functionality as the Breakpoint Editor (see Editing all Breakpoints). As an additional feature, you can click on Print to see the current value of a watched variable.


Node:Deleting Watchpoints, Previous:Editing all Watchpoints, Up:Watchpoints

Deleting Watchpoints

To delete a watchpoint, enter the name of the watched variable in the argument field and click the Unwatch button.


Node:Interrupting, Next:, Previous:Watchpoints, Up:Stopping

Interrupting

If the program is already running (see Running), you can interrupt it any time by clicking the Interrupt button or typing <ESC> in a DDD window.19 Using GDB, this is equivalent to sending a SIGINT (Interrupt) signal.

Interrupt and <ESC> also interrupt a running debugger command, such as printing data.


Node:Stopping X Programs, Previous:Interrupting, Up:Stopping

Stopping X Programs

If your program is a modal X application, DDD may interrupt it while it has grabbed the mouse pointer, making further interaction impossible--your X display will be unresponsive to any user actions.

By default, DDD will check after each interaction whether the pointer is grabbed. If the pointer is grabbed, DDD will continue the debugged program such that you can continue to use your X display.

This is how this feature works: When the program stops, DDD checks for input events such as keyboard or mouse interaction. If DDD does not receive any event within the next 5 seconds, DDD checks whether the mouse pointer is grabbed by attempting to grab and ungrab it. If this attempt fails, then DDD considers the pointer grabbed.

Unfortunately, DDD cannot determine the program that grabbed the pointer--it may be the debugged program, or another program. Consequently, you have another 10 seconds to cancel continuation before DDD continues the program automatically.

There is one situation where this fails: if you lock your X display while DDD is running, then DDD will consider a resulting pointer grab as a result of running the program--and automatically continue execution of the debugged program. Consequently, you can turn off this feature via Edit => Preferences => General => Continue Automatically when Mouse Pointer is Frozen.


Node:Customizing Grab Checking, Up:Stopping X Programs

Customizing Grab Checking

The grab checks are controlled by the following resources:

checkGrabs (class CheckGrabs) Resource
If this is on (default), DDD will check after each interaction whether the pointer is grabbed. If this is so, DDD will automatically continue execution of debugged program.

checkGrabDelay (class CheckGrabDelay) Resource
The time to wait (in ms) after a debugger command before checking for a grabbed pointer. If DDD sees some pointer event within this delay, the pointer cannot be grabbed and an explicit check for a grabbed pointer is unnecessary. Default is 5000, or 5 seconds.

grabAction (class grabAction) Resource
The action to take after having detected a grabbed mouse pointer. This is a list of newline-separated commands. Default is cont, meaning to continue the debuggee. Other possible choices include kill (killing the debuggee) or quit (exiting DDD).

grabActionDelay (class grabActionDelay) Resource
The time to wait (in ms) before taking an action due to having detected a grabbed pointer. During this delay, a working dialog pops up telling the user about imminent execution of the grab action (see the grabAction resource, above). If the pointer grab is released within this delay, the working dialog pops down and no action is taken. This is done to exclude pointer grabs from sources other than the debugged program (including DDD). Default is 10000, or 10 seconds.


Node:Running, Next:, Previous:Stopping, Up:Top

Running the Program

You may start the debugged program with its arguments, if any, in an environment of your choice. You may redirect your program's input and output, debug an already running process, or kill a child process.


Node:Starting Program Execution, Next:, Up:Running

Starting Program Execution

To start execution of the debugged program, select Program => Run. You will then be prompted for the arguments to pass to your program. You can either select from a list of previously used arguments or enter own arguments in the text field. Afterwards, press the Run button to start execution with the selected arguments.

PICS/ddd-arguments.jpg

To run your program again, with the same arguments, select Program => Run Again or press the Run button on the command tool. You may also enter run, followed by arguments at the debugger prompt instead.

When you click on Run, your program begins to execute immediately. See Stopping, for a discussion of how to arrange for your program to stop. Once your program has stopped, you may call functions in your program to examine data. See Examining Data, for details.

If the modification time of your symbol file has changed since the last time GDB read its symbols, GDB discards its symbol table, and reads it again. When it does this, GDB and DDD try to retain your current debugger state, such as breakpoints.


Node:Arguments, Next:, Up:Starting Program Execution

Your Program's Arguments

The arguments to your program are specified by the arguments of the run command, as composed in Program => Run.

In GDB, the arguments are passed to a shell, which expands wildcard characters and performs redirection of I/O, and thence to your program. Your SHELL environment variable (if it exists) specifies what shell GDB uses. If you do not define SHELL, GDB uses /bin/sh.

If you use another inferior debugger, the exact semantics on how the arguments are interpreted depend on the inferior debugger you are using. Normally, the shell is used to pass the arguments, so that you may use normal conventions (such as wildcard expansion or variable substitution) in describing the arguments.


Node:Environment, Next:, Previous:Arguments, Up:Starting Program Execution

Your Program's Environment

Your program normally inherits its environment from the inferior debugger, which again inherits it from DDD, which again inherits it from its parent process (typically the shell or desktop).

In GDB, you can use the commands set environment and unset environment to change parts of the environment that affect your program. See Your program's environment, for details.

The following environment variables are set by DDD:

DDD
Set to a string indicating the DDD version. By testing whether DDD is set, a debuggee (or inferior debugger) can determine whether it was invoked by DDD.
TERM
Set to dumb, the DDD terminal type. This is set for the inferior debugger only.20
TERMCAP
Set to `' (none), the DDD terminal capabilities.
PAGER
Set to cat, the preferred DDD pager.

The inferior debugger, in turn, might also set or unset some environment variables.


Node:Working Directory, Next:, Previous:Environment, Up:Starting Program Execution

Your Program's Working Directory

Your program normally inherits its working directory from the inferior debugger, which again inherits it from DDD, which again inherits it from its parent process (typically the shell or desktop).

You can change the working directory of the inferior debugger via File => Change Directory or via the cd command of the inferior debugger.


Node:Input/Output, Previous:Working Directory, Up:Starting Program Execution

Your Program's Input and Output

By default, the program you run under DDD does input and output to the debugger console. Normally, you can redirect your program's input and/or output using shell redirections with the arguments--that is, additional arguments like < input or > output. You can enter these shell redirections just like other arguments (see Arguments).

Warning: While input and output redirection work, you cannot use pipes to pass the output of the program you are debugging to another program; if you attempt this, DDD may wind up debugging the wrong program. See Attaching to a Process, for an alternative.

If command output is sent to the debugger console, it is impossible for DDD to distinguish between the output of the debugged program and the output of the inferior debugger.

Program output that confuses DDD includes:

If your program outputs any of these strings, you may encounter problems with DDD mistaking them for debugger output. These problems can easily be avoided by redirecting program I/O, for instance to the separate execution window (see Using the Execution Window).

If the inferior debugger changes the default TTY settings, for instance through a stty command in its initialization file, DDD may also become confused. The same applies to debugged programs which change the default TTY settings.

The behavior of the debugger console can be controlled using the following resource:

lineBufferedConsole (class LineBuffered) Resource
If this is on (default), each line from the inferior debugger is output on each own, such that the final line is placed at the bottom of the debugger console. If this is off, all lines are output as a whole. This is faster, but results in a random position of the last line.


Node:Using the Execution Window, Next:, Previous:Starting Program Execution, Up:Running

Using the Execution Window

By default, input and output of your program go to the debugger console. As an alternative, DDD can also invoke an execution window, where the program terminal input and output is shown.21

To activate the execution window, select Program => Run in Execution Window.

Using the execution window has an important side effect: The output of your program no longer gets intermixed with the output of the inferior debugger. This makes it far easier for DDD to parse the debugger output correctly. See Debugger Communication, for details on the bufferGDBOutput resource.

The execution window is opened automatically as soon as you start the debugged program. While the execution window is active, DDD redirects the standard input, output, and error streams of your program to the execution window. Note that the device /dev/tty still refers to the debugger console, not the execution window.

You can override the DDD stream redirection by giving alternate redirection operations as arguments. For instance, to have your program read from file, but to write to the execution window, invoke your program with < file as argument. Likewise, to redirect the standard error output to the debugger console, use 2> /dev/tty (assuming the inferior debugger and/or your UNIX shell support standard error redirection).


Node:Customizing the Execution Window, Up:Using the Execution Window

Customizing the Execution Window

You can customize the DDD execution window and use a different TTY command. The command is set by Edit => Preferences => Helpers => Execution Window:

termCommand (class TermCommand) Resource
The command to invoke for the execution window--a TTY emulator that shows the input/output of the debugged program. A Bourne shell command to run in the separate TTY is appended to this string. The string @FONT@ is replaced by the name of the fixed width font used by DDD. A simple value is
          Ddd*termCommand: xterm -fn @FONT@ -e /bin/sh -c
          

You can also set the terminal type:

termType (class TermType) Resource
The terminal type provided by the termCommand resource--that is, the value of the TERM environment variable to be passed to the debugged program. Default: xterm.

Whether the execution window is active or not, as set by Program => Run in Execution Window, is saved using this resource:

separateExecWindow (class Separate) Resource
If on, the debugged program is executed in a separate execution window. If off (default), the debugged program is executed in the console window.


Node:Attaching to a Process, Next:, Previous:Using the Execution Window, Up:Running

Attaching to a Running Process

If the debugged program is already running in some process, you can attach to this process (instead of starting a new one with Run).22

To attach DDD to a process, select File => Attach to Process. You can now choose from a list of processes. Then, press the Attach button to attach to the specified process.

PICS/ddd-attach.jpg

The first thing DDD does after arranging to debug the specified process is to stop it. You can examine and modify an attached process with all the DDD commands that are ordinarily available when you start processes with Run. You can insert breakpoints; you can step and continue; you can modify storage. If you would rather the process continue running, you may use Continue after attaching DDD to the process.

When using Attach to Process, you should first use Open Program to specify the program running in the process and load its symbol table.

When you have finished debugging the attached process, you can use the File => Detach Process to release it from DDD control. Detaching the process continues its execution. After Detach Process, that process and DDD become completely independent once more, and you are ready to attach another process or start one with Run.

You can customize the list of processes shown by defining an alternate command to list processes. See Edit => Preferences => Helpers => List Processes; See Customizing Attaching to Processes, for details.


Node:Customizing Attaching to Processes, Up:Attaching to a Process

Customizing Attaching to Processes

When attaching to a process (see Attaching to a Process), DDD uses a ps command to get the list of processes. This command is defined by the psCommand resource.

psCommand (class PsCommand) Resource
The command to get a list of processes. Usually ps. Depending on your system, useful alternate values include ps -ef and ps ux. The first line of the output must either contain a PID title, or each line must begin with a process ID.

Note that the output of this command is filtered by DDD; a process is only shown if it can be attached to. The DDD process itself as well as the process of the inferior debugger are suppressed, too.


Node:Program Stop, Next:, Previous:Attaching to a Process, Up:Running

Program Stops

After the program has been started, it runs until one of the following happens:

DDD shows the current program status in the debugger console. The current execution position is highlighted by an arrow.

If Edit => Preferences => General => Uniconify When Ready is set, DDD automatically deiconifies itself when the program stops. This way, you can iconify DDD during a lengthy computation and have it uniconify as soon as the program stops.


Node:Resuming Execution, Next:, Previous:Program Stop, Up:Running

Resuming Execution

Continuing

To resume execution, at the current execution position, click on the Continue button. Any breakpoints set at the current execution position are bypassed.

Stepping one Line

To execute just one source line, click on the Step button. The program is executed until control reaches a different source line, which may be in a different function. Then, the program is stopped and control returns to DDD.

Warning: If you use the Step button while control is within a function that was compiled without debugging information, execution proceeds until control reaches a function that does have debugging information. Likewise, it will not step into a function which is compiled without debugging information. To step through functions without debugging information, use the Stepi button (see Machine Code Execution).

In GDB, the Step button only stops at the first instruction of a source line. This prevents the multiple stops that used to occur in switch statements, for loops, etc. Step continues to stop if a function that has debugging information is called within the line.

Also, the Step in GDB only enters a subroutine if there is line number information for the subroutine. Otherwise it acts like the Next button.

Continuing to the Next Line

To continue to the next line in the current function, click on the Next button. This is similar to Step, but any function calls appearing within the line of code are executed without stopping.

Execution stops when control reaches a different line of code at the original stack level that was executing when you clicked on Next.

Continuing Until Here

To continue running until a specific location is reached, use the Continue Until Here facility from the line popup menu. See Temporary Breakpoints, for a discussion.

Continuing Until a Greater Line is Reached

To continue until a greater line in the current function is reached, click on the Until button. This is useful to avoid single stepping through a loop more than once.

Until is like Next, except that when Until encounters a jump, it automatically continues execution until the program counter is greater than the address of the jump.

This means that when you reach the end of a loop after single stepping though it, until makes your program continue execution until it exits the loop. In contrast, clicking on Next at the end of a loop simply steps back to the beginning of the loop, which forces you to step through the next iteration.

Until always stops your program if it attempts to exit the current stack frame.

Until works by means of single instruction stepping, and hence is slower than continuing until a breakpoint is reached.

Continuing Until Function Returns

To continue running until the current function returns, use the Finish button. The returned value (if any) is printed.


Node:Continuing Somewhere Else, Next:, Previous:Resuming Execution, Up:Running

Continuing at a Different Address

Ordinarily, when you continue your program, you do so at the place where it stopped. You can instead continue at an address of your own choosing.

The most common occasion to use this feature is to back up--perhaps with more breakpoints set-over a portion of a program that has already executed, in order to examine its execution in more detail.

To set the execution position to the current location, use Set Execution Position from the breakpoint popup menu. This item is also accessible by pressing and holding the Break/Clear button.23

As a quicker alternative, you can also press mouse button 1 on the arrow and drag it to a different location.24

PICS/ddd-drag.jpg

Moving the execution position does not change the current stack frame, or the stack pointer, or the contents of any memory location or any register other than the program counter.

Some inferior debuggers (notably GDB) allow you to set the new execution position into a different function from the one currently executing. This may lead to bizarre results if the two functions expect different patterns of arguments or of local variables. For this reason, moving the execution position requests confirmation if the specified line is not in the function currently executing.

After moving the execution position, click on Continue to resume execution.


Node:Stack, Next:, Previous:Continuing Somewhere Else, Up:Running

Examining the Stack

When your program has stopped, the first thing you need to know is where it stopped and how it got there.

Each time your program performs a function call, information about the call is generated. That information includes the location of the call in your program, the arguments of the call, and the local variables of the function being called. The information is saved in a block of data called a stack frame. The stack frames are allocated in a region of memory called the call stack.

When your program stops, the DDD commands for examining the stack allow you to see all of this information.

One of the stack frames is selected by DDD and many DDD commands refer implicitly to the selected frame. In particular, whenever you ask DDD for the value of a variable in your program, the value is found in the selected frame. There are special DDD commands to select whichever frame you are interested in.


Node:Frames, Next:, Up:Stack

Stack Frames

The call stack is divided up into contiguous pieces called stack frames, or frames for short; each frame is the data associated with one call to one function. The frame contains the arguments given to the function, the function's local variables, and the address at which the function is executing.

When your program is started, the stack has only one frame, that of the function main. This is called the initial frame or the outermost frame. Each time a function is called, a new frame is made. Each time a function returns, the frame for that function invocation is eliminated. If a function is recursive, there can be many frames for the same function. The frame for the function in which execution is actually occurring is called the innermost frame. This is the most recently created of all the stack frames that still exist.

Inside your program, stack frames are identified by their addresses. A stack frame consists of many bytes, each of which has its own address; each kind of computer has a convention for choosing one byte whose address serves as the address of the frame. Usually this address is kept in a register called the frame pointer register while execution is going on in that frame.

GDB assigns numbers to all existing stack frames, starting with zero for the innermost frame, one for the frame that called it, and so on upward. These numbers do not really exist in your program; they are assigned by GDB to give you a way of designating stack frames in GDB commands.


Node:Backtraces, Next:, Previous:Frames, Up:Stack

Backtraces

DDD provides a backtrace window showing a summary of how your program got where it is. It shows one line per frame, for many frames, starting with the currently executing frame (frame zero), followed by its caller (frame one), and on up the stack.

To enable the backtrace window, select Status => Backtrace.

PICS/ddd-backtrace.jpg

Using GDB, each line in the backtrace shows the frame number and the function name. The program counter value is also shown--unless you use the GDB command set print address off. The backtrace also shows the source file name and line number, as well as the arguments to the function. The program counter value is omitted if it is at the beginning of the code for that line number.


Node:Selecting a frame, Previous:Backtraces, Up:Stack

Selecting a Frame

Most commands for examining the stack and other data in your program work on whichever stack frame is selected at the moment. Here are the commands for selecting a stack frame.25

In the backtrace window, you can select an arbitrary frame to move from one stack frame to another. Just click on the desired frame.

The Up button selects the function that called the current one--that is, it moves one frame up.

The Down button selects the function that was called by the current one--that is, it moves one frame down.

You can also directly type the up and down commands at the debugger prompt. Typing <Ctrl+Up> and <Ctrl+Down>, respectively, will also move you through the stack.

Up and Down actions can be undone via Edit => Undo.


Node:Undoing Program Execution, Next:, Previous:Stack, Up:Running

"Undoing" Program Execution

If you take a look at the Edit => Undo menu item after an execution command, you'll find that DDD offers you to undo execution commands just as other commands. Does this mean that DDD allows you to go backwards in time, undoing program execution as well as undoing any side-effects of your program?

Sorry--we must disappoint you. DDD cannot undo what your program did. (After a little bit of thought, you'll find that this would be impossible in general.) However, DDD can do something different: it can show previously recorded states of your program.

After "undoing" an execution command (via Edit => Undo, or the Undo button), the execution position moves back to the earlier position and displayed variables take their earlier values. Your program state is in fact unchanged, but DDD gives you a view on the earlier state as recorded by DDD.

In this so-called historic mode, most normal DDD commands that would query further information from the program are disabled, since the debugger cannot be queried for the earlier state. However, you can examine the current execution position, or the displayed variables. Using Undo and Redo, you can move back and forward in time to examine how your program got into the present state.

To let you know that you are operating in historic mode, the execution arrow gets a dashed-line appearance (indicating a past position); variable displays also come with dashed lines. Furthermore, the status line informs you that you are seeing an earlier program state.

Here's how historic mode works: each time your program stops, DDD collects the current execution position and the values of displayed variables. Backtrace, thread, and register information is also collected if the corresponding dialogs are open. When "undoing" an execution command, DDD updates its view from this collected state instead of querying the program.

If you want to collect this information without interrupting your program--within a loop, for instance--you can place a breakpoint with an associated cont command (see Breakpoint Commands). When the breakpoint is hit, DDD will stop, collect the data, and execute the cont command, resuming execution. Using a later Undo, you can step back and look at every single loop iteration.

To leave historic mode, you can use Redo until you are back in the current program state. However, any DDD command that refers to program state will also leave historic mode immediately by applying to the current program state instead. For instance, Up leaves historic mode immediately and selects an alternate frame in the restored current program state.

If you want to see the history of a specific variable, as recorded during program stops, you can enter the DDD command

     graph history name
     

This returns a list of all previously recorded values of the variable name, using array syntax. Note that name must have been displayed at earlier program stops in order to record values.


Node:Threads, Next:, Previous:Undoing Program Execution, Up:Running

Examining Threads

In some operating systems, a single program may have more than one thread of execution. The precise semantics of threads differ from one operating system to another, but in general the threads of a single program are akin to multiple processes--except that they share one address space (that is, they can all examine and modify the same variables). On the other hand, each thread has its own registers and execution stack, and perhaps private memory.

For debugging purposes, DDD lets you display the list of threads currently active in your program and lets you select the current thread--the thread which is the focus of debugging. DDD shows all program information from the perspective of the current thread.26

PICS/ddd-threads.jpg

To view all currently active threads in your program, select Status => Threads. The current thread is highlighted. Select any thread to make it the current thread.

Using JDB, additional functionality is available:

For more information on threads, see the JDB and GDB documentation (see Debugging programs with multiple threads).


Node:Signals, Next:, Previous:Threads, Up:Running

Handling Signals

A signal is an asynchronous event that can happen in a program. The operating system defines the possible kinds of signals, and gives each kind a name and a number. For example, in UNIX, SIGINT is the signal a program gets when you type an interrupt; SIGSEGV is the signal a program gets from referencing a place in memory far away from all the areas in use; SIGALRM occurs when the alarm clock timer goes off (which happens only if your program has requested an alarm).

Some signals, including SIGALRM, are a normal part of the functioning of your program. Others, such as SIGSEGV, indicate errors; these signals are fatal (kill your program immediately) if the program has not specified in advance some other way to handle the signal. SIGINT does not indicate an error in your program, but it is normally fatal so it can carry out the purpose of the interrupt: to kill the program.

GDB has the ability to detect any occurrence of a signal in your program. You can tell GDB in advance what to do for each kind of signal.

Normally, DDD is set up to ignore non-erroneous signals like SIGALRM (so as not to interfere with their role in the functioning of your program) but to stop your program immediately whenever an error signal happens. In DDD, you can view and edit these settings via Status => Signals.

Status => Signals pops up a panel showing all the kinds of signals and how GDB has been told to handle each one. The settings available for each signal are:

Stop
If set, GDB should stop your program when this signal happens. This also implies Print being set.
Print
If set, GDB should print a message when this signal happens.

If unset, GDB should not mention the occurrence of the signal at all. This also implies Stop being unset.

Pass
If set, GDB should allow your program to see this signal; your program can handle the signal, or else it may terminate if the signal is fatal and not handled.

If unset, GDB should not allow your program to see this signal.


PICS/ddd-signals.jpg

The entry All Signals is special. Changing a setting here affects all signals at once--except those used by the debugger, typically SIGTRAP and SIGINT.

To undo any changes, use Edit => Undo. The Reset button restores the saved settings.

When a signal stops your program, the signal is not visible until you continue. Your program sees the signal then, if Pass is in effect for the signal in question at that time. In other words, after GDB reports a signal, you can change the Pass setting in Status => Signals to control whether your program sees that signal when you continue.

You can also cause your program to see a signal it normally would not see, or to give it any signal at any time. The Send button will resume execution where your program stopped, but immediately give it the signal shown.

On the other hand, you can also prevent your program from seeing a signal. For example, if your program stopped due to some sort of memory reference error, you might store correct values into the erroneous variables and continue, hoping to see more execution; but your program would probably terminate immediately as a result of the fatal signal once it saw the signal. To prevent this, you can resume execution using Commands => Continue Without Signal.

Signal settings are not saved across DDD invocations, since changed signal settings are normally useful within specific projects only. Instead, signal settings are saved with the current session, using File => Save Session As.


Node:Killing the Program, Previous:Signals, Up:Running

Killing the Program

You can kill the process of the debugged program at any time using the Kill button.

Killing the process is useful if you wish to debug a core dump instead of a running process. GDB ignores any core dump file while your program is running.

The Kill button is also useful if you wish to recompile and relink your program, since on many systems it is impossible to modify an executable file while it is running in a process. In this case, when you next click on Run, GDB notices that the file has changed, and reads the symbol table again (while trying to preserve your current debugger state).


Node:Examining Data, Next:, Previous:Running, Up:Top

Examining Data

DDD provides several means to examine data.


Node:Value Tips, Next:, Up:Examining Data

Showing Simple Values using Value Tips

To display the value of a simple variable, move the mouse pointer on its name. After a second, a small window (called value tip) pops up showing the value of the variable pointed at. The window disappears as soon as you move the mouse pointer away from the variable. The value is also shown in the status line.

PICS/ddd-value-tip.jpg

You can disable value tips via Edit => Preferences => General => Automatic display of variable values as popup tips.

You can disable displaying variable values in the status line via Edit => Preferences => General => Automatic display of variable values in the status line.

These customizations are tied to the following resources:

valueTips (class Tips) Resource
Whether value tips are enabled (on, default) or not (off). Value tips affect DDD performance and may be distracting for some experienced users.

valueDocs (class Docs) Resource
Whether the display of variable values in the status line is enabled (on, default) or not (off).

You can turn off value tips via Edit => Preferences => General => Automatic Display of Variable Values.


Node:Printing Values, Next:, Previous:Value Tips, Up:Examining Data

Printing Simple Values in the Debugger Console

The variable value can also be printed in the debugger console, making it available for future operations. To print a variable value, select the desired variable by clicking mouse button 1 on its name. The variable name is copied to the argument field. By clicking the Print button, the value is printed in the debugger console. The printed value is also shown in the status line.

As a shorter alternative, you can simply press mouse button 3 on the variable name and select the Print item from the popup menu.

PICS/ddd-print-popup.jpg

In GDB, the Print button generates a print command, which has several more options. See Examining Data, for GDB-specific expressions, variables, and output formats.


Node:Displaying Values, Next:, Previous:Printing Values, Up:Examining Data

Displaying Complex Values in the Data Window

To explore complex data structures, you can display them permanently in the data window. The data window displays selected data of your program, showing complex data structures graphically. It is updated each time the program stops.


Node:Display Basics, Next:, Up:Displaying Values

Display Basics

This section discusses how to create, manipulate, and delete displays. The essentials are:


Node:Creating Single Displays, Next:, Up:Display Basics
Creating Single Displays

To create a new display showing a specific variable, select the variable by clicking mouse button 1 on its name. The variable name is copied to the argument field. By clicking the Display button, a new display is created in the data window. The data window opens automatically as soon as you create a display.

PICS/ddd-display.jpg

As a shorter alternative, you can simply press mouse button 3 on the variable name and select Display from the popup menu.

As an even faster alternative, you can also double-click on the variable name.

As another alternative, you may also enter the expression to be displayed in the argument field and press the Display button.

Finally, you may also type in a command at the debugger prompt:

     graph display expr [clustered] [at (x, y)]
         [dependent on display] [[now or] when in scope]
     

This command creates a new display showing the value of the expression expr. The optional parts have the following meaning:

clustered
If given, the new display is created in a cluster. See Clustering, for a discussion.
at (x, y)
If given, the new display is created at the position (x, y). Otherwise, a default position is assigned.
dependent on display
If given, an edge from the display numbered or named display to the new display is created. Otherwise, no edge is created. See Dependent Values, for details.
when in scope
now or when in scope
If when in is given, the display creation is deferred until execution reaches the given scope (a function name, as in the backtrace output).

If now or when in is given, DDD first attempts to create the display immediately. The display is deferred only if display creation fails.

If neither when in suffix nor now or when in suffix is given, the display is created immediately.


Node:Selecting Displays, Next:, Previous:Creating Single Displays, Up:Display Basics
Selecting Displays

Each display in the data window has a title bar containing the display number and the displayed expression (the display name). Below the title, the display value is shown.

You can select single displays by clicking on them with mouse button 1.

You can extend an existing selection by pressing the <Shift> key while selecting. You can also toggle an existing selection by pressing the <Shift> key while selecting already selected displays.

Single displays may also be selected by using the arrow keys <Up>, <Down>, <Left>, and <Right>.

Multiple displays are selected by pressing and holding mouse button 1 somewhere on the window background. By moving the pointer while holding the button, a selection rectangle is shown; all displays fitting in the rectangle are selected when mouse button 1 is released.

If the <Shift> key is pressed while selecting, the existing selection is extended.

By double-clicking on a display title, the display itself and all connected displays are automatically selected.

PICS/ddd-select-display.jpg


Node:Showing and Hiding Details, Next:, Previous:Selecting Displays, Up:Display Basics
Showing and Hiding Details

Aggregate values (i.e. records, structs, classes, and arrays) can be shown expanded, that is, displaying all details, or hidden, that is, displayed as {...}.

To show details about an aggregate, select the aggregate by clicking mouse button 1 on its name or value and click on the Show button. Details are shown for the aggregate itself as well as for all contained sub-aggregates.

To hide details about an aggregate, select the aggregate by clicking mouse button 1 on its name or value and click on the Hide button.

PICS/ddd-hide-display.jpg

When pressing and holding mouse button 1 on the Show/Hide button, a menu pops up with even more alternatives:

Show More ()
Shows details of all aggregates currently hidden, but not of their sub-aggregates. You can invoke this item several times in a row to reveal more and more details of the selected aggregate.
Show Just ()
Shows details of the selected aggregate, but hides all sub-aggregates.
Show All ()
Shows all details of the selected aggregate and of its sub-aggregates. This item is equivalent to the Show button.
Hide ()
Hide all details of the selected aggregate. This item is equivalent to the Hide button.

As a faster alternative, you can also press mouse button 3 on the aggregate and select the appropriate menu item.

As an even faster alternative, you can also double-click mouse button 1 on a value. If some part of the value is hidden, more details will be shown; if the entire value is shown, double-clicking will hide the value instead. This way, you can double-click on a value until you get the right amount of details.

If all details of a display are hidden, the display is called disabled; this is indicated by the string (Disabled).

Displays can also be disabled or enabled via a DDD command, which you enter at the debugger prompt:

     graph disable display displays...
     

disables the given displays.

     graph enable display displays...
     

re-enables the given displays.

In both commands, displays... is either

Use Edit => Undo to undo disabling or enabling displays.


Node:Rotating Displays, Next:, Previous:Showing and Hiding Details, Up:Display Basics
Rotating Displays

Arrays, structures and lists can be oriented horizontally or vertically. To change the orientation of a display, select it and then click on the Rotate button.

As a faster alternative, you can also press mouse button 3 on the array and select Rotate from the popup menu.

PICS/ddd-rotate-display.jpg

If a structure or list is oriented horizontally, DDD automatically suppresses the member names. This can be handy for saving space.

The last chosen display orientation is used for the creation of new displays. If you recently rotated an array to horizontal orientation, the next array you create will also be oriented horizontally. These settings are tied to the following resources:

arrayOrientation (class Orientation) Resource
How arrays are to be oriented. Possible values are XmVERTICAL (default) and XmHORIZONTAL.

showMemberNames (class ShowMemberNames) Resource
Whether to show struct member names or not. Default is on.

structOrientation (class Orientation) Resource
How structs are to be oriented. Possible values are XmVERTICAL (default) and XmHORIZONTAL.


Node:Displaying Local Variables, Next:, Previous:Rotating Displays, Up:Display Basics
Displaying Local Variables

You can display all local variables at once by choosing Data => Display Local Variables. When using DBX, XDB, JDB, or Perl, this displays all local variables, including the arguments of the current function. When using GDB or PYDB, function arguments are contained in a separate display, activated by Data => Display Arguments.

The display showing the local variables can be manipulated just like any other data display. Individual variables can be selected and dereferenced.

PICS/ddd-locals.jpg


Node:Displaying Program Status, Next:, Previous:Displaying Local Variables, Up:Display Basics
Displaying Program Status

You can create a display from the output of an arbitrary debugger command. By entering

     graph display `command`
     

the output of command is turned into a status display updated each time the program stops.

For instance, the command

     graph display `where`
     

creates a status display named Where that shows the current backtrace.

If you are using GDB, DDD provides a panel from which you can choose useful status displays. Select Data => Status Displays and pick your choice from the list.

PICS/ddd-status-displays.jpg

Refreshing status displays at each stop takes time; you should delete status displays as soon as you don't need them any more.


Node:Refreshing the Data Window, Next:, Previous:Displaying Program Status, Up:Display Basics
Refreshing the Data Window

The data window is automatically updated or refreshed each time the program stops. Values that have changed since the last refresh are highlighted.

However, there may be situations where you should refresh the data window explicitly. This is especially the case whenever you changed debugger settings that could affect the data format, and want the data window to reflect these settings.

You can refresh the data window by selecting Data => Refresh Displays.

As an alternative, you can press mouse button 3 on the background of the data window and select the Refresh Displays item.

Typing

     graph refresh
     

at the debugger prompt has the same effect.


Node:Placement, Next:, Previous:Refreshing the Data Window, Up:Display Basics
Display Placement

By default, displays are created from top to bottom--that is, each new display is placed below the downmost one. You can change this setting to left to right via Edit => Preferences => Data => Placement => Left to right.

PICS/ddd-data-prefs.jpg

This setting is tied to the following resource:

displayPlacement (class Orientation) Resource
If this is XmVERTICAL (default), DDD places each new independent display below the downmost one. If this is XmHORIZONTAL, each new independent display is placed on the right of the rightmost one.

Note that changing the placement of new displays also affects the placement of dependent displays (see Dependent Values). In top to bottom mode, dependent displays are created on the right of the originating display; in left to right mode, dependent displays are created on the below the originating display.


Node:Clustering, Next:, Previous:Placement, Up:Display Basics
Clustering Displays

If you examine several variables at once, having a separate display for each of them uses a lot of screen space. This is why DDD supports clusters. A cluster merges several logical data displays into one physical display, saving screen space.

There are two ways to create clusters:


PICS/ddd-clusters.jpg

Displays in a cluster can be selected and manipulated like parts of an ordinary display; in particular, you can show and hide details, or dereference pointers. However, edges leading to clustered displays can not be shown, and you must either select one or all clustered displays.

Disabling a cluster is called unclustering, and again, there are two ways of doing it:


Node:Creating Multiple Displays, Next:, Previous:Clustering, Up:Display Basics
Creating Multiple Displays

To display several successive objects of the same type (a section of an array, or an array of dynamically determined size), you can use the notation from..to in display expressions.

from and to are numbers that denote the first and last expression to display. Thus,

     graph display argv[0..9]
     

creates 10 new displays for argv[0], argv[1], ..., argv[9]. The displays are clustered automatically (see Clustering), such that you can easily handle the set just like an array.

The from..to notation can also be used multiple times. For instance,

     graph display 1..5 * 1..5
     

creates a handy small multiplication table.

The from..to notation creates several displays, which takes time to create and update. If you want to display only a part of an array, array slices are a more efficient way. See Array Slices, for a discussion.


Node:Editing all Displays, Next:, Previous:Creating Multiple Displays, Up:Display Basics
Editing all Displays

You can view the state of all displays by selecting Data => Displays. This invokes the Display Editor.

PICS/ddd-edit-displays.jpg

The Display Editor shows the properties of each display, using the following fields:

Num
The display number.
Expression
The displayed expression.
State
One of
enabled
Normal state.
disabled
Disabled; all details are hidden. Use Show to enable.
not active
Out of scope.
deferred
Will be created as soon as its Scope is reached (see Creating Single Displays).
clustered
Part of a cluster (see Clustering). Use Undisp => Uncluster to uncluster.
alias of display
A suppressed alias of display display (see Shared Structures).

Scope
The scope in which the display was created. For deferred displays, this is the scope in which the display will be created.
Address
The address of the displayed expression. Used for resolving aliases (see Shared Structures).


Node:Deleting Displays, Previous:Editing all Displays, Up:Display Basics
Deleting Displays

To delete a single display, select its title or value and click on the Undisp button. As an alternative, you can also press mouse button 3 on the display and select the Undisplay item.

When a display is deleted, its immediate ancestors and descendants are automatically selected, so that you can easily delete entire graphs.

If you have selected only part of a display, clicking on the Undisp button allows you to suppress this part--by applying the Suppress Values theme on the part. You'll be asked for confirmation first. See Using Data Themes, for details.

PICS/ddd-suppress.jpg

To delete several displays at once, use the Undisp button in the Display Editor (invoked via Data => Displays). Select any number of display items in the usual way and delete them by pressing Undisp.

As an alternative, you can also use a DDD command:

     graph undisplay displays...
     

Here, displays... is either

If you are using stacked windows, deleting the last display from the data window also automatically closes the data window. (You can change this via Edit => Preferences => Data => Close data window when deleting last display.)

If you deleted a display by mistake, use Edit => Undo to re-create it.

Finally, you can also cut, copy, and paste displays using the Cut, Copy, and Paste items from the Edit menu. The clipboard holds the commands used to create the displays; Paste inserts the display commands in the debugger console. This allows you to save displays for later usage or to copy displays across multiple DDD instances.


Node:Arrays, Next:, Previous:Display Basics, Up:Displaying Values

Arrays

DDD has some special features that facilitate handling of arrays.


Node:Array Slices, Next:, Up:Arrays
Array Slices

It is often useful to print out several successive objects of the same type in memory; a slice (section) of an array, or an array of dynamically determined size for which only a pointer exists in the program.

Using DDD, you can display slices using the from..to notation (see Creating Multiple Displays). But this requires that you already know from and to; it is also inefficient to create several single displays. If you use GDB, you have yet another alternative.

Using GDB, you can display successive objects by referring to a contiguous span of memory as an artificial array, using the binary operator @. The left operand of @ should be the first element of the desired array and be an individual object. The right operand should be the desired length of the array. The result is an array value whose elements are all of the type of the left argument. The first element is actually the left argument; the second element comes from bytes of memory immediately following those that hold the first element, and so on.

Here is an example. If a program says

     int *array = (int *) malloc (len * sizeof (int));
     

you can print the contents of array with

     print array[0]@len
     

and display the contents with

     graph display array[0]@len
     

The general form of displaying an array slice is thus

     graph display array[first]@nelems
     

where array is the name of the array to display, first is the index of the first element, and nelems is the number of elements to display.

The left operand of @ must reside in memory. Array values made with @ in this way behave just like other arrays in terms of subscripting, and are coerced to pointers when used in expressions.


Node:Repeated Values, Next:, Previous:Array Slices, Up:Arrays
Repeated Values

Using GDB, an array value that is repeated 10 or more times is displayed only once. The value is shown with a <nx> postfix added, where n is the number of times the value is repeated. Thus, the display 0x0 <30x> stands for 30 array elements, each with the value 0x0. This saves a lot of display space, especially with homogeneous arrays.

PICS/ddd-repeats.jpg

The default GDB threshold for repeated array values is 10. You can change it via Edit => GDB Settings => Threshold for repeated print elements. Setting the threshold to 0 will cause GDB (and DDD) to display each array element individually. Be sure to refresh the data window via Data => Refresh Displays after a change in GDB settings.

You can also configure DDD to display each array element individually:

expandRepeatedValues (class ExpandRepeatedValues) Resource
GDB can print repeated array elements as value <repeated n times>. If expandRepeatedValues is on, DDD will display n instances of value instead. If expandRepeatedValues is off (default), DDD will display value with <nx> appended to indicate the repetition.


Node:Arrays as Tables, Previous:Repeated Values, Up:Arrays
Arrays as Tables

By default, DDD lays out two-dimensional arrays as tables, such that all array elements are aligned with each other.27 To disable this feature, unset Edit => Preferences => Data => Display Two-Dimensional Arrays as Tables. This is tied to the following resource:

align2dArrays (class Align2dArrays) Resource
If on (default), DDD lays out two-dimensional arrays as tables, such that all array elements are aligned with each other. If off, DDD treats a two-dimensional array as an array of one-dimensional arrays, each aligned on its own.


Node:Assignment, Next:, Previous:Arrays, Up:Displaying Values

Assignment to Variables

During program execution, you can change the values of arbitrary variables.28

To change the value of a variable, enter its name in ()--for instance, by selecting an occurrence or a display. Then, click on the Set button. In a dialog, you can edit the variable value at will; clicking the OK or Apply button commits your change and assigns the new value to the variable.

PICS/ddd-set.jpg

To change a displayed value, you can also select Set Value menu from the data popup menu,

If you made a mistake, you can use Edit => Undo to re-set the variable to its previous value.


Node:Examining Structures, Next:, Previous:Assignment, Up:Displaying Values

Examining Structures

Besides displaying simple values, DDD can also visualize the Dependencies between values--especially pointers and other references that make up complex data structures.


Node:Dependent Values, Next:, Up:Examining Structures
Displaying Dependent Values

Dependent displays are created from an existing display. The dependency is indicated by an edge leading from the originating display to the dependent display.

To create a dependent display, select the originating display or display part and enter the dependent expression in the (): argument field. Then click on the Display button.

Using dependent displays, you can investigate the data structure of a tree for example and lay it out according to your intuitive image of the tree data structure.

By default, DDD does not recognize shared data structures (i.e. a data object referenced by multiple other data objects). See Shared Structures, for details on how to examine such structures.


Node:Dereferencing Pointers, Next:, Previous:Dependent Values, Up:Examining Structures
Dereferencing Pointers

There are special shortcuts for creating dependent displays showing the value of a dereferenced pointer. This allows for rapid examination of pointer-based data structures.

To dereference a pointer, select the originating pointer value or name and click on the Disp * button. A new display showing the dereferenced pointer value is created.

As a faster alternative, you can also press mouse button 3 on the originating pointer value or name and select the Display * menu item.

As an even faster alternative, you can also double-click mouse button 1 on the originating pointer value or name. If you press <Ctrl> while double-clicking, the display will be dereferenced in place-that is, it will be replaced by the dereferenced display.

The Display *() function is also accessible by pressing and holding the Display button.


Node:Shared Structures, Next:, Previous:Dereferencing Pointers, Up:Examining Structures
Shared Structures

By default, DDD does not recognize shared data structures--that is, a data object referenced by multiple other data objects. For instance, if two pointers p1 and p2 point at the same data object d, the data displays d, *p1, and *p2 will be separate, although they denote the same object.

DDD provides a special mode which makes it detect these situations. DDD recognizes if two or more data displays are stored at the same physical address, and if this is so, merges all these aliases into one single data display, the original data display. This mode is called Alias Detection; it is enabled via Data => Detect Aliases.

When alias detection is enabled, DDD inquires the memory location (the address) of each data display after each program step. If two displays have the same address, they are merged into one. More specifically, only the one which has least recently changed remains (the original data display); all other aliases are suppressed, i.e. completely hidden. The edges leading to the aliases are replaced by edges leading to the original data display.

An edge created by alias detection is somewhat special: rather than connecting two displays directly, it goes through an edge hint, describing an arc connecting the two displays and the edge hint.

Each edge hint is a placeholder for a suppressed alias; selecting an edge hint is equivalent to selecting the alias. This way, you can easily delete display aliases by simply selecting the edge hint and clicking on Undisp.

PICS/ddd-aliases.jpg

To access suppressed display aliases, you can also use the Display Editor. Suppressed displays are listed in the Display Editor as aliases of the original data display. Via the Display Editor, you can select, change, and delete suppressed displays.

Suppressed displays become visible again as soon as

Please note the following caveats with alias detection:

Alias detection is controlled by the following resources:

deleteAliasDisplays (class DeleteAliasDisplays) Resource
If this is on (default), the Undisplay () button also deletes all aliases of the selected displays. If this is off, only the selected displays are deleted; the aliases remain, and one of the aliases will be unsuppressed.

detectAliases (class DetectAliases) Resource
If on (default), DDD attempts to recognize shared data structures. If off, shared data structures are not recognized.

typedAliases (class TypedAliases) Resource
If on (default), DDD requires structural equivalence in order to recognize shared data structures. If this is off, two displays at the same address are considered aliases, regardless of their structure.


Node:Display Shortcuts, Previous:Shared Structures, Up:Examining Structures
Display Shortcuts

DDD maintains a shortcut menu of frequently used display expressions. This menu is activated

By default, the shortcut menu contains frequently used base conversions.

The Other entry in the shortcut menu lets you create a new display that extends the shortcut menu.

As an example, assume you have selected a display named date_ptr. Selecting Display => Other pops up a dialog that allows you to enter a new expression to be displayed--for instance, you can cast the display date_ptr to a new display (char *)date_ptr. If the Include in New Display Menu toggle was activated, the shortcut menu will then contain a new entry Display (char *)() that will cast any selected display display to (char *)display. Such shortcuts can save you a lot of time when examining complex data structures.

PICS/ddd-shortcuts.jpg

You can edit the contents of the New Display menu by selecting its Edit Menu item. This pops up the Shortcut Editor containing all shortcut expressions, which you can edit at leisure. Each line contains the expression for exactly one menu item. Clicking on Apply re-creates the New Display menu from the text. If the text is empty, the New Display menu will be empty, too.

PICS/ddd-shortcut-editor.jpg

DDD also allows you to specify individual labels for user-defined buttons. You can write such a label after the expression, separated by //. This feature is used in the default contents of the GDB New Display menu, where each of the base conversions has a label:

     /t ()   // Convert to Bin
     /d ()   // Convert to Dec
     /x ()   // Convert to Hex
     /o ()   // Convert to Oct
     

Feel free to add other conversions here. DDD supports up to 20 New Display menu items.

The shortcut menu is controlled by the following resources:

dbxDisplayShortcuts (class DisplayShortcuts) Resource
A newline-separated list of display expressions to be included in the New Display menu for DBX.

If a line contains a label delimiter29, the string before the delimiter is used as expression, and the string after the delimiter is used as label. Otherwise, the label is Display expression. Upon activation, the string () in expression is replaced by the name of the currently selected display.

gdbDisplayShortcuts (class DisplayShortcuts) Resource
A newline-separated list of display expressions to be included in the New Display menu for GDB. See the description of dbxDisplayShortcuts, above.

jdbDisplayShortcuts (class DisplayShortcuts) Resource
A newline-separated list of display expressions to be included in the New Display menu for JDB. See the description of dbxDisplayShortcuts, above.

perlDisplayShortcuts (class DisplayShortcuts) Resource
A newline-separated list of display expressions to be included in the New Display menu for Perl. See the description of dbxDisplayShortcuts, above.

bashDisplayShortcuts (class DisplayShortcuts) Resource
A newline-separated list of display expressions to be included in the New Display menu for Bash. See the description of dbxDisplayShortcuts, above.

pydbDisplayShortcuts (class DisplayShortcuts) Resource
A newline-separated list of display expressions to be included in the New Display menu for PYDB. See the description of dbxDisplayShortcuts, above.

xdbDisplayShortcuts (class DisplayShortcuts) Resource
A newline-separated list of display expressions to be included in the New Display menu for XDB. See the description of dbxDisplayShortcuts, above.


Node:Customizing Displays, Next:, Previous:Examining Structures, Up:Displaying Values

Customizing Displays


Node:Using Data Themes, Next:, Up:Customizing Displays
Using Data Themes

DDD provides a simple method to customize displays. DDD comes with a number of visual modifiers, called data themes.

Each theme modifies a particular aspect of a data display. It can be applied to individual displays or to a number of displays. The themes installed with DDD include:

Small Titles
Apply this theme to show display titles in a smaller font.
Small Values
Apply this theme to display values in a smaller font.
Tiny Values
Apply this theme to display values in a tiny font.
Suppress Values
Apply this theme to display values not at all.

Each of these themes can be applied for specific displays.

PICS/ddd-themes.jpg

To apply a theme on a display,

  1. Press mouse button 3 on the display.
  2. Select Theme
  3. Select the theme to apply.

For instance, to display the variable s in a tiny font, click mouse button 3 on the display of s, and select Theme => Tiny Values => Apply.

To unapply a theme, just click on Undo (if you just applied it) or repeat the sequence as above.


Node:Applying Data Themes to Several Values, Next:, Previous:Using Data Themes, Up:Customizing Displays
Applying Data Themes to Several Values

Whenever you want to apply a theme on a struct member or an array element, you will be asked whether to

Suppose, for instance, that you don't want to see vptr members anymore. Then you'd apply the theme Suppress Values on all similar values.

On the other hand, if you want to highlight one single value only, you'd apply the theme Red Background on only one single value.

If you find this confirmation annoying, you can define a command button which directly applies the theme. See Defining Commands, for details on defining commands.

Applying and unapplying themes is associated with the following commands:

     graph apply theme name pattern
     
applies the theme name on pattern.
     graph unapply theme name pattern
     
unapplies the theme name on pattern.
     graph toggle theme name pattern
     
applies the theme name on pattern if it was not already applied, and unapplies it otherwise.


Node:Editing Themes, Next:, Previous:Applying Data Themes to Several Values, Up:Customizing Displays
Editing Themes

Each theme can be globally activated or not. If a theme is activated, it is applied to all expressions that match its pattern.

Normally, these patterns are automatically maintained by simply selecting the themes for the individual displays. However, you can also edit patterns directly.

Patterns are separated by ; and contain shell-like metacharacters:

To edit the set of themes, invoke Data => Themes.

To apply changes you made to the themes, click on Apply. To revert the themes to the last saved, click on Reset.


Node:Writing Data Themes, Next:, Previous:Editing Themes, Up:Customizing Displays
Writing Data Themes

You can write your own data themes, customizing the display to match your need. See Top, for details.


Node:Display Resources, Next:, Previous:Writing Data Themes, Up:Customizing Displays
Display Resources

You can use these resources to control display appearance:

autoCloseDataWindow (class AutoClose) Resource
If this is on (default) and DDD is in stacked window mode, deleting the last display automatically closes the data window. If this is off, the data window stays open even after deleting the last display.

bumpDisplays (class BumpDisplays) Resource
If some display d changes size and this resource is on (default), DDD assigns new positions to displays below and on the right of d such that the distance between displays remains constant. If this is off, other displays are not rearranged.

clusterDisplays (class ClusterDisplays) Resource
If on, new independent data displays will automatically be clustered. Default is off, meaning to leave new displays unclustered.

hideInactiveDisplays (class HideInactiveDisplays) Resource
If some display gets out of scope and this resource is on (default), DDD removes it from the data display. If this is off, it is simply disabled.

showBaseDisplayTitles (class ShowDisplayTitles) Resource
Whether to assign titles to base (independent) displays or not. Default is on.

showDependentDisplayTitles (class ShowDisplayTitles) Resource
Whether to assign titles to dependent displays or not. Default is off.

suppressTheme (class Theme) Resource
The theme to apply when selecting Undisp on a data value. Default is suppress.vsl.

themes (class Themes) Resource
A newline-separated list of themes. Each theme has the format name, tabulator character, pattern.


Node:VSL Resources, Previous:Display Resources, Up:Customizing Displays
VSL Resources

The following resources control the VSL interpreter:

vslBaseDefs (class VSLDefs) Resource
A string with additional VSL definitions that are appended to the builtin VSL library. This resource is prepended to the vslDefs resource below and set in the DDD application defaults file; don't change it.

vslDefs (class VSLDefs) Resource
A string with additional VSL definitions that are appended to the builtin VSL library. The default value is an empty string. This resource can be used to override specific VSL definitions that affect the data display. The preferred method, though, is to write a specific data theme (see Writing Data Themes).

vslLibrary (class VSLLibrary) Resource
The VSL library to use. builtin (default) means to use the built-in library, any other value is used as file name.

vslPath (class VSLPath) Resource
A colon-separated list of directories to search for VSL include files. The following directory names are special:
  • The special directory name user_themes stands for your individual theme directory, typically ~/.ddd/themes/.
  • The special directory name ddd_themes stands for the installed theme directory, typically /usr/local/share/ddd-3.3.9-test2/themes/.
Default is user_themes:ddd_themes:., which means that DDD first searches your theme directory, followed by the system directory and the current directory.

If your DDD source distribution is installed in /opt/src, you can use the following settings to read the VSL library from /home/joe/ddd.vsl:

     Ddd*vslLibrary: /home/joe/ddd.vsl
     Ddd*vslPath:    user_themes:.:/opt/src/ddd/ddd:/opt/src/ddd/vsllib
     

VSL include files referenced by /home/joe/ddd.vsl are searched first in the current directory ., then in your theme directory, then in /opt/src/ddd/ddd/, and then in /opt/src/ddd/vsllib/.

Instead of supplying another VSL library, it is often easier to specify some minor changes to the built-in library (see Writing Data Themes).


Node:Layouting the Graph, Next:, Previous:Customizing Displays, Up:Displaying Values

Layouting the Graph

If you have several displays at once, you may wish to arrange them according to your personal preferences. This section tells you how you can do this.


Node:Moving Displays, Next:, Up:Layouting the Graph
Moving Displays

From time to time, you may wish to move displays at another place in the data window. You can move a single display by pressing and holding mouse button 1 on the display title. Moving the pointer while holding the button causes all selected displays to move along with the pointer.

Edge hints can be selected and moved around like other displays. If an arc goes through the edge hint, you can change the shape of the arc by moving the edge hint around.

For fine-grain movements, selected displays may also be moved using the arrow keys. Pressing <Shift> and an arrow key moves displays by single pixels. Pressing <Ctrl> and arrow keys moves displays by grid positions.


Node:Scrolling Data, Next:, Previous:Moving Displays, Up:Layouting the Graph
Scrolling Data

If the data window becomes too small to hold all displays, scroll bars are created. If your DDD is set up to use panners instead, a panner is created in the lower right edge. When the panner is moved around, the window view follows the position of the panner.

To change from scroll bars to panners, use Edit => Startup => Data Scrolling and choose either Panner or Scrollbars.

This setting is tied to the following resource:

pannedGraphEditor (class PannedGraphEditor) Resource
The control to scroll the graph.
  • If this is on, an Athena panner is used (a kind of two-directional scrollbar).
  • If this is off (default), two M*tif scrollbars are used.

See Options, for the --scrolled-graph-editor and --panned-graph-editor options.


Node:Aligning Displays, Next:, Previous:Scrolling Data, Up:Layouting the Graph
Aligning Displays

You can align all displays on the nearest grid position by selecting Data => Align on Grid. This is useful for keeping edges strictly horizontal or vertical.

You can enforce alignment by selecting Edit => Preferences => Data => Auto-align Displays on Nearest Grid Point. If this feature is enabled, displays can be moved on grid positions only.


Node:Automatic Layout, Next:, Previous:Aligning Displays, Up:Layouting the Graph
Automatic Layout

You can layout the entire graph as a tree by selecting Data => Layout Graph. The layout direction is determined from the display placement (see Placement) and from the last rotation (see Rotating the Graph).

PICS/ddd-layout.jpg

Layouting the graph may introduce edge hints; that is, edges are no more straight lines, but lead to an edge hint and from there to their destination. Edge hints can be moved around like arbitrary displays.

To enable a more compact layout, you can set the Edit => Preferences => Data => Compact Layout option. This realizes an alternate layout algorithm, where successors are placed next to their parents. This algorithm is suitable for homogeneous data structures only.

You can enforce layout by setting Edit => Preferences => Data => Automatic Layout. If automatic layout is enabled, the graph is layouted after each change.


Node:Rotating the Graph, Previous:Automatic Layout, Up:Layouting the Graph
Rotating the Graph

You can rotate the entire graph clockwise by 90 degrees by selecting Data => Rotate Graph. You may need to layout the graph after rotating it; See Automatic Layout, for details.


Node:Printing the Graph, Previous:Layouting the Graph, Up:Displaying Values

Printing the Graph

DDD allows for printing the graph picture on PostScript printers or into files. This is useful for documenting program states.

PICS/ddd-print-graph.jpg

To print the graph on a PostScript printer, select File => Print Graph. Enter the printing command in the Print Command field. Click on the OK or the Apply button to start printing.

As an alternative, you may also print the graph in a file. Click on the File button and enter the file name in the File Name field. Click on the Print button to create the file.

When the graph is printed in a file, two formats are available:


PICS/ddd-print-output.jpg

Please note the following caveats related to printing graphs:

These settings are tied to the following resources:

printCommand (class PrintCommand) Resource
The command to print a PostScript file. Usually lp or lpr.

paperSize (class PaperSize) Resource
The paper size used for printing, in format width x height. The default is ISO A4 format, or 210mm x 297mm.


Node:Plotting Values, Next:, Previous:Displaying Values, Up:Examining Data

Plotting Values

If you have huge amounts of numerical data to examine, a picture often says more than a thousand numbers. Therefore, DDD allows you to draw numerical values in nice 2-D and 3-D plots.


Node:Plotting Arrays, Next:, Up:Plotting Values

Plotting Arrays

Basically, DDD can plot two types of numerical values:

To plot a fixed-size array, select its name by clicking mouse button 1 on an occurrence. The array name is copied to the argument field. By clicking the Plot button, a new display is created in the data window, followed by a new top-level window containing the value plot.

To plot a dynamically sized array, you must use an array slice (see Array Slices). In the argument field, enter

     array[first]@nelems
     

where array is the name of the array to display, first is the index of the first element, and nelems is the number of elements to display. Then, click on Plot to start the plot.

To plot a value, you can also enter a command at the debugger prompt:

     graph plot expr
     

works like graph display expr (and takes the same arguments; see Creating Single Displays), but the value is additionally shown in the plot window.

Each time the value changes during program execution, the plot is updated to reflect the current values. The plot window remains active until you close it (via File => Close) or until the associated display is deleted.


Node:Plot Appearance, Next:, Previous:Plotting Arrays, Up:Plotting Values

Changing the Plot Appearance

The actual drawing is not done by DDD itself. Instead, DDD relies on an external gnuplot program to create the drawing.

DDD adds a menu bar to the Gnuplot plot window that lets you influence the appearance of the plot:

In a 3-D plot, you can use the scroll bars to change your view position. The horizontal scroll bar rotates the plot around the z axis, that is, to the left and right. The vertical scroll bar rotates the plot around the y axis, that is, up and down.

PICS/ddd-plots.jpg

You can also resize the plot window as desired.


Node:Scalars and Composites, Next:, Previous:Plot Appearance, Up:Plotting Values

Plotting Scalars and Composites

Besides plotting arrays, DDD also allows you to plot scalars (simple numerical values). This works just like plotting arrays--you select the numerical variable, click on Plot, and here comes the plot. However, plotting a scalar is not very exciting. A plot that contains nothing but a scalar simply draws the scalar's value as a y constant--that is, a horizontal line.

So why care about scalars at all? DDD allows you to combine multiple values into one plot. The basic idea is: if you want to plot something that is neither an array nor a scalar, DDD takes all numerical sub-values it can find and plots them all together in one window. For instance, you can plot all local variables by selecting Data => Display Local Variables, followed by Plot. This will create a plot containing all numerical values as found in the current local variables. Likewise, you can plot all numeric members contained in a structure by selecting it, followed by Plot.

If you want more control about what to include in a plot and what not, you can use display clusters (see Clustering). A common scenario is to plot a one-dimensional array together with the current index position. This is done in three steps:

  1. Display the array and the index, using Display.
  2. Cluster both displays: select them and choose Undisp => Cluster ().
  3. Plot the cluster by pressing Plot.

Scalars that are displayed together with arrays can be displayed either as vertical lines or horizontal lines. By default, scalars are plotted as horizontal lines. However, if a scalar is a valid index for an array that was previously plotted, it is shown as a vertical line. You can change this initial orientation by selecting the scalar display, followed by Rotate.


Node:Plotting Histories, Next:, Previous:Scalars and Composites, Up:Plotting Values

Plotting Display Histories

At each program stop, DDD records the values of all displayed variables, such that you can "undo" program execution (see Undoing Program Execution). These display histories can be plotted, too. The menu item Plot => Plot history of () creates a plot that shows all previously recorded values of the selected display.


Node:Printing Plots, Next:, Previous:Plotting Histories, Up:Plotting Values

Printing Plots

If you want to print the plot, select File => Print Plot. This pops up the DDD printing dialog, set up for printing plots. Just as when printing graphs, you have the choice between printing to a printer or a file and setting up appropriate options.

The actual printing is also performed by Gnuplot, using the appropriate driver. Please note the following caveats related to printing:


Node:Entering Plotting Commands, Next:, Previous:Printing Plots, Up:Plotting Values

Entering Plotting Commands

Via File => Command, you can enter Gnuplot commands directly. Each command entered at the gnuplot> prompt is passed to Gnuplot, followed by a Gnuplot replot command to update the view. This is useful for advanced Gnuplot tasks.

Here's a simple example. The Gnuplot command

     set xrange [xmin:xmax]
     

sets the horizontal range that will be displayed to xmin...xmax. To plot only the elements 10 to 20, enter:

     gnuplot> set xrange [10:20]
     gnuplot> _
     

After each command entered, DDD adds a replot command, such that the plot is updated automatically.

Here's a more complex example. The following sequence of Gnuplot commands saves the plot in TeX format:

     gnuplot> set output "plot.tex" # Set the output filename
     gnuplot> set term latex        # Set the output format
     gnuplot> set term x11          # Show original picture again
     gnuplot> _
     

Due to the implicit replot command, the output is automatically written to plot.tex after the set term latex command.

The dialog keeps track of the commands entered; use the arrow keys to restore previous commands. Gnuplot error messages (if any) are also shown in the history area.

The interaction between DDD and Gnuplot is logged in the file ~/.ddd/log (see Logging). The DDD --trace option logs this interaction on standard output.


Node:Exporting Plot Data, Next:, Previous:Entering Plotting Commands, Up:Plotting Values

Exporting Plot Data

If you want some external program to process the plot data (a stand-alone Gnuplot program or the xmgr program, for instance), you can save the plot data in a file, using File => Save Data As. This pops up a dialog that lets you choose a data file to save the plotted data in.

The generated file starts with a few comment lines. The actual data follows in X/Y or X/Y/Z format. It is the same file as processed by Gnuplot.


Node:Animating Plots, Next:, Previous:Exporting Plot Data, Up:Plotting Values

Animating Plots

If you want to see how your data evolves in time, you can set a breakpoint whose command sequence ends in a cont command (see Breakpoint Commands. Each time this "continue" breakpoint is reached, the program stops and DDD updates the displayed values, including the plots. Then, DDD executes the breakpoint command sequence, resuming execution.

This way, you can set a "continue" breakpoint at some decisive point within an array-processing algorithm and have DDD display the progress graphically. When your program has stopped for good, you can use Undo and Redo to redisplay and examine previous program states. See Undoing Program Execution, for details.


Node:Customizing Plots, Previous:Animating Plots, Up:Plotting Values

Customizing Plots

You can customize the Gnuplot program to invoke, as well as a number of basic settings.


Node:Gnuplot Invocation, Next:, Up:Customizing Plots
Gnuplot Invocation

Using Edit => Preferences => Helpers => Plot, you can choose the Gnuplot program to invoke. This is tied to the following resource:

plotCommand (class PlotCommand) Resource
The name of a Gnuplot executable. Default is gnuplot, followed by some options to set up colors and the initial geometry.

Using Edit => Preferences => Helpers => Plot Window, you can choose whether to use the Gnuplot plot window (External) or to use the plot window supplied by DDD (builtin). This is tied to the following resource:

plotTermType (class PlotTermType) Resource
The Gnuplot terminal type. Can have one of two values:
  • If this is x11, DDD "swallows" the external Gnuplot output window into its own user interface. Some window managers, notably mwm, have trouble with swallowing techniques.
  • Setting this resource to xlib (default) makes DDD provide a builtin plot window instead. In this mode, plots work well with any window manager, but are less customizable (Gnuplot resources are not understood).

You can further control interaction with the external plot window:

plotWindowClass (class PlotWindowClass) Resource
The class of the Gnuplot output window. When invoking Gnuplot, DDD waits for a window with this class and incorporates it into its own user interface (unless plotTermType is xlib; see above). Default is Gnuplot.

plotWindowDelay (class WindowDelay) Resource
The time (in ms) to wait for the creation of the Gnuplot window. Before this delay, DDD looks at each newly created window to see whether this is the plot window to swallow. This is cheap, but unfortunately, some window managers do not pass the creation event to DDD. If this delay has passed, and DDD has not found the plot window, DDD searches all existing windows, which is pretty expensive. Default time is 2000.


Node:Gnuplot Settings, Previous:Gnuplot Invocation, Up:Customizing Plots
Gnuplot Settings

To change Gnuplot settings, use these resources:

plotInitCommands (class PlotInitCommands) Resource
The initial Gnuplot commands issued by DDD. Default is:
          set parametric
          set urange [0:1]
          set vrange [0:1]
          set trange [0:1]
          

The parametric setting is required to make Gnuplot understand the data files as generated DDD. The range commands are used to plot scalars.

See the Gnuplot documentation for additional commands.

plot2dSettings (class PlotSettings) Resource
Additional initial settings for 2-D plots. Default is set noborder. Feel free to customize these settings as desired.

plot3dSettings (class PlotSettings) Resource
Additional initial settings for 3-D plots. Default is set border. Feel free to customize these settings as desired.


Node:Examining Memory, Previous:Plotting Values, Up:Examining Data

Examining Memory

Using GDB or DBX, you can examine memory in any of several formats, independently of your program's data types. The item Data => Memory pops up a panel where you can choose the format to be shown.

PICS/ddd-examine.jpg

In the panel, you can enter

There are two ways to examine the values:


Node:Machine-Level Debugging, Next:, Previous:Examining Data, Up:Top

Machine-Level Debugging

Sometimes, it is desirable to examine a program not only at the source level, but also at the machine level. DDD provides special machine code and register windows for this task.


Node:Machine Code, Next:, Up:Machine-Level Debugging

Examining Machine Code

To enable machine-level support, select Source => Display Machine Code. With machine code enabled, an additional machine code window shows up, displaying the machine code of the current function.30 By moving the sash at the right of the separating line between source and machine code, you can resize the source and machine code windows.

PICS/ddd-code.jpg

The machine code window works very much like the source window. You can set, clear, and change breakpoints by selecting the address and pressing a Break or Clear button; the usual popup menus are also available. Breakpoints and the current execution position are displayed simultaneously in both source and machine code.

The Lookup button can be used to look up the machine code for a specific function--or the function for a specific address. Just click on the location in one window and press Lookup to see the corresponding code in the other window.

If source code is not available, only the machine code window is updated.

You can customize various aspects of the disassembling window. See Customizing Machine Code, for details.


Node:Machine Code Execution, Next:, Previous:Machine Code, Up:Machine-Level Debugging

Machine Code Execution

All execution facilities available in the source code window are available in the machine code window as well. Two special facilities are convenient for machine-level debugging:

To execute just one machine instruction, click on the Stepi button or select Program => Step Instruction.

To continue to the next instruction in the current function, click on the Nexti button select Program => Next Instruction.. This is similar to Stepi, but any subroutine calls are executed without stopping.

Using GDB, it is often useful to do

     graph display /i $pc
     

when stepping by machine instructions. This makes DDD automatically display the next instruction to be executed, each time your program stops.


Node:Registers, Next:, Previous:Machine Code Execution, Up:Machine-Level Debugging

Examining Registers

DDD provides a register window showing the machine register values after each program stop. To enable the register window, select Status => Registers.31

PICS/ddd-registers.jpg

By selecting one of the registers, its name is copied to the argument field. You can use it as value for Display, for instance, to have its value displayed in the data window.


Node:Customizing Machine Code, Previous:Registers, Up:Machine-Level Debugging

Customizing Machine Code

Enabling machine code via Source => Display Machine Code (see Machine Code) toggles the following resource:

disassemble (class Disassemble) Resource
If this is on, the source code is automatically disassembled. The default is off. See Options, for the --disassemble and --no-disassemble options.

You can keep disassembled code in memory, using Edit => Preferences => Source => Cache Machine Code:

cacheMachineCode (class CacheMachineCode) Resource
Whether to cache disassembled machine code (on, default) or not (off). Caching machine code requires more memory, but makes DDD run faster.

You can control the indentation of machine code, using Edit => Preferences => Source => Machine Code Indentation:

indentCode (class Indent) Resource
The number of columns to indent the machine code, such that there is enough place to display breakpoint locations. Default: 4.

The maxDisassemble resource controls how much is to be disassembled. If maxDisassemble is set to 256 (default) and the current function is larger than 256 bytes, DDD only disassembles the first 256 bytes below the current location. You can set the maxDisassemble resource to a larger value if you prefer to have a larger machine code view.

maxDisassemble (class MaxDisassemble) Resource
Maximum number of bytes to disassemble (default: 256). If this is zero, the entire current function is disassembled.


Node:Changing the Program, Next:, Previous:Machine-Level Debugging, Up:Top

Changing the Program

DDD offers some basic facilities to edit and recompile the source code, as well as patching executables and core files.


Node:Editing Source Code, Next:, Up:Changing the Program

Editing Source Code

In DDD itself, you cannot change the source file currently displayed. Instead, DDD allows you to invoke a text editor. To invoke a text editor for the current source file, select the Edit button or Source => Edit Source.

By default, DDD tries a number of common editors. You can customize DDD to use your favorite editor; See Customizing Editing, for details.

After the editor has exited, the source code shown is automatically updated.

If you have DDD and an editor running in parallel, you can also update the source code manually via Source => Reload Source. This reloads the source code shown from the source file. Since DDD automatically reloads the source code if the debugged program has been recompiled, this should seldom be necessary.


Node:Customizing Editing, Next:, Up:Editing Source Code

Customizing Editing

You can customize the editor to be used via Edit => Preferences => Helpers => Edit Sources. This is tied to the following resource:

editCommand (class EditCommand) Resource
A command string to invoke an editor on the specific file. @LINE@ is replaced by the current line number, @FILE@ by the file name. The default is to invoke $XEDITOR first, then $EDITOR, then vi:
          Ddd*editCommand: \
          ${XEDITOR-false} +@LINE@ @FILE@ || \
          xterm -e ${EDITOR-vi} +@LINE@ @FILE@
          

This ~/.ddd/init setting invokes an editing session for an XEmacs editor running gnuserv:

     Ddd*editCommand: gnuclient +@LINE@ @FILE@
     

This ~/.ddd/init setting invokes an editing session for an Emacs editor running emacsserver:

     Ddd*editCommand: emacsclient +@LINE@ @FILE@
     


Node:In-Place Editing, Previous:Customizing Editing, Up:Editing Source Code

In-Place Editing

This resource is experimental:

sourceEditing (class SourceEditing) Resource
If this is on, the displayed source code becomes editable. This is an experimental feature; Default is off.


Node:Recompiling, Next:, Previous:Editing Source Code, Up:Changing the Program

Recompiling

To recompile the source code using make, you can select File => Make. This pops up a dialog where you can enter a Make Target--typically the name of the executable. Clicking on the Make button invokes the make program with the given target.

The Make button on the command tool re-invokes make with the most recently given arguments.


Node:Patching, Previous:Recompiling, Up:Changing the Program

Patching

Using GDB, you can open your program's executable code (and the core file) for both reading and writing. This allows alterations to machine code, such that you can intentionally patch your program's binary. For example, you might want to turn on internal debugging flags, or even to make emergency repairs.

Note that depending on your operating system, special preparation steps, such as setting permissions, may be needed before you can change executable files.

To patch the binary, enable Edit => GDB Settings => Writing into executable and core files. This makes GDB open executable and core files for both reading and writing. If you have already loaded a file, you must load it again (using Edit => Open File or Edit => Open Core), for your new setting to take effect.

Be sure to turn off Writing into executable and core files as soon as possible, to prevent accidental alterations to machine code.


Node:Commands, Next:, Previous:Changing the Program, Up:Top

The Command-Line Interface

All the buttons you click within DDD get eventually translated into some debugger command, shown in the debugger console. You can also type in and edit these commands directly.


Node:Entering Commands, Next:, Up:Commands

Entering Commands

In the debugger console, you can interact with the command interface of the inferior debugger. Enter commands at the debugger prompt--that is, (gdb) for GDB, (dbx) for DBX, (ladebug) for Ladebug, > for XDB, > and thread[depth] for JDB, or (Pydb) for PYDB, or DB<> for Perl, or bashdb<> for Bash. You can use arbitrary debugger commands; use the <Return> key to enter them.


Node:Command Completion, Next:, Up:Entering Commands

Command Completion

When using GDB or Perl, you can use the <TAB> key for completing commands and arguments. This works in the debugger console as well as in all other text windows.

GDB can fill in the rest of a word in a command for you, if there is only one possibility; it can also show you what the valid possibilities are for the next word in a command, at any time. This works for GDB commands, GDB subcommands, and the names of symbols in your program.

Press the <TAB> key whenever you want GDB to fill out the rest of a word. If there is only one possibility, GDB fills in the word, and waits for you to finish the command (or press <RET> to enter it). For example, if you type

     (gdb) info bre_<TAB>
     

GDB fills in the rest of the word breakpoints, since that is the only info subcommand beginning with bre:

     (gdb) info breakpoints
     

You can either press <RET> at this point, to run the info breakpoints command, or backspace and enter something else, if breakpoints does not look like the command you expected. (If you were sure you wanted info breakpoints in the first place, you might as well just type <RET> immediately after info bre, to exploit command abbreviations rather than command completion).

If there is more than one possibility for the next word when you press <TAB>, DDD sounds a bell. You can either supply more characters and try again, or just press <TAB> a second time; GDB displays all the possible completions for that word. For example, you might want to set a breakpoint on a subroutine whose name begins with make_, but when you type b make_<TAB>, DDD just sounds the bell. Typing <TAB> again displays all the function names in your program that begin with those characters. If you type <TAB> again, you cycle through the list of completions, for example:

     (gdb) b make_ <TAB>

DDD sounds bell; press <TAB> again, to see:
make_a_section_from_file make_environ make_abs_section make_function_type make_blockvector make_pointer_type make_cleanup make_reference_type make_command make_symbol_completion_list (gdb) b make_ <TAB>
DDD presents one expansion after the other:
(gdb) b make_a_section_from_file <TAB> (gdb) b make_abs_section <TAB> (gdb) b make_blockvector <TAB>

After displaying the available possibilities, GDB copies your partial input (b make_ in the example) so you can finish the command--by pressing <TAB> again, or by entering the remainder manually.

Sometimes the string you need, while logically a "word", may contain parentheses or other characters that GDB normally excludes from its notion of a word. To permit word completion to work in this situation, you may enclose words in ' (single quote marks) in GDB commands.

The most likely situation where you might need this is in typing the name of a C++ function. This is because C++ allows function overloading (multiple definitions of the same function, distinguished by argument type). For example, when you want to set a breakpoint you may need to distinguish whether you mean the version of name that takes an int parameter, name(int), or the version that takes a float parameter, name(float). To use the word-completion facilities in this situation, type a single quote ' at the beginning of the function name. This alerts GDB that it may need to consider more information than usual when you press <TAB> to request word completion:

     (gdb) b 'bubble(_<TAB>
     bubble(double,double)    bubble(int,int)
     (gdb) b 'bubble(_
     

In some cases, DDD can tell that completing a name requires using quotes. When this happens, DDD inserts the quote for you (while completing as much as it can) if you do not type the quote in the first place:

     (gdb) b bub_<TAB>

DDD alters your input line to the following, and rings a bell:
(gdb) b 'bubble(_

In general, DDD can tell that a quote is needed (and inserts it) if you have not yet started typing the argument list when you ask for completion on an overloaded symbol.

If you prefer to use the <TAB> key for switching between items, unset Edit => Preferences => General => TAB Key completes in All Windows. This is useful if you have pointer-driven keyboard focus (see below) and no special usage for the <TAB> key. If the option is set, the <TAB> key completes in the debugger console only.

This option is tied to the following resource:

globalTabCompletion (class GlobalTabCompletion) Resource
If this is on (default), the <TAB> key completes arguments in all windows. If this is off, the <TAB> key completes arguments in the debugger console only.


Node:Command History, Next:, Previous:Command Completion, Up:Entering Commands

Command History

You can repeat previous and next commands by pressing the <Up> and <Down> arrow keys, respectively. This presents you previous and later commands on the command line; use <Return> to apply the current command.

If you enter an empty line (just use <Return> at the debugger prompt), the last command is repeated as well.

Commands => Command History shows the command history.

PICS/ddd-history.jpg

You can search for previous commands by pressing <Ctrl+B>. This invokes incremental search mode, where you can enter a string to be searched in previous commands. Press <Ctrl+B> again to repeat the search, or <Ctrl+F> to search in the reverse direction. To return to normal mode, press <ESC>, or use any cursor command.

The command history is automatically saved when exiting DDD. You can turn off this feature by setting the following resource to off:

saveHistoryOnExit (class SaveOnExit) Resource
If on (default), the command history is automatically saved when DDD exits.


Node:Typing in the Source Window, Previous:Command History, Up:Entering Commands

Typing in the Source Window

As a special convenience, anything you type into the source window is automatically forwarded to the debugger console. Thus, you don't have to change the keyboard focus explicitly in order to enter commands.

You can change this behaviour using the following resource:

consoleHasFocus (class ConsoleHasFocus) Resource
If on (default), all keyboard events in the source window are automatically forwarded to the debugger console. If off, keyboard events are not forwarded. If auto, keyboard events forwarded only if the debugger console is open.


Node:TTY mode, Next:, Previous:Entering Commands, Up:Commands

Entering Commands at the TTY

Rather than entering commands at the debugger console, you may prefer to enter commands at the terminal window DDD was invoked from.

When DDD is invoked using the --tty option, it enables its TTY interface, taking additional debugger commands from standard input and forwarding debugger output to standard output, just as if the inferior debugger had been invoked directly. All remaining DDD functionality stays unchanged.

By default, the debugger console remains closed if DDD is invoked using the --tty option. Use View => Debugger Console to open it.

DDD can be configured to use the readline library for reading in commands from standard input. This GNU library provides consistent behavior for programs which provide a command line interface to the user. Advantages are GNU Emacs-style or vi-style inline editing of commands, csh-like history substitution, and a storage and recall of command history across debugging sessions. See Command Line Editing, for details on command-line editing via the TTY interface.


Node:Integrating DDD, Next:, Previous:TTY mode, Up:Commands

Integrating DDD

You can run DDD as an inferior debugger in other debugger front-ends, combining their special abilities with those of DDD.

To have DDD run as an inferior debugger in other front-ends, the general idea is to set up your debugger front-end such that ddd --tty is invoked instead of the inferior debugger. When DDD is invoked using the --tty option, it enables its TTY interface, taking additional debugger commands from standard input and forwarding debugger output to standard output, just as if the inferior debugger had been invoked directly. All remaining DDD functionality stays unchanged.

In case your debugger front-end uses the GDB -fullname option to have GDB report source code positions, the --tty option is not required. DDD recognizes the -fullname option, finds that it has been invoked from a debugger front-end and automatically enables the TTY interface.

If DDD is invoked with the -fullname option, the debugger console and the source window are initially disabled, as their facilities are supposed to be provided by the integrating front-end. In case of need, you can use the View menu to re-enable these windows.

Using DDD with Emacs

To integrate DDD with Emacs, use M-x gdb or M-x dbx in Emacs to start a debugging session. At the prompt, enter ddd --tty (followed by --dbx or --gdb, if required), and the name of the program to be debugged. Proceed as usual.

Using DDD with XEmacs

To integrate DDD with XEmacs, set the variable gdb-command-name to "ddd", by inserting the following line in your ~/.emacs file:

     (setq gdb-command-name "ddd")
     

You can also evaluate this expression by pressing <ESC> <:> and entering it directly (<ESC> <ESC> for XEmacs 19.13 and earlier).

To start a DDD debugging session in XEmacs, use M-x gdb or M-x gdbsrc. Proceed as usual.

Using DDD with XXGDB

To integrate DDD with XXGDB, invoke xxgdb as

     xxgdb -db_name ddd -db_prompt '(gdb) '
     


Node:Defining Buttons, Next:, Previous:Integrating DDD, Up:Commands

Defining Buttons

To facilitate interaction, you can add own command buttons to DDD. These buttons can be added below the debugger console (Console Buttons), the source window (Source Buttons), or the data window (Data Buttons).

To define individual buttons, use the Button Editor, invoked via Commands => Edit Buttons. The button editor displays a text, where each line contains the command for exactly one button. Clicking on OK creates the appropriate buttons from the text. If the text is empty (the default), no button is created.

As a simple example, assume you want to create a print i button. Invoke Commands => Edit Buttons and enter a line saying print i in the button editor. Then click on OK. A button named Print i will now appear below the debugger console--try it! To remove the button, reopen the button editor, clear the print i line and press OK again.

If a button command contains (), the string () will automatically be replaced by the contents of the argument field. For instance, a button named return () will execute the GDB return command with the current content of the argument field as argument.

By default, DDD disables buttons whose commands are not supported by the inferior debugger. To enable such buttons, unset the Enable supported buttons only toggle in the button editor.

PICS/ddd-button-editor.jpg

DDD also allows you to specify control sequences and special labels for user-defined buttons. See Customizing Buttons, for details.


Node:Customizing Buttons, Up:Defining Buttons

Customizing Buttons

DDD allows defining additional command buttons; See Defining Buttons, for doing this interactively. This section describes the resources that control user-defined buttons.

consoleButtons (class Buttons) Resource
A newline-separated list of buttons to be added under the debugger console. Each button issues the command given by its name.

The following characters have special meanings:

  • Commands ending with ... insert their name, followed by a space, in the debugger console.
  • Commands ending with a control character (that is, ^ followed by a letter or ?) insert the given control character.
  • The string () is replaced by the current contents of the argument field ().
  • The string specified in the labelDelimiter resource (usually //) separates the command name from the button label. If no button label is specified, the capitalized command will be used as button label.

The following button names are reserved:

Apply
Send the given command to the debugger.
Back
Lookup previously selected source position.
Clear
Clear current command
Complete
Complete current command.
Edit
Edit current source file.
Forward
Lookup next selected source position.
Make
Invoke the make program, using the most recently given arguments.
Next
Show next command
No
Answer current debugger prompt with no. This button is visible only if the debugger asks a yes/no question.
Prev
Show previous command
Reload
Reload source file.
Yes
Answer current debugger prompt with yes. This button is visible only if the debugger asks a yes/no question.

The default resource value is empty--no console buttons are created.

Here are some examples to insert into your ~/.ddd/init file. These are the settings of DDD 1.x:

          Ddd*consoleButtons: Yes\nNo\nbreak^C
          

This setting creates some more buttons:

            Ddd*consoleButtons: \
            Yes\nNo\nrun\nClear\nPrev\nNext\nApply\nbreak^C
          

See also the dataButtons, sourceButtons and toolButtons resources.

dataButtons (class Buttons) Resource
A newline-separated list of buttons to be added under the data display. Each button issues the command given by its name. See the consoleButtons resource, above, for details on button syntax.

The default resource value is empty--no source buttons are created.

sourceButtons (class Buttons) Resource
A newline-separated list of buttons to be added under the debugger console. Each button issues the command given by its name. See the consoleButtons resource, above, for details on button syntax.

The default resource value is empty--no source buttons are created.

Here are some example to insert into your ~/.ddd/init file. These are the settings of DDD 1.x:

          Ddd*sourceButtons: \
            run\nstep\nnext\nstepi\nnexti\ncont\n\
            finish\nkill\nup\ndown\n\
            Back\nForward\nEdit\ninterrupt^C
          

This setting creates some buttons which are not found on the command tool:

            Ddd*sourceButtons: \
            print *()\ngraph display *()\nprint /x ()\n\
            whatis ()\nptype ()\nwatch ()\nuntil\nshell
          

An even more professional setting uses customized button labels.

            Ddd*sourceButtons: \
            print *(()) // Print *()\n\
            graph display *(()) // Display *()\n\
            print /x ()\n\
            whatis () // What is ()\n\
            ptype ()\n\
            watch ()\n\
            until\n\
            shell
          

See also the consoleButtons and dataButtons resources, above, and the toolButtons resource, below.

toolButtons (class Buttons) Resource
A newline-separated list of buttons to be included in the command tool or the command tool bar (see Disabling the Command Tool). Each button issues the command given by its name. See Defining Buttons, for details on button syntax.

The default resource value is

          Ddd*toolButtons: \
          run\nbreak^C\nstep\nstepi\nnext\nnexti\n\
          until\nfinish\ncont\n\kill\n\
          up\ndown\nBack\nForward\nEdit\nMake
          

For each button, its location in the command tool must be specified using XmForm constraint resources. See the Ddd application defaults file for instructions.

If the toolButtons resource value is empty, the command tool is not created.

The following resources set up button details:

labelDelimiter (class LabelDelimiter) Resource
The string used to separate labels from commands and shortcuts. Default is //.

verifyButtons (class VerifyButtons) Resource
If on (default), verify for each button whether its command is actually supported by the inferior debugger. If the command is unknown, the button is disabled. If this resource is off, no checking is done: all commands are accepted "as is".


Node:Defining Commands, Previous:Defining Buttons, Up:Commands

Defining Commands

Aside from breakpoint commands (see Breakpoint Commands), DDD also allows you to define user-defined commands. A user-defined command is a sequence of commands to which you assign a new name as a command. This new command can be entered at the debugger prompt or invoked via a button.


Node:GDB Simple Commands, Next:, Up:Defining Commands

Defining Simple Commands using GDB

Aside from breakpoint commands (see Breakpoint commands, above), DDD also allows you to store sequences of commands as a user-defined GDB command. A user-defined command is a sequence of GDB commands to which you assign a new name as a command. Using DDD, this is done via the Command Editor, invoked via Commands => Define Command.

A GDB command is created in five steps:

  1. Enter the name of the command in the Command field. Use the drop-down list on the right to select from already defined commands.
  2. Click on Record to begin the recording of the command sequence.
  3. Now interact with DDD. While recording, DDD does not execute commands, but simply records them to be executed when the breakpoint is hit. The recorded debugger commands are shown in the debugger console.
  4. To stop the recording, click on End or enter end at the GDB prompt. To cancel the recording, click on Interrupt or press <ESC>.
  5. Click on Edit >> to edit the recorded commands. When done with editing, click on Edit << to close the commands editor.

After the command is defined, you can enter it at the GDB prompt. You may also click on Execute to test the given user-defined command.

For convenience, you can assign a button to the defined command. Enabling one of the Button locations will add a button with the given command to the specified location. If you want to edit the button, select Commands => Edit Buttons. See Defining Buttons, for a discussion.

PICS/ddd-define-command.jpg

When user-defined GDB commands are executed, the commands of the definition are not printed. An error in any command stops execution of the user-defined command.32

If used interactively, commands that would ask for confirmation proceed without asking when used inside a user-defined command. Many GDB commands that normally print messages to say what they are doing omit the messages when used in a user-defined command.

Command definitions are saved across DDD sessions.


Node:GDB Argument Commands, Next:, Previous:GDB Simple Commands, Up:Defining Commands

Defining Argument Commands using GDB

If you want to pass arguments to user-defined commands, you can enable the () toggle button in the Command Editor. Enabling () has two effects:

While defining a command, you can toggle the () button as you wish to switch between using the argument field symbolically and literally.

As an example, let us define a command contuntil that will set a breakpoint in the given argument and continue execution.

  1. Enter contuntil in the Command field.
  2. Enable the () toggle button.
  3. Now click on Record to start recording. Note that the contents of the argument field change to $arg0.
  4. Click on Break at () to create a breakpoint. Note that the recorded breakpoint command refers to $arg0.
  5. Click on Cont to continue execution.
  6. Click on End to end recording. Note that the argument field is restored to its original value.
  7. Finally, click on one of the Button locations. This creates a Contuntil () button where () will be replaced by the current contents of the argument field--and thus passed to the contuntil command.
  8. You can now either use the Contuntil () button or enter a contuntil command at the GDB prompt. (If you plan to use the command frequently, you may wish to define a cu command, which again calls contuntil with its argument. This is a nice exercise.)

There is a little drawback with argument commands: a user-defined command in GDB has no means to access the argument list as a whole; only the first argument (up to whitespace) is processed. This may change in future GDB releases.


Node:Commands with Other Debuggers, Previous:GDB Argument Commands, Up:Defining Commands

Defining Commands using Other Debuggers

If your inferior debugger allows you to define own command sequences, you can also use these user-defined commands within DDD; just enter them at the debugger prompt.

However, you may encounter some problems:

As a solution, DDD provides a simple facility called auto-commands. If DDD receives any output from the inferior debugger in the form prefix command, it will interpret command as if it had been entered at the debugger prompt. prefix is a user-defined string, for example ddd: .

Suppose you want to define a command gd that serves as abbreviation for graph display. All the command gd has to do is to issue a string

     ddd: graph display argument
     

where argument is the argument given to gd. Using GDB, this can be achieved using the echo command. In your ~/.gdbinit file, insert the lines

     define gd
       echo ddd: graph display $arg0\n
     end
     

To complete the setting, you must also set the autoCommandPrefix resource to the ddd: prefix you gave in your command. In ~/.ddd/init, write:

     Ddd*autoCommandPrefix: ddd:\
     

(Be sure to leave a space after the trailing backslash.)

Entering gd foo will now have the same effect as entering graph display foo at the debugger prompt.

Please note: In your commands, you should choose some other prefix than ddd: . This is because auto-commands raise a security problem, since arbitrary commands can be executed. Just imagine some malicious program issuing a string like prefix shell rm -fr ~ when being debugged! As a consequence, be sure to choose your own prefix; it must be at least three characters long.


Node:Application Defaults, Next:, Previous:Commands, Up:Top

Application Defaults

Like any good X citizen, DDD comes with a large application-defaults file named Ddd. This appendix documents the actions and images referenced in Ddd, such that you can easily modify them.


Node:Actions, Next:, Up:Application Defaults

Actions

The following DDD actions may be used in translation tables.


Node:General Actions, Next:, Up:Actions

General Actions

ddd-get-focus () Action
Assign focus to the element that just received input.

ddd-next-tab-group () Action
Assign focus to the next tab group.

ddd-prev-tab-group () Action
Assign focus to the previous tab group.

ddd-previous-tab-group () Action
Assign focus to the previous tab group.


Node:Data Display Actions, Next:, Previous:General Actions, Up:Actions

Data Display Actions

These actions are used in the DDD graph editor.

end () Action
End the action initiated by select. Bound to a button up event.

extend () Action
Extend the current selection. Bound to a button down event.

extend-or-move () Action
Extend the current selection. Bound to a button down event. If the pointer is dragged, move the selection.

follow () Action
Continue the action initiated by select. Bound to a pointer motion event.

graph-select () Action
Equivalent to select, but also updates the current argument.

graph-select-or-move () Action
Equivalent to select-or-move, but also updates the current argument.

graph-extend () Action
Equivalent to extend, but also updates the current argument.

graph-extend-or-move () Action
Equivalent to extend-or-move, but also updates the current argument.

graph-toggle () Action
Equivalent to toggle, but also updates the current argument.

graph-toggle-or-move () Action
Equivalent to toggle-or-move, but also updates the current argument.

graph-popup-menu ([graph|node|shortcut]) Action
Pops up a menu. graph pops up a menu with global graph operations, node pops up a menu with node operations, and shortcut pops up a menu with display shortcuts.

If no argument is given, pops up a menu depending on the context: when pointing on a node with the <Shift> key pressed, behaves like shortcut; when pointing on a without the <Shift> key pressed, behaves like node; otherwise, behaves as if graph was given.

graph-dereference () Action
Dereference the selected display.

graph-detail () Action
Show or hide detail of the selected display.

graph-rotate () Action
Rotate the selected display.

graph-dependent () Action
Pop up a dialog to create a dependent display.

hide-edges ([any|both|from|to]) Action
Hide some edges. any means to process all edges where either source or target node are selected. both means to process all edges where both nodes are selected. from means to process all edges where at least the source node is selected. to means to process all edges where at least the target node is selected. Default is any.

layout ([regular|compact], [[+|-] degrees]) Action
Layout the graph. regular means to use the regular layout algorithm; compact uses an alternate layout algorithm, where successors are placed next to their parents. Default is regular. degrees indicates in which direction the graph should be layouted. Default is the current graph direction.

move-selected (x-offset, y-offset) Action
Move all selected nodes in the direction given by x-offset and y-offset. x-offset and y-offset is either given as a numeric pixel value, or as +grid, or -grid, meaning the current grid size.

normalize () Action
Place all nodes on their positions and redraw the graph.

rotate ([[+|-]degrees]) Action
Rotate the graph around degrees degrees. degrees must be a multiple of 90. Default is +90.

select () Action
Select the node pointed at. Clear all other selections. Bound to a button down event.

select-all () Action
Select all nodes in the graph.

select-first () Action
Select the first node in the graph.

select-next () Action
Select the next node in the graph.

select-or-move () Action
Select the node pointed at. Clear all other selections. Bound to a button down event. If the pointer is dragged, move the selected node.

select-prev () Action
Select the previous node in the graph.

show-edges ([any|both|from|to]) Action
Show some edges. any means to process all edges where either source or target node are selected. both means to process all edges where both nodes are selected. from means to process all edges where at least the source node is selected. to means to process all edges where at least the target node is selected. Default is any.

snap-to-grid () Action
Place all nodes on the nearest grid position.

toggle () Action
Toggle the current selection--if the node pointed at is selected, it will be unselected, and vice versa. Bound to a button down event.

toggle-or-move () Action
Toggle the current selection--if the node pointed at is selected, it will be unselected, and vice versa. Bound to a button down event. If the pointer is dragged, move the selection.

unselect-all () Action
Clear the selection.


Node:Debugger Console Actions, Next:, Previous:Data Display Actions, Up:Actions

Debugger Console Actions

These actions are used in the debugger console and other text fields.

gdb-backward-character () Action
Move one character to the left. Bound to Left.

gdb-beginning-of-line () Action
Move cursor to the beginning of the current line, after the prompt. Bound to HOME.

gdb-control (control-character) Action
Send the given control-character to the inferior debugger. control-character must be specified in the form ^X, where X is an upper-case letter, or ?.

gdb-command (command) Action
Execute command in the debugger console. The following replacements are performed on command:
  • If command has the form name..., insert name, followed by a space, in the debugger console.
  • All occurrences of () are replaced by the current contents of the argument field ().

gdb-complete-arg (command) Action
Complete current argument as if command was prepended. Bound to <Ctrl+T>.

gdb-complete-command () Action
Complete current command line in the debugger console. Bound to <TAB>.

gdb-complete-tab (command) Action
If global <TAB> completion is enabled, complete current argument as if command was prepended. Otherwise, proceed as if the <TAB> key was hit. Bound to <TAB>.

gdb-delete-or-control (control-character) Action
Like gdb-control, but effective only if the cursor is at the end of a line. Otherwise, control-character is ignored and the character following the cursor is deleted. Bound to <Ctrl+D>.

gdb-end-of-line () Action
Move cursor to the end of the current line. Bound to End.

gdb-forward-character () Action
Move one character to the right. Bound to Right.

gdb-insert-graph-arg () Action
Insert the contents of the data display argument field ().

gdb-insert-source-arg () Action
Insert the contents of the source argument field ().

gdb-interrupt () Action
If DDD is in incremental search mode, exit it; otherwise call gdb-control(^C).

gdb-isearch-prev () Action
Enter reverse incremental search mode. Bound to <Ctrl+B>.

gdb-isearch-next () Action
Enter incremental search mode. Bound to <Ctrl+F>.

gdb-isearch-exit () Action
Exit incremental search mode. Bound to <ESC>.

gdb-next-history () Action
Recall next command from history. Bound to Down.

gdb-prev-history () Action
Recall previous command from history. Bound to Up.

gdb-previous-history () Action
Recall previous command from history. Bound to Up.

gdb-process ([action [, args...]]) Action
Process the given event in the debugger console. Bound to key events in the source and data window. If this action is bound to the source window, and the source window is editable, perform action(args...) on the source window instead; if action is not given, perform self-insert().

gdb-select-all () Action
If the selectAllBindings resource is set to Motif, perform beginning-of-line. Otherwise, perform select-all. Bound to <Ctrl+A>.

gdb-set-line (value) Action
Set the current line to value. Bound to <Ctrl+U>.


Node:Source Window Actions, Previous:Debugger Console Actions, Up:Actions

Source Window Actions

These actions are used in the source and code windows.

source-delete-glyph () Action
Delete the breakpoint related to the glyph at cursor position.

source-double-click ([text-action [, line-action [, function-action]]]) Action
The double-click action in the source window.
  • If this action is taken on a breakpoint glyph, edit the breakpoint properties.
  • If this action is taken in the breakpoint area, invoke gdb-command(line-action). If line-action is not given, it defaults to break ().
  • If this action is taken in the source text, and the next character following the current selection is (, invoke gdb-command(function-action). If function-action is not given, it defaults to list ().
  • Otherwise, invoke gdb-command(text-action). If text-action is not given, it defaults to graph display ().

source-drag-glyph () Action
Initiate a drag on the glyph at cursor position.

source-drop-glyph ([action]) Action
Drop the dragged glyph at cursor position. action is either move, meaning to move the dragged glyph, or copy, meaning to copy the dragged glyph. If no action is given, move is assumed.

source-end-select-word () Action
End selecting a word.

source-follow-glyph () Action
Continue a drag on the glyph at cursor position. Usually bound to some motion event.

source-popup-menu () Action
Pop up a menu, depending on the location.

source-set-arg () Action
Set the argument field to the current selection. Typically bound to some selection operation.

source-start-select-word () Action
Start selecting a word.

source-update-glyphs () Action
Update all visible glyphs. Usually invoked after a scrolling operation.


Node:Images, Previous:Actions, Up:Application Defaults

Images

DDD installs a number of images that may be used as pixmap resources, simply by giving a symbolic name. For button images, three variants are installed as well:

break_at Image
Break at () button.

clear_at Image
Clear at () button.

ddd Image
DDD icon.

delete Image
Delete () button.

disable Image
Disable button.

dispref Image
Display * () button.

display Image
Display () button.

drag_arrow Image
The execution pointer (being dragged).

drag_cond Image
A conditional breakpoint (being dragged).

drag_stop Image
A breakpoint (being dragged).

drag_temp Image
A temporary breakpoint (being dragged).

enable Image
Enable button.

find_forward Image
Find>> () button.

find_backward Image
Find<< () button.

grey_arrow Image
The execution pointer (not in lowest frame).

grey_cond Image
A conditional breakpoint (disabled).

grey_stop Image
A breakpoint (disabled).

grey_temp Image
A temporary breakpoint (disabled).

hide Image
Hide () button.

lookup Image
Lookup () button.

maketemp Image
Make Temporary button.

new_break Image
New Breakpoint button.

new_display Image
New Display button.

new_watch Image
New Watchpoint button.

plain_arrow Image
The execution pointer.

plain_cond Image
A conditional breakpoint (enabled).

plain_stop Image
A breakpoint (enabled).

plain_temp Image
A temporary breakpoint (enabled).

print Image
Print () button.

properties Image
Properties button.

rotate Image
Rotate () button.

set Image
Set () button.

show Image
Show () button.

signal_arrow Image
The execution pointer (stopped by signal).

undisplay Image
Undisplay () button.

unwatch Image
Unwatch () button.

watch Image
Watch () button.


Node:Bugs, Next:, Previous:Application Defaults, Up:Top

Bugs and How To Report Them

Sometimes you will encounter a bug in DDD. Although we cannot promise we can or will fix the bug, and we might not even agree that it is a bug, we want to hear about bugs you encounter in case we do want to fix them.

To make it possible for us to fix a bug, you must report it. In order to do so effectively, you must know when and how to do it.


Node:Where to Send Bug Reports, Next:, Up:Bugs

Where to Send Bug Reports

Send bug reports for DDD via electronic mail to

     bug-ddd@gnu.org
     


Node:Is it a DDD Bug?, Next:, Previous:Where to Send Bug Reports, Up:Bugs

Is it a DDD Bug?

Before sending in a bug report, try to find out whether the problem cause really lies within DDD. A common cause of problems are incomplete or missing X or M*tif installations, for instance, or bugs in the X server or M*tif itself. Running DDD as

     $ ddd --check-configuration
     

checks for common problems and gives hints on how to repair them.

Another potential cause of problems is the inferior debugger; occasionally, they show bugs, too. To find out whether a bug was caused by the inferior debugger, run DDD as

     $ ddd --trace
     

This shows the interaction between DDD and the inferior debugger on standard error while DDD is running. (If --trace is not given, this interaction is logged in the file ~/.ddd/log; see Logging) Compare the debugger output to the output of DDD and determine which one is wrong.


Node:How to Report Bugs, Next:, Previous:Is it a DDD Bug?, Up:Bugs

How to Report Bugs

Here are some guidelines for bug reports:


Node:Bug Reports, Next:, Previous:How to Report Bugs, Up:Bugs

What to Include in a Bug Report

To enable us to fix a DDD bug, you must include the following information:

Be sure to include this information in every single bug report.


Node:Diagnostics, Previous:Bug Reports, Up:Bugs

Getting Diagnostics


Node:Logging, Next:, Up:Diagnostics

Logging

If things go wrong, the first and most important information source is the DDD log file. This file, created in ~/.ddd/log (~ stands for your home directory), records the following information:

This information, all in one place, should give you (and anyone maintaining DDD) a first insight of what's going wrong.


Node:Disabling Logging, Up:Logging
Disabling Logging

The log files created by DDD can become quite large, so you might want to turn off logging. There is no explicit DDD feature that allows you to do that. However, you can easily create a symbolic link from ~/.ddd/log to /dev/null, such that logging information is lost. Enter the following commands at the shell prompt:

     $ cd
     $ rm .ddd/log
     $ ln -s /dev/null .ddd/log
     $ _
     

Be aware, though, that having logging turned off makes diagnostics much more difficult; in case of trouble, it may be hard to reproduce the error.


Node:Debugging DDD, Next:, Previous:Logging, Up:Diagnostics

Debugging DDD

As long as DDD is compiled with -g (see Compiling for Debugging), you can invoke a debugger on DDD--even DDD itself, if you wish. From within DDD, a special Maintenance menu is provided that invokes GDB on the running DDD process. See Maintenance Menu, for details.

The DDD distribution comes with a .gdbinit file that is suitable for debugging DDD. Among others, this defines a ddd command that sets up an environment for debugging DDD and a string command that lets you print the contents of DDD string variables; just use print var followed by string.

You can cause DDD to dump core at any time by sending it a SIGUSR1 signal. DDD resumes execution while you can examine the core file with GDB.

When debugging DDD, it can be useful to make DDD not catch fatal errors. This can be achieved by setting the environment variable DDD_NO_SIGNAL_HANDLERS before invoking DDD.


Node:Customizing Diagnostics, Previous:Debugging DDD, Up:Diagnostics

Customizing Diagnostics

You can use these additional resources to obtain diagnostics about DDD. Most of them are tied to a particular invocation option.

appDefaultsVersion (class Version) Resource
The version of the DDD app-defaults file. If this string does not match the version of the current DDD executable, DDD issues a warning.

checkConfiguration (class CheckConfiguration) Resource
If on, check the DDD environment (in particular, the X configuration), report any possible problem causes and exit. See Options, for the --check-configuration option.

dddinitVersion (class Version) Resource
The version of the DDD executable that last wrote the ~/.ddd/init file. If this string does not match the version of the current DDD executable, DDD issues a warning.

debugCoreDumps (class DebugCoreDumps) Resource
If on, DDD invokes a debugger on itself when receiving a fatal signal. See Maintenance Menu, for setting this resource.

dumpCore (class DumpCore) Resource
If on (default), DDD dumps core when receiving a fatal signal. See Maintenance Menu, for setting this resource.

maintenance (class Maintenance) Resource
If on, enables the top-level Maintenance menu (see Maintenance Menu) with additional options. See Options, for the --maintenance option.

showConfiguration (class ShowConfiguration) Resource
If on, show the DDD configuration on standard output and exit. See Options, for the --configuration option.

showFonts (class ShowFonts) Resource
If on, show the DDD font definitions on standard output and exit. See Options, for the --fonts option.

showInvocation (class ShowInvocation) Resource
If on, show the DDD invocation options on standard output and exit. See Options, for the --help option.

showLicense (class ShowLicense) Resource
If on, show the DDD license on standard output and exit. See Options, for the --license option.

showManual (class ShowManual) Resource
If on, show this DDD manual page on standard output and exit. If the standard output is a terminal, the manual page is shown in a pager ($PAGER, less or more). See Options, for the --manual option.

showNews (class ShowNews) Resource
If on, show the DDD news on standard output and exit. See Options, for the --news option.

showVersion (class ShowVersion) Resource
If on, show the DDD version on standard output and exit. See Options, for the --version option.

suppressWarnings (class SuppressWarnings) Resource
If on, X warnings are suppressed. This is sometimes useful for executables that were built on a machine with a different X or M*tif configuration. By default, this is off. See X Warnings, for details.

trace (class Trace) Resource
If on, show the dialog between DDD and the inferior debugger on standard output. Default is off. See Options, for the --trace option.


Node:Configuration Notes, Next:, Previous:Bugs, Up:Top

Configuration Notes


Node:GDB, Next:, Up:Configuration Notes

Using DDD with GDB

Some GDB settings are essential for DDD to work correctly. These settings with their correct values are:

     set height 0
     set width 0
     set verbose off
     set annotate 1
     set prompt (gdb)
     

DDD sets these values automatically when invoking GDB; if these values are changed, there may be some malfunctions, especially in the data display.

When debugging at the machine level with GDB 4.12 and earlier as inferior debugger, use a display /x $pc command to ensure the program counter value is updated correctly at each stop. You may also enter the command in ~/.gdbinit or (better yet) upgrade to the most recent GDB version.


Node:WDB, Next:, Up:GDB

Using DDD with WDB

HP's WildeBeest (WDB) is essentially a variant of GDB. To start DDD with WDB as inferior debugger, use

     ddd --wdb program
     

See GDB, for further configuration notes.


Node:WindRiver GDB, Previous:WDB, Up:GDB

Using DDD with WindRiver GDB (Tornado)

DDD now supports WindRiver's version of GDB.34 DDD can be integrated into the Launch window by placing the launch.tcl script (see below) into the the directory ~/.wind.

Currently, DDD only supports the PowerPC and has been only tested on a Solaris 2.6 host.

DDD launches the version of GDB that is either in the current path, or the one specified on the command line using the --debugger command.

Normally, the Tornado environment is set up by sourcing a script file which, among other things, sets up the PATH variable.

It is suggested that a soft link for the version of GDB used for the target (i.e. gdbppc) be made in the same directory:

     bin>ls -l gdb*
     39 Mar  6 16:14 gdb -> /usr/wind/host/sun4-solaris2/bin/gdbppc*
     1619212 Mar 11  1997 gdbppc*
     bin>_
     

This way DDD will start the correct version of GDB automatically.

It is also suggested that you use DDD's execution window to facilitate parsing of GDB output. See Debugger Communication, for details.

Tornado reads the default TCL scripts first, then the ones in the users .wind directory. The following procedures can be cut and pasted into the user's launch.tcl file:

     # Launch.tcl - Launch application Tcl user customization file.
     #
     
     ######
     #
     # setupDDD - sets up DDD for use by the launcher
     #
     # This routine adds the DDD to the application bar
     #
     # SYNOPSIS:
     # setupDDD
     #
     # PARAMETERS: N/A
     #
     # RETURNS: N/A
     #
     # ERRORS: N/A
     #
     
     proc setupDDD {} {
         # Add to the default application bar
         objectCreate app ddd DDD {launchDDD}
     }
     
     ######
     #
     # launchDDD - launch the DDD debugger
     #
     # SYNOPSIS:
     # launchDDD
     #
     # PARAMETERS: N/A
     #
     # RETURNS: N/A
     #
     # ERRORS: N/A
     #
     
     proc launchDDD {} {
     
         global tgtsvr_selected
         global tgtsvr_cpuid
     
         if {$tgtsvr_selected == "" || $tgtsvr_cpuid == 0} {
             noticePost error "Select an attached target first."
             return
         }
     
         set startFileName /tmp/dddstartup.[pid]
     
         if [catch {open $startFileName w} file] {
              # couldn't create a startup file.  Oh, well.
              exec ddd --gdb &
         }
         else
         {
              # write out a little /tmp file that attaches to the
              # selected target server and then deletes itself.
              puts $file "set wtx-tool-name ddd"
              puts $file "target wtx $tgtsvr_selected"
              puts $file "tcl exec rm $startFileName"
              close $file
              exec ddd --gdb --command=$startFileName &
         }
     }
     
     ######
     #
     # Launch.tcl - Initialization
     #
     # The user's resource file sourced from the initial Launch.tcl
     #
     
     # Add DDD to the laucher
       setupDDD
     

In order for DDD to automatically display the source of a previously loaded file, the entry point must be named either vxworks_main or main_vxworks.

See GDB, for further configuration notes.


Node:DBX, Next:, Previous:GDB, Up:Configuration Notes

Using DDD with DBX

When used for debugging Pascal-like programs, DDD does not infer correct array subscripts and always starts to count with 1.

With some DBX versions (notably Solaris DBX), DDD strips C-style and C++-style comments from the DBX output in order to interpret it properly. This also affects the output of the debugged program when sent to the debugger console. Using the separate execution window avoids these problems.

In some DBX versions (notably DEC DBX and AIX DBX), there is no automatic data display. As an alternative, DDD uses the DBX print command to access data values. This means that variable names are interpreted according to the current frame; variables outside the current frame cannot be displayed.


Node:Ladebug, Next:, Previous:DBX, Up:Configuration Notes

Using DDD with Ladebug

All DBX limitations (see DBX) apply to Ladebug as well.


Node:XDB, Next:, Previous:Ladebug, Up:Configuration Notes

Using DDD with XDB

There is no automatic data display in XDB. As a workaround, DDD uses the p command to access data values. This means that variable names are interpreted according to the current frame; variables outside the current frame cannot be displayed.


Node:JDB, Next:, Previous:XDB, Up:Configuration Notes

Using DDD with JDB

There is no automatic data display in JDB. As a workaround, DDD uses the dump command to access data values. This means that variable names are interpreted according to the current frame; variables outside the current frame cannot be displayed.

In JDB 1.1, the dump and print commands do not support expression evaluation. Hence, you cannot display arbitrary expressions.

Parsing of JDB output is quite CPU-intensive, due to the recognition of asynchronous prompts (any thread may output anything at any time, including prompts). Hence, a program producing much console output is likely to slow down DDD considerably. In such a case, have the program run with -debug in a separate window and attach JDB to it using the -passwd option.


Node:Perl, Next:, Previous:JDB, Up:Configuration Notes

Using DDD with Perl

There is no automatic data display in Perl. As a workaround, DDD uses the x command to access data values. This means that variable names are interpreted according to the current frame; variables outside the current frame cannot be displayed.


Node:Bash, Next:, Previous:Perl, Up:Configuration Notes

Using DDD with Bash

BASH support is rather new. As a programming language, BASH is not feature rich: there are no record structures or hash tables (yet), no pointers, package variable scoping or methods. So much of the data display and visualization features of DDD are disabled.

As with any scripting or interpreted language like Perl, stepping a machine-language instructions (commands Stepi/Nexti) doesn't exist.

Some BASH settings are essential for DDD to work correctly. These settings with their correct values are:

     set annotate 1
     set prompt set prompt bashdb$_Dbg_less$_Dbg_greater$_Dbg_space
     

DDD sets these values automatically when invoking BASH; if these values are changed, there may be some malfunctions.

Pay special attention when the prompt has extra angle brackets (a nested shell) or has any parenthesis (is in a subshell). Quitting may merely exit out of one of these nested (sub)shells rather than leave the program.


Node:LessTif, Previous:Bash, Up:Configuration Notes

Using DDD with LessTif

DDD includes a number of hacks that make DDD run with LessTif, a free M*tif library without loss of functionality. Since a DDD binary may be dynamically bound and used with either an OSF/Motif or LessTif library, these lesstif hacks can be enabled and disabled at run time.

Whether the lesstif hacks are included at run-time depends on the setting of the lessTifVersion resource:

lessTifVersion (class LessTifVersion) Resource
Indicates the LessTif version DDD is running against. For LessTif version x.y, the value is x multiplied by 1000 plus y--for instance, the value 79 stands for LessTif 0.79 and the value 1005 stands for LessTif 1.5.

If the value of this resource is less than 1000, indicating LessTif 0.99 or earlier, DDD enables version-specific hacks to make DDD work around LessTif bugs and deficiencies.

If DDD was compiled against LessTif, the default value is the value of the LessTifVersion macro in <Xm/Xm.h>. If DDD was compiled against OSF/Motif, the default value is 1000, disabling all LessTif-specific hacks.

To set the lessTifVersion resource at DDD invocation and to specify the version number of the LessTif library, you can also use the option --lesstif-version version.

The default value of the lessTifVersion resource is derived from the LessTif library DDD was compiled against (or 1000 when compiled against OSF/Motif). Hence, you normally don't need to worry about the value of this resource. However, if you use a dynamically linked DDD binary with a library other than the one DDD was compiled against, you must specify the version number of the library using this resource. (Unfortunately, DDD cannot detect this at run-time.)

Here are a few scenarios to illustrate this scheme:

To find out the LessTif or OSF/Motif version DDD was compiled against, invoke DDD with the --configuration option.

In the DDD source, LessTif-specific hacks are controlled by the string lesstif_version.


Node:Dirty Tricks, Next:, Previous:Configuration Notes, Up:Top

Dirty Tricks

Do you miss anything in this manual? Do you have any material that should be added? Please send any contributions to ddd@gnu.org.


Node:Extending, Next:, Previous:Dirty Tricks, Up:Top

Extending DDD

If you have any contributions to be incorporated into DDD, please send them to ddd@gnu.org. For suggestions on what might be done, see the file TODO in the DDD distribution.


Node:FAQ, Next:, Previous:Extending, Up:Top

Frequently Answered Questions

See the DDD WWW page for frequently answered questions not covered in this manual.


Node:License, Next:, Previous:FAQ, Up:Top

GNU General Public License

Version 2, June 1991
     Copyright © 1989, 1991 Free Software Foundation, Inc.  675
     Mass Ave, Boston, MA 02111-1307, USA
     
     Everyone is permitted to copy and distribute verbatim copies
     of this license document, but changing it is not allowed.
     

Preamble

The licenses for most software are designed to take away your freedom to share and change it. By contrast, the GNU General Public License is intended to guarantee your freedom to share and change free software--to make sure the software is free for all its users. This General Public License applies to most of the Free Software Foundation's software and to any other program whose authors commit to using it. (Some other Free Software Foundation software is covered by the GNU Library General Public License instead.) You can apply it to your programs, too.

When we speak of free software, we are referring to freedom, not price. Our General Public Licenses are designed to make sure that you have the freedom to distribute copies of free software (and charge for this service if you wish), that you receive source code or can get it if you want it, that you can change the software or use pieces of it in new free programs; and that you know you can do these things.

To protect your rights, we need to make restrictions that forbid anyone to deny you these rights or to ask you to surrender the rights. These restrictions translate to certain responsibilities for you if you distribute copies of the software, or if you modify it.

For example, if you distribute copies of such a program, whether gratis or for a fee, you must give the recipients all the rights that you have. You must make sure that they, too, receive or can get the source code. And you must show them these terms so they know their rights.

We protect your rights with two steps: (1) copyright the software, and (2) offer you this license which gives you legal permission to copy, distribute and/or modify the software.

Also, for each author's protection and ours, we want to make certain that everyone understands that there is no warranty for this free software. If the software is modified by someone else and passed on, we want its recipients to know that what they have is not the original, so that any problems introduced by others will not reflect on the original authors' reputations.

Finally, any free program is threatened constantly by software patents. We wish to avoid the danger that redistributors of a free program will individually obtain patent licenses, in effect making the program proprietary. To prevent this, we have made it clear that any patent must be licensed for everyone's free use or not licensed at all.

The precise terms and conditions for copying, distribution and modification follow.

  1. This License applies to any program or other work which contains a notice placed by the copyright holder saying it may be distributed under the terms of this General Public License. The "Program", below, refers to any such program or work, and a "work based on the Program" means either the Program or any derivative work under copyright law: that is to say, a work containing the Program or a portion of it, either verbatim or with modifications and/or translated into another language. (Hereinafter, translation is included without limitation in the term "modification".) Each licensee is addressed as "you".

    Activities other than copying, distribution and modification are not covered by this License; they are outside its scope. The act of running the Program is not restricted, and the output from the Program is covered only if its contents constitute a work based on the Program (independent of having been made by running the Program). Whether that is true depends on what the Program does.

  2. You may copy and distribute verbatim copies of the Program's source code as you receive it, in any medium, provided that you conspicuously and appropriately publish on each copy an appropriate copyright notice and disclaimer of warranty; keep intact all the notices that refer to this License and to the absence of any warranty; and give any other recipients of the Program a copy of this License along with the Program.

    You may charge a fee for the physical act of transferring a copy, and you may at your option offer warranty protection in exchange for a fee.

  3. You may modify your copy or copies of the Program or any portion of it, thus forming a work based on the Program, and copy and distribute such modifications or work under the terms of Section 1 above, provided that you also meet all of these conditions:
    1. You must cause the modified files to carry prominent notices stating that you changed the files and the date of any change.
    2. You must cause any work that you distribute or publish, that in whole or in part contains or is derived from the Program or any part thereof, to be licensed as a whole at no charge to all third parties under the terms of this License.
    3. If the modified program normally reads commands interactively when run, you must cause it, when started running for such interactive use in the most ordinary way, to print or display an announcement including an appropriate copyright notice and a notice that there is no warranty (or else, saying that you provide a warranty) and that users may redistribute the program under these conditions, and telling the user how to view a copy of this License. (Exception: if the Program itself is interactive but does not normally print such an announcement, your work based on the Program is not required to print an announcement.)

    These requirements apply to the modified work as a whole. If identifiable sections of that work are not derived from the Program, and can be reasonably considered independent and separate works in themselves, then this License, and its terms, do not apply to those sections when you distribute them as separate works. But when you distribute the same sections as part of a whole which is a work based on the Program, the distribution of the whole must be on the terms of this License, whose permissions for other licensees extend to the entire whole, and thus to each and every part regardless of who wrote it.

    Thus, it is not the intent of this section to claim rights or contest your rights to work written entirely by you; rather, the intent is to exercise the right to control the distribution of derivative or collective works based on the Program.

    In addition, mere aggregation of another work not based on the Program with the Program (or with a work based on the Program) on a volume of a storage or distribution medium does not bring the other work under the scope of this License.

  4. You may copy and distribute the Program (or a work based on it, under Section 2) in object code or executable form under the terms of Sections 1 and 2 above provided that you also do one of the following:
    1. Accompany it with the complete corresponding machine-readable source code, which must be distributed under the terms of Sections 1 and 2 above on a medium customarily used for software interchange; or,
    2. Accompany it with a written offer, valid for at least three years, to give any third party, for a charge no more than your cost of physically performing source distribution, a complete machine-readable copy of the corresponding source code, to be distributed under the terms of Sections 1 and 2 above on a medium customarily used for software interchange; or,
    3. Accompany it with the information you received as to the offer to distribute corresponding source code. (This alternative is allowed only for noncommercial distribution and only if you received the program in object code or executable form with such an offer, in accord with Subsection b above.)

    The source code for a work means the preferred form of the work for making modifications to it. For an executable work, complete source code means all the source code for all modules it contains, plus any associated interface definition files, plus the scripts used to control compilation and installation of the executable. However, as a special exception, the source code distributed need not include anything that is normally distributed (in either source or binary form) with the major components (compiler, kernel, and so on) of the operating system on which the executable runs, unless that component itself accompanies the executable.

    If distribution of executable or object code is made by offering access to copy from a designated place, then offering equivalent access to copy the source code from the same place counts as distribution of the source code, even though third parties are not compelled to copy the source along with the object code.

  5. You may not copy, modify, sublicense, or distribute the Program except as expressly provided under this License. Any attempt otherwise to copy, modify, sublicense or distribute the Program is void, and will automatically terminate your rights under this License. However, parties who have received copies, or rights, from you under this License will not have their licenses terminated so long as such parties remain in full compliance.
  6. You are not required to accept this License, since you have not signed it. However, nothing else grants you permission to modify or distribute the Program or its derivative works. These actions are prohibited by law if you do not accept this License. Therefore, by modifying or distributing the Program (or any work based on the Program), you indicate your acceptance of this License to do so, and all its terms and conditions for copying, distributing or modifying the Program or works based on it.
  7. Each time you redistribute the Program (or any work based on the Program), the recipient automatically receives a license from the original licensor to copy, distribute or modify the Program subject to these terms and conditions. You may not impose any further restrictions on the recipients' exercise of the rights granted herein. You are not responsible for enforcing compliance by third parties to this License.
  8. If, as a consequence of a court judgment or allegation of patent infringement or for any other reason (not limited to patent issues), conditions are imposed on you (whether by court order, agreement or otherwise) that contradict the conditions of this License, they do not excuse you from the conditions of this License. If you cannot distribute so as to satisfy simultaneously your obligations under this License and any other pertinent obligations, then as a consequence you may not distribute the Program at all. For example, if a patent license would not permit royalty-free redistribution of the Program by all those who receive copies directly or indirectly through you, then the only way you could satisfy both it and this License would be to refrain entirely from distribution of the Program.

    If any portion of this section is held invalid or unenforceable under any particular circumstance, the balance of the section is intended to apply and the section as a whole is intended to apply in other circumstances.

    It is not the purpose of this section to induce you to infringe any patents or other property right claims or to contest validity of any such claims; this section has the sole purpose of protecting the integrity of the free software distribution system, which is implemented by public license practices. Many people have made generous contributions to the wide range of software distributed through that system in reliance on consistent application of that system; it is up to the author/donor to decide if he or she is willing to distribute software through any other system and a licensee cannot impose that choice.

    This section is intended to make thoroughly clear what is believed to be a consequence of the rest of this License.

  9. If the distribution and/or use of the Program is restricted in certain countries either by patents or by copyrighted interfaces, the original copyright holder who places the Program under this License may add an explicit geographical distribution limitation excluding those countries, so that distribution is permitted only in or among countries not thus excluded. In such case, this License incorporates the limitation as if written in the body of this License.
  10. The Free Software Foundation may publish revised and/or new versions of the General Public License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns.

    Each version is given a distinguishing version number. If the Program specifies a version number of this License which applies to it and "any later version", you have the option of following the terms and conditions either of that version or of any later version published by the Free Software Foundation. If the Program does not specify a version number of this License, you may choose any version ever published by the Free Software Foundation.

  11. If you wish to incorporate parts of the Program into other free programs whose distribution conditions are different, write to the author to ask for permission. For software which is copyrighted by the Free Software Foundation, write to the Free Software Foundation; we sometimes make exceptions for this. Our decision will be guided by the two goals of preserving the free status of all derivatives of our free software and of promoting the sharing and reuse of software generally.
  12. BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION.
  13. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.

How to Apply These Terms to Your New Programs

If you develop a new program, and you want it to be of the greatest possible use to the public, the best way to achieve this is to make it free software which everyone can redistribute and change under these terms.

To do so, attach the following notices to the program. It is safest to attach them to the start of each source file to most effectively convey the exclusion of warranty; and each file should have at least the "copyright" line and a pointer to where the full notice is found.

     one line to give the program's name and an idea of what it does.
     Copyright (C) 19yy  name of author
     
     This program is free software; you can redistribute it and/or
     modify it under the terms of the GNU General Public License
     as published by the Free Software Foundation; either version 2
     of the License, or (at your option) any later version.
     
     This program is distributed in the hope that it will be useful,
     but WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
     GNU General Public License for more details.
     
     You should have received a copy of the GNU General Public License
     along with this program; if not, write to the Free Software
     Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
     

Also add information on how to contact you by electronic and paper mail.

If the program is interactive, make it output a short notice like this when it starts in an interactive mode:

     Gnomovision version 69, Copyright (C) 19yy name of author
     Gnomovision comes with ABSOLUTELY NO WARRANTY; for details
     type `show w'.  This is free software, and you are welcome
     to redistribute it under certain conditions; type `show c'
     for details.
     

The hypothetical commands show w and show c should show the appropriate parts of the General Public License. Of course, the commands you use may be called something other than show w and show c; they could even be mouse-clicks or menu items--whatever suits your program.

You should also get your employer (if you work as a programmer) or your school, if any, to sign a "copyright disclaimer" for the program, if necessary. Here is a sample; alter the names:

     Yoyodyne, Inc., hereby disclaims all copyright
     interest in the program `Gnomovision'
     (which makes passes at compilers) written
     by James Hacker.
     
     signature of Ty Coon, 1 April 1989
     Ty Coon, President of Vice
     

This General Public License does not permit incorporating your program into proprietary programs. If your program is a subroutine library, you may consider it more useful to permit linking proprietary applications with the library. If this is what you want to do, use the GNU Library General Public License instead of this License.


Node:Help and Assistance, Next:, Previous:License, Up:Top

Help and Assistance

We have set up a mailing list for general DDD discussions. If you need help and assistance for solving a DDD problem, you find the right people here.

Send message to all receivers of the mailing list to:

     ddd@gnu.org
     

This mailing list is also the place where new DDD releases are announced. If you want to subscribe the list, or get more information, send a mail to

     ddd-request@gnu.org
     

See also the DDD WWW page for recent announcements and other news related to DDD.


Node:Documentation License, Next:, Previous:Help and Assistance, Up:Top

GNU Free Documentation License

Version 1.1, March 2000
     Copyright (C) 2000  Free Software Foundation, Inc.
     59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
     
     Everyone is permitted to copy and distribute verbatim copies
     of this license document, but changing it is not allowed.
     

  1. PREAMBLE

    The purpose of this License is to make a manual, textbook, or other written document "free" in the sense of freedom: to assure everyone the effective freedom to copy and redistribute it, with or without modifying it, either commercially or noncommercially. Secondarily, this License preserves for the author and publisher a way to get credit for their work, while not being considered responsible for modifications made by others.

    This License is a kind of "copyleft", which means that derivative works of the document must themselves be free in the same sense. It complements the GNU General Public License, which is a copyleft license designed for free software.

    We have designed this License in order to use it for manuals for free software, because free software needs free documentation: a free program should come with manuals providing the same freedoms that the software does. But this License is not limited to software manuals; it can be used for any textual work, regardless of subject matter or whether it is published as a printed book. We recommend this License principally for works whose purpose is instruction or reference.

  2. APPLICABILITY AND DEFINITIONS

    This License applies to any manual or other work that contains a notice placed by the copyright holder saying it can be distributed under the terms of this License. The "Document", below, refers to any such manual or work. Any member of the public is a licensee, and is addressed as "you".

    A "Modified Version" of the Document means any work containing the Document or a portion of it, either copied verbatim, or with modifications and/or translated into another language.

    A "Secondary Section" is a named appendix or a front-matter section of the Document that deals exclusively with the relationship of the publishers or authors of the Document to the Document's overall subject (or to related matters) and contains nothing that could fall directly within that overall subject. (For example, if the Document is in part a textbook of mathematics, a Secondary Section may not explain any mathematics.) The relationship could be a matter of historical connection with the subject or with related matters, or of legal, commercial, philosophical, ethical or political position regarding them.

    The "Invariant Sections" are certain Secondary Sections whose titles are designated, as being those of Invariant Sections, in the notice that says that the Document is released under this License.

    The "Cover Texts" are certain short passages of text that are listed, as Front-Cover Texts or Back-Cover Texts, in the notice that says that the Document is released under this License.

    A "Transparent" copy of the Document means a machine-readable copy, represented in a format whose specification is available to the general public, whose contents can be viewed and edited directly and straightforwardly with generic text editors or (for images composed of pixels) generic paint programs or (for drawings) some widely available drawing editor, and that is suitable for input to text formatters or for automatic translation to a variety of formats suitable for input to text formatters. A copy made in an otherwise Transparent file format whose markup has been designed to thwart or discourage subsequent modification by readers is not Transparent. A copy that is not "Transparent" is called "Opaque".

    Examples of suitable formats for Transparent copies include plain ASCII without markup, Texinfo input format, LaTeX input format, SGML or XML using a publicly available DTD, and standard-conforming simple HTML designed for human modification. Opaque formats include PostScript, PDF, proprietary formats that can be read and edited only by proprietary word processors, SGML or XML for which the DTD and/or processing tools are not generally available, and the machine-generated HTML produced by some word processors for output purposes only.

    The "Title Page" means, for a printed book, the title page itself, plus such following pages as are needed to hold, legibly, the material this License requires to appear in the title page. For works in formats which do not have any title page as such, "Title Page" means the text near the most prominent appearance of the work's title, preceding the beginning of the body of the text.

  3. VERBATIM COPYING

    You may copy and distribute the Document in any medium, either commercially or noncommercially, provided that this License, the copyright notices, and the license notice saying this License applies to the Document are reproduced in all copies, and that you add no other conditions whatsoever to those of this License. You may not use technical measures to obstruct or control the reading or further copying of the copies you make or distribute. However, you may accept compensation in exchange for copies. If you distribute a large enough number of copies you must also follow the conditions in section 3.

    You may also lend copies, under the same conditions stated above, and you may publicly display copies.

  4. COPYING IN QUANTITY

    If you publish printed copies of the Document numbering more than 100, and the Document's license notice requires Cover Texts, you must enclose the copies in covers that carry, clearly and legibly, all these Cover Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on the back cover. Both covers must also clearly and legibly identify you as the publisher of these copies. The front cover must present the full title with all words of the title equally prominent and visible. You may add other material on the covers in addition. Copying with changes limited to the covers, as long as they preserve the title of the Document and satisfy these conditions, can be treated as verbatim copying in other respects.

    If the required texts for either cover are too voluminous to fit legibly, you should put the first ones listed (as many as fit reasonably) on the actual cover, and continue the rest onto adjacent pages.

    If you publish or distribute Opaque copies of the Document numbering more than 100, you must either include a machine-readable Transparent copy along with each Opaque copy, or state in or with each Opaque copy a publicly-accessible computer-network location containing a complete Transparent copy of the Document, free of added material, which the general network-using public has access to download anonymously at no charge using public-standard network protocols. If you use the latter option, you must take reasonably prudent steps, when you begin distribution of Opaque copies in quantity, to ensure that this Transparent copy will remain thus accessible at the stated location until at least one year after the last time you distribute an Opaque copy (directly or through your agents or retailers) of that edition to the public.

    It is requested, but not required, that you contact the authors of the Document well before redistributing any large number of copies, to give them a chance to provide you with an updated version of the Document.

  5. MODIFICATIONS

    You may copy and distribute a Modified Version of the Document under the conditions of sections 2 and 3 above, provided that you release the Modified Version under precisely this License, with the Modified Version filling the role of the Document, thus licensing distribution and modification of the Modified Version to whoever possesses a copy of it. In addition, you must do these things in the Modified Version:

    A. Use in the Title Page (and on the covers, if any) a title distinct from that of the Document, and from those of previous versions (which should, if there were any, be listed in the History section of the Document). You may use the same title as a previous version if the original publisher of that version gives permission.
    B. List on the Title Page, as authors, one or more persons or entities responsible for authorship of the modifications in the Modified Version, together with at least five of the principal authors of the Document (all of its principal authors, if it has less than five).
    C. State on the Title page the name of the publisher of the Modified Version, as the publisher.
    D. Preserve all the copyright notices of the Document.
    E. Add an appropriate copyright notice for your modifications adjacent to the other copyright notices.
    F. Include, immediately after the copyright notices, a license notice giving the public permission to use the Modified Version under the terms of this License, in the form shown in the Addendum below.
    G. Preserve in that license notice the full lists of Invariant Sections and required Cover Texts given in the Document's license notice.
    H. Include an unaltered copy of this License.
    I. Preserve the section entitled "History", and its title, and add to it an item stating at least the title, year, new authors, and publisher of the Modified Version as given on the Title Page. If there is no section entitled "History" in the Document, create one stating the title, year, authors, and publisher of the Document as given on its Title Page, then add an item describing the Modified Version as stated in the previous sentence.
    J. Preserve the network location, if any, given in the Document for public access to a Transparent copy of the Document, and likewise the network locations given in the Document for previous versions it was based on. These may be placed in the "History" section. You may omit a network location for a work that was published at least four years before the Document itself, or if the original publisher of the version it refers to gives permission.
    K. In any section entitled "Acknowledgements" or "Dedications", preserve the section's title, and preserve in the section all the substance and tone of each of the contributor acknowledgements and/or dedications given therein.
    L. Preserve all the Invariant Sections of the Document, unaltered in their text and in their titles. Section numbers or the equivalent are not considered part of the section titles.
    M. Delete any section entitled "Endorsements". Such a section may not be included in the Modified Version.
    N. Do not retitle any existing section as "Endorsements" or to conflict in title with any Invariant Section.

    If the Modified Version includes new front-matter sections or appendices that qualify as Secondary Sections and contain no material copied from the Document, you may at your option designate some or all of these sections as invariant. To do this, add their titles to the list of Invariant Sections in the Modified Version's license notice. These titles must be distinct from any other section titles.

    You may add a section entitled "Endorsements", provided it contains nothing but endorsements of your Modified Version by various parties-for example, statements of peer review or that the text has been approved by an organization as the authoritative definition of a standard.

    You may add a passage of up to five words as a Front-Cover Text, and a passage of up to 25 words as a Back-Cover Text, to the end of the list of Cover Texts in the Modified Version. Only one passage of Front-Cover Text and one of Back-Cover Text may be added by (or through arrangements made by) any one entity. If the Document already includes a cover text for the same cover, previously added by you or by arrangement made by the same entity you are acting on behalf of, you may not add another; but you may replace the old one, on explicit permission from the previous publisher that added the old one.

    The author(s) and publisher(s) of the Document do not by this License give permission to use their names for publicity for or to assert or imply endorsement of any Modified Version.

  6. COMBINING DOCUMENTS

    You may combine the Document with other documents released under this License, under the terms defined in section 4 above for modified versions, provided that you include in the combination all of the Invariant Sections of all of the original documents, unmodified, and list them all as Invariant Sections of your combined work in its license notice.

    The combined work need only contain one copy of this License, and multiple identical Invariant Sections may be replaced with a single copy. If there are multiple Invariant Sections with the same name but different contents, make the title of each such section unique by adding at the end of it, in parentheses, the name of the original author or publisher of that section if known, or else a unique number. Make the same adjustment to the section titles in the list of Invariant Sections in the license notice of the combined work.

    In the combination, you must combine any sections entitled "History" in the various original documents, forming one section entitled "History"; likewise combine any sections entitled "Acknowledgements", and any sections entitled "Dedications". You must delete all sections entitled "Endorsements."

  7. COLLECTIONS OF DOCUMENTS

    You may make a collection consisting of the Document and other documents released under this License, and replace the individual copies of this License in the various documents with a single copy that is included in the collection, provided that you follow the rules of this License for verbatim copying of each of the documents in all other respects.

    You may extract a single document from such a collection, and distribute it individually under this License, provided you insert a copy of this License into the extracted document, and follow this License in all other respects regarding verbatim copying of that document.

  8. AGGREGATION WITH INDEPENDENT WORKS

    A compilation of the Document or its derivatives with other separate and independent documents or works, in or on a volume of a storage or distribution medium, does not as a whole count as a Modified Version of the Document, provided no compilation copyright is claimed for the compilation. Such a compilation is called an "aggregate", and this License does not apply to the other self-contained works thus compiled with the Document, on account of their being thus compiled, if they are not themselves derivative works of the Document.

    If the Cover Text requirement of section 3 is applicable to these copies of the Document, then if the Document is less than one quarter of the entire aggregate, the Document's Cover Texts may be placed on covers that surround only the Document within the aggregate. Otherwise they must appear on covers around the whole aggregate.

  9. TRANSLATION

    Translation is considered a kind of modification, so you may distribute translations of the Document under the terms of section 4. Replacing Invariant Sections with translations requires special permission from their copyright holders, but you may include translations of some or all Invariant Sections in addition to the original versions of these Invariant Sections. You may include a translation of this License provided that you also include the original English version of this License. In case of a disagreement between the translation and the original English version of this License, the original English version will prevail.

  10. TERMINATION

    You may not copy, modify, sublicense, or distribute the Document except as expressly provided for under this License. Any other attempt to copy, modify, sublicense or distribute the Document is void, and will automatically terminate your rights under this License. However, parties who have received copies, or rights, from you under this License will not have their licenses terminated so long as such parties remain in full compliance.

  11. FUTURE REVISIONS OF THIS LICENSE

    The Free Software Foundation may publish new, revised versions of the GNU Free Documentation License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns. See http://www.gnu.org/copyleft/.

    Each version of the License is given a distinguishing version number. If the Document specifies that a particular numbered version of this License "or any later version" applies to it, you have the option of following the terms and conditions either of that specified version or of any later version that has been published (not as a draft) by the Free Software Foundation. If the Document does not specify a version number of this License, you may choose any version ever published (not as a draft) by the Free Software Foundation.

ADDENDUM: How to use this License for your documents

To use this License in a document you have written, include a copy of the License in the document and put the following copyright and license notices just after the title page:

     
       Copyright (C)  year  your name.
       Permission is granted to copy, distribute and/or modify this document
       under the terms of the GNU Free Documentation License, Version 1.1
       or any later version published by the Free Software Foundation;
       with the Invariant Sections being list their titles, with the
       Front-Cover Texts being list, and with the Back-Cover Texts being list.
       A copy of the license is included in the section entitled ``GNU
       Free Documentation License''.
     
If you have no Invariant Sections, write "with no Invariant Sections" instead of saying which ones are invariant. If you have no Front-Cover Texts, write "no Front-Cover Texts" instead of "Front-Cover Texts being list"; likewise for Back-Cover Texts.

If your document contains nontrivial examples of program code, we recommend releasing these examples in parallel under your choice of free software license, such as the GNU General Public License, to permit their use in free software.


Node:Label Index, Next:, Previous:Documentation License, Up:Top

Label Index


Node:Key Index, Next:, Previous:Label Index, Up:Top

Key Index


Node:Command Index, Next:, Previous:Key Index, Up:Top

Command Index


Node:Resource Index, Next:, Previous:Command Index, Up:Top

Resource Index


Node:File Index, Next:, Previous:Resource Index, Up:Top

File Index


Node:Concept Index, Previous:File Index, Up:Top

Concept Index


Footnotes

  1. Within DDD (and this manual), Ladebug is considered a DBX variant. Hence, everything said for DBX also applies to Ladebug, unless stated otherwise.

  2. XDB will no longer be maintained in future DDD releases. Use a recent GDB version instead.

  3. Actual numbers and behavior on your system may vary.

  4. Re-invoke DDD with --gdb, if you do not see a (gdb) prompt here (see Choosing an Inferior Debugger)

  5. Only if a core file is included.

  6. If a core file is not to be included in the session, DDD data displays are saved as deferred; that is, they will be restored as soon as program execution reaches the scope in which they were created. See Creating Single Displays, for details.

  7. Requires X11R6 or later.

  8. If you use a Ddd application-defaults file, you will not be able to maintain multiple DDD versions at the same time. This is why the suiting Ddd is normally compiled into the DDD executable.

  9. If you use DDD to debug Perl, Python or Bash scripts, then this section does not apply.

  10. With XDB and some DBX variants, the debugged program must be specified upon invocation and cannot be changed at run time.

  11. JDB, PYDB, Perl, and Bash do not support core dumps.

  12. JDB does not support breakpoint disabling.

  13. JDB does not support temporary breakpoints.

  14. GDB has no way to make a temporary breakpoint non-temporary again.

  15. JDB, Perl and some DBX variants do not support breakpoint ignore counts.

  16. JDB, PYDB, and some DBX variants do not support breakpoint commands.

  17. When glyphs are disabled (see Customizing Source), breakpoints cannot be dragged. Delete and set breakpoints instead.

  18. Watchpoints are available in GDB and some DBX variants only. In XDB, a similar feature is available via XDB assertions; see the XDB documentation for details.

  19. If <Ctrl+C> is not bound to Copy (see Customizing the Edit Menu), you can also use <Ctrl+C> to interrupt the running program.

  20. If the debuggee runs in a separate execution window, the debuggee's TERM value is set according to the termType resource; See Customizing the Execution Window, for details.

  21. The execution window is not available in JDB.

  22. JDB, PYDB, Perl, and Bash do not support attaching the debugger to running processes.

  23. JDB, PYDB, Perl, and Bash do not support altering the execution position.

  24. When glyphs are disabled (see Customizing Source), dragging the execution position is not possible. Set the execution position explicitly instead.

  25. Perl does not allow changing the current stack frame.

  26. Currently, threads are supported in GDB and JDB only.

  27. This requires that the full array size is known to the debugger.

  28. JDB 1.1 does not support changing variable values.

  29. The string //; can be changed via the labelDelimiter resource. See Customizing Buttons, for details.

  30. The machine code window is available with GDB and some DBX variants only.

  31. The machine code window is available with GDB and some DBX variants only.

  32. If you use DDD commands within command definitions, or if you include debugger commands that resume execution, these commands will be realized transparently as auto-commands--that is, they won't be executed directly by the inferior debugger, but result in a command string being sent to DDD. This command string is then interpreted by DDD and sent back to the inferior debugger, possibly prefixed by some other commands such that DDD can update its state. See Commands with Other Debuggers, for a discussion.

  33. Since the inferior debugger is invoked through a virtual TTY, standard error is normally redirected to standard output, so DDD never receives standard error from the inferior debugger.

  34. This section was contributed by Gary Cliff from Computing Devices Canada Ltd., gary.cliff@cdott.com.