IBM extension

The #warning directive

A preprocessor warning directive causes the preprocessor to generate a warning message but allows compilation to continue. The argument to #warning is not subject to macro expansion.

Read syntax diagramSkip visual syntax diagram#warning directive syntax
 
               .--------------------.
               V                    |
>>-#--warning----preprocessor_token-+--------------------------><
 

The preprocessor #warning directive is a language extension provided to facilitate handling programs developed with GNU C. The IBM implementation preserves multiple white spaces.

End of IBM extension