Portability of #warning preprocessor directive
Solution 1:
It should be noted that MSVC uses the syntax:
#pragma message ( "your warning text here" )
The usual #warning syntax generates a fatal error
C1021: invalid preprocessor command 'warning'
so it is not portable to those compilers.
Solution 2:
It is likely that if a compiler doesn't support #warning, then it will issue an error. Unlike #pragma, there is no recommendation that the preprocessor ignore directives it doesn't understand.
Having said that, I've used compilers on various different (reasonably common) platforms and they have all supported #warning.