c++ - Portability of #warning preprocessor directive

Question

I know that the #warning directive is not standard C/C++, but several compilers support it, including gcc/g++. But for those that don't support it, will they silently ignore it or will it result in a compile failure? In other words, can I safely use it in my project without breaking the build for compilers that don't support it?

Answer 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.