[CMake] Problem with Fortran module enclosed in #ifdef

[Arjen Markus]

>>
> You are right, that this is uncommon. But I'm trying to replace an
> existing "build system" for some thousands of files, which preprocesses
> all Fortran files, even those with ".f" suffix. Unfortunately this is
> something I can't change.
> I could use the approach you suggest, but I'd like a more general
> solution, because I cannot be sure, that this is the only file, where
> preprocessing makes a difference. There might
> be other files containing a USE directive enclosed in ifdefs.
>

Most compilers seem to have a switch to turn preprocessing on,
no matter what the extension is. While that is not very portable
(but then, .F is not either!), it will get you going.

Regards,

Arjen