Preprocessor Macro not working on Windows in Fortr

Question

Dear All I have a small Fortran program containing preprocessor macro. Below is a minimal example. On mac os x, it works well but when I compile it on windows 7 (64-bit) it always prints unknown operating system. I am using gfortran-4.8.0 (mingw32) on windows 7.

      program foo
      implicit integer(i-n), double precision (a-h,o-p),
     + character*8(x-z)
*
#ifdef _WIN64
      zterm = 'wxt'
#elif _WIN32
      zterm = 'wxt'
#elif __APPLE__
      zterm = 'aqua'
#elif __linux
      zterm = 'x11'
#elif __unix
      zterm = 'x11'
#elif __posix
      zterm = 'x11'
#else
      print*, 'unknown operating system'
#endif
      end program foo

Changing #ifdef _WIN64 to #if defined (_WIN64) did not help. Any suggestion will be appreciated.

Answer 1

This might be GFortran PR 42954. Since GFortran started using libcpp instead of running cpp in a separate process, many of these built-in macros are missing.

As a workaround, you can as part of your build process generate a file with these builtin macro definitions which you can then include. E.g. have a make target which runs

gcc -E -dM - < /dev/null > builtins.inc

Then your sources should depend on builtins.inc in the Makefile, and in the beginning of your source files you

#include "builtins.inc"