AC_FC_DUMMY_MAIN broken with gcc4/gfortran

[Bill Northcott]

Following my last post I have done some digging on AC_FC_DUMMY_MAIN.

The current version of this macro uses a test program like:

#define F77_DUMMY_MAIN some_candidate_for_dummy_main
#ifdef F77_DUMMY_MAIN

#  ifdef __cplusplus
     extern "C"
#  endif
   int F77_DUMMY_MAIN() { return 1; }

#endif
int
main ()
{

  ;
  return 0;
}

Using gcc4 and gfortran FLIBS include '-lgfortranbegin -lgfortran'.   
libgfortranbegin defines _main and needs _MAIN__

Since the test program also defines _main it will never link because  
of the multiply defined symbol!  So the test for a dummy main will  
never succeed.

If I use a test program like this (just change the main function from  
'main' to 'foo'), the test structure correctly identifies dummy main  
on my system (Darwin 8.7 ppc or i386 with gcc4.0.3/gfortran) as 'MAIN__'

#define F77_DUMMY_MAIN some_candidate_for_dummy_main
#ifdef F77_DUMMY_MAIN

#  ifdef __cplusplus
     extern "C"
#  endif
   int F77_DUMMY_MAIN() { return 1; }

#endif
int
foo ()
{

  ;
  return 0;
}

Again, I do not understand how such a change might play on other  
systems.

Cheers
Bill Northcott