undefined reference to `MAIN__'

[Kai Ruottu]

chao sun wrote:

> Dear friends
> I compiled the Prep_sources_chem_cptec_wrf with the gfortran 4.4.0 and
> encountered some error.
> 
> After I seted up the Fortran/C compilers and conducted ‘make’ the
> error message as follows came out::
> 
> gfortran -o prep_chem_sources  \
>     prep_chem_sources.a ..//utils/bin/libutils-2.0-opt.a
> -I/usr/local/include -L/usr/local/lib -lnetcdf

This command line doesn't seem to have any "main Fortran program" as
a source ('.f'?) or an object ('.o') file, the 'prep_chem_sources.a'
must be an archive (for self-made objects required in the application),
the '.a' usually means a library (archive)... So it contains only
'programs' (routines/functions) which the old Fortran language marked
as 'SUBROUTINE's. The main Fortran program didn't have this row in its 
beginning.

Maybe Chao Sun has no clue about the structure of a Fortran program? :)
I too had to dig the 1982 "FORTRAN Programs for Scientists and
Engineers" (for 8-bit Z80 with CP/M and MS Fortran-80) book from my
bookshelf in order to refresh my memory :(

> /usr/lib/gcc/i586-redhat-linux/4.4.0/libgfortranbegin.a(fmain.o): In
> function `main':
> (.text+0x27): undefined reference to `MAIN__'
> collect2: ld returned 1 exit status
> make: *** [prep_chem_sources] Error 1

The function 'main()' in the 'libgfortran.a' calls this 'main Fortran
program' (Please see: 'libgfortran/fmain.c') :

----------------- clip -------------------
/* The main Fortran program actually is a function, called MAIN__.
    We call it from the main() function in this file.  */
void MAIN__ (void);

/* Main procedure for fortran programs.  All we do is set up the environment
    for the Fortran program.  */
int
main (int argc, char *argv[])
{
   /* Store the path of the executable file.  */
   store_exe_path (argv[0]);

   /* Set up the runtime environment.  */
   set_args (argc, argv);


   /* Call the Fortran main program.  Internally this is a function
      called MAIN__ */
   MAIN__ ();

   /* Bye-bye!  */
   return 0;
}
----------------- clip -------------------

So the executable should start at the C function 'main()' in the
'libgfortran.a', then call 'MAIN__()' (in the user-made main Fortran
program) and finally return. Nothing unexpected...

> I seted up the gfortran as follows:
> F_COMP=gfortran
> C_COMP=gcc
> LOADER=gfortran
> C_LOADER=gcc
> LIBS=-L/usr/local/lib -L/usr/lib -L/usr/lib/gcc/i586-redhat-linux/3.4.6
> MOD_EXT=mod
> # Compiler options
> F_OPTS=-fconvert=big-endian -ffree-form $(NCDF_LIBS) -g
> C_OPTS=-O2  -DMAIN__=main_

Why this definition for 'MAIN__' as 'main_() ? Does the
'prep_chem_sources.a' include the function 'main_()'?  What is the logic
with this?

This definition maybe should be used when producing the
'libgfortran.a', then the 'main()' there would call 'main_()',
not 'MAIN__()'...