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From: "Steven G. Kargl" <sgk@REMOVEtroutmask.apl.washington.edu>
Newsgroups: comp.lang.fortran
Subject: Re: how do you send a fortran character string from GCC to GFortran ?
Date: Thu, 2 Jan 2025 18:40:54 -0000 (UTC)
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On Thu, 02 Jan 2025 02:27:54 -0600, Lynn McGuire wrote:

> How do you send a fortran character string from GCC to GFortran ?
> 
> I cannot get this to link.  I can do the reverse, send a fortran 
> character string from Gfortran to GCC.
> 
> I do have the additional complication that I do not know the length of 
> the fortran character string being sent from GCC to Gfortran at compile 
> time, only run time.  So that is a character*(*) string.
> 
> I am not using the ISO C binding.

As Thomas as indicated, ISO C binding was introduced into the
Fortran standard to address your needs.  But, if you want to
go old school with gcc/gfortran, then 

% cat aa.c
#include <string.h>

void
string_(char *s, int *slen)
{
   strncpy(s, "abc", *slen);
}

% cat bb.f90
program foo
   external :: string
   character(len=10) str
   call string(str, len(str))
   print *, '>>' // str //'<<'
end program foo

% ~/work/bin/gcc -c aa.c
% gfcx -o z bb.f90 aa.o
% ./z
 >>abc<<

-- 
steve