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Given Microsoft FORTRAN 5.1 and Microsoft C/C++ 14.0, along with the linker that comes with that version of FORTRAN (that must be used for other dependencies) how do I create a C function and call it from the FORTRAN application?

LittleBobbyTables - Au Revoir
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rck
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2 Answers2

1

You have two choices.
1) I can show with example

FORTRAN

program ftest
use iso_c_bindings
implicit none
interface
function saythis(a) ! should be subroutine if saythis returns void
import :: c_ptr
type(c_ptr), value :: a
end function saythis
end interface

character(len=80), target :: str
type(c_ptr) cstr
integer :: r

str='Hello World From Fortran' // C_NULL_CHAR
cstr=c_loc(str(1:1))
r=saythis(cstr)

C/C++

#ifdef __cpluscplus
#include &ltl;cstdio>
using namespace std;
#else
#inlcude <stdio.h>
#endif

#ifdef __GNUC__
#define FORT(func) func ## _
#else
#define FORT(func) __stdcall func ## _
#endif

#ifdef __cpluscplus
extern "C" {
#endif
__declspec(dllexport) int FORT(sayit)(char* c)
{
return printf("%s\n",c);
}

#ifdef __cpluscplus
}
#endif

This works w/gcc toolchain. You'll have to dumpbin on the DLL and fortran object code to see if the names match up correctly.
The other way is similar:

//This is for gcc toolchain
//you'll have to find the symbol conversion yourself
//I think that Visual Studio converts fortran names
//to ALL CAPS so instead of func => _func you'll need func => FUNC

FORTRAN

program ftest
integer aa,bb,cc
common/vari/aa,bb,cc

aa=7
bb=11
cc=0
call dosomething
call dosomethingelse(aa,bb,cc)

C/C++

#ifdef __cplusplus
extern "C" {
#endif
int _dosomething();
int _dosomethingelse(int*,int*,int*); //all fortran is pass by reference
struct { int aa,bb,cc; } vari;
#ifdef __cplusplus
}
#endif

//function def's go here
//struct vari should be the same memory as common/vari block

COMPILE COMMAND

$>g++ -c ctest.c <br/>
$>gfortran -c ftest.f90 <br/>
$>gfortran *.o -lstdc++ -o test_prog <br/>

Hope this helps

KitsuneYMG
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  • This code would never compile in MS Powerstation. At least it shows the good direction, but that old compiler newer knew Fortran (not FORTRAN) 2003. Modern compilers that do know Fortran 2003 will complain that the name of the module is actually `iso_c_binding`. – Vladimir F Героям слава Aug 16 '23 at 06:42
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Maybe better late than never. I remember using ms fortran 5.1 with visual studio 1. I am not sure which visual studio 14.0 is equivalent to but I think it is relatively recent and not 13 years old. I think this combination is a non starter as 5.1 is a 16bit compiler for windows 3.

hugok
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