Calling C Code from FORTRAN

Question

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?

Answer 1

There's an article on MSDN with sample code here: FORTRAN calls to C

Answer 2

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

Answer 3

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.