Q57652: Example of Older FORTRAN Main to Newer C Procedure Call

Article: Q57652
Product(s): See article
Version(s): 5.10   | 5.10
Operating System(s): MS-DOS | OS/2
Keyword(s): ENDUSER | H_FORTRAN 4.00 | mspl13_c
Last Modified: 21-JAN-1990

When you link a mixed-language program, you must specify the newer
version of the run-time library before the earlier version library on
the link line, even if the earlier version of the library belongs to
the main procedure in a mixed-language call.

The following code is an example of a mixed-language program that uses
a FORTRAN main program to call a C procedure to handle the graphics
for the program. The code is intended to demonstrate correct compile
and link switches when a FORTRAN routine is compiled with an earlier
version of the FORTRAN package, which calls a C routine compiled with
a newer version of the C package.

The code begins execution in the FORTRAN main, then calls the C
routine to handle elementary graphics routines. Notice the order of
libraries specified on the link line.

C*****************  FORMOD.FOR *****************
C  FORMOD.FOR - FORTRAN 4.0 module to be used with CGRAPH

       INTERFACE TO SUBROUTINE CGRAPH[C, ALIAS:'_cgraph']
       END

       PROGRAM FORMOD
       CALL CGRAPH
       END

/******************  CGRAPH.C *****************    */
/* CGRAPH.C - C Graphics module. Used with FORMOD. */

#include <stdio.h>
#include <graph.h>
#include <conio.h>

void cgraph(void)
{
    int i;

    i = _setvideomode(_MRES16COLOR);
    printf("return = %d", i); /* check for failed return */
    getch();
    _setvideomode(_DEFAULTMODE);
}

# ****************** FORMOD.MAK ***********************

formod.obj: formod.for
        fl /Od /Zi /c /AL formod.for

cgraph.obj: cgraph.c
        cl /Od /Zi /W3 /c /AL cgraph.c

formod.exe: cgraph.obj formod.obj
        link /CO /NOE /NOD
        formod cgraph,,,llibcer.lib+llibfore.lib+graphics.lib;

Note: The C graphics calls will fail if the earlier libraries (in this
case, the FORTRAN libraries) are specified first on the link line.
This is expected, as you always want newer definitions of the repeated
code linked into your EXE file.

For more information about FORTRAN and C mixed-language programming,
see the "Mixed-Language Programming Guide" in your compiler
documentation.

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