KB133104 - FORTRAN PowerStation 32 MIXLANG.TXT

MORE INFORMATION

Part 1: Building C Projects

You can build C projects using FORTRAN code in the C++ Visual Workbench. Compile your FORTRAN code one of the following ways:

Using the FL32 command on the command line.
Compiling within FORTRAN Visual Workbench.
Using a makefile in C++ Visual Workbench.

Use the FORTRAN compiler option /c to suppress linking.

Include your FORTRAN object (.OBJ) and static library (.LIB) files by listing them in the Files in Project box on the Project menu.

Run-time libraries must support the FORTRAN code integrated into the C project. You can access the correct versions through the following steps:

From the Options menu, choose Directories. In the Library Files Path box, insert as the first item the directory path containing the FORTRAN versions of the C run-time libraries. This assures that the correct versions of libc.lib, libcmt.lib, and msvcrt.lib will be loaded by the linker. The typical item list should begin with c:\fpsnt\lib;... .
From the Options menu, choose Project. In the new menu, choose Linker Options. Under Category Setting: Input, in the Object\Library Modules box, type libf.lib and console.lib.

If you are using the Win32 System Development Kit, make certain that directory MSTOOLS\BIN from the Win32 SDK does not appear before MSVCNT\BIN or FPSNT\BIN in the executables directory path; otherwise LINK32 from SDK will be inappropriately picked up instead of LINK.

Part 2: Building FORTRAN Projects

Passing Strings to C

The following sample code illustrates passing strings from FORTRAN to C and back using the C convention and using _stdcall. In the first case, the string is terminated in FORTRAN with the C terminator (\n). In the second case, a standard FORTRAN string is passed, and the C program must allow for the hidden length integer at the end of the string. You can copy this code to the Clipboard and paste it into your files.

CC    FSTR_F.FOR    FORTRAN MAIN PROGRAM
CC
      INTERFACE TO SUBROUTINE Ucase1 [C,ALIAS:'_Ucase1'] (text)
      CHARACTER*(*) text
      END
      INTERFACE TO SUBROUTINE Ucase2 [ALIAS:'_Ucase2@8'] (text)
      CHARACTER*(*) text
      END

      CHARACTER*40 string1,string2
      DATA string1 /'This is a null-terminated string.'C/ 
      DATA string2 /'This is a standard Fortran string.'/ 

      WRITE (*, *) string1
      CALL Ucase1 (string1)
      WRITE (*, *) string1

      WRITE (*, *) string2
      CALL Ucase2 (string2)
      WRITE (*, *) string2

      END

//    FSTR_C.C    C Subprograms       Make strings uppercase
// 
#include <ctype.h>

void Ucase1( char *string )
{
    char *ptr;

    for (ptr = string; *ptr; ptr++)
        *ptr = toupper( *ptr );
}

void __stdcall Ucase2( char *string, int length )
{
    char *ptr;

    for (ptr = string; *ptr; ptr++)
        *ptr = toupper( *ptr );
}

Part 3: Using DLLs with Mixed Languages

The following programs are examples of mixed C and FORTRAN programs using DLLs where the main program is in one language and the DLL is in the other. The examples communicate data between the main program and the DLL through a common data structure (a FORTRAN common block and a C structure).

Redirecting the output of a mixed-language DLL program can produce unexpected results due to the different I/O buffering performed by the C and FORTRAN run-time libraries.

These samples can be copied to the Clipboard and pasted into a file to use as examples and templates for this type of program.

Case 1. A FORTRAN Main Program calls a C DLL

CC    FORTRAN MAIN PROGRAM
CC
      INTERFACE TO SUBROUTINE csub [C,ALIAS:'_csub']()
      END

      INTEGER i
      REAL x
      CHARACTER*4 s
      COMMON /BRIDGE[dllimport]/ i, x, s
      i = 1
      x = 2.5
      s = 'fail'
      WRITE(*,'(5X,A)')       'before calling dll '
      WRITE(*,'(5X,A,I5)')    'i = ', i
      WRITE(*,'(5X,A,F4.2)')  'x = ', x
      WRITE(*,'(5X,A,A)')     's = ', s
      CALL csub()
      WRITE(*,'(5X,A)')       'after calling dll '
      WRITE(*,'(5X,A,I5)')    'i = ', i
      WRITE(*,'(5X,A,F4.2)')  'x = ', x
      WRITE(*,'(5X,A,A)')     's = ', s
      END

//    C DLL Subprogram
// 
#include <stdio.h>
#include <string.h>
#define DLLexport _declspec(dllexport)


DLLexport void csub();

DLLexport struct {
   int i;
   float x;
   char s[4];
} BRIDGE;

void csub()
{
   BRIDGE.i = BRIDGE.i + 1;
   BRIDGE.x = BRIDGE.x + 1.5F;
   strcpy(BRIDGE.s, "pass");
   printf("\n\n%s\n%s%d\n%s%f\n%s%s\n",
         "in the dll",
         "i = ", BRIDGE.i,
         "x = ", BRIDGE.x,
         "s = ", BRIDGE.s);
}

Output redirected to a file:

Before calling dll:
i =     1
x = 2.50
s = fail

After calling dll:
i =     2
x = 4.00
s = pass

Output in the dll:
i = 2
x = 4.000000
s = pass

Case 2. A C Main Program calls a FORTRAN DLL

//    C Main Program
// 
#include <stdio.h>
#include <string.h>
#define DLLimport _declspec(dllimport)

extern void _stdcall FSUB ();

extern DLLimport struct {
   int i;
   float x;
   char s[4];
} BRIDGE;

void main(){
   BRIDGE.i = 1;
   BRIDGE.x = 2.5F;
   strcpy(BRIDGE.s, "fail");
   printf("\n\n%s\n%s%d\n%s%f\n%s%s\n",
         "before calling dll", "i = ", BRIDGE.i,
         "x = ", BRIDGE.x,
         "s = ", BRIDGE.s);
   FSUB();
   printf("\n\n%s\n%s%d\n%s%f\n%s%s\n",
         "before calling dll", "i = ", BRIDGE.i,
         "x = ", BRIDGE.x,
         "s = ", BRIDGE.s);
}

CC    FORTRAN DLL SUBROUTINE
CC
      SUBROUTINE FSUB[dllexport]()
      COMMON /BRIDGE[dllexport]/ i, x, s
      INTEGER i
      REAL x
      CHARACTER*4 s
      i = i + 1
      x = x + 1.5
      s = 'pass'
      WRITE(*,*)
      WRITE(*,'(5X,A)')       'in the dll '
      WRITE(*,'(5X,A,I5)')    'i = ', i
      WRITE(*,'(5X,A,F4.2)')  'x = ', x
      WRITE(*,'(5X,A,A)')     's = ', s
      END

Output redirected to a file:

In the dll:
i =     2
x = 4.00
s = pass

Before calling dll:
i = 1
x = 2.500000
s = fail

After calling dll:
i = 2
x = 4.000000
s = pass