BUG: Passing LOC() Intrinsic Result to C Function Fails

  - Microsoft Fortran PowerStation for Windows 95 and Windows NT,
    version 4.0

SYMPTOMS

Using a variable character substring as an argument to the LOC() intrinsic function and passing the result to a C function causes the variable character substring to become corrupted.

RESOLUTION

• Use a literal character substring as the LOC() intrinsic argument.

  -or-

• Assign the variable character substring to a temporary character variable, and use it as the LOC() intrinsic argument.

STATUS

Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article. We are researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.

MORE INFORMATION

Sample Code to Illustrate Problem and Workarounds

C Fortran Main Source Code C Compile options needed: none

      INTERFACE
          SUBROUTINE MYFUNC(I)
          INTEGER I
          !MS$ATTRIBUTES VALUE :: I
          !MS$ATTRIBUTES C,ALIAS:'_myfunc' :: myfunc
          END SUBROUTINE MYFUNC
      END INTERFACE

      CHARACTER STR*3, TEMP*4
      INTEGER L

      STR = 'ABC'
      L = 3

      CALL MYFUNC(LOC(STR(1:L)//CHAR(0)))

      CALL MYFUNC(LOC(STR//CHAR(0)))
      CALL MYFUNC(LOC(STR(1:3)//CHAR(0)))
      TEMP=STR(1:L)//CHAR(0)
      CALL MYFUNC(LOC(TEMP))
      END

/* C Function Source Code:
   Compile options needed: /c
*/

#include <stdio.h>
void myfunc(char *s)

    long x;
    x = (long) s;
    printf("s: %x  String: %s\n", x, s);

Program Output

s: 12ffa8 String: - s: 12ffa4 String: ABC s: 12ffa0 String: ABC s: 41bac8 String: ABC