Q148203: BUG: Passing LOC() Intrinsic Result to C Function Fails

Article: Q148203
Product(s): Microsoft Fortran Compiler
Version(s): 4.0
Operating System(s): 
Keyword(s): kbFortranPS kbLangFortrankbbuglist
Last Modified: 04-NOV-1999

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The information in this article applies to:

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

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

  C these work
        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

Additional query words: 4.00

======================================================================
Keywords          : kbFortranPS kbLangFortran kbbuglist
Technology        : kbAudDeveloper kbPTProdChange kbFortranSearch kbFORTRANPower400NT
Version           : :4.0

=============================================================================

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