Monitoring the Stack Using Assembly or C

• Microsoft FORTRAN for MS-DOS, versions 4.0, 4.1, 5.0 and 5.1
• Microsoft FORTRAN for OS/2, version 4.0, 4.1, 5.0 and 5.1

SUMMARY

If, for any reason, you believe that the stack in a FORTRAN program is being corrupted, you can monitor the stack segment (SS) register and stack pointer (SP) register by using either the Microsoft Assembler package. Since CodeView may use the stack for its own purposes, this allows a more direct monitoring method.

A function for each package is shown below along with the appropriate interface statement. Each function returns an integer*4 to FORTRAN.

To extract the hexadecimal values from that integer, use a format statement something similar to the following example:

      write (*,'(1x,A7,1x,4Z,A1,4Z)')
     + 'seg:off',stackloc(),':',ISHC(stackloc(),16)

      seg:off 2BC0:111A

MORE INFORMATION

The assembly code and interface statement are shown below.

      interface to integer*4 function stackloc()
      end
      integer*4 stackloc

       mov dx,ss
       mov ax,sp
       ret

       end

      interface to integer*4 function stackloc [C,
     + alias:'_stackloc'] ()
      end
      integer*4 stackloc

int * stackloc(void)

        int j[2];

        _asm {
                mov     j[0],ss
                mov     j[1],sp
        }
        return j;
}