DOCUMENT:Q106725  24-MAR-2000  [fortran]
TITLE   :FIX: Alternate Return Compiled with /Ox Can GPF at Run Time
PRODUCT :Microsoft Fortran Compiler
PROD/VER::1.0
OPER/SYS:
KEYWORDS:

======================================================================
-------------------------------------------------------------------------------
The information in this article applies to:

 - Microsoft FORTRAN PowerStation for MS-DOS, version 1.0 
-------------------------------------------------------------------------------

SYMPTOMS
========

The FORTRAN PowerStation optimizer may generate incorrect code when compiling
routines containing alternate returns. If routines containing alternate returns
are compiled with /Ox, the following errors may occur at run time:

   DOSXMSF : fatal error DX1020: unhandled exception: General
   protection fault;

   Fault occurred in a System Call

RESOLUTION
==========

Altering code around the alternate return may alleviate this problem. If this
doesn't work, then do not compile routines using alternate returns with /Ox.
Note that other routines in the program can still be optimized.

STATUS
======

Microsoft has confirmed this to be a problem in FORTRAN PowerStation version 1.0
for MS-DOS. This problem has been resolved with FORTRAN PowerStation maintenance
release version 1.0A for MS-DOS.

MORE INFORMATION
================

To duplicate the error, compile the sample code with /Ox and then run the
program to get the DX1020 error. This problem is dependent on the surrounding
code. Replacing "var=1.0" with "continue", or commenting out "goto 10" in the
sample below removes the problem:

FORTRAN PowerStation version 1.0 can be differentiated from the maintenance
release version 1.0A by invoking the linker. Typing "link32 | more" (without the
quotation marks) from /F32/BIN directory will show version 2.8 for FORTRAN
Powerstation maintenance release version 1.0A for MS-DOS."

Sample Code
-----------

         call test(*10,*20)
      10 var=1.0
      20 if (var.ne.0) return
         goto 10
         end

         subroutine test(*,*)
         return 1
         end

Additional query words: 1.00 GP fault gp-fault gpf buglist1.00 fixlist1.00A

======================================================================
Keywords          :  
Technology        : kbAudDeveloper kbFortranSearch kbZNotKeyword3 kbFORTRANPower100DOS
Version           : :1.0
Issue type        : kbbug
Solution Type     : kbfix

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