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Q106725: FIX: Alternate Return Compiled with /Ox Can GPF at Run Time

Article: Q106725
Product(s): Microsoft Fortran Compiler
Version(s): 1.0
Operating System(s): 
Keyword(s): 
Last Modified: 24-MAR-2000

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The information in this article applies to:

- Microsoft FORTRAN PowerStation for MS-DOS, version 1.0 
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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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