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Q104776: BUG: Endless Loop in Code Containing Graphics & Compiled -Ox

Article: Q104776
Product(s): Microsoft Fortran Compiler
Version(s): 1.0,1.0a
Operating System(s): 
Keyword(s): 
Last Modified: 02-NOV-1999

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

- Microsoft FORTRAN PowerStation for MS-DOS, versions 1.0, 1.0a 
-------------------------------------------------------------------------------

SYMPTOMS
========

A program may execute in an infinite loop if it was compiled with full
optimization (-Ox) and contains a do loop calling some of the graphics routines
[such as POLYGON_W()].

CAUSE
=====

Some of the graphics functions (such as POLYGON_W) prevent optimized code from
recognizing the end condition for the loop.

STATUS
======

Microsoft has confirmed this to be a problem in FORTRAN PowerStation for MS-DOS,
version 1.0 and 1.0a.

This problems does not apply to FORTRAN PowerStation 32.

RESOLUTION
==========

Compile the program with no optimization (this is the default).

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

  c Compile options needed:    -Ox
  c The following program will output in an infinite loop:

        include 'fgraph.fi'
        include 'fgraph.fd'
        INTEGER*2  status, npts

        RECORD     / wxycoord /  wxyarr(3)

        status = setvideomode(18)
        do it=1,2
           write (*,'(i4\)') it
           wxyarr(1).wx = 43.d0
           wxyarr(1).wy = 85.d0
           wxyarr(2).wx = 50.d0
           wxyarr(2).wy = 71.d0
           wxyarr(3).wx = 45.d0
           wxyarr(3).wy = 85.d0
           npts = 3
           status = POLYGON_W($GBORDER, wxyarr, npts)
        enddo
        END

Additional query words: nofpsnt 1.00

======================================================================
Keywords          :  
Technology        : kbAudDeveloper kbFortranSearch kbZNotKeyword3 kbFORTRANPower100DOS kbFORTRANPower100aDOS
Version           : :1.0,1.0a

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

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