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Q149517: BUG: /Ox and /4Ya Options Together Cause Incorrect Results

Article: Q149517
Product(s): Microsoft Fortran Compiler
Version(s): 4.0
Operating System(s): 
Keyword(s): kbCodeGenkbbuglist
Last Modified: 02-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
========

Compiling source code that performs arithmetic calculations along with the /Ox
and /4Ya compiler options together creates object code that may produce
incorrect arithmetic calculation results at run time.

RESOLUTION
==========

Do not use the /Ox and /4Ya compiler options together.

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
---------------------------------

  C Compile options needed: /Ox /4Ya

     REAL*8 a(3), x, y

     a(1) = -1.D0
     a(2) = -2.D0
     a(3) = -3.D0

     x = 0.D0
     y = 0.23D0

     a(3) = 1.D0/SQRT(1.D0+x*x+y*y)
     a(1) = x*a(3)
     a(2) = y*a(3)

     PRINT *,'a(1) = ',a(1)
     PRINT *,'a(2) = ',a(2)
     PRINT *,'a(3) = ',a(3)

     END

Correct Output
--------------

  a(1) = 0.000000000000000E+000
  a(2) = 2.241476929214269E-001
  a(3) = 9.745551866148997E-001

Output with /Ox /4Ya
--------------------

  a(1) = 0.000000000000000E+000
  a(2) = 2.241476929214269E-001
  a(3) = 2.241476929214269E-001

Additional query words: 4.00

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Keywords          : kbCodeGen kbbuglist
Technology        : kbAudDeveloper kbPTProdChange kbFortranSearch kbFORTRANPower400NT
Version           : :4.0

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