FIX: The /G5 and /Ox compiler options may cause numeric calculations to be incorrect in Visual C++ .NET (884845)


The information in this article applies to:

  • Microsoft Visual C++ .NET (2003)
  • Microsoft Visual Studio .NET (2003), Enterprise Architect Edition
  • Microsoft Visual Studio .NET (2003), Enterprise Developer Edition
  • Microsoft Visual Studio .NET (2003), Academic Edition

SYMPTOMS

When you compile your Microsoft Visual C++ .NET code, some numeric calculations may be incorrect when you specify the following compiler options:
  • /G5: This compiler option optimizes code for the Pentium processor.
  • /Ox: This compiler option uses maximum optimization.
The resulting difference in the calculations could lead to problems with floating-point precision.

CAUSE

This problem occurs when the compiler optimizes inverse factorization. The assembly code that is generated for the division operation is different. The difference in the assembly code leads to the difference in the calculated result.

RESOLUTION

A supported hotfix is now available from Microsoft, but it is only intended to correct the problem that this article describes. Apply it only to systems that are experiencing this specific problem.

To resolve this problem, contact Microsoft Product Support Services to obtain the hotfix. For a complete list of Microsoft Product Support Services telephone numbers and information about support costs, visit the following Microsoft Web site:

http://support.microsoft.com/contactus/?ws=support

Note In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question.

Prerequisites

No prerequisites are required.

Restart requirement

You do not have to restart your computer after you apply this hotfix.

Hotfix replacement information

This hotfix does not replace any other hotfixes.

File information

The hotfix version of this English has the file attributes (or later file attributes) that are listed in the following table. The dates and times for these files are listed in coordinated universal time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time tool in Control Panel. 
   Date         Time   Version            Size    File name
   --------------------------------------------------------------
   20-Aug-2004  03:41  13.10.4233.0    1,867,776  c2.dll
   20-Aug-2004  03:17  13.10.4233.0       86,016  cl.exe

STATUS

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

REFERENCES

For more information about Visual C++ .NET compiler options, visit the following Microsoft Developer Network (MSDN) Web site:

http://msdn.microsoft.com/library/default.asp?url=/library/en-us/vccore/html/_core_Compiler_Reference.asp

For additional information about the standard terminology that is used to describe Microsoft software updates, click the following article number to view the article in the Microsoft Knowledge Base:

824684 Description of the standard terminology that is used to describe Microsoft software updates

Modification Type:MajorLast Reviewed:5/15/2006
Keywords:kbfix kbBug kbQFE kbprb kbHotfixServer KB884845 kbAudDeveloper
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