Microsoft KB Archive/884845

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

Article ID: 884845

Article Last Modified on 5/21/2007

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APPLIES TO


 * Microsoft Visual C++ .NET 2003 Standard Edition
 * Microsoft Visual Studio .NET 2003 Enterprise Architect
 * Microsoft Visual Studio .NET 2003 Enterprise Developer
 * Microsoft Visual Studio .NET 2003 Academic Edition

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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 &quot;Applies to&quot; section.

