FIX: An incorrect result is generated when an optimization option is turned on in a project that has floating-point code in Visual C++ 2008 SP1


When you use Microsoft Visual C++ 2008 Service Pack 1 (SP1), an incorrect result is generated. This problem occurs when the following conditions are true:
  • The project has floating-point code.

  • The C/C++ /O2 (Maximize Speed) optimization option or the /Ox (Full Optimization) optimization option is turned on.
Note The problem only occurs on the x86 platform.

To confirm that you are experiencing this problem, compare the incorrect result to the result that is generated when the no optimization /O2 option is turned on or when the /Ox compiling option is turned on.


A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problemP1 that P2 described in this article. Apply this hotfix only to systems that are experiencing the problemP1 described in this article. This hotfix might receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next software update that contains this hotfix.

If the hotfix is available for download, there is a "Hotfix download available" section at the top of this Knowledge Base article. If this section does not appear, contact Microsoft Customer Service and Support to obtain the hotfix.

Note If additional issues occur or if any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft Web site: Note The "Hotfix download available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language.


You must have Visual Studio 2008 Service Pack 1 installed to apply this hotfix.

Restart requirement

You do not have to restart the computer after you install the hotfix if no Visual Studio 2008 instance is being used.

Hotfix replacement information

This hotfix does not replace any other hotfixes.

File information

The English version of this hotfix 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
item in Control Panel.
File nameFile versionFile sizeDateTimePlatform


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

Article ID: 960257 - Last Review: Feb 6, 2009 - Revision: 1