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Consider the following scenario:

  • You develop a Microsoft Visual C++ 2010 application in Microsoft Visual Studio 2010.

  • You enable one of the following optimization compiler options for the application:

    • /O1 (Minimize Size)

    • /O2 (Maximize Speed)

    • /Ox (Full Optimization)

  • You set up the application to target Win32 (x86 platform).

  • You build the application in release mode.

In this scenario, incorrect machine code is generated.


This issue occurs because of a bug in the Visual C++ 2010 optimizer (x86 platform).


Hotfix information

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

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


To apply this hotfix, you must have Visual Studio 2010 Service Pack 1 (SP1) installed.

Restart requirement

You do not have to restart the computer after you apply this hotfix if the affected files are not being used. We recommend that you close Visual Studio 2010-related components before you apply this hotfix.

File information

The global 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 name

File version

File size











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


To work around this issue, use one of the following methods:

  • Use the /Od optimization compiler option to turn off optimization.

  • Use the optimize pragma to turn on or turn off the optimization on a function-by-function basis.

    Note Turn off optimization for only the affected functions.

More Information

For more information about compiler options, go to the following MSDN website:

General information about compiler optionsFor more information about the optimize pragma, go to the following MSDN website:

General information about the optimize pragma

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