FIX: Incorrect machine code is generated for a "switch" statement in the Visual C++ 2010 x64 compiler


Assume that you compile a C or C++ source code file to an x64-based binary file by using the Visual C/C++ compiler (Cl.exe) in Microsoft Visual Studio 2010. The source code file contains a function that uses a switch statement. In this situation, incorrect machine code may be generated for the switch statement if the following conditions are true:
  • The /Ob1 (Only_inline) compiler option is enabled.
  • The /O1 (Minimize Size), /O2 (Maximize Speed), /Ox (Full Optimization), or /Og (Global Optimizations) optimization compiler option is enabled.
  • The /GL (Whole Program Optimization) compiler option is disabled.


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: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.


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 nameFile versionFile sizeDateTimePlatformPath
C2.dll16.0.40219.4442,606,71211-Mar-201319:24x86Microsoft Visual Studio 10.0\VC\bin
C2.dll16.0.40219.4442,493,56012-Mar-201316:48x86Microsoft Visual Studio 10.0\VC\bin\x86_amd64
C2.dll16.0.40219.4442,593,92812-Mar-201316:48x86Microsoft Visual Studio 10.0\VC\bin\x86_ia64
C2.dll16.0.40219.4442,960,50412-Mar-201316:48x64Microsoft Visual Studio 10.0\VC\bin\amd64

More Information

To reproduce this issue, create a C or C++ source file that contains the following code:
#include <stdio.h>

int test(int bps, int sflags)
if (sflags & (1 << bps))
switch (bps)
case 1: return 1;
case 2: return 3;
default: return 0;
switch (bps)
case 1: return 2;
default: return 0;

void main()
int res = test(1, -1);
printf("%d\n", res);

Then, open Visual Studio x64 Cross Tools Command Prompt or Visual Studio x64 Win64 Command Prompt in Visual Studio 2010, and compile the source file by using the following command:
cl /Ob1 /O2 'Source File Path'

The expected result is 1. However, the actual result is 0.


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


For more information about the /Ob compiler option, go to the following MSDN website: For more information about the /GL compiler option, go to the following MSDN website: For more information about the /O optimization options, go to the following MSDN website:

Id. de artículo: 2802711 - Última revisión: 29 mar. 2013 - Revisión: 1