MATLAB: “Unable to locate compiler” mex error when using Visual C++ 2010 Express SP1 on 64-bit Windows

64-bitMATLABmexvisual c++

I had a working combination of Visual C++ 2010 Express and Microsoft Windows SDK 7.1. After installing Service Pack 1 for Visual Studio, I now get the following MEX error:
Error: Could not find the compiler "cl" on the DOS path. 
       Use mex -setup to configure your environment properly. 
     C:\Program Files\MATLAB\R2010B\BIN\MEX.PL: Error: Unable to locate compiler.
How can I get back to a working configuration?

Best Answer

This problem impacts MATLAB users with the following combination of software on 64-bit Windows (win64):
  • Visual C++ 2010 Express
  • Microsoft Windows SDK 7.1
  • Visual Studio 2010 SP1
There is a bug in the installer for Visual Studio 2010 SP1. The installer will delete the 64-bit compiler previously installed by the SDK, or prevent the compiler from being later installed by the SDK.
This will prevent MEX and other products and features dependent on a compiler from functioning. "mex –setup" will continue to locate the Visual C++ compiler, but a "mex" call will later fail with a message like the following:
Error: Could not find the compiler "cl" on the DOS path. 
       Use mex -setup to configure your environment properly. 
     C:\Program Files\MATLAB\R2010B\BIN\MEX.PL: Error: Unable to locate compiler.
Microsoft has issued an update to address this issue. It is available for download at:
<http://www.microsoft.com/downloads/en/details.aspx?FamilyID=689655B4-C55D-4F9B-9665-2C547E637B70&displaylang=en>
After downloading and installing the update, MEX and other capabilities should work as anticipated.
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