fatal error LNK1112: module machine type 'x64' conflicts with target machine type 'X86'

Question

I wrote a blog entry about this, as I encountered this maddening problem, and finally yanked my system back into working order.

These are the things to check, in this order:

1. Check your properties options in your linker settings at: Properties > Configuration Properties > Linker > Advanced > Target Machine. Select MachineX64 if you are targeting a 64 bit build, or MachineX86 if you are making a 32 bit build.

2. Select Build > Configuration Manager from the main menu in visual studio. Make sure your project has the correct platform specified. It is possible for the IDE to be set to build x64 but an individual project in the solution can be set to target win32. So yeah, visual studio leaves a lot of rope to hang yourself, but that's life.

3. Check your library files that they really are of the type of platform are targeting. This can be used by using dumpbin.exe which is in your visual studio VC\bin directory. use the -headers option to dump all your functions. Look for the machine entry for each function. it should include x64 if it's a 64 bit build.

4. In visual studio, select Tools > Options from the main menu. select Projects and Solutions > VC++ Directories. Select x64 from the Platform dropdown. Make sure that the first entry is: $(VCInstallDir)\bin\x86_amd64 followed by $(VCInstallDir)\bin.

Once I did step 4 everything worked again for me. The thing was I was encountering this problem on all my projects where I wanted to compile towards a 64 bit target.

In addition to C Johnson list I would add the following point:

Check in Visual Studio:
Project Properties -> Configuration Properties -> Linker -> Command line.

"Additional Options" should NOT contain /machine:X86

I have such key, generated by CMake output: CMake generated x86 project, then I added x64 platform via Configuration Manager in Visual Studio 2010 - everything was created fine for the new platform except that the linker command line, specified /machine:X86 separately.

I experienced the same problem in VS2008 when I tried to add a X64 build to a project converted from VS2003.

I looked at everything found when searching for this error on Google (Target machine, VC++Directories, DUMPBIN....) and everything looked OK.

Finally I created a new test project and did the same changes and it seemed to work.

Doing a diff between the vcproj files revealed the problem....

My converted project had /MACHINE:i386 set as additional option set under Linker->Command Line. Thus there was two /MACHINE options set (both x64 and i386) and the additional one took preference.

Removing this and setting it properly under Linker->Advanced->Target Machine made the problem disappeared.

All project settings seemed perfect, but I still got the error. Looking into the .vcxproj file and searching for "x86" revealed the problem:

<Lib>
  <AdditionalOptions> /machine:X86 %(AdditionalOptions)</AdditionalOptions>
</Lib>

A quick search/replace for all occurrances (ten individual file settings) fixed the problem.

You probably have one .OBJ or .LIB file that's targeted for x64 (that's the module machine type) while you're linking for x86 (that's the target machine type).

Use DUMPBIN /HEADERS on your .OBJ files and check for the machine entry in the FILE HEADER VALUES block.