VC9: LINK : warning LNK4068: /MACHINE not specified; defaulting to X86

当把32位程序改成X64的配置编译后，可能会出现错误：

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

通常是因为某些编译单元被编译成了X86的机器码，进一步的原因是编译选项中缺少 /MACHINE，默认会选择X86；在属性中的link面板中加入/MACHINE:X64 即可。

The error is explicit, you are trying to link libraries that were compiled with different CPU targets. An executable image can only contain pure x86 (32-bit) or pure x64 (64-bit) code. Mixing is not possible.

You change the target CPU by creating a new configuration for the project, only changing the linker setting isn't enough. Build + Configuration Manager, Active solution platform combo on upper right, choose New and select x64. That creates a new configuration with several modified project settings, most importantly the compiler that will be used.

Beware that prior to VS2010, the 64-bit compilers are not installed by default. If you don't see x64 in the platform combo then you'll need to re-run setup.exe and turn on the option to install the 64-bit compilers. Then also re-run any service pack installer you may have applied.

A possible approach with less pain points is to use the 32-bit version of the library.

bumped into this too and found a solution.

First on how I got into this problem. I have a project which builds in x86. Then I use the Configuration Manager to add x64, and I hit this problem.

By looking at BuildLog.htm carefully, I see both of these listed as linker options: /MACHINE:X64 /machine:X86

I can't find any where in the Property Pages dialog where I can change this, so I open up the .vcproj file and look for the appropriate line and change it to: AdditionalOptions=" /STACK:10000000 /machine:x64 /debug"