msbuild: set a specific preprocessor #define in the command line

Our solution was to use an environment variable with /D defines in it, combined with the Additional Options box in visual studio.

1. In Visual Studio, add an environment variable macro, $(ExternalCompilerOptions), to the Additional Options under project options->C/C++->Command Line (remember both Debug and Release configs)
2. Set the environment variable prior to calling msbuild. Use the /D compiler option to define your macros

    c:\> set ExternalCompilerOptions=/DFOO /DBAR 
    c:\> msbuild

Item #1 ends up looking like this in the vcxproj file:

    <ClCompile>
      <AdditionalOptions>$(ExternalCompilerOptions) ... </AdditionalOptions>
    </ClCompile>

This works for me with VS 2010. We drive msbuild from various build scripts, so the environment variable ugliness is hidden a bit. Note that I have not tested if this works when you need to set the define to specific value ( /DACTIVATE=1 ). I think it would work, but I’m concerned about having multiple ‘=’s in there.

H^2