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

Question

In a C++ file, I have a code like this:

#if ACTIVATE
#   pragma message( \"Activated\" )
#else
#   pragma message( \"Not Activated\")
#endif

I

Answer 1

I think you want:

/p:DefineConstants=ACTIVATE

Answer 2

The answer is : YOU CANNOT

Answer 3

Use the CL environment variable to define preprocessor macros

Before calling MSBUILD, simply set the environment variable 'CL' with '/D' options like so:

set CL=/DACTIVATE to define ACTIVATE

You can use the '#' symbol to replace '=' sign

set CL=/DACTIVATE#1 will define ACTIVATE=1

Then make the call to MSBUILD

More documentation on the CL Environment Variables can be found at: https://msdn.microsoft.com/en-us/library/kezkeayy(v=vs.140).aspx

Answer 4

C++ projects (and solutions) are not (yet ?) integrated in the MSBuild environment. As part of the build process, the VCBuild task is called, which is just a wrapper around vcbuild.exe.

You could :

• create a specific configuration for your solution where ACTIVATE=1 would be defined, and compile it with devenv.exe (with the /ProjectConfig switch).
• create your own target file to wrap your own call to the VCBuild task (see the Override parameter)...
• use vcbuild.exe instead of msbuild.exe. (vcbuild.exe does not seem to have the equivalent of an Override parameter).

Note that your solution would not work for C# projects either unless you tweaked your project files a bit. For reference, here is how I would do this :

• Add the following code before the call to <Import Project="$(MSBuildBinPath)\Microsoft.CSharp.targets" /> :

<PropertyGroup Condition=" '$(MyConstants)' != '' ">
  <DefineConstants>$(DefineConstants);$(MyConstants)</DefineConstants>
</PropertyGroup>

• Call MSBuild like this :

msbuild /p:MyConstants="ACTIVATE=1"

Answer 5

If you need to define some constant (not just true/false), you can do it the following way:

On command line:

MSBuild /p:MyDefine=MyValue

In vcxproj file (in section <ClCompile>; and/or <ResourceCompile>, depending on where you need it):

<PreprocessorDefinitions>MY_DEFINE=$(MyDefine);$(PreprocessorDefinitions)</PreprocessorDefinitions>

Note that if you don't specify /p:MyDefine=MyValue in a call to MSBuild then empty string will be assigned to MY_DEFINE macro. If it's OK for you, that's it. If not, keep reading.

How to make a macro undefined if corresponding MSBuild parameter is not specified

To have MY_DEFINE macro undefined instead of empty string, you can use the following trick:

<ClCompile>
  ....
  <PreprocessorDefinitions>_DEBUG;_CONSOLE;OTHER_UNCONDITIONAL_MACROS;%(PreprocessorDefinitions)</PreprocessorDefinitions>
  <PreprocessorDefinitions Condition="'$(MyDefine)'!=''">MY_DEFINE=$(MyDefine);%(PreprocessorDefinitions)</PreprocessorDefinitions>
  ....
</ClCompile>

First PreprocessorDefinitions defines unconditional macros. Second PreprocessorDefinitions additionally defines MY_DEFINE macro when MyDefine is not empty string. You can test this by placing the following piece of code into your cpp file:

#define STRINGIZE2(x) #x
#define STRINGIZE(x) STRINGIZE2(x)

#ifndef MY_DEFINE
#pragma message("MY_DEFINE is not defined.")
#else
#pragma message("MY_DEFINE is defined to: [" STRINGIZE(MY_DEFINE) "]")
#endif

and running:

> MSBuild SandBox.sln /p:Configuration=Debug /p:MyDefine=test /t:Rebuild
...
MY_DEFINE is defined to: [test]
...

> MSBuild SandBox.sln /p:Configuration=Debug /p:MyDefine= /t:Rebuild
...
MY_DEFINE is not defined.
...

> MSBuild SandBox.sln /p:Configuration=Debug /t:Rebuild
...
MY_DEFINE is not defined.
...

Answer 6

For VS2010 and up, see my answer here for a solution that requires no modification of the original project file.