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 want to set this ACTIVE define to 1 with the msbuild command line.

It tried this but it doesn't work:

msbuild /p:DefineConstants="ACTIVATE=1"

Any idea?

score 37 · Answer 1 · edited Feb 22 '23 at 19:20

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

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)
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

For setting the defines while building resource files, also set the Additional Options under Configuration Properties -> Resources -> Command Line — Rado, Apr 13 '16 at 16:27

4LegsDrivenCat · Answer 2 · 2019-11-13T21:49:56.883

14

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.
...

edited Nov 13 '19 at 21:49

answered Apr 01 '13 at 15:23

4LegsDrivenCat

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Is it possible to add `MY_DEFINE=$(MyDefine)` in projects properties? – s4eed May 18 '18 at 10:48
1

@s4eed Yes, open project properties dialog, select specific Configuration (e.g. Debug) and Platform (e.g. Win32), go to C/C++ -> Preprocessor section, and add "MY_DEFINE=$(MyDefine);" in front of other definitions in Preprocessor Definitions field. For example, if you had "a=b;$(PreprocessorDefinitions)" in that field, then make it "MY_DEFINE=$(MyDefine);a=b;$(PreprocessorDefinitions)". Do the same in Resources -> General section if needed. – 4LegsDrivenCat Jul 19 '18 at 13:56
Repeat this for other configurations and platforms. – 4LegsDrivenCat Jul 19 '18 at 14:02
This seems cleaner than the top answer, which sets environment variables, and works on MSBuild 16.1.76. You may want to add `#ifndef` guards to the constants to silence warnings. – MakotoE Jul 02 '19 at 01:15
1

The challenge with this solution is that MY_DEFINE is always defined - at least to the empty string. This is difficult to test for. @MakotoE 's suggestion with #ifndef does not work. – Troels Blum Nov 13 '19 at 14:59
@TroelsBlum What we now do is use a build script to replace the version constants file with a generated one. – MakotoE Nov 13 '19 at 19:38
@TroelsBlum I've updated the answer, please try. I've just tested this with VS2019 and it works for me. – 4LegsDrivenCat Nov 13 '19 at 21:29
If you are using this method to version your executable it is easy to forget that the resource compiler is used to compile the resource file. So the `` needs the same conditional ``. – omahena Jul 25 '23 at 12:49
@omahena Yes, I wrote about this: and/or – 4LegsDrivenCat Jul 25 '23 at 13:57

Mac · Answer 3 · 2008-10-03T12:47:41.850

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"

I can use vcbuild.exe instead of msbuild.exe but the question is the same. How to set a specific preprocessor in the vcbuild command line? — acemtp, Oct 03 '08 at 12:31
You're right : I wrongly assumed that vcbuild.exe had the same set of parameters as the VCBuild task. Answer updated. — Mac, Oct 03 '08 at 12:49
Good shot, `$(DefineConstants);$(MyConstants)`, that's what my want. — JasonMing, Sep 29 '14 at 03:31

score 12 · Answer 4 · answered Oct 03 '08 at 12:03

12

I think you want:

/p:DefineConstants=ACTIVATE

answered Oct 03 '08 at 12:03

Matt Howells

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@Matt, I suggested the same answer and was told by two commenters that this doesn't work. So I deleted my answer so that others with more experience with MSBuild might offer ideas. – Onorio Catenacci Oct 03 '08 at 12:07
Oh and acemtp told me that he already tried this and it didn't work. – Onorio Catenacci Oct 03 '08 at 12:07
This works for me as well. I did put quotes around the list of constants i defined but that probably doesn't matter. – blak3r Oct 28 '09 at 21:04
2

it seems like this overwrites constants defined in the .csproj-file – anion Jun 20 '19 at 07:53
/p:DefineConstants doesn't work in C++. Seems to only work for C#. – Adam Gross Jan 19 '23 at 19:32

score 9 · Answer 5 · answered Apr 03 '18 at 12:45

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

Lex Sergeev · Answer 6 · 2018-03-05T17:18:20.160

Maybe it is a bad idea to answer such old question, but recently I googled a similar problem and found this topic. I wrote a cmd script for some build system and I was succeed to find a solution. I leave it here for future generations (:

According to @acemtp's problem, my solution would look like this:

@echo off

:: it is considered that Visual Studio tools are in the PATH
if "%1"=="USE_ACTIVATE_MACRO" (
    :: if parameter USE_ACTIVATE_MACRO is passed to script
    :: the macro ACTIVATE will be defined for the project
    set CL=/DACTIVATE#1
)
call msbuild /t:Rebuild /p:Configuration=Release

UPD: I tried to use set CL=/DACTIVATE=1 and it also worked, but the official documentation recommends to use number sign

score -1 · Answer 7 · edited May 23 '17 at 12:17

-1

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

edited May 23 '17 at 12:17

Community

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answered Jul 03 '13 at 11:25

stijn

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score -1 · Answer 8 · answered Aug 23 '17 at 10:23

As @bigh_29 has mentioned, using environment variables to define or undefine a preprocessor.

What he suggested the way to undefine a preprocessor is actually /UACTIVATE.

This way, any preprocessor matching ACTIVATE will be negated and compiler wouldn't go through your #if ACTIVATE #endif enclosure.

score -1 · Answer 9 · answered Feb 20 '09 at 00:04

I needed to do this too - needed to be able to build two different versions of my app and wanted to be able to script the build using VCBUILD. VCBUILD does have the /override command line switch, but I am not sure it can be used to modify #define symbols that can then be tested using #if conditional compilation.

The solution I cam up with was to write a simple utility to create a header file that #defined the symbol based on the state of an environment variable and run the utility from a pre-build step. Prior to each execution of the VCBUILD step the script sets the environment variable and "touches" a file in the app to ensure that the prebuild step is executed.

Yes, it is an ugly hack, but it was the best I could come up with!

score -1 · Answer 10 · answered May 08 '22 at 03:30

I got pretty fed up with trying to do this without modifying solution or project files so I came up with the following:

Create empty file as part of build e.g. feature_flag.h
Replace #if FEATURE_FLAG with #if !__has_include("feature_flag.h")
Remove feature_flag.h at the end of the build

It's not using #define but it does use the preprocessor which was what I needed.

score -2 · Answer 11 · answered Oct 03 '08 at 12:07

-2

It should probably be:

#ifdef ACTIVATE
#   pragma message( "Activated" )
#else
#   pragma message( "Not Activated")
#endif

answered Oct 03 '08 at 12:07

Robert Deml

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No it's not #ifdef, it's a #if And anyway, it doesn't work with #ifdef too – acemtp Oct 03 '08 at 12:14

score -5 · Accepted Answer · answered Oct 07 '08 at 10:48

-5

The answer is : YOU CANNOT

answered Oct 07 '08 at 10:48

acemtp

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Shrug, perhaps it doesn't in C++ but Matt Howells answer did work for me with a C# project. Can't think of any reason it wouldn't work in C++. – blak3r Oct 28 '09 at 21:06
This accepted answer is so deep I can't even see it. – Sergio Basurco Oct 09 '15 at 07:56
@blak3r Matts answer does not work in C++ and this question is specifically about C++. And there seem to be no way to do it with only adding flags on the command line without additional changes either to the project file or another external file. – Zitrax Aug 16 '17 at 11:03
Not sure why you get the down votes. The question was for C++ and the trick with '/p:DefineConstants' doesn't work for vcxproj for me either. – gast128 Mar 20 '19 at 12:27

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

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