http://xit0.org/2013/04/cmake-use-git-branch-and-commit-details-in-project/

CMake: Use Git Branch & Commit Details in Project

APR 10TH, 2013

To use git branch and commit hash information in a CMake project, add the following lines to CMakeLists.txt

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# Get the current working branch execute_process( COMMAND git rev-parse --abbrev-ref HEAD WORKING_DIRECTORY ${CMAKE_SOURCE_DIR} OUTPUT_VARIABLE GIT_BRANCH OUTPUT_STRIP_TRAILING_WHITESPACE ) # Get the latest abbreviated commit hash of the working branch execute_process( COMMAND git log -1 --format=%h WORKING_DIRECTORY ${CMAKE_SOURCE_DIR} OUTPUT_VARIABLE GIT_COMMIT_HASH OUTPUT_STRIP_TRAILING_WHITESPACE )

execute_process() runs a single command or a sequence of commands and optionally gathers the output into CMake variables. The COMMAND is executed in WORKING_DIRECTORY and the STDOUT is saved to OUTPUT_VARIABLE after stripping trailing whitespace. The output of git log can be customized.

Now that these values are available for CMake, there are two ways to use them in a project.

• The easiest and simplest way is to use add_definitions() in CMakeLists.txt to make the variables available to the C/C++ project.

1 2	add_definitions("-DGIT_COMMIT_HASH=${GIT_COMMIT_HASH}") add_definitions("-DGIT_BRANCH=${GIT_BRANCH}")

• CMake also has the capability to generate a header file (or any file for that matter) with the configure_file() command. We can utilize this to generate a header file with these definitions and include it in the project.

You’ll need to include a template header file in the project source with some CMake specific annotations to achieve this. I choose to put version.h.in in the include folder in my source directory.

version.h.in

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#ifndef VERSION_H #define VERSION_H #define GIT_BRANCH "@GIT_BRANCH@" #define GIT_COMMIT_HASH "@GIT_COMMIT_HASH@" #endif

@GIT_BRANCH@ & @GIT_COMMIT_HASH@ will be substituted with the corresponding values obtained as the output of execute_process() command. The double quotes around the substitution variables are necessary if these variables have to be used as strings in a C/C++ project.

Add the following command to CMakeLists.txt to perform the generation.

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configure_file( ${CMAKE_SOURCE_DIR}/include/version.h.in ${CMAKE_BINARY_DIR}/generated/version.h )

This will write a version.h file to generated directory of ${CMAKE_BINARY_DIR}. Next, the folder generated has to be added to the C/C++ INCLUDE_PATH in CMakeLists.txt

1	include_directories(${CMAKE_BINARY_DIR}/generated)

Include version.h in a C/C++ file and you are done.

I’ve created a sample C project which uses this on Github.

PS: Ryan Pavlik has a CMake module for this available on Github. stackoverflow has a thread detailing it’s usage.