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In a Makefile this would be done with something like:

g++ -DGIT_SHA1="`git log -1 | head -n 1`" ...

This is very useful, because the binary knows exact commit SHA1 so it can dump it in case of segfault.

How can I achieve the same with CMake?

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Use git describe (producing output such as 'v1.6.5-rc1-17-g059f3d9') or git rev-parse -q HEAD (producing full SHA-1) instead of your git log -1 | head -n 1 pipeline. –  Jakub Narębski Sep 17 '09 at 8:05
git describe --tags works great –  Łukasz Lew Sep 17 '09 at 12:15

8 Answers 8

up vote 35 down vote accepted

I've made some CMake modules that peer into a git repo for versioning and similar purposes - they're all in my repository at https://github.com/rpavlik/cmake-modules

The good thing about these functions is, they will force a re-configure (a rerun of cmake) before a build every time the HEAD commit changes. Unlike doing something just once with execute_process, you don't need to remember to re-cmake to update the hash definition.

For this specific purpose, you'd need at least the GetGitRevisionDescription.cmake and GetGitRevisionDescription.cmake.in files. Then, in your main CMakeLists.txt file, you'd have something like this

get_git_head_revision(GIT_REFSPEC GIT_SHA1)

Then, you could either add it as a system-wide definition (which unfortunately would cause lots of rebuilding)


or, my suggested alternative: Make a generated source file. Create these two files in your source:


#define GIT_SHA1 "@GIT_SHA1@"
const char g_GIT_SHA1[] = GIT_SHA1;


extern const char g_GIT_SHA1[];

Add this to your CMakeLists.txt (assuming you have a list of source files in SOURCES):

configure_file("${CMAKE_CURRENT_SOURCE_DIR}/GitSHA1.cpp.in" "${CMAKE_CURRENT_BINARY_DIR}/GitSHA1.cpp" @ONLY)

Then, you have a global variable containing your SHA string - the header with the extern doesn't change when the SHA does, so you can just include that any place you want to refer to the string, and then only the generated CPP needs to be recompiled on every commit to give you access to the SHA everywhere.

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Thanks. This is EXACTLY what I needed. –  Łukasz Lew Dec 11 '10 at 19:06
Do you have a module to ensure out of source build? –  Łukasz Lew Dec 11 '10 at 19:07
Have you tried to contribute your modules to Cmake? –  Łukasz Lew Dec 11 '10 at 19:18
Yes, there's one for out of source build - it's in the cmake-2.9.0-modules directory, and if you do include(UseBackportedModules) that automatically gets included. I've contributed some patches back to cmake, but haven't felt the need to have new modules included - I'm fine with having them up on GitHub for easy sharing and collaboration unlinked from the CMake release cycle. –  rpavlik Dec 19 '10 at 3:09
FWIW, I believe I have incorporated the patch mentioned by @PiQuer. –  rpavlik Aug 14 at 16:13

I'd use sth. like this in my CMakeLists.txt:

    ARGS "describe"


add_definitions( -DGIT_SHA1="${VERSION_SHA1}" )
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I can't help you with the CMake side, but with respect to Git side I would recommend taking a look how Linux kernel and Git project itself does it, via GIT-VERSION-GEN script, or how tig does it in its Makefile, by using git describe if there is git repository present, falling back to "version" / "VERSION" / "GIT-VERSION-FILE" generated and present in tarballs, finally falling back to default value hardcoded in script (or Makefile).

The first part (using git describe) requires that you tag releases using annotated (and possibly GPG signed) tags. Or use git describe --tags to use also lightweight tags.

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If CMake doesn't have a built-in capability to do this substitution, then you could write a wrapper shell script that reads a template file, substitutes the SHA1 hash as above in the correct location (using sed, for example), creates the real CMake build file, and then calls CMake to build your project.

A slightly different approach might be to make the SHA1 substitution optional. You would create the CMake file with a dummy hash value such as "NO_OFFICIAL_SHA1_HASH". When developers build their own builds from their working directories, the built code would not include a SHA1 hash value (only the dummy value) because the code from the working directory doesn't even have a corresponding SHA1 hash value yet.

On the other hand, when an official build is made by your build server, from sources pulled from a central repository, then you know the SHA1 hash value for the source code. At that point, you can substitute the hash value in the CMake file and then run CMake.

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Here's my solution, which I think is reasonably short yet effective ;-)

First, a file is needed in the source tree (I name it git-rev.h.in), it should looks something like this:

#define STR_EXPAND(x) #x
#define STR(x) STR_EXPAND(x)
#define GIT_REV_ \ 

(Please never mind those macros, that's a little bit insane trick to make a string out of a raw value.) It is essential that this file has exactly one empty newline at the end so that value can be appended.

And now this code goes in respective CMakeLists.txt file:

# --- Git revision ---
add_dependencies(your_awesome_target gitrev)      #put name of your target here
include_directories(${CMAKE_CURRENT_BINARY_DIR})  #so that the include file is found
set(gitrev_in git-rev.h.in)                       #just filenames, feel free to change them...
set(gitrev git-rev.h)
  ${CMAKE_COMMAND} -E remove -f ${CMAKE_CURRENT_BINARY_DIR}/${gitrev}
  COMMAND git rev-parse HEAD >> ${CMAKE_CURRENT_BINARY_DIR}/${gitrev}
  WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR}         #very important, otherwise git repo might not be found in shadow build
  VERBATIM                                              #portability wanted

This command ensuers that the git-rev.h.in is copied in the build tree as git-rev.h and git revision is appended at its end.

So all you need to do next is include git-rev.h in one of your files and do whatever you want with the GIT_REV macro, which yields current git revision hash as a string value.

The nice thing about this solution is that the git-rev.h is recreated each time you build the associated target, so you don't have to run cmake over and over again.

It also should be pretty portable - no non-portable external tools were used and even the bloody stupid windows cmd supports the > and >> operators ;-)

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For a quick and dirty, possibly not portable way to get the git SHA-1 into a C or C++ project using CMake, I use this in CMakeLists.txt:

 git log -1 "--format=format:#define GIT_REVISION \"%H\"%n" HEAD > git_revision.h

It assumes that CMAKE_SOURCE_DIR is part of a git repository, and that git is available on the system, and that an output redirection will be properly parsed by the shell.

You can then make this target a dependency of any other target using

add_dependencies(your_program git_revision.h)

Each time your_program is built, the Makefile (or other build system, if this works on other build systems) will recreate git_revision.h in the source directory, with the contents

#define GIT_REVISION "<SHA-1 of the current git revision>"

So you can #include git_revision.h from some source code file and use it that way. Note that the header is created at literally every build, i.e. even if every other object file is up to date, it will still run this command to recreate git_revision.h. I figure that shouldn't be a huge problem because usually you don't rebuild the same git revision over and over again, but it's something to be aware of, and if it is a problem for you, then don't use this. (It's probably possible to hack up a workaround using add_custom_command but I haven't needed it so far.)

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I did this in such as way as to generate:

const std::string Version::GIT_SHA1 = "e7fb69fb8ee93ac66f006406781138562d0250fb";
const std::string Version::GIT_DATE = "Thu Jan 9 14:17:56 2014";
const std::string Version::GIT_COMMIT_SUBJECT = "Fix all the bugs";

If the workspace that performed the build had pending, uncommitted changes, the above SHA1 string will be suffixed with -dirty.

In CMakeLists.txt:

# the commit's SHA1, and whether the building workspace was dirty or not
  "${GIT_EXECUTABLE}" describe --match=NeVeRmAtCh --always --abbrev=40 --dirty

# the date of the commit
  "${GIT_EXECUTABLE}" log -1 --format=%ad --date=local

# the subject of the commit
  "${GIT_EXECUTABLE}" log -1 --format=%s

# generate version.cc
configure_file("${CMAKE_CURRENT_SOURCE_DIR}/version.cc.in" "${CMAKE_CURRENT_BINARY_DIR}/version.cc" @ONLY)

list(APPEND SOURCES "${CMAKE_CURRENT_BINARY_DIR}/version.cc" version.hh)

This requires version.cc.in:

#include "version.hh"

using namespace my_app;

const std::string Version::GIT_SHA1 = "@GIT_SHA1@";
const std::string Version::GIT_DATE = "@GIT_DATE@";
const std::string Version::GIT_COMMIT_SUBJECT = "@GIT_COMMIT_SUBJECT@";

And version.hh:

#pragma once

#include <string>

namespace my_app
  struct Version
    static const std::string GIT_SHA1;
    static const std::string GIT_DATE;
    static const std::string GIT_COMMIT_SUBJECT;

Then in code I can write:

cout << "Build SHA1: " << Version::GIT_SHA1 << endl;
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The following solution is based on the observation that Git updates the HEAD log whenever you pull or commit something. Note that e.g. Drew's suggestion above will update the Git information only if you rebuild the CMake cache manually after every commit.

I use a CMake "custom command" that generates a one-line header file ${SRCDIR}/gitrevision.hh where ${SRCDIR} is the root of your source tree. It will be re-made only when a new commit is made. Here is the necessary CMake magic with some comments:

# Generate gitrevision.hh if Git is available
# and the .git directory is present
# this is the case when the software is checked out from a Git repo
find_program(GIT_SCM git DOC "Git version control")
    # Create gitrevision.hh
    # that depends on the Git HEAD log
    add_custom_command(OUTPUT ${SRCDIR}/gitrevision.hh
        COMMAND ${CMAKE_COMMAND} -E echo_append "#define GITREVISION " > ${SRCDIR}/gitrevision.hh
        COMMAND ${GIT_SCM} log -1 "--pretty=format:%h %ai" >> ${SRCDIR}/gitrevision.hh
        DEPENDS ${GITDIR}/logs/HEAD
    # No version control
    # e.g. when the software is built from a source tarball
    # and gitrevision.hh is packaged with it but no Git is available
    message(STATUS "Will not remake ${SRCDIR}/gitrevision.hh")

The contents of gitrevision.hh will look like this:

#define GITREVISION cb93d53 2014-03-13 11:08:15 +0100

If you want to change this then edit the --pretty=format: specification accordingly. E.g. using %H instead of %h will print the full SHA1 digest. See the Git manual for details.

Making gitrevision.hh a fully-fledged C++ header file with include guards etc. is left as an exercise to the reader :-)

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