how to include git commit-number into a c++ executable?

Question

i use git as a version tracker for my c++ project.

sometimes i need to repeat a calculation and i would like to know which version of the program i used.

wh

Answer 1

I use git describe to get a version which either uses a tag or commit number. This usually gives nice versions like: v0.1-1-g787c667 if the tip of the branch has additional commits above the 'v0.1' tag.

The git command I use is: git describe --tags --always. I usually use it with the SCons build system and define it as a constant, relevant parts of the SConstruct:

import os, sys 
from subprocess import *

def getGitDesc():   
  return Popen('git describe --tags --always', stdout=PIPE, shell=True).stdout.read ().strip ()

GIT_DESC = getGitDesc () 
print "Building " + getGitDesc () + ".." 
env = Environment ()

# set up environment 
env.Append (CPPDEFINES = { 'GIT_DESC' : ('\\"%s\\"' % GIT_DESC) } )

# build your program
env.Program (....)

In the C or C++ program I can now access GIT_DESC as a string-constant:

# include 

using namespace std;

int main (int argc, char ** argv) {
  cout << "Version: " << GIT_DESC << endl;
  return 42;
}

note: the --abbrev=N argument to git describe might be useful to achieve consistent version output independent of a users git configuration.