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.

what would be a good way to put a # of the commit into the main executable? in other words. i'd like the program to tell me the # of the current commit in an introductory message as i run the program.

one way i can think of is to make the c++ program lunch "git log" from shell and extract the commit # but i'm not sure how to do it during make.

(I use linux)

Answer 1

Probably the easiest way to do this would be to add to your makefile a rule to generate a .c file with the current git commit ID:

gitversion.c: .git/HEAD .git/index     echo "const char *gitversion = \"$(shell git rev-parse HEAD)\";" > $@ 

Now simply add gitversion.c to your build process as normal. Make sure to remove it on make clean, and add it to .gitignore so it's not added to the git repository accidentally. Add an extern const char *gitversion; to a header somewhere, and you can access it like that.

Answer 2

I do the following in CMakeLists.txt:

IF(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/.git)   FIND_PACKAGE(Git)   IF(GIT_FOUND)     EXECUTE_PROCESS(       COMMAND ${GIT_EXECUTABLE} rev-parse --short HEAD       WORKING_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}"       OUTPUT_VARIABLE "kml2maps_BUILD_VERSION"       ERROR_QUIET       OUTPUT_STRIP_TRAILING_WHITESPACE)     MESSAGE( STATUS "Git version: ${kml2maps_BUILD_VERSION}" )   ELSE(GIT_FOUND)     SET(kml2maps_BUILD_VERSION 0)   ENDIF(GIT_FOUND) ENDIF(EXISTS ${CMAKE_CURRENT_SOURCE_DIR}/.git)  CONFIGURE_FILE(${CMAKE_CURRENT_SOURCE_DIR}/kml2mapsVersion.h.in ${CMAKE_CURRENT_BINARY_DIR}/kml2mapsVersion.h @ONLY) 

So the git rev-parse --short HEAD's output is good to build in the binary.