Debugging Git

Debugging Git using the GNU debugger (GDB)

First of all, Git's .exe files should be rebuilt with debugging information, and without optimization (because gdb has serious troubles single-stepping code compiled using -O2 for some reason). To this end:

1. install the Git for Windows SDK
2. edit /usr/src/git/Makefile to remove the -O2 from the CFLAGS = -g -O2 -Wall line,
3. edit /usr/src/git/config.mak.uname to remove the line BASIC_LDFLAGS += -Wl,--dynamicbase, and then
4. run make in /usr/src/git/.

After that, you can run Git's executables in GDB like so:

gdb --args ./git.exe --exec-path=/usr/src/git rev-parse HEAD

Stopping at certain errors

Sometimes it is useful to ask the debugger to pause the program when the code path is entered that outputs an error message. The functions in Git that output error messages are error_builtin() and die_builtin(). So you can set the breakpoints

b error_builtin
b die_builtin

before calling run in gdb to stop execution at the appropriate time.