Re: Crash on MSYS2 with GIT_WORK_TREE

Johannes Schindelin [off-list ref] writes:

The problem is actually even worse: On *Linux*, this happens:

	$ GIT_WORK_TREE=c:/invalid git rev-parse HEAD
	Segmentation fault (core dumped)

The reason is this: when set_git_work_tree() was converted from using
xstrdup(real_path()) to real_pathdup(), we completely missed the fact that
the former passed die_on_error = 1 to strbuf_realpath(), while the latter
passed die_on_error = 0. As a consequence, work_tree can be NULL now, and
the current code does not expect set_git_work_tree() to return
successfully after setting work_tree to NULL.

Ouch.

Brandon, I have a hunch that pretty much all of the xstrdup(real_path())
-> real_pathdup() sites have a problem now. The previous contract was that
real_path() would die() if the passed path is invalid. The new contract is
that real_pathdup() returns NULL in such a case.

OK, so it appears that we'd better audit all the callsites of
real_pathdup() and see if anybody _assumes_ that the return values
are not NULL.  They all need fixing.

Thanks for digging it through to the root cause.