From 2acf4cf0010379f10b39eba1fb4e0868a5ba4114 Mon Sep 17 00:00:00 2001 From: Johannes Schindelin Date: Tue, 24 May 2022 00:23:06 +0000 Subject: dir.c: avoid "exceeds maximum object size" error with GCC v12.x Technically, the pointer difference `end - start` _could_ be negative, and when cast to an (unsigned) `size_t` that would cause problems. In this instance, the symptom is: dir.c: In function 'git_url_basename': dir.c:3087:13: error: 'memchr' specified bound [9223372036854775808, 0] exceeds maximum object size 9223372036854775807 [-Werror=stringop-overread] CC ewah/bitmap.o 3087 | if (memchr(start, '/', end - start) == NULL | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ While it is a bit far-fetched to think that `end` (which is defined as `repo + strlen(repo)`) and `start` (which starts at `repo` and never steps beyond the NUL terminator) could result in such a negative difference, GCC has no way of knowing that. See also https://gcc.gnu.org/bugzilla//show_bug.cgi?id=85783. Let's just add a safety check, primarily for GCC's benefit. Signed-off-by: Johannes Schindelin Signed-off-by: Junio C Hamano --- dir.c | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'dir.c') diff --git a/dir.c b/dir.c index 5aa6fbad0b..ea78f60623 100644 --- a/dir.c +++ b/dir.c @@ -3076,6 +3076,15 @@ char *git_url_basename(const char *repo, int is_bundle, int is_bare) end--; } + /* + * It should not be possible to overflow `ptrdiff_t` by passing in an + * insanely long URL, but GCC does not know that and will complain + * without this check. + */ + if (end - start < 0) + die(_("No directory name could be guessed.\n" + "Please specify a directory on the command line")); + /* * Strip trailing port number if we've got only a * hostname (that is, there is no dir separator but a -- cgit v1.2.3