From 7109c889f11b39a2c5a5122e3726be7ffce09faf Mon Sep 17 00:00:00 2001 From: Junio C Hamano Date: Mon, 29 Oct 2007 11:53:55 -0700 Subject: [PATCH] sha1_file.c: avoid gcc signed overflow warnings With the recent gcc, we get: sha1_file.c: In check_packed_git_: sha1_file.c:527: warning: assuming signed overflow does not occur when assuming that (X + c) < X is always false sha1_file.c:527: warning: assuming signed overflow does not occur when assuming that (X + c) < X is always false for a piece of code that tries to make sure that off_t is large enough to hold more than 2^32 offset. The test tried to make sure these do not wrap-around: /* make sure we can deal with large pack offsets */ off_t x = 0x7fffffffUL, y = 0xffffffffUL; if (x > (x + 1) || y > (y + 1)) { but gcc assumes it can do whatever optimization it wants for a signed overflow (undefined behaviour) and warns about this construct. Follow Linus's suggestion to check sizeof(off_t) instead to work around the problem. Signed-off-by: Junio C Hamano --- sha1_file.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) diff --git a/sha1_file.c b/sha1_file.c index 9978a58da..95b5a403d 100644 --- a/sha1_file.c +++ b/sha1_file.c @@ -521,13 +521,15 @@ static int check_packed_git_idx(const char *path, struct packed_git *p) munmap(idx_map, idx_size); return error("wrong index v2 file size in %s", path); } - if (idx_size != min_size) { - /* make sure we can deal with large pack offsets */ - off_t x = 0x7fffffffUL, y = 0xffffffffUL; - if (x > (x + 1) || y > (y + 1)) { - munmap(idx_map, idx_size); - return error("pack too large for current definition of off_t in %s", path); - } + if (idx_size != min_size && + /* + * make sure we can deal with large pack offsets. + * 31-bit signed offset won't be enough, neither + * 32-bit unsigned one will be. + */ + (sizeof(off_t) <= 4)) { + munmap(idx_map, idx_size); + return error("pack too large for current definition of off_t in %s", path); } } -- 2.30.2