# [PATCH] Fix a comparison bug in diff-delta.c 3 messages from 2006-08-23 to 2006-08-23. Participants: Pierre Habouzit, Nicolas Pitre. Thread: https://gitlist.dev/t/5359 ## Pierre Habouzit, 2006-08-23 02:32 Subject: [PATCH] Fix a comparison bug in diff-delta.c Message-ID: <1156300368160-git-send-email-madcoder@debian.org> URL: https://gitlist.dev/e/1156300368160-git-send-email-madcoder%40debian.org ``` (1 << i) < hspace is compared in the `int` space rather that in the unsigned one. the result will be wrong if hspace is between 0x40000000 and 0x80000000. Signed-off-by: Pierre Habouzit --- I'm currently trying to make git compile with more strict gcc flags (-g -O2 -Wall -Wextra -Wno-unused -Werror to be precise) and I've spotted a first bug due to a signed/unsigned comparison. If I do understand that bit of code, it should not bite a lot of people, but this is still a bug ;) diff-delta.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-) diff --git a/diff-delta.c b/diff-delta.c index 7da9205..a1fadc9 100644 --- a/diff-delta.c +++ b/diff-delta.c @@ -152,7 +152,7 @@ struct delta_index * create_delta_index( initialization in create_delta(). */ entries = (bufsize - 1) / RABIN_WINDOW; hsize = entries / 4; - for (i = 4; (1 << i) < hsize && i < 31; i++); + for (i = 4; (unsigned)(1 << i) < hsize && i < 31; i++); hsize = 1 << i; hmask = hsize - 1; -- 1.4.1.1 ``` ## Pierre Habouzit, 2006-08-23 02:38 Subject: Re: [PATCH] Fix a comparison bug in diff-delta.c Message-ID: <200608230438.06053.madcoder@debian.org> URL: https://gitlist.dev/e/200608230438.06053.madcoder%40debian.org In-Reply-To: <1156300368160-git-send-email-madcoder@debian.org> ``` Le mer 23 août 2006 04:32, Pierre Habouzit a écrit : >   I'm currently trying to make git compile with more strict gcc flags > (-g -O2 -Wall -Wextra -Wno-unused -Werror to be precise) and I've > spotted a first bug due to a signed/unsigned comparison. still in the same kind of "problems" sha1_name.c:512 has: if (active_nr < 0) return -1; but active_nr is defined as an unsigned (in cache.h/cache-read.c). Also note that there is a *lot* of signed/unsigned comparisons due to the fact that it's unsigned, and that it's often compared to positions that are ints (I assume pos need the negative values to mean "error"). so either those two lines are too much, or active_nr has to be a plain signed int. I'm not used to git sources enough yet to be able to make the right decision. -- ·O· Pierre Habouzit ··O madcoder@debian.org OOO http://www.madism.org ``` ## Nicolas Pitre, 2006-08-23 03:17 Subject: Re: [PATCH] Fix a comparison bug in diff-delta.c Message-ID: URL: https://gitlist.dev/e/Pine.LNX.4.64.0608222311060.3683%40localhost.localdomain In-Reply-To: <1156300368160-git-send-email-madcoder@debian.org> ``` On Wed, 23 Aug 2006, Pierre Habouzit wrote: > (1 << i) < hspace is compared in the `int` space rather that in the unsigned one. > the result will be wrong if hspace is between 0x40000000 and 0x80000000. > > Signed-off-by: Pierre Habouzit Could you use (1u << i) instead of (unsigned)(1 << i) ? That looks prettier to me at least. Nicolas ```