# [PATCH] sha1_name: make wraparound of the index into ring-buffer explicit 2 messages from 2016-11-01 to 2016-11-01. Participants: René Scharfe, Jeff King. Thread: https://gitlist.dev/t/44405 ## René Scharfe, 2016-11-01 08:49 Subject: [PATCH] sha1_name: make wraparound of the index into ring-buffer explicit Message-ID: URL: https://gitlist.dev/e/a1e2c4a4-4720-fc26-c866-6ab959543c3b%40web.de ``` Overflow is defined for unsigned integers, but not for signed ones. Wrap around explicitly for the new ring-buffer in find_unique_abbrev() as we did in bb84735c for the ones in sha1_to_hex() and get_pathname(), thus avoiding signed overflows and getting rid of the magic number 3. Signed-off-by: Rene Scharfe --- sha1_name.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/sha1_name.c b/sha1_name.c index 06409a3..73a915f 100644 --- a/sha1_name.c +++ b/sha1_name.c @@ -510,7 +510,8 @@ const char *find_unique_abbrev(const unsigned char *sha1, int len) { static int bufno; static char hexbuffer[4][GIT_SHA1_HEXSZ + 1]; - char *hex = hexbuffer[3 & ++bufno]; + char *hex = hexbuffer[bufno]; + bufno = (bufno + 1) % ARRAY_SIZE(hexbuffer); find_unique_abbrev_r(hex, sha1, len); return hex; } -- 2.10.2 ``` ## Jeff King, 2016-11-01 15:04 Subject: Re: [PATCH] sha1_name: make wraparound of the index into ring-buffer explicit Message-ID: <20161101150429.fohpchtlfvohzood@sigill.intra.peff.net> URL: https://gitlist.dev/e/20161101150429.fohpchtlfvohzood%40sigill.intra.peff.net In-Reply-To: ``` On Tue, Nov 01, 2016 at 09:49:07AM +0100, René Scharfe wrote: > Overflow is defined for unsigned integers, but not for signed ones. > Wrap around explicitly for the new ring-buffer in find_unique_abbrev() > as we did in bb84735c for the ones in sha1_to_hex() and get_pathname(), > thus avoiding signed overflows and getting rid of the magic number 3. Thanks. I didn't mean to make you do this, but my procrastination won again. > diff --git a/sha1_name.c b/sha1_name.c > index 06409a3..73a915f 100644 > --- a/sha1_name.c > +++ b/sha1_name.c > @@ -510,7 +510,8 @@ const char *find_unique_abbrev(const unsigned char *sha1, int len) > { > static int bufno; > static char hexbuffer[4][GIT_SHA1_HEXSZ + 1]; > - char *hex = hexbuffer[3 & ++bufno]; > + char *hex = hexbuffer[bufno]; > + bufno = (bufno + 1) % ARRAY_SIZE(hexbuffer); Code looks obviously correct (and it even does the "start at 0" thing). -Peff ```