Jeff King <peff@xxxxxxxx> writes:
> On Mon, Oct 24, 2016 at 04:53:50PM -0700, Junio C Hamano wrote:
>
>> > So how about this? It gets rid of magic number 3 and works for array
>> > size that's not a power of two. And as a nice side effect it can't
>> > trigger a signed overflow anymore.
>>
>> Looks good to me. Peff?
>
> Any of the variants discussed in this thread is fine by me.
OK, here is what I'll queue then.
I assumed that René wants to sign it off ;-).
-- >8 --
From: René Scharfe <l.s.r@xxxxxx>
Date: Sun, 23 Oct 2016 19:57:30 +0200
Subject: [PATCH] hex: make wraparound of the index into ring-buffer explicit
Overflow is defined for unsigned integers, but not for signed ones.
We could make the ring-buffer index in sha1_to_hex() and
get_pathname() unsigned to be on the safe side to resolve this, but
let's make it explicit that we are wrapping around at whatever the
number of elements the ring-buffer has. The compiler is smart enough
to turn modulus into bitmask for these codepaths that use
ring-buffers of a size that is a power of 2.
Signed-off-by: René Scharfe <l.s.r@xxxxxx>
Signed-off-by: Junio C Hamano <gitster@xxxxxxxxx>
---
hex.c | 3 ++-
path.c | 3 ++-
2 files changed, 4 insertions(+), 2 deletions(-)
diff --git a/hex.c b/hex.c
index ab2610e498..845b01a874 100644
--- a/hex.c
+++ b/hex.c
@@ -78,7 +78,8 @@ char *sha1_to_hex(const unsigned char *sha1)
{
static int bufno;
static char hexbuffer[4][GIT_SHA1_HEXSZ + 1];
- return sha1_to_hex_r(hexbuffer[3 & ++bufno], sha1);
+ bufno = (bufno + 1) % ARRAY_SIZE(hexbuffer);
+ return sha1_to_hex_r(hexbuffer[bufno], sha1);
}
char *oid_to_hex(const struct object_id *oid)
diff --git a/path.c b/path.c
index fe3c4d96c6..9bfaeda207 100644
--- a/path.c
+++ b/path.c
@@ -24,7 +24,8 @@ static struct strbuf *get_pathname(void)
STRBUF_INIT, STRBUF_INIT, STRBUF_INIT, STRBUF_INIT
};
static int index;
- struct strbuf *sb = &pathname_array[3 & ++index];
+ struct strbuf *sb = &pathname_array[index];
+ index = (index + 1) % ARRAY_SIZE(pathname_array);
strbuf_reset(sb);
return sb;
}
--
2.10.1-777-gd068e6bde7