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@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/hex.c b/hex.c
index ab2610e498615b197787a8c22cd00f979e488fc8..845b01a874b45314a22e6000bb4e7762c3dd846a 100644 (file)
--- 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 fe3c4d96c6d82b2c8f4e1553f1a52e410c8c02d3..9bfaeda2071636ec8a5a5ee32491494f5f83211c 100644 (file)
--- 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;
 }