hex: make wraparound of the index into ring-buffer explicitrs/ring-buffer-wraparound

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>

1 files changed, 2 insertions, 1 deletions

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;
 }