Subject: [PATCH 1/3] pkt-line: simplify starts_with checks in packet tracing

From: Jeff King <[email-masked]>
Date: Fri, 12 Jun 2015 17:28:08 -0400

We carefully check that our pkt buffer has enough characters
before seeing if it starts with "PACK". The intent is to
avoid reading random memory if we get a short buffer like
"PAC".

However, we know that the traced packets are always
NUL-terminated. They come from one of these sources:

  1. A string literal.

  2. `format_packet`, which uses a strbuf.

  3. `packet_read`, which defensively NUL-terminates what we
     read.

We can therefore drop the length checks, as we know we will
hit the trailing NUL if we have a short input.

Signed-off-by: Jeff King <[email-masked]>
---
 pkt-line.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/pkt-line.c b/pkt-line.c
index 187a229..0477d2e 100644
--- a/pkt-line.c
+++ b/pkt-line.c
@@ -24,8 +24,7 @@ static void packet_trace(const char *buf, unsigned int len, int write)
 	strbuf_addf(&out, "packet: %12s%c ",
 		    packet_trace_prefix, write ? '>' : '<');
 
-	if ((len >= 4 && starts_with(buf, "PACK")) ||
-	    (len >= 5 && starts_with(buf+1, "PACK"))) {
+	if (starts_with(buf, "PACK") || starts_with(buf + 1, "PACK")) {
 		strbuf_addstr(&out, "PACK ...");
 		trace_disable(&trace_packet);
 	}
-- 
2.4.2.752.geeb594a