diff mbox series

[v2,1/2] mailinfo: use starts_with() for clarity

Message ID 20190401215334.18678-1-rybak.a.v@gmail.com (mailing list archive)
State New, archived
Headers show
Series [v2,1/2] mailinfo: use starts_with() for clarity | expand

Commit Message

Andrei Rybak April 1, 2019, 9:53 p.m. UTC 
Existing checks using memcmp(3) never read past the end of the line,
because all substrings we are interested in are two characters long, and
the outer loop guarantees we have at least one character. So at most we
will look at the NUL.

However, this is too subtle and may lead to bugs in code which copies
this behavior without realizing substring length requirement.  So use
starts_with() instead, which will stop at NUL regardless of the length
of the prefix. Remove extra pair of parentheses while we are here.

Helped-by: Jeff King <peff@peff.net>
Signed-off-by: Andrei Rybak <rybak.a.v@gmail.com>
---

On Mon, Apr 01, 2019 at 06:11:57 -0400, Jeff King wrote:
> I wonder if it's worth re-writing it like:

Turned Peff's suggestion into a patch.

 mailinfo.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Comments

Jeff King April 2, 2019, 2:28 p.m. UTC | #1 
On Mon, Apr 01, 2019 at 11:53:33PM +0200, Andrei Rybak wrote:

> Existing checks using memcmp(3) never read past the end of the line,
> because all substrings we are interested in are two characters long, and
> the outer loop guarantees we have at least one character. So at most we
> will look at the NUL.
> 
> However, this is too subtle and may lead to bugs in code which copies
> this behavior without realizing substring length requirement.  So use
> starts_with() instead, which will stop at NUL regardless of the length
> of the prefix. Remove extra pair of parentheses while we are here.
> 
> Helped-by: Jeff King <peff@peff.net>
> Signed-off-by: Andrei Rybak <rybak.a.v@gmail.com>
> ---
> 
> On Mon, Apr 01, 2019 at 06:11:57 -0400, Jeff King wrote:
> > I wonder if it's worth re-writing it like:
> 
> Turned Peff's suggestion into a patch.

Thanks. I think this may be worth doing regardless of what happens with
patch 2.

-Peff
diff mbox series

Patch

diff --git a/mailinfo.c b/mailinfo.c
index b395adbdf2..f4aaa89788 100644
--- a/mailinfo.c
+++ b/mailinfo.c
@@ -693,8 +693,8 @@  static int is_scissors_line(const char *line)
 			perforation++;
 			continue;
 		}
-		if ((!memcmp(c, ">8", 2) || !memcmp(c, "8<", 2) ||
-		     !memcmp(c, ">%", 2) || !memcmp(c, "%<", 2))) {
+		if (starts_with(c, ">8") || starts_with(c, "8<") ||
+		    starts_with(c, ">%") || starts_with(c, "%<")) {
 			in_perforation = 1;
 			perforation += 2;
 			scissors += 2;