From: Thomas Rast <trast@student.ethz.ch>
To: Antoine Pelisse <apelisse@gmail.com>
Cc: <git@vger.kernel.org>, Junio C Hamano <gitster@pobox.com>
Subject: [PATCH] diff: prevent pprint_rename from underrunning input
Date: Tue, 26 Feb 2013 21:47:01 +0100 [thread overview]
Message-ID: <d74fcfa693e5feb7249023feda8d3ad1f22ab16d.1361911196.git.trast@student.ethz.ch> (raw)
In-Reply-To: <1361638125-11245-1-git-send-email-apelisse@gmail.com>
The logic described in d020e27 (diff: Fix rename pretty-print when
suffix and prefix overlap, 2013-02-23) is wrong: The proof in the
comment is valid only if both strings are the same length. *One* of
old/new can reach a-1 (b-1, resp.) if 'a' is a suffix of 'b' (or vice
versa).
Since the intent was to let the loop run down to the '/' at the end of
the common prefix, fix it by making that distinction explicit: if
there is no prefix, allow no underrun.
Signed-off-by: Thomas Rast <trast@student.ethz.ch>
---
Hi Antoine,
Unfortunately there's this bug in your patch. Luckily it was found by
valgrind on t4016 and others.
Cheers
Thomas
diff.c | 17 ++++++++++-------
1 file changed, 10 insertions(+), 7 deletions(-)
diff --git a/diff.c b/diff.c
index 7d49cab..8396527 100644
--- a/diff.c
+++ b/diff.c
@@ -1264,6 +1264,7 @@ static char *pprint_rename(const char *a, const char *b)
const char *new = b;
struct strbuf name = STRBUF_INIT;
int pfx_length, sfx_length;
+ int pfx_adjust_for_slash;
int len_a = strlen(a);
int len_b = strlen(b);
int a_midlen, b_midlen;
@@ -1291,14 +1292,16 @@ static char *pprint_rename(const char *a, const char *b)
new = b + len_b;
sfx_length = 0;
/*
- * Note:
- * if pfx_length is 0, old/new will never reach a - 1 because it
- * would mean the whole string is common suffix. But then, the
- * whole string would also be a common prefix, and we would not
- * have pfx_length equals 0.
+ * If there is a common prefix, it must end in a slash. In
+ * that case we let this loop run 1 into the prefix to see the
+ * same slash.
+ *
+ * If there is no common prefix, we cannot do this as it would
+ * underrun the input strings.
*/
- while (a + pfx_length - 1 <= old &&
- b + pfx_length - 1 <= new &&
+ pfx_adjust_for_slash = (pfx_length ? 1 : 0);
+ while (a + pfx_length - pfx_adjust_for_slash <= old &&
+ b + pfx_length - pfx_adjust_for_slash <= new &&
*old == *new) {
if (*old == '/')
sfx_length = len_a - (old - a);
--
1.8.2.rc1.307.ge0d2dea
next prev parent reply other threads:[~2013-02-26 20:47 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-02-23 16:48 [PATCH] diff: Fix rename pretty-print when suffix and prefix overlap Antoine Pelisse
2013-02-24 9:15 ` Junio C Hamano
2013-02-25 19:50 ` Antoine Pelisse
2013-02-25 22:36 ` Philip Oakley
2013-02-25 22:41 ` Antoine Pelisse
2013-02-28 21:55 ` Antoine Pelisse
2013-02-28 22:14 ` Thomas Rast
2013-02-28 22:22 ` Antoine Pelisse
2013-02-28 22:29 ` Junio C Hamano
2013-03-02 14:38 ` [PATCH] tests: make sure rename pretty print works Antoine Pelisse
2013-03-03 6:50 ` Junio C Hamano
2013-03-06 21:36 ` [PATCH v2] " Antoine Pelisse
2013-03-06 22:03 ` Junio C Hamano
2013-02-26 20:47 ` Thomas Rast [this message]
2013-02-26 21:44 ` [PATCH] diff: prevent pprint_rename from underrunning input Junio C Hamano
2013-02-27 13:27 ` Antoine Pelisse
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