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From: Jeff King <peff@peff.net>
To: Orgad Shaneh <orgads@gmail.com>
Cc: Stefan Beller <sbeller@google.com>, git <git@vger.kernel.org>
Subject: Re: Out of memory with diff.colormoved enabled
Date: Thu, 12 Oct 2017 16:05:36 -0400
Message-ID: <20171012200536.m6oz4zrjcze3yw4i@sigill.intra.peff.net> (raw)
In-Reply-To: <CAGHpTBLQ8vi00e3Tt3KTrCfaAWhZKQX6u6Ca17t2ySVQdoGc5g@mail.gmail.com>

On Thu, Oct 12, 2017 at 10:53:23PM +0300, Orgad Shaneh wrote:

> There is an infinite loop when colormoved is used with --ignore-space-change:
> 
> git init
> seq 20 > test
> git add test
> sed -i 's/9/42/' test
> git -c diff.colormoved diff --ignore-space-change -- test

Thanks for an easy reproduction recipe.

It looks like the problem is that next_byte() doesn't make any forward
progress in the buffer with --ignore-space-change. We try to convert
whitespace into a single space (I'm not sure why, but I'm not very
familiar with this part of the code). But if there's no space, then the
"cp" pointer never gets advanced.

This fixes it, but I have no idea if it's doing the right thing:

diff --git a/diff.c b/diff.c
index 69f03570ad..e8dedc7357 100644
--- a/diff.c
+++ b/diff.c
@@ -713,13 +713,17 @@ static int next_byte(const char **cp, const char **endp,
 		return -1;
 
 	if (DIFF_XDL_TST(diffopt, IGNORE_WHITESPACE_CHANGE)) {
-		while (*cp < *endp && isspace(**cp))
+		int saw_whitespace = 0;
+		while (*cp < *endp && isspace(**cp)) {
 			(*cp)++;
+			saw_whitespace = 1;
+		}
 		/*
 		 * After skipping a couple of whitespaces, we still have to
 		 * account for one space.
 		 */
-		return (int)' ';
+		if (saw_whitespace)
+			return (int)' ';
 	}
 
 	if (DIFF_XDL_TST(diffopt, IGNORE_WHITESPACE)) {

I guess it would be equally correct to not enter that if-block unless
isspace(**cp).

-Peff

  reply index

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-10-12 19:53 Orgad Shaneh
2017-10-12 20:05 ` Jeff King [this message]
2017-10-12 22:39   ` Stefan Beller
2017-10-12 23:33   ` [PATCH] diff.c: increment buffer pointer in all code path Stefan Beller
2017-10-13  0:18     ` Jeff King
2017-10-13  0:20       ` Jeff King
2017-10-13  0:24         ` Stefan Beller
2017-10-19  5:04         ` Jeff King
2017-10-19  5:24           ` Jeff King
2017-10-19  5:30             ` Junio C Hamano
2017-10-19  5:32               ` Junio C Hamano
2017-10-19  5:32                 ` Jeff King
2017-10-19  5:42               ` Jeff King
2017-10-19 19:55                 ` Stefan Beller
2017-10-19 20:23                 ` [PATCH 0/5] fix "diff --color-moved --ignore-space-at-eol" Jeff King
2017-10-19 20:24                   ` [PATCH 1/5] t4015: refactor --color-moved whitespace test Jeff King
2017-10-19 20:56                     ` Stefan Beller
2017-10-19 21:10                       ` Jeff King
2017-10-19 20:25                   ` [PATCH 2/5] t4015: check "negative" case for "-w --color-moved" Jeff King
2017-10-19 20:54                     ` Stefan Beller
2017-10-19 20:26                   ` [PATCH 3/5] t4015: test the output of "diff --color-moved -b" Jeff King
2017-10-19 21:03                     ` Stefan Beller
2017-10-19 21:14                       ` Jeff King
2017-10-19 20:29                   ` [PATCH 4/5] diff: fix whitespace-skipping with --color-moved Jeff King
2017-10-19 21:15                     ` Stefan Beller
2017-10-19 21:19                       ` Jeff King
2017-10-20  7:23                     ` Simon Ruderich
2017-10-20 22:37                       ` Jeff King
2017-10-19 20:31                   ` [PATCH 5/5] diff: handle NULs in get_string_hash() Jeff King
2017-10-19 21:31                     ` Stefan Beller
2017-10-19 21:39                       ` Jeff King
2017-10-19 21:50                         ` Stefan Beller
2017-10-19 19:53             ` [PATCH] diff.c: increment buffer pointer in all code path Stefan Beller
2017-10-19 19:55               ` Jeff King

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