Re: Out of memory with diff.colormoved enabled

From: Jeff King <peff@peff.net>
Date: Oct 12, 2017, 20:05 UTC
Message-ID: <20171012200536.m6oz4zrjcze3yw4i@sigill.intra.peff.net>
In-Reply-To: <CAGHpTBLQ8vi00e3Tt3KTrCfaAWhZKQX6u6Ca17t2ySVQdoGc5g@mail.gmail.com>

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

Show 7 quoted lines

> 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