Re: [PATCH] diff.c: increment buffer pointer in all code path
- From
Jeff King <peff@peff.net>
- Date
- Oct 13, 2017, 00:18 UTC
- Message-ID
- <20171013001837.43nx5paeqisbrflq@sigill.intra.peff.net>
- In-Reply-To
- <20171012233322.31203-1-sbeller@google.com>
On Thu, Oct 12, 2017 at 04:33:22PM -0700, Stefan Beller wrote:
> Peff, feel free to take ownership here. I merely made it to a patch.
I think compared to my original, it makes sense to actually wrap the whole thing with a check for the whitespace. You can do it just in the IGNORE_WHITESPACE_CHANGE conditional, but I think it makes more sense to cover both. Like the patch below (view with "-w" to see the logic more clearly).
I also tweaked the test to remove "sed -i", which isn't portable, and fixed up a few style nits.
-- >8 -- Subject: diff: fix infinite loop with --color-moved --ignore-space-change
The --color-moved code uses next_byte() to advance through the blob contents. When the user has asked to ignore whitespace changes, we try to collapse any whitespace change down to a single space.
However, we enter the conditional block whenever we see the IGNORE_WHITESPACE_CHANGE flag, even if the next byte isn't whitespace.
This means that the combination of "--color-moved and --ignore-space-change" was completely broken. Worse, because we return from next_byte() without having advanced our pointer, the function makes no forward progress in the buffer and loops infinitely.
Fix this by entering the conditional only when we actually see whitespace. We can apply this also to the IGNORE_WHITESPACE change. That code path isn't buggy (because it falls through to returning the next non-whitespace byte), but it makes the logic more clear if we only bother to look at whitespace flags after seeing that the next byte is whitespace.
Reported-by: Orgad Shaneh <orgads@gmail.com> Signed-off-by: Jeff King <peff@peff.net> --- diff.c | 28 +++++++++++++++------------- t/t4015-diff-whitespace.sh | 9 +++++++++ 2 files changed, 24 insertions(+), 13 deletions(-)
diff --git a/diff.c b/diff.c index 69f03570ad..d76bb937c1 100644 --- a/diff.c +++ b/diff.c @@ -712,20 +712,22 @@ static int next_byte(const char **cp, const char **endp, if (*cp > *endp) return -1; - if (DIFF_XDL_TST(diffopt, IGNORE_WHITESPACE_CHANGE)) { - while (*cp < *endp && isspace(**cp)) - (*cp)++; - /* - * After skipping a couple of whitespaces, we still have to - * account for one space. - */ - return (int)' '; - } + if (isspace(**cp)) { + if (DIFF_XDL_TST(diffopt, IGNORE_WHITESPACE_CHANGE)) { + while (*cp < *endp && isspace(**cp)) + (*cp)++; + /* + * After skipping a couple of whitespaces, + * we still have to account for one space. + */ + return (int)' '; + } - if (DIFF_XDL_TST(diffopt, IGNORE_WHITESPACE)) { - while (*cp < *endp && isspace(**cp)) - (*cp)++; - /* return the first non-ws character via the usual below */ + if (DIFF_XDL_TST(diffopt, IGNORE_WHITESPACE)) { + while (*cp < *endp && isspace(**cp)) + (*cp)++; + /* return the first non-ws character via the usual below */ + } } retval = (unsigned char)(**cp); diff --git a/t/t4015-diff-whitespace.sh b/t/t4015-diff-whitespace.sh index bd0f75d9f7..87083f728f 100755 --- a/t/t4015-diff-whitespace.sh +++ b/t/t4015-diff-whitespace.sh @@ -1530,4 +1530,13 @@ test_expect_success 'move detection with submodules' ' test_cmp expect decoded_actual ' +test_expect_success 'move detection with whitespace changes' ' + test_when_finished "git reset --hard" && + test_seq 10 >test && + git add test && + sed s/3/42/ <test >test.tmp && + mv test.tmp test && + git -c diff.colormoved diff --ignore-space-change -- test +' + test_done
-- 2.15.0.rc1.381.g94fac273d4