[PATCH] exclude: fix a bug in prefix comparison optimization

[PATCH] exclude: fix a bug in prefix comparison optimization

[Nguyễn Thái Ngọc Duy]

When "namelen" becomes zero at this stage, we have matched the fixed
part, but whether it actually matches the pattern still depends on the
pattern in "exclude". As demonstrated in t3001, path "three/a.3"
exists and it matches the "three/a.3" part in pattern "three/a.3[abc]",
but that does not mean a true match.

Don't be too optimistic and let fnmatch() do the job.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
---
 dir.c                              | 2 +-
 t/t3001-ls-files-others-exclude.sh | 6 ++++++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/dir.c b/dir.c
index 4868339..90bf3a4 100644
--- a/dir.c
+++ b/dir.c
@@ -575,7 +575,7 @@ int excluded_from_list(const char *pathname,
 			namelen -= prefix;
 		}
 
-		if (!namelen || !fnmatch_icase(exclude, name, FNM_PATHNAME))
+		if (!fnmatch_icase(exclude, name, FNM_PATHNAME))
 			return to_exclude;
 	}
 	return -1; /* undecided */
diff --git a/t/t3001-ls-files-others-exclude.sh b/t/t3001-ls-files-others-exclude.sh
index c8fe978..dc2f045 100755
--- a/t/t3001-ls-files-others-exclude.sh
+++ b/t/t3001-ls-files-others-exclude.sh
@@ -214,4 +214,10 @@ test_expect_success 'subdirectory ignore (l1)' '
 	test_cmp expect actual
 '
 
+test_expect_success 'pattern matches prefix completely' '
+	: >expect &&
+	git ls-files -i -o --exclude "/three/a.3[abc]" >actual &&
+	test_cmp expect actual
+'
+
 test_done
-- 
1.8.0.rc2.11.g2b79d01

Re: [PATCH] exclude: fix a bug in prefix comparison optimization

[Junio C Hamano]

Nguyễn Thái Ngọc Duy <pclouds@gmail.com> writes:

> When "namelen" becomes zero at this stage, we have matched the fixed
> part, but whether it actually matches the pattern still depends on the
> pattern in "exclude". As demonstrated in t3001, path "three/a.3"
> exists and it matches the "three/a.3" part in pattern "three/a.3[abc]",
> but that does not mean a true match.
>
> Don't be too optimistic and let fnmatch() do the job.

Yeah, the existing code is correct _only_ if the pattern part can
match an empty string (e.g. "three/a.3*") and this is a correct fix.

With your "teach attr.c match the same optimization as dir.c"
series, you would need something like this

diff --git i/attr.c w/attr.c
index 6d39406..528e935 100644
--- i/attr.c
+++ w/attr.c
@@ -710,7 +710,7 @@ static int path_matches(const char *pathname, int pathlen,
 	 * if the non-wildcard part is longer than the remaining
 	 * pathname, surely it cannot match.
 	 */
-	if (!namelen || prefix > namelen)
+	if (prefix > namelen)
 		return 0;
 	if (baselen != 0)
 		baselen++;

Comparing the corresponding code in dir.c, there is no "compare the
literal prefix part with strcmp() before doing the fnmatch()"
optimization.  Intended?

(warning: I haven't had my caffeine yet)

Re: [PATCH] exclude: fix a bug in prefix comparison optimization

[Junio C Hamano]

Junio C Hamano <gitster@pobox.com> writes:

> Comparing the corresponding code in dir.c, there is no "compare the
> literal prefix part with strcmp() before doing the fnmatch()"
> optimization.  Intended?
>
> (warning: I haven't had my caffeine yet)

And it turns out that at the point I wrote the response, I still had
the attr-match-optim-more updates to be read in my mailbox ;-)
 

Re: [PATCH] exclude: fix a bug in prefix comparison optimization

[Nguyen Thai Ngoc Duy]

On Mon, Oct 15, 2012 at 12:36 AM, Junio C Hamano <gitster@pobox.com> wrote:
> With your "teach attr.c match the same optimization as dir.c"
> series, you would need something like this
>
> diff --git i/attr.c w/attr.c
> index 6d39406..528e935 100644
> --- i/attr.c
> +++ w/attr.c
> @@ -710,7 +710,7 @@ static int path_matches(const char *pathname, int pathlen,
>          * if the non-wildcard part is longer than the remaining
>          * pathname, surely it cannot match.
>          */
> -       if (!namelen || prefix > namelen)
> +       if (prefix > namelen)
>                 return 0;
>         if (baselen != 0)
>                 baselen++;

If there's still a chance to rewrite attr-match-optim-more series (I
see it's in next now), then I could reorder the patches so that
excluded_from_list code refactoring goes first, then rewrite "teach
attr.c match... as dir.c" patch makes use of the new functions without
code duplication. The end result would be the same, except that we
won't see this bug in attr.c's history. Not much value so if it may
take a lot of your time, don't bother.
--
Duy

Re: [PATCH] exclude: fix a bug in prefix comparison optimization

[Junio C Hamano]

Nguyen Thai Ngoc Duy <pclouds@gmail.com> writes:

> On Mon, Oct 15, 2012 at 12:36 AM, Junio C Hamano <gitster@pobox.com> wrote:
>> With your "teach attr.c match the same optimization as dir.c"
>> series, you would need something like this
>>
>> diff --git i/attr.c w/attr.c
>> index 6d39406..528e935 100644
>> --- i/attr.c
>> +++ w/attr.c
>> @@ -710,7 +710,7 @@ static int path_matches(const char *pathname, int pathlen,
>>          * if the non-wildcard part is longer than the remaining
>>          * pathname, surely it cannot match.
>>          */
>> -       if (!namelen || prefix > namelen)
>> +       if (prefix > namelen)
>>                 return 0;
>>         if (baselen != 0)
>>                 baselen++;
>
> If there's still a chance to rewrite attr-match-optim-more series (I
> see it's in next now), then I could reorder the patches so that
> excluded_from_list code refactoring goes first, then rewrite "teach
> attr.c match... as dir.c" patch makes use of the new functions without
> code duplication. The end result would be the same, except that we
> won't see this bug in attr.c's history. Not much value so if it may
> take a lot of your time, don't bother.

Actually it started to become nuisance to deal with conflicts among
as/check-ignore and the attr/dir/wildmatch series, and I've been
wondering if it makes sense to eject all of these out of 'next' (as
they won't advance beyond 'next' until the next release anyway).

So please go ahead and reroll the whole thing if you think the end
result would be a history with better organization.