Attachment 131802 Details for Bug 101349 – Commit (as output by 'git format-patch')

[patch] Commit (as output by 'git format-patch')

0001-Fix-an-off-by-one-error-in-FcLangSetIndex.patch (text/plain), 2.67 KB, created by Florent Rougon on 2017-06-08 13:59:25 UTC

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Creator: Florent Rougon

Created: 2017-06-08 13:59:25 UTC

Size: 2.67 KB

patch

obsolete

>From 5006886a312afb256d327c0e5db7c28882593344 Mon Sep 17 00:00:00 2001
>From: Florent Rougon <f.rougon@free.fr>
>Date: Tue, 6 Jun 2017 23:32:28 +0200
>Subject: [PATCH] Fix an off-by-one error in FcLangSetIndex()
>To: fontconfig@lists.freedesktop.org
>
>This commit fixes a bug that can be reproduced like this:
>  - remove all languages starting with 'a' in fc-lang/Makefile.am (in
>    ORTH's definition);
>  - rebuild fontconfig with this change (-> new fc-lang/fclang.h);
>  - create an FcLangSet 'ls1' that contains at least the first language
>    from fcLangCharSets (i.e., the first *remaining* in lexicographic
>    order); let's assume it is "ba" for the sake of this description;
>  - create an FcLangSet 'ls2' that only contains the language "aa" (any
>    language starting with 'a' should work as well);
>  - check the return value of FcLangSetContains(ls1, ls2);
>
>The expected return value is FcFalse, however it is FcTrue if you use
>the code before this commit.
>
>What happens is that FcLangSetIndex() returns 0, because this is the
>index of the first slot after the not-found language "aa" in
>fcLangCharSets (since we removed all languages starting with 'a').
>However, this index happens to be non-negative, therefore
>FcLangSetContainsLang() mistakenly infers that the language "aa" was
>found in fcLangCharSets, and thus calls FcLangSetBitGet(ls1, 0), which
>returns FcTrue since we've put the first remaining language "ba" in the
>'ls1' language set.
>
>The "return -low;" statement previously in FcLangSetIndex() was
>inconsistent with the final return statement. "return -(low+1);" fixes
>this inconsistency as well as the incorrect behavior described above.
>---
> src/fclang.c | 11 ++++++++++-
> 1 file changed, 10 insertions(+), 1 deletion(-)
>
>diff --git a/src/fclang.c b/src/fclang.c
>index b1fd1bc..19f3ddd 100644
>--- a/src/fclang.c
>+++ b/src/fclang.c
>@@ -505,6 +505,15 @@ bail0:
>     return 0;
> }
> 
>+/* When the language isn't found, the return value r is such that:
>+ *  1) r < 0
>+ *  2) -r -1 is the index of the first language in fcLangCharSets that comes
>+ *     after the 'lang' argument in lexicographic order.
>+ *
>+ *  The -1 is necessary to avoid problems with language id 0 (otherwise, we
>+ *  wouldn't be able to distinguish between âlanguage found, id is 0â and
>+ *  âlanguage not found, sorts right before the language with id 0â).
>+ */
> static int
> FcLangSetIndex (const FcChar8 *lang)
> {
>@@ -529,7 +538,7 @@ FcLangSetIndex (const FcChar8 *lang)
> 	high = fcLangCharSetRanges[firstChar - 'a'].end;
> 	/* no matches */
> 	if (low > high)
>-	    return -low; /* next entry after where it would be */
>+	    return -(low+1); /* one past next entry after where it would be */
>     }
> 
>     while (low <= high)
>-- 
>2.11.0
>

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