54 lines
1.6 KiB
Diff
54 lines
1.6 KiB
Diff
https://gitlab.freedesktop.org/fontconfig/fontconfig/-/merge_requests/333
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From 8db62f5a77fd53543dd58e12da7bd96082228893 Mon Sep 17 00:00:00 2001
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From: Sam James <sam@gentoo.org>
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Date: Tue, 8 Oct 2024 16:48:19 +0100
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Subject: [PATCH] fontconfig: mark _FcPatternIter as may_alias
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We had a report of GCC 14 with -O3 -flto causing wrong font
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sizes with fontconfig (showing up in qalculate-gtk).
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It turns out to be because _FcPatternIter and _FcPatternPrivateIter
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are punned between which violates strict-aliasing rules, which
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manifested in FcDefaultSubstitute getting a bogus value from
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FcValueCanonicalize for size.
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void* isn't allowed to alias anything -- you can pass addresses
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around provided you cast back to the original type, but if you
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access through the wrong type, you've violated aliasing rules.
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Bug: https://bugs.gentoo.org/940923
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Signed-off-by: Sam James <sam@gentoo.org>
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--- a/fontconfig/fontconfig.h
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+++ b/fontconfig/fontconfig.h
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@@ -32,8 +32,10 @@
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#if defined(__GNUC__) && (__GNUC__ >= 4)
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#define FC_ATTRIBUTE_SENTINEL(x) __attribute__((__sentinel__(0)))
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+#define FC_ATTRIBUTE_MAY_ALIAS __attribute__((may_alias))
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#else
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#define FC_ATTRIBUTE_SENTINEL(x)
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+#define FC_ATTRIBUTE_MAY_ALIAS
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#endif
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#ifndef FcPublic
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@@ -253,7 +255,7 @@ typedef enum _FcValueBinding {
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typedef struct _FcPattern FcPattern;
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-typedef struct _FcPatternIter {
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+typedef struct FC_ATTRIBUTE_MAY_ALIAS _FcPatternIter {
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void *dummy1;
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void *dummy2;
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} FcPatternIter;
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@@ -1160,6 +1162,7 @@ FcConfigParseAndLoadFromMemory (FcConfig *config,
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_FCFUNCPROTOEND
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#undef FC_ATTRIBUTE_SENTINEL
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+#undef FC_ATTRIBUTE_MAY_ALIAS
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#ifndef _FCINT_H_
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--
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GitLab
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