media-libs/fontconfig: fix aliasing violation

We had a report of GCC 14 with -O3 -flto causing wrong font
sizes with fontconfig (showing up in qalculate-gtk).

It turns out to be because _FcPatternIter and _FcPatternPrivateIter
are punned between which violates strict-aliasing rules, which
manifested in FcDefaultSubstitute getting a bogus value from
FcValueCanonicalize for size.

Mark the bad struct as may_alias to fix that.

Closes: https://bugs.gentoo.org/940923
Signed-off-by: Sam James <sam@gentoo.org>

2 files changed, 287 insertions, 0 deletions

diff --git a/media-libs/fontconfig/files/fontconfig-2.15.0-aliasing.patch b/media-libs/fontconfig/files/fontconfig-2.15.0-aliasing.patch
new file mode 100644
index 000000000000..03709ac2c3a7
--- /dev/null
+++ b/media-libs/fontconfig/files/fontconfig-2.15.0-aliasing.patch
@@ -0,0 +1,53 @@
+https://gitlab.freedesktop.org/fontconfig/fontconfig/-/merge_requests/333
+
+From 8db62f5a77fd53543dd58e12da7bd96082228893 Mon Sep 17 00:00:00 2001
+From: Sam James <sam@gentoo.org>
+Date: Tue, 8 Oct 2024 16:48:19 +0100
+Subject: [PATCH] fontconfig: mark _FcPatternIter as may_alias
+
+We had a report of GCC 14 with -O3 -flto causing wrong font
+sizes with fontconfig (showing up in qalculate-gtk).
+
+It turns out to be because _FcPatternIter and _FcPatternPrivateIter
+are punned between which violates strict-aliasing rules, which
+manifested in FcDefaultSubstitute getting a bogus value from
+FcValueCanonicalize for size.
+
+void* isn't allowed to alias anything -- you can pass addresses
+around provided you cast back to the original type, but if you
+access through the wrong type, you've violated aliasing rules.
+
+Bug: https://bugs.gentoo.org/940923
+Signed-off-by: Sam James <sam@gentoo.org>
+--- a/fontconfig/fontconfig.h
++++ b/fontconfig/fontconfig.h
+@@ -32,8 +32,10 @@
+ 
+ #if defined(__GNUC__) && (__GNUC__ >= 4)
+ #define FC_ATTRIBUTE_SENTINEL(x) __attribute__((__sentinel__(0)))
++#define FC_ATTRIBUTE_MAY_ALIAS __attribute__((may_alias))
+ #else
+ #define FC_ATTRIBUTE_SENTINEL(x)
++#define FC_ATTRIBUTE_MAY_ALIAS
+ #endif
+ 
+ #ifndef FcPublic
+@@ -253,7 +255,7 @@ typedef enum _FcValueBinding {
+ 
+ typedef struct _FcPattern   FcPattern;
+ 
+-typedef struct _FcPatternIter {
++typedef struct FC_ATTRIBUTE_MAY_ALIAS _FcPatternIter {
+     void *dummy1;
+     void *dummy2;
+ } FcPatternIter;
+@@ -1160,6 +1162,7 @@ FcConfigParseAndLoadFromMemory (FcConfig       *config,
+ _FCFUNCPROTOEND
+ 
+ #undef FC_ATTRIBUTE_SENTINEL
++#undef FC_ATTRIBUTE_MAY_ALIAS
+ 
+ 
+ #ifndef _FCINT_H_
+-- 
+GitLab
diff --git a/media-libs/fontconfig/fontconfig-2.15.0-r1.ebuild b/media-libs/fontconfig/fontconfig-2.15.0-r1.ebuild
new file mode 100644
index 000000000000..f1472130c4cc
--- /dev/null
+++ b/media-libs/fontconfig/fontconfig-2.15.0-r1.ebuild
@@ -0,0 +1,234 @@
+# Copyright 1999-2024 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+EAPI=8
+
+PYTHON_COMPAT=( python3_{10..13} )
+inherit multilib meson-multilib python-any-r1 readme.gentoo-r1
+
+DESCRIPTION="A library for configuring and customizing font access"
+HOMEPAGE="https://fontconfig.org/"
+SRC_URI="https://fontconfig.org/release/${P}.tar.xz"
+
+LICENSE="MIT"
+SLOT="1.0"
+if ! [[ $(ver_cut 3) -ge 90 ]] ; then
+	KEYWORDS="~alpha ~amd64 ~arm ~arm64 ~hppa ~loong ~m68k ~mips ~ppc ~ppc64 ~riscv ~s390 ~sparc ~x86 ~amd64-linux ~x86-linux ~arm64-macos ~ppc-macos ~x64-macos ~x64-solaris"
+fi
+IUSE="doc nls test"
+RESTRICT="!test? ( test )"
+
+# - Check minimum freetype & other deps on bumps. See
+#   https://gitlab.freedesktop.org/fontconfig/fontconfig/-/blob/main/configure.ac#L314.
+#   Note that FT versioning is confusing, need to map it using
+#   https://git.savannah.gnu.org/cgit/freetype/freetype2.git/tree/docs/VERSIONS.TXT
+#   But sometimes it's actually greater than that, e.g. see Fedora's spec file
+#   https://src.fedoraproject.org/rpms/fontconfig/blob/rawhide/f/fontconfig.spec#_1
+#
+# - Purposefully dropped the xml USE flag and libxml2 support. Expat is the
+#   default and used by every distro. See bug #283191.
+#
+# - There's a test-only dep on json-c.
+#   It might become an optional(?) runtime dep in future though. Who knows.
+#   Keep an eye on it.
+RDEPEND="
+	>=dev-libs/expat-2.1.0-r3[${MULTILIB_USEDEP}]
+	>=media-libs/freetype-2.9.1[${MULTILIB_USEDEP}]
+	virtual/libintl[${MULTILIB_USEDEP}]
+	!elibc_Darwin? ( !elibc_SunOS? ( sys-apps/util-linux[${MULTILIB_USEDEP}] ) )
+	elibc_Darwin? ( sys-libs/native-uuid )
+	elibc_SunOS? ( sys-libs/libuuid )
+"
+DEPEND="
+	${RDEPEND}
+	test? ( dev-libs/json-c )
+"
+BDEPEND="
+	${PYTHON_DEPS}
+	dev-util/gperf
+	virtual/pkgconfig
+	doc? (
+		=app-text/docbook-sgml-dtd-3.1*
+		app-text/docbook-sgml-utils[jadetex]
+	)
+	nls? ( >=sys-devel/gettext-0.19.8 )
+"
+PDEPEND="virtual/ttf-fonts"
+# We need app-eselect/eselect-fontconfig in IDEPEND to update ROOT
+# when cross-compiling.
+IDEPEND="app-eselect/eselect-fontconfig"
+
+PATCHES=(
+	# bug #130466 + make liberation default
+	"${FILESDIR}"/${PN}-2.14.0-latin-update.patch
+	# Avoid test failure (bubblewrap doesn't work within sandbox)
+	"${FILESDIR}"/${PN}-2.14.0-skip-bubblewrap-tests.patch
+	# Fix aliasing (bug #940923)
+	"${FILESDIR}"/${PN}-2.15.0-aliasing.patch
+
+	# Patches from upstream (can usually be removed with next version bump)
+	"${FILESDIR}"/${PN}-2.14.2-math-fabs.patch
+)
+
+DOC_CONTENTS="Please make fontconfig configuration changes using
+\`eselect fontconfig\`. Any changes made to /etc/fonts/fonts.conf will be
+overwritten. If you need to reset your configuration to upstream defaults,
+delete the directory ${EROOT}/etc/fonts/conf.d/ and re-emerge fontconfig."
+
+src_prepare() {
+	default
+
+	# Test needs network access
+	# https://gitlab.freedesktop.org/fontconfig/fontconfig/-/issues/319
+	# On bumps, please check to see if this has been fixed
+	# to allow local access!
+	sed -i -e '/test-crbug1004254/d' test/meson.build || die
+}
+
+multilib_src_configure() {
+	local addfonts=(
+		"${EPREFIX}"/usr/local/share/fonts
+	)
+
+	# Harvest some font locations, such that users can benefit from the
+	# host OS's installed fonts
+	case ${CHOST} in
+		*-darwin*)
+			addfonts+=(
+				/Library/Fonts
+				/System/Library/Fonts
+			)
+		;;
+
+		*-solaris*)
+			[[ -d /usr/X/lib/X11/fonts/TrueType ]] && \
+				addfonts+=( /usr/X/lib/X11/fonts/TrueType )
+			[[ -d /usr/X/lib/X11/fonts/Type1 ]] &&
+				addfonts+=( /usr/X/lib/X11/fonts/Type1 )
+		;;
+
+		*-linux-gnu)
+			use prefix && [[ -d /usr/share/fonts ]] && \
+				addfonts+=( /usr/share/fonts )
+		;;
+	esac
+
+	local emesonargs=(
+		# USE=doc only controls the additional bits like html/pdf
+		# and regeneration of man pages from source. We always install
+		# the prebuilt man pages.
+		$(meson_native_use_feature doc)
+		$(meson_native_use_feature doc doc-txt)
+		$(meson_native_use_feature doc doc-html)
+		$(meson_native_use_feature doc doc-man)
+		$(meson_native_use_feature doc doc-pdf)
+
+		$(meson_native_use_feature nls)
+		$(meson_feature test tests)
+
+		-Dcache-build=disabled
+		-Dcache-dir="${EPREFIX}"/var/cache/fontconfig
+		-Ddefault-fonts-dirs="${EPREFIX}"/usr/share/fonts
+		-Dadditional-fonts-dirs=$(IFS=, ; echo "${addfonts[*]}" )
+		-Dtemplate-dir="${EPREFIX}"/etc/fonts/conf.avail
+
+		# Let users choose via eselect-fontconfig. See bug #900681
+		# and https://gitlab.freedesktop.org/fontconfig/fontconfig/-/issues/356.
+		-Ddefault-sub-pixel-rendering=none
+	)
+
+	meson_src_configure
+}
+
+multilib_src_install() {
+	MULTILIB_CHOST_TOOLS=( /usr/bin/fc-cache$(get_exeext) )
+
+	meson_src_install
+
+	# Avoid calling this multiple times, bug #459210
+	if multilib_is_native_abi; then
+		insinto /etc/fonts
+		doins fonts.conf
+	fi
+}
+
+multilib_src_install_all() {
+	einstalldocs
+
+	# fc-lang directory contains language coverage datafiles
+	# which are needed to test the coverage of fonts.
+	insinto /usr/share/fc-lang
+	doins fc-lang/*.orth
+
+	dodoc doc/fontconfig-user.{txt,pdf}
+
+	if ! use doc ; then
+		find "${S}" -name "*.[[:digit:]]" -type f -exec doman '{}' + || die
+	fi
+
+	if [[ -e ${ED}/usr/share/doc/fontconfig/ ]] ;  then
+		mv "${ED}"/usr/share/doc/fontconfig/* "${ED}"/usr/share/doc/${PF} || die
+		rm -rf "${ED}"/usr/share/doc/fontconfig || die
+	fi
+
+	# Changes should be made to /etc/fonts/local.conf, and as we had
+	# too much problems with broken fonts.conf we force update it ...
+	echo 'CONFIG_PROTECT_MASK="/etc/fonts/fonts.conf"' > "${T}"/37fontconfig || die
+	doenvd "${T}"/37fontconfig
+
+	# As of fontconfig 2.7, everything sticks their noses in here.
+	dodir /etc/sandbox.d
+	echo 'SANDBOX_PREDICT="/var/cache/fontconfig"' > "${ED}"/etc/sandbox.d/37fontconfig || die
+
+	readme.gentoo_create_doc
+}
+
+pkg_preinst() {
+	# bug #193476
+	# /etc/fonts/conf.d/ contains symlinks to ../conf.avail/ to include various
+	# config files.  If we install as-is, we'll blow away user settings.
+	ebegin "Syncing fontconfig configuration to system"
+	if [[ -e ${EROOT}/etc/fonts/conf.d ]] ; then
+		local file f
+		for file in "${EROOT}"/etc/fonts/conf.avail/* ; do
+			f=${file##*/}
+			if [[ -L ${EROOT}/etc/fonts/conf.d/${f} ]] ; then
+				[[ -f ${ED}/etc/fonts/conf.avail/${f} ]] \
+					&& ln -sf ../conf.avail/"${f}" \
+						"${ED}"/etc/fonts/conf.d/ &>/dev/null
+			else
+				[[ -f ${ED}/etc/fonts/conf.avail/${f} ]] \
+					&& rm "${ED}"/etc/fonts/conf.d/"${f}" &>/dev/null
+			fi
+		done
+	fi
+	eend $?
+}
+
+pkg_postinst() {
+	einfo "Cleaning broken symlinks in ${EROOT}/etc/fonts/conf.d/"
+	find -L "${EROOT}"/etc/fonts/conf.d/ -type l -delete
+
+	readme.gentoo_print_elog
+
+	local ver
+	for ver in ${REPLACING_VERSIONS} ; do
+		# 2.14.2 and 2.14.2-r1 included the bad 10-sub-pixel-none.conf
+		if ver_test ${ver} -lt 2.14.2-r2 && ver_test ${ver} -ge 2.14.2 ; then
+			if [[ -e "${EROOT}"/etc/fonts/conf.d/10-sub-pixel-none.conf ]] ; then
+				einfo "Deleting 10-sub-pixel-none.conf from bad fontconfig-2.14.2 (bug #900681)"
+				rm "${EROOT}"/etc/fonts/conf.d/10-sub-pixel-none.conf || die
+			fi
+		fi
+	done
+
+	if [[ -z ${ROOT} ]] ; then
+		multilib_pkg_postinst() {
+			ebegin "Creating global font cache for ${ABI}"
+			"${EPREFIX}"/usr/bin/${CHOST}-fc-cache -srf
+			eend $?
+		}
+
+		multilib_parallel_foreach_abi multilib_pkg_postinst
+	fi
+}