--- firefox-21.0.ebuild.orig	2013-06-19 00:05:05.000000000 +0200
+++ firefox-21.0.ebuild	2013-06-17 04:22:52.000000000 +0200
@@ -39,7 +39,7 @@
 KEYWORDS="~alpha ~amd64 ~arm ~hppa ~ia64 ~ppc ~ppc64 ~x86 ~amd64-linux ~x86-linux"
 SLOT="0"
 LICENSE="MPL-2.0 GPL-2 LGPL-2.1"
-IUSE="bindist gstreamer +jit +minimal pgo pulseaudio selinux system-cairo system-jpeg system-sqlite"
+IUSE="address-sanitizer bindist gstreamer +jit +minimal pgo pulseaudio selinux system-cairo system-jpeg system-sqlite"
 
 # More URIs appended below...
 SRC_URI="${SRC_URI}
@@ -238,6 +238,50 @@
 	mozconfig_use_enable jit ion
 	mozconfig_use_enable system-cairo
 
+	# compiler-dependent settings
+	if [[ $(tc-getCC) =~ clang ]]; then
+		mozconfig_annotate 'from ebuild, CC=clang detected' --enable-llvm-hacks
+
+		# methodjit causes clang builds to segfault on x86_64 (see bug #462608)
+		# same for ion code..
+		if use amd64; then
+			sed -e '/javascript.options.methodjit/ s/true/false/' \
+				-e '/javascript.options.ion/ s/true/false/' \
+				-i "${S}"/modules/libpref/src/init/all.js
+		fi
+
+		# https://developer.mozilla.org/en-US/docs/Building_Firefox_with_Address_Sanitizer
+		if use address-sanitizer; then
+			echo "export MOZ_JEMALLOC=0" >> ${S}/.mozconfig
+			mozconfig_annotate '+address-sanitizer' --disable-crash-reporter
+			mozconfig_annotate '+address-sanitizer' --disable-elf-hack
+			mozconfig_annotate '+address-sanitizer' --disable-jemalloc
+			mozconfig_annotate '+address-sanitizer' --disable-replace-malloc
+
+			echo "export MOZ_DEBUG_SYMBOLS=1" >> ${S}/.mozconfig
+			mozconfig_use_enable address-sanitizer debug-symbols
+			mozconfig_use_enable address-sanitizer
+			append-flags "-fsanitize=address"
+			append-flags "-Dxmalloc=myxmalloc"
+		fi
+	else
+		use address-sanitizer && die "Use flag address-sanitizer can only be \
+			enabled if CC=clang is set. You're using a different compiler."
+
+		if [[ $(gcc-major-version) -lt 4 ]]; then
+			append-cxxflags -fno-stack-protector
+		elif [[ $(gcc-major-version) -gt 4 || $(gcc-minor-version) -gt 3 ]]; then
+			if use amd64 || use x86; then
+				append-flags -mno-avx
+			fi
+		fi
+	fi
+
+	# support EXTRA_ECONF, maybe this should be in mozcoreconf-2.eclass ..
+	for eeopt in $EXTRA_ECONF; do
+		mozconfig_annotate 'from ebuild, passed using EXTRA_ECONF' $eeopt
+	done
+
 	# Allow for a proper pgo build
 	if use pgo; then
 		echo "mk_add_options PROFILE_GEN_SCRIPT='\$(PYTHON) \$(OBJDIR)/_profile/pgo/profileserver.py'" >> "${S}"/.mozconfig
@@ -245,14 +289,6 @@
 
 	# Finalize and report settings
 	mozconfig_final
-
-	if [[ $(gcc-major-version) -lt 4 ]]; then
-		append-cxxflags -fno-stack-protector
-	elif [[ $(gcc-major-version) -gt 4 || $(gcc-minor-version) -gt 3 ]]; then
-		if use amd64 || use x86; then
-			append-flags -mno-avx
-		fi
-	fi
 }
 
 src_compile() {