--- memory/jemalloc/Makefile.in~
+++ memory/jemalloc/Makefile.in
@@ -12,3 +12,7 @@ include $(topsrcdir)/config/rules.mk
 ifdef GNU_CC
 CFLAGS += -std=gnu99
 endif
+
+# XXX startup crash workaround for gcc47 on amd64
+jemalloc.$(OBJ_SUFFIX): OS_CFLAGS := $(filter-out -O3 -Ofast,$(OS_CFLAGS))
+jemalloc.$(OBJ_SUFFIX): MOZ_OPTIMIZE_FLAGS=