@@ -36,6 +36,13 @@ MAKEFLAGS += --no-builtin-rules
CFLAGS = -Wall -O2 -I $(top_srcdir) $(EXTRA_CFLAGS) $(KHDR_INCLUDES) $(TOOLS_INCLUDES)
LDLIBS = -lrt -lpthread -lm
+# Some distributions (such as Ubuntu) configure GCC so that _FORTIFY_SOURCE is
+# automatically enabled at -O1 or above. This triggers various unused-result
+# warnings where functions such as read() or write() are called and their
+# return value is not checked. Disable _FORTIFY_SOURCE to silence those
+# warnings.
+CFLAGS += -U_FORTIFY_SOURCE
+
KDIR ?= /lib/modules/$(shell uname -r)/build
ifneq (,$(wildcard $(KDIR)/Module.symvers))
ifneq (,$(wildcard $(KDIR)/include/linux/page_frag_cache.h))
Switching to -O2 when building the mm tests has the unexpected side effect of triggering many unused-result warnings on certain distros like Ubuntu, where GCC is configured so that -O2 implies -D_FORTIFY_SOURCE. Explicitly disable FORTIFY_SOURCE to avoid those warnings. This has no effect on upstream toolchains where FORTIFY_SOURCE is not implicitly enabled. Suggested-by: Ryan Roberts <ryan.roberts@arm.com> Signed-off-by: Kevin Brodsky <kevin.brodsky@arm.com> --- Hi Andrew, Could you please take this fixup patch for "selftests/mm: Build with -O2" in mm-unstable? Ryan found that building the mm kselftests on Ubuntu yields a bunch of warnings, this patch suppresses them. Cheers, - Kevin Cc: aruna.ramakrishna@oracle.com Cc: catalin.marinas@arm.com Cc: dave.hansen@linux.intel.com Cc: joey.gouly@arm.com Cc: keith.lucas@oracle.com Cc: shuah@kernel.org Cc: linux-arm-kernel@lists.infradead.org Cc: linux-kselftest@vger.kernel.org Cc: linux-mm@kvack.org Cc: x86@kernel.org --- tools/testing/selftests/mm/Makefile | 7 +++++++ 1 file changed, 7 insertions(+)