From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:59993) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZWcD8-00026u-Az for qemu-devel@nongnu.org; Mon, 31 Aug 2015 23:26:15 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZWcD4-0006XU-Cd for qemu-devel@nongnu.org; Mon, 31 Aug 2015 23:26:14 -0400 From: David Gibson Date: Tue, 1 Sep 2015 13:17:18 +1000 Message-Id: <1441077438-24900-1-git-send-email-david@gibson.dropbear.id.au> Subject: [Qemu-devel] [RFC] spapr_drc: Fix potential undefined behaviour List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: peter.maydell@linaro.org, aik@ozlabs.ru, agraf@suse.de, benh@kernel.crashing.org Cc: qemu-ppc@nongnu.org, qemu-devel@nongnu.org, David Gibson The DRC_INDEX_ID_MASK macro does a left shift on ~0, which is a signed quantity, and therefore undefined behaviour according to the C spec. In particular this causes warnings from the clang sanitizer. This fixes it by calculating the same mask without using ~0 (I think the new method is a more common idiom for generating masks anyway). For good measure I also use 1ULL to force the expression's type to unsigned long long, which should be good for assigning to anything we're going to want to. Reported-by: Peter Maydell Signed-off-by: David Gibson --- hw/ppc/spapr_drc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) I'm hoping to get some Reviewed-bys for this patch so that I'm ready to merge my spapr-next queue. diff --git a/hw/ppc/spapr_drc.c b/hw/ppc/spapr_drc.c index ee87432..8cbcf4d 100644 --- a/hw/ppc/spapr_drc.c +++ b/hw/ppc/spapr_drc.c @@ -32,7 +32,7 @@ #define DRC_CONTAINER_PATH "/dr-connector" #define DRC_INDEX_TYPE_SHIFT 28 -#define DRC_INDEX_ID_MASK (~(~0 << DRC_INDEX_TYPE_SHIFT)) +#define DRC_INDEX_ID_MASK ((1ULL << DRC_INDEX_TYPE_SHIFT) - 1) static sPAPRDRConnectorTypeShift get_type_shift(sPAPRDRConnectorType type) { -- 2.4.3