From mboxrd@z Thu Jan 1 00:00:00 1970 From: Maxime Coquelin Subject: Re: [PATCH] vhost: fix false-positive warning from clang 5 Date: Wed, 11 Oct 2017 12:12:07 +0200 Message-ID: <0a77b5a9-fa1a-6409-2518-5e2738888da9@redhat.com> References: <20171011095907.229893-1-bruce.richardson@intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Cc: dev@dpdk.org To: Bruce Richardson , yliu@fridaylinux.org Return-path: Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) by dpdk.org (Postfix) with ESMTP id 31C767D34 for ; Wed, 11 Oct 2017 12:12:11 +0200 (CEST) In-Reply-To: <20171011095907.229893-1-bruce.richardson@intel.com> Content-Language: en-US List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" On 10/11/2017 11:59 AM, Bruce Richardson wrote: > When compiling with clang extra warning flags, such as used by default with > meson, a warning is given in iotlb.c: > > ../lib/librte_vhost/iotlb.c:318:6: warning: variable 'socket' is used uninitialized whenever 'if' condition is false [-Wsometimes-uninitialized] > > This is a false positive, as the socket value will be initialized by the > call to get_mempolicy in the case where the NUMA build-time flag is set, > and in cases where it is not set, "if (ret)" will always be true as ret is > initialized to -1 and never changed. > > However, this is not immediately obvious, and is perhaps a little fragile, > as it will break if other code using ret is subsequently added above the > call to get_mempolicy by someone unaware of this subtle dependency. > Therefore, we can fix the warning and making the code more robust by > explicitly initializing socket to zero, and moving the extra condition > check on ret into the #ifdef alongside the call to get_mempolicy which sets > ret. > > Fixes: d012d1f293f4 ("vhost: add IOTLB helper functions") > > CC: Maxime Coquelin > Signed-off-by: Bruce Richardson > --- > lib/librte_vhost/iotlb.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > I agree this is a bit fragile. Thanks for handling this: Reviewed-by: Maxime Coquelin Thanks, Maxime