From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:60682) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cUEIq-0007Kd-Um for qemu-devel@nongnu.org; Thu, 19 Jan 2017 10:07:09 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cUEIn-0001r1-Iw for qemu-devel@nongnu.org; Thu, 19 Jan 2017 10:07:04 -0500 Received: from mx1.redhat.com ([209.132.183.28]:36602) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1cUEIn-0001qe-E0 for qemu-devel@nongnu.org; Thu, 19 Jan 2017 10:07:01 -0500 Date: Thu, 19 Jan 2017 17:06:59 +0200 From: "Michael S. Tsirkin" Message-ID: <20170119170645-mutt-send-email-mst@kernel.org> References: <1484772931-16272-1-git-send-email-mst@redhat.com> <1484772931-16272-5-git-send-email-mst@redhat.com> <29f56f57-76f5-8585-c286-70bc0eb60b92@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <29f56f57-76f5-8585-c286-70bc0eb60b92@redhat.com> Subject: Re: [Qemu-devel] [PATCH v2 4/4] ARRAY_SIZE: check that argument is an array List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eric Blake Cc: qemu-devel@nongnu.org, pbonzini@redhat.com, Peter Maydell , Markus Armbruster , Sergey Fedorov On Thu, Jan 19, 2017 at 08:53:34AM -0600, Eric Blake wrote: > On 01/18/2017 02:55 PM, Michael S. Tsirkin wrote: > > It's a familiar pattern: some code uses ARRAY_SIZE, then refactoring > > changes the argument from an array to a pointer to a dynamically > > allocated buffer. Code keeps compiling but any ARRAY_SIZE calls now > > return the size of the pointer divided by element size. > > > > Let's add build time checks to ARRAY_SIZE before we allow more > > of these in the code-base. > > > > Signed-off-by: Michael S. Tsirkin > > --- > > include/qemu/osdep.h | 8 +++++++- > > > > > #ifndef ARRAY_SIZE > > -#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0])) > > +/* > > + * &(x)[0] is always a pointer - if it's same type as x then the argument is a > > + * pointer, not an array as expected. > > + */ > > +#define ARRAY_SIZE(x) ((sizeof(x) / sizeof((x)[0])) + QEMU_BUILD_BUG_ON_ZERO( \ > > + __builtin_types_compatible_p(typeof(x), \ > > Are we sure that __builtin_types_compatible_p() is supported for all > versions of gcc and clang that we support, or does this need further > #ifdefs? > > > -- > Eric Blake eblake redhat com +1-919-301-3266 > Libvirt virtualization library http://libvirt.org > We seem to use it without ifdefs elsewhere. -- MST