From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ian Campbell Subject: Re: [PATCH 24/29] libxl: Introduce FILLZERO Date: Tue, 24 Mar 2015 12:03:41 +0000 Message-ID: <1427198621.21742.372.camel@citrix.com> References: <1423599016-32639-1-git-send-email-ian.jackson@eu.citrix.com> <1423599016-32639-25-git-send-email-ian.jackson@eu.citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1423599016-32639-25-git-send-email-ian.jackson@eu.citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Ian Jackson Cc: xen-devel@lists.xensource.com, Euan Harris List-Id: xen-devel@lists.xenproject.org On Tue, 2015-02-10 at 20:10 +0000, Ian Jackson wrote: > FILLZERO is a macro for memset(&foo,0,sizeof(foo)). It eliminates the > possiblity to make the error memset(&foo,0,sizeof(&foo)). but not: foo *p = allocate_a_foo() memset(p, 0, sizeof(p)) although that's probably less likely to go wrong and I don't think it can be avoided by the sorts of tricks used here. > No callers yet, but document it in CODING_STYLE. (In accordance with > existing libxl policy, I haven't gone through all existing possible > call sites.) We don't usually expose such helpers in the public API, but I suppose you have a good reason to do so here, could you mention it in the commit log please. > > + > +#define LIBXL_FILLZERO(object) (memset(&(object), 0, sizeof((object)))) Evaluates object twice, so LIBXL_FILEZERO(*(p++)), would behave surprisingly. I'm not sure if this can be resolved though, so this might be a Don't Do That Then situation. Only answer I can think of is to require the type be passed to the macro and validating it matches the object via a pointer comparison. Ian.