From mboxrd@z Thu Jan 1 00:00:00 1970 From: Josh Triplett Subject: Re: [PATCH 2/2] parser: define __builtin_unreachable Date: Tue, 13 Jul 2010 11:12:13 -0700 Message-ID: <20100713181212.GB20289@feather> References: <1278751162-10053-2-git-send-email-jslaby@suse.cz> <20100710090705.GA14881@feather> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Chris Li Cc: Jiri Slaby , jirislaby@gmail.com, Larry Finger , linux-kernel@vger.kernel.org, linux-sparse@vger.kernel.org List-Id: linux-sparse@vger.kernel.org On Tue, Jul 13, 2010 at 12:52:48AM -0700, Chris Li wrote: > On Sat, Jul 10, 2010 at 2:07 AM, Josh Triplett wrote: > > __builtin_unreachable has special semantics beyond just a function. > > This definition will suffice to allow compilation, but > > __builtin_unreachable should have the same effect in sparse that it= does > > in GCC: mark the point (and the remainder of the basic block) as > > unreachable. =A0Something like the mechanism used for handling nore= turn > > would work here as well; declaring the function to have attribute > > noreturn would probably have almost the right semantics. > > >=20 > The attribute noreturn will apply to the whole function. The function > NEVER returns. > __builtin_unreachable only apply to current basic block. e.g. some > error handling path like panic. The function can still return a value= on the > normal path. It has different meaning than attribute noreturn. So I d= on't think > automatically give the function noreturn attribute is the right thing= to do. No, I didn't mean that using __builtin_unreachable should mark the function calling it as noreturn. I meant that as an approximation to the right behavior, __builtin_unreachable *itself* could have attribute noreturn. - Josh Triplett