Date: Wed, 5 Jan 2011 22:30:43 +0100 From: Ulrich =?utf-8?B?U3DDtnJsZWlu?= <uqs@spoerlein.net> To: Jilles Tjoelker <jilles@stack.nl> Cc: freebsd-current@freebsd.org, Erik Cederstrand <erik@cederstrand.dk> Subject: Re: FYI: clang static analyzer page has moved to http://scan.freebsd.your.org/freebsd-head/ Message-ID: <20110105213043.GT23329@acme.spoerlein.net> In-Reply-To: <20110105193653.GA49285@stack.nl> References: <20110105131439.GN23329@acme.spoerlein.net> <4184C8F2-3C6D-46FB-8F10-DDEBA6DB1C35@cederstrand.dk> <AD2AEFFB-37A4-4DAB-9094-7289C1C8B0DD@cederstrand.dk> <201101050934.49845.jhb@freebsd.org> <20110105165545.GP23329@acme.spoerlein.net> <20110105193653.GA49285@stack.nl>
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On Wed, 05.01.2011 at 20:36:53 +0100, Jilles Tjoelker wrote: > On Wed, Jan 05, 2011 at 05:55:45PM +0100, Ulrich Spörlein wrote: > > On Wed, 05.01.2011 at 09:34:49 -0500, John Baldwin wrote: > > > These are all marked as __dead2, so the compiler should "know" that these do > > > not return. > > > And clang did the right thing here in the past. Beware that it does no > > inter-procedural analysis yet, so it will usually miss that usage() > > calls exit unconditionally. > > > *But*, it should grok that for err(3) and exit(3). Now there are some > > possible remedies: > > > - get IPA to work with clang, or at least file a bug > > > - mark functions as __dead2 (please don't do that) > > Why not? Cause IMHO it adds clutter, is noisy and needs to be maintained manually, when we have these "computer" things that should deduct this by themselves. > I have done this in some cases because it leads to better code with gcc > (the system version in 9-current). See SVN commit r212508 to > bin/sh/parser.c. Although synexpect() and synerror() are static, adding > __dead2 to both makes the executable 576 bytes smaller on i386 (these > functions are called many times). Adding __dead2 to synexpect() only > causes a warning "noreturn function does return" (it calls synerror()). > Adding __dead2 to synerror() only also makes the executable smaller but > not as much as adding it to both. > > Reordering the functions in the file does not help to make gcc see that > the functions do not return. This is too bad and really makes me sad. It shouldn't be necessary to hand-hold the compilers like that. Could you try some tests with gcc 4.5 to confirm this is still required? Uli
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