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Re: BUG: GCC-4.4.x changes the function frame on some functions
- From: Linus Torvalds <torvalds at linux-foundation dot org>
- To: Andrew Haley <aph at redhat dot com>
- Cc: Richard Guenther <richard dot guenther at gmail dot com>, rostedt at goodmis dot org, Thomas Gleixner <tglx at linutronix dot de>, Ingo Molnar <mingo at elte dot hu>, "H. Peter Anvin" <hpa at zytor dot com>, LKML <linux-kernel at vger dot kernel dot org>, Andrew Morton <akpm at linux-foundation dot org>, Heiko Carstens <heiko dot carstens at de dot ibm dot com>, feng dot tang at intel dot com, Fr??d??ric Weisbecker <fweisbec at gmail dot com>, Peter Zijlstra <peterz at infradead dot org>, jakub at redhat dot com, gcc at gcc dot gnu dot org
- Date: Thu, 19 Nov 2009 10:43:41 -0800 (PST)
- Subject: Re: BUG: GCC-4.4.x changes the function frame on some functions
- References: <alpine.LFD.2.00.0911181933540.24119@localhost.localdomain> <tip-887a29f59b93cf54e21814869a4ab6e80b6fa623@git.kernel.org> <20091119072040.GA23579@elte.hu> <alpine.LFD.2.00.0911191053390.24119@localhost.localdomain> <alpine.LFD.2.00.0911191423190.24119@localhost.localdomain> <alpine.LFD.2.00.0911191607440.24119@localhost.localdomain> <alpine.LFD.2.00.0911190934070.2793@localhost.localdomain> <1258653562.22249.682.camel@gandalf.stny.rr.com> <84fc9c000911191003t244eb864o3d5b355ab5485f@mail.gmail.com> <4B058CCD.8050605@redhat.com> <alpine.LFD.2.00.0911191039470.2793@localhost.localdomain>
On Thu, 19 Nov 2009, Linus Torvalds wrote:
>
> Oh Gods, are we back to gcc people saying "sure, we do stupid things, but
> it's allowed, so we don't consider it a bug because it doesn't matter that
> real people care about real life, we only care about some paper, and real
> life doesn't matter, if it's 'undefined' we can make our idiotic choices
> regardless of what people need, and regardless of whether it actually
> generates better code or not".
Put another way: the stack alignment itself may not be a bug, but gcc
generating God-awful code for the mcount handling that results in problems
in real life sure as hell is *stupid* enough to be called a bug.
I bet other people than just the kernel use the mcount hook for subtler
things than just doing profiles. And even if they don't, the quoted code
generation is just crazy _crap_.
Linus