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Re: BUG: GCC-4.4.x changes the function frame on some functions
- From: "H. Peter Anvin" <hpa at zytor dot com>
- To: rostedt at goodmis dot org
- Cc: Andrew Haley <aph at redhat dot com>, Thomas Gleixner <tglx at linutronix dot de>, Ingo Molnar <mingo at elte dot hu>, 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 10:37:01 -0800
- 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> <4B058C76.9090609@redhat.com> <1258655585.22249.751.camel@gandalf.stny.rr.com>
On 11/19/2009 10:33 AM, Steven Rostedt wrote:
>
> It has to align the entire stack? Why not just the variable within the
> stack?
>
Because if the stack pointer isn't aligned, it won't know where it can
stuff the variable. It has to pad *somewhere*, and since you may have
more than one such variable, the most efficient way -- and by far least
complex -- is for the compiler to align the stack when it sets up the
stack frame.
-hpa
--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel. I don't speak on their behalf.