From owner-freebsd-net@FreeBSD.ORG  Mon Jan 30 08:47:00 2006
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Date: Mon, 30 Jan 2006 08:46:57 +0000
From: Brian Candler <B.Candler@pobox.com>
To: Aluminium Oxide <orac000@internet-mail.org>
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Cc: freebsd-net@freebsd.org
Subject: Re: /usr/src/lib/libc/net/res_debug.c: compile problem fixed
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On Mon, Jan 30, 2006 at 08:50:00AM +1030, Aluminium Oxide wrote:
> Awwww...
> 
> You're right, but there's only a handlful of these that stop buildworld
> with -O3....

I think the issue is that although you may be able to get FreeBSD to *build*
using -O3, it's quite unlikely that it will *work* properly.

If I understand correctly, gcc -O3 makes a lot of assumptions about when
it's OK to keep values around in registers, which may not be valid when
there are interrupts or other threads modifying memory. I think it's
possible to make the code -O3 safe, e.g. by putting loads of 'volatile'
declarations in, but catching every single case where this is required is
extremely different.

This may be more of a problem with the kernel than with userland though.

Regards,

Brian.