linux-kernel - Re: [PATCH] x86, vsyscall: Fix build warning in vsyscall

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Message-ID: <BANLkTimXYaf_14VbB6ex0kG6sPnTUfzu6g@mail.gmail.com>
Date:	Tue, 14 Jun 2011 17:33:50 -0400
From:	Andrew Lutomirski <luto@....edu>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Rakib Mullick <rakib.mullick@...il.com>, hpa@...or.com,
	tglx@...utronix.de, x86@...nel.org, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] x86, vsyscall: Fix build warning in vsyscall_64.c

On Tue, Jun 14, 2011 at 5:31 PM, Ingo Molnar <mingo@...e.hu> wrote:
>
> * Linus Torvalds <torvalds@...ux-foundation.org> wrote:
>
>> On Tue, Jun 14, 2011 at 2:16 PM, Ingo Molnar <mingo@...e.hu> wrote:
>> >
>> > I think correctness trumps code size and turning BUG() and BUG_ON()
>> > into a NOP is just crazy ...
>>
>> Umm. It's even CRAZIER to turn it into a "compiler generates random code".
>
> Sigh, i assumed it got turned into an infinite loop - that is what
> i've done in a prior patch.
>
> You are right, unreachable() is bogus and you'd also be right to
> suggest that i should not comment on patches after 11pm ;-)

What we want is a magic GCC trick that says "don't warn about code
paths that go through here but generate the same code as you would
without this annotation."  I don't think such a thing exists.

--Andy
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