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Date: Thu, 19 Feb 2009 17:41:04 +0100
From: Ingo Molnar <mingo@elte.hu>
To: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: Petr Tesarik <ptesarik@suse.cz>, "H. Peter Anvin" <hpa@zytor.com>,
       LKML <linux-kernel@vger.kernel.org>
Subject: Re: Definition of BUG on x86
Message-ID: <20090219164104.GA20941@elte.hu>
References: <20090219122211.GE1703@elte.hu> <1235047082.15053.49.camel@nathan.suse.cz> <20090219124702.GC22044@elte.hu> <1235048535.15053.52.camel@nathan.suse.cz> <20090219144902.GA8650@elte.hu> <499D7B9D.7060001@goop.org> <20090219153544.GA31637@elte.hu> <1235059883.15053.68.camel@nathan.suse.cz> <20090219161649.GC9556@elte.hu> <499D8A0C.5030908@goop.org>
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* Jeremy Fitzhardinge <jeremy@goop.org> wrote:

> Ingo Molnar wrote:
>> Well, the important question is thatGCC will optimize out whatever 
>> comes after the __builtin_trap(), right? To guarantee an assert we can 
>> do something like:
>>
>>  	__builtin_trap();
>> 	panic("should never get here");
>>
>> to guarantee a message. (But realistically GCC will at most generate a 
>> build error.)
>
> Ah, right, I remember the problem.  There's no guaranteed way 
> of getting the address of the ud2a instruction __builtin_trap 
> generates to put it into the bug table.

hm, indeed.

So that 2 byte overhead will be there for now, until gcc (or 
some other compiler) is improved.

	Ingo