Re: [PATCH][RFC] getting rid of stupid loop in BUG()
From: David Miller
Date: Wed Jul 25 2007 - 15:35:18 EST
From: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Date: Wed, 25 Jul 2007 10:36:49 -0700
> I tried that, but there's still no way of getting a pointer to the ud2a
> instruction in there. gcc just generates garbage if you try to use use
> the &&label syntax on a label which isn't (potentially) the target of a
> goto (it just gets placed somewhere random).
>
> But there's a bigger problem than that. If the BUG is in code which can
> be replicated (ie inlined or unrolled), then it would also require
> replicating the static variable...
Another issue is that if you have a conditional trap instruction on
your cpu, and you try the __label__ trick, GCC no longer converts:
BUG_ON(test)
into just a:
set condition codes;
conditional_trap;
sequence because the "stuff" inside the basic block is something
more than just the __builtin_trap().
The holy grail would be being able to get the perfect conditional
trap sequence, plus the annotations in a seperate section.
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