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Cc: Albert Cahalan <albert@users.sourceforge.net>, axboe@suse.de,
       bunk@fs.tum.de, Linus Torvalds <torvalds@osdl.org>, arjanv@redhat.com,
       linux-kernel mailing list <linux-kernel@vger.kernel.org>
From: Kyle Moffett <mrmacman_g4@mac.com>
Subject: Re: What policy for BUG_ON()?
Date: Tue, 31 Aug 2004 17:30:24 -0400
To: Albert Cahalan <albert@users.sf.net>
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On Aug 31, 2004, at 13:39, Albert Cahalan wrote:
> Expensive function calls won't get optimized away unless you
> mark them __attribute__((__const__)) or __attribute__((__pure__)).
> (perhaps that should be encouraged)
>
> Then of course the compiler must assume that the function
> really needed the arguments it was passed, and that it
> might have modified memory, and so on.
>
> Eh, how about a BUG_ON_WITH_SIDE_EFFECT() macro?

Due to the potentially large number of existing BUG_ON() usages with 
side
effects, it might be better to do this:

#if DEBUG
# define	BUG_ON(cond)		do { if (cond) BUG(); } while(0)
# define	BUG_CHECK(cond)		do { if (cond) BUG(); } while(0)
#else
# define	BUG_ON(cond)		do { if (cond); } while(0)
# define	BUG_CHECK(cond)		do { } while(0)
#endif

Then in most cases new statements would use BUG_CHECK, especially if
they contain expensive unnecessary function calls or critical sections.

This would break the least amount of existing code, and provide both
methods to kernel developers.

Cheers,
Kyle Moffett

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