linux-kernel - RE: [patch 2.6.19-rc6] Stop gcc 4.1.0 optimizing wait_hpet

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Message-ID: <Pine.LNX.4.61.0612020959070.1635@yvahk01.tjqt.qr>
Date:	Sat, 2 Dec 2006 10:02:39 +0100 (MET)
From:	Jan Engelhardt <jengelh@...ux01.gwdg.de>
To:	David Schwartz <davids@...master.com>
cc:	mrmacman_g4@....com,
	"Linux-Kernel@...r. Kernel. Org" <linux-kernel@...r.kernel.org>
Subject: RE: [patch 2.6.19-rc6] Stop gcc 4.1.0 optimizing wait_hpet_tick away


>> Next you stick a my_other_func declaration in a header and use
>> my_other_func instead of my_func() in the main function.  Now the
>> result is that the compiler has no damn clue what my_other_func()
>> contains so it can't optimize it out of the loop with either
>> version.  You cannot treat "volatile" the way you are saying it is
>> treated without severely violating both the C99 spec *and* common sense.
>
>The compiler *happens* to have no damn clue because such inter-module
>optimizations don't exist. That doesn't make the code correct, just not
>likely to demonstrate its brokenness.

GCC has inter-module optimization, it's just not used everyday. I think 
I have seen a discussion on this.

Right there it is -> http://lkml.org/lkml/2006/8/24/212



	-`J'
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