linux-kernel - Re: kernel + gcc 4.1 = several problems

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Message-Id: <200701030205.l0325lki008679@laptop13.inf.utfsm.cl>
Date:	Tue, 02 Jan 2007 23:05:47 -0300
From:	"Horst H. von Brand" <vonbrand@....utfsm.cl>
To:	"D. Hazelton" <dhazelton@...er.net>
cc:	Adrian Bunk <bunk@...sta.de>,
	Alistair John Strachan <s0348365@....ed.ac.uk>,
	"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>,
	LKML <linux-kernel@...r.kernel.org>, Greg KH <greg@...ah.com>,
	Chuck Ebbert <76306.1226@...puserve.com>,
	Linus Torvalds <torvalds@...l.org>,
	Andrew Morton <akpm@...l.org>
Subject: Re: kernel + gcc 4.1 = several problems 

D. Hazelton <dhazelton@...er.net> wrote:

[...]

> None. I didn't file a report on this because I didn't find the big, just
> noted a problem that appears to occur. In this case the call's generated
> seem to wrap loops - something I've never heard of anyone doing.

Example code showing this weirdness?

>                                                                  These
> *might* be causing the off-by-one that is causing the function to
> re-enter in the middle of an instruction.

If something like this happened, programs would be crashing left and right.

> Seeing this I'd guess that this follows for all system-level code
> generated by 4.1.1

Define "system-level code". What makes it different from, say,
bog-of-the-mill compiler code (yes, gcc compiles itself as part of its
sanity checking)?

>                    and this is exactly what I was reporting. If you'd
> like I'll go dig up the dumps he posted and post the two related segments
> side-by-side to give you a better example what I'm referring to.

If the related segments show code that is somehow wrong, by all means
report it /with your detailed analysis/ to the compiler people. Just a
warning, gcc is pretty smart in what it does, its code is often surprising
to the unwashed. Also, the C standard is subtle, the error might be in a
unwarranted assumption in the source code.
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