linux-kernel - Re: Kernel Bug in 2.4.35 when compiled gcc>=4.2.0 and -march=c3

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Message-ID: <46B75CD0.7080408@zytor.com>
Date:	Mon, 06 Aug 2007 10:39:28 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Willy Tarreau <w@....eu>
CC:	Segher Boessenkool <segher@...nel.crashing.org>,
	Axel Reinhold <axel@...akout.de>, linux-kernel@...r.kernel.org
Subject: Re: Kernel Bug in 2.4.35 when compiled gcc>=4.2.0 and -march=c3

Willy Tarreau wrote:
> 
> Just to enlighten me on the subject, could you please explain me
> what is wrong in the code ? Granted I found it awful, but even on
> the GCC-4.2 page where -fno-toplevel-reorder is explained, it is
> said that asm statements can be instantiated between functions
> blocks, which is exactly what is used here.
> 

A stray semicolon:

__attribute__((regparm(0))) void call_do_IRQ(void); __asm__(...

... is actually a prototype followed by a top-level asm statement
(because of the semicolon), *not* a function with a single-statement
body (which is itself uglier than hell, use braces please...)

	-hpa
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