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Date: Sat, 21 Apr 2001 21:34:30 +0100
From: Russell King <rmk@arm.linux.org.uk>
To: Jochen Striepe <jochen@tolot.escape.de>
Cc: linux-kernel@vger.kernel.org
Subject: Re: 2.4.4-pre6 does not compile
Message-ID: <20010421213430.D7576@flint.arm.linux.org.uk>
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In-Reply-To: <20010421221728.C4077@tolot.escape.de>; from jochen@tolot.escape.de on Sat, Apr 21, 2001 at 10:17:28PM +0200
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On Sat, Apr 21, 2001 at 10:17:28PM +0200, Jochen Striepe wrote:
> 2.4.4-pre6 actually is the 4th 2.4.4pre-Patch that does not compile
> without further patching on my system. :-(
> rwsem.o(.text+0x30): undefined reference to `__builtin_expect'
> rwsem.o(.text+0x73): undefined reference to `__builtin_expect'

Its because you're using a version of gcc which doesn't have
__builtin_expect (eg, egcs 1.1.2, some versions of gcc 2.95).
I'm told that gcc 2.95.[12] are not suitable for kernel compilation...

I've currently got the following in my tree (sorry, no diff since I've
got other changes in this file).  lib/rwsem.c, line 9, add:

#if __GNUC__ < 2 || (__GNUC__ == 2 && __GNUC_MINOR__ < 96)
#define __builtin_expect(exp,c) (exp)
#endif

I'm not sure if this is correct, or which compilers work, which don't
(so don't anyone go and drop it into Linus/Alans kernels), but it
seems to work for me.

--
Russell King (rmk@arm.linux.org.uk)                The developer of ARM Linux
             http://www.arm.linux.org.uk/personal/aboutme.html

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