linux-kernel - Re: [PATCH/RFC] m68k: Add -ffreestanding to KBUILD

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Message-ID: <51653C5D.4060408@suse.cz>
Date:	Wed, 10 Apr 2013 12:18:05 +0200
From:	Michal Marek <mmarek@...e.cz>
To:	Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:	linux-m68k@...ts.linux-m68k.org, linux-arch@...r.kernel.org,
	linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
	Andi Kleen <andi@...stfloor.org>
Subject: Re: [PATCH/RFC] m68k: Add -ffreestanding to KBUILD_CFLAGS

(Added Andi to CC)

On 10.4.2013 11:24, Geert Uytterhoeven wrote:
[...]
> E.g. gcc turned
> 
>     strncat(name, "%d", 2);
> 
> into a call to strlen() and a 16-bit store, causing a link failure, as
> arch/m68k/include/asm/string.h provides strlen() using a macro:
> 
>     ERROR: "strlen" [net/ipv4/ip_tunnel.ko] undefined!
[...]
> QUESTION: Should we re-enable -ffreestanding in the main Makefile instead?
> 
> It was removed in
> 
> commit 6edfba1b33c701108717f4e036320fc39abe1912
> Author: Andi Kleen <ak@...e.de>
> Date:   Sat Mar 25 16:29:49 2006 +0100
> 
>     [PATCH] x86_64: Don't define string functions to builtin

My understanding is, that with -fnobuiltin, the compiler is not allowed
to make assumptions about functions if it does not see their definition,
even if they resemble standard functions. E.g. on x86_64, strlen() is
out-of-line, so gcc would have to assume, that strcmp() has side
effects. How about just naming the m68k inline function 'strlen'?

Michal
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