linux-kernel - Re: [2.6 patch] re-add -ffreestanding

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Message-ID: <20060907003758.GD25473@stusta.de>
Date:	Thu, 7 Sep 2006 02:37:58 +0200
From:	Adrian Bunk <bunk@...sta.de>
To:	Roman Zippel <zippel@...ux-m68k.org>
Cc:	Andi Kleen <ak@...e.de>, Andrew Morton <akpm@...l.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [2.6 patch] re-add -ffreestanding

On Thu, Sep 07, 2006 at 02:05:59AM +0200, Roman Zippel wrote:
> Hi,
> 
> On Thu, 7 Sep 2006, Adrian Bunk wrote:
> 
> > it's correct, since with -ffreestanding gcc no longer has the right to 
> > assume it had a full libc available.
> 
> BS, even without it gcc can't make such assumption.
> There is not a single optimization, which would be invalid in a kernel 
> environment and would be "fixed" by this option, so please stop this 
> nonsense.

You are wrong.

Section 5.1.2.2.2 of ISO/IEC 9899:1999 says:
In a hosted environment, a program may use all functions, macros, type 
definitions, and objects described in the library clause (clause 7).

Since a hosted environment means gcc+libc, it's therefore clear that gcc 
can assume the presence of a full libc if gcc isn't told that it's used 
as a freestanding environment.

> bye, Roman

cu
Adrian

-- 

       "Is there not promise of rain?" Ling Tan asked suddenly out
        of the darkness. There had been need of rain for many days.
       "Only a promise," Lao Er said.
                                       Pearl S. Buck - Dragon Seed

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