linux-kernel - Re: sparse -Wptr-subtraction-blows: still needed?

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Message-ID: <4637D47D.7040203@freedesktop.org>
Date:	Tue, 01 May 2007 16:59:57 -0700
From:	Josh Triplett <josh@...edesktop.org>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	linux-sparse@...r.kernel.org, linux-kernel@...r.kernel.org,
	Al Viro <viro@....linux.org.uk>
Subject: Re: sparse -Wptr-subtraction-blows: still needed?

Linus Torvalds wrote:
> 
> On Tue, 1 May 2007, Josh Triplett wrote:
>> Does this still apply?  Do current versions of GCC still have this problem?
>> If not, can the option and warning go away?
> 
> Even if current versions of gcc don't triple the build time (and for the 
> kernel, I suspect it doesn't, because we've tried to clean up our header 
> files), the generated _code_ will invariably suck.

"invariably"?

Do you know whether the current version of GCC generates poor code for pointer
subtraction?

If so, does anything in particular make this an unfixable problem?

Has anyone reported this poor code generation to the GCC bugzilla?  If so, I
can add a reference to the bug in any (hypothetical) documentation for
-Wptr-subtraction-blows.

> So I'd not want to remove the warning.

Regardless of whether it addresses a current GCC issue or not, I have no
problem leaving the warning in if people want it, given that it requires an
explicit switch.

- Josh Triplett



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