From: Josh Triplett <josh@freedesktop.org>
To: linux-sparse@vger.kernel.org, linux-kernel@vger.kernel.org
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Al Viro <viro@ftp.linux.org.uk>
Subject: sparse -Wptr-subtraction-blows: still needed?
Date: Tue, 01 May 2007 14:08:13 -0700 [thread overview]
Message-ID: <4637AC3D.6000008@freedesktop.org> (raw)
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Sparse has a warning -Wptr-subtraction-blows (off by default) which generates
a warning for any pointer subtractions. This warning relates to GCC
shortcomings observed in 2005; the original log message:
> commit 6889bd0f84939675c743229d6fe623513b95e057
> Author: Linus Torvalds <torvalds@ppc970.osdl.org>
> Date: Fri Jan 7 15:06:24 2005 -0700
>
> Add option "-Wptr-subtraction-blows" to warn about expensive
> pointer subtractions.
>
> Not only does it generate bad code (that can often be rewritten
> to not do that), it also causes gcc to go into horrible contortions,
> and Al Viro reports that it can make a factor of 2.5 difference in
> kernel build times to have just a few of these in common header
> file inline functions.
Does this still apply? Do current versions of GCC still have this problem?
If not, can the option and warning go away?
- Josh Triplett
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next reply other threads:[~2007-05-01 21:08 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-05-01 21:08 Josh Triplett [this message]
2007-05-01 21:43 ` sparse -Wptr-subtraction-blows: still needed? Linus Torvalds
2007-05-01 23:59 ` Josh Triplett
2007-05-02 0:24 ` Linus Torvalds
2007-05-02 0:35 ` Al Viro
2007-05-02 12:02 ` Alan Cox
2007-05-02 13:19 ` Andi Kleen
2007-05-02 0:26 ` Al Viro
2007-05-02 0:02 ` Al Viro
2007-05-02 2:42 ` Dave Jones
2007-05-02 13:03 ` Andi Kleen
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