From: Arnd Bergmann <arnd@arndb.de>
To: Dave Jones <davej@redhat.com>
Cc: Keith Owens <kaos@ocs.com.au>, linux-kernel@vger.kernel.org
Subject: Re: 2.6.14 assorted warnings
Date: Fri, 28 Oct 2005 10:07:41 +0200 [thread overview]
Message-ID: <200510281007.42758.arnd@arndb.de> (raw)
In-Reply-To: <20051028073049.GA27389@redhat.com>
On Freedag 28 Oktober 2005 09:30, Dave Jones wrote:
> gcc is dumb, it doesn't realise that the variable will be filled by another
> function if its passed thus..
>
> unsigned long foo
> bar(&foo)
> if (foo==1)
> ...
>
> With bar() filling in content of foo.
> I believe there's at least once instance of this in gcc bugzilla.
>
The case is more complicated here. gcc before 4.0 always assumed that
bar(&foo); initializes foo. gcc-4.0 now looks into bar if it is inlining
that and tries to find out if that really initializes foo in every
case.
In the example, bvec_alloc_bs does not initialize &idx when nr is not
between 1 and BIO_MAX_PAGES, so gcc is telling the truth here.
Arnd <><
next prev parent reply other threads:[~2005-10-28 8:06 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-10-28 7:21 2.6.14 assorted warnings Keith Owens
2005-10-28 7:28 ` Jens Axboe
2005-10-28 7:30 ` Dave Jones
2005-10-28 8:07 ` Arnd Bergmann [this message]
2005-10-28 8:29 ` Jens Axboe
2005-10-29 5:59 ` Richard Knutsson
2005-10-29 6:03 ` Al Viro
2005-10-28 8:10 ` Richard Knutsson
2005-10-30 22:15 ` Alan Cox
2005-10-30 22:25 ` Al Viro
2005-10-30 22:32 ` Al Viro
2005-10-30 22:29 ` Stephen Rothwell
2005-10-31 0:53 ` Paul Mackerras
2005-10-31 0:57 ` Al Viro
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