From: Nick Piggin <nickpiggin@yahoo.com.au>
To: Kyle Moffett <mrmacman_g4@mac.com>
Cc: Jakub Jelinek <jakub@redhat.com>,
Paulo Marques <pmarques@grupopie.com>,
akpm@osdl.org, Shankar Unni <shankarunni@netscape.net>,
linux-kernel@vger.kernel.org, bunk@stusta.de, khali@linux-fr.org
Subject: Re: Not a GCC bug (was Re: Big GCC bug!!! [Was: Re: Do not misuse Coverity please])
Date: Thu, 31 Mar 2005 11:12:21 +1000 [thread overview]
Message-ID: <424B4E75.4010107@yahoo.com.au> (raw)
In-Reply-To: <e8fc51864bab0a24b04af9867d748f5f@mac.com>
Kyle Moffett wrote:
> On Mar 30, 2005, at 18:38, Jakub Jelinek wrote:
>
>> This testcase violates ISO C99 6.3.2.3:
>> If a null pointer constant is converted to a pointer type, the resulting
>> pointer, called a null pointer, is guaranteed to compare unequal to a
>> pointer to any object or function.
>
>
> Except that the result of dereferencing a null pointer is implementation
> defined according to the C99 standard. My implementation allows me to mmap
> stuff at NULL, and therefore its compiler should be able to handle that
> case. I would have no problem with either the standard or implementation
> if it either properly handled the case or didn't allow it in the first
> place.
>
> On another note, I've discovered the flag
> "-fno-delete-null-pointer-checks",
> which should probably be included in the kernel makefiles to disable that
> optimization for the kernel. (Ok, yes, I apologize, this isn't really a
> GCC
> bug, the behavior is documented, although it can be quite confusing. I
> suspect it may bite some platform-specific code someday. It also muddies
> the waters somewhat with respect to the original note (and the effects on
> the generated code):
>
>> int x = my_struct->the_x;
>> if (!my_struct) return;
>
Why should this be in the kernel makefiles? If my_struct is NULL,
then the kernel will never reach the if statement.
A warning might be nice though.
next prev parent reply other threads:[~2005-03-31 1:12 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-03-27 20:50 [2.6 patch] sound/oss/cs46xx.c: fix a check after use Adrian Bunk
2005-03-27 21:21 ` Do not misuse Coverity please (Was: sound/oss/cs46xx.c: fix a check after use) Jean Delvare
2005-03-27 21:43 ` Adrian Bunk
2005-03-27 22:34 ` Jean Delvare
2005-03-27 22:45 ` Russell King
2005-03-28 12:54 ` Matthias-Christian Ott
2005-03-28 23:57 ` L. A. Walsh
2005-03-29 6:05 ` Daniel Barkalow
2005-03-29 6:23 ` Andrew Morton
2005-03-29 10:46 ` Jean Delvare
2005-03-29 14:12 ` Chris Friesen
2005-03-30 1:25 ` Horst von Brand
2005-03-30 7:53 ` Do not misuse Coverity please Jean Delvare
2005-03-30 17:09 ` Horst von Brand
2005-04-11 20:23 ` Pavel Machek
2005-03-30 18:29 ` Shankar Unni
2005-03-30 18:55 ` Olivier Galibert
2005-03-31 2:01 ` Patrick McFarland
2005-03-30 19:14 ` Paulo Marques
2005-03-30 23:11 ` Big GCC bug!!! [Was: Re: Do not misuse Coverity please] Kyle Moffett
2005-03-30 23:38 ` Not a GCC bug (was Re: Big GCC bug!!! [Was: Re: Do not misuse Coverity please]) Jakub Jelinek
2005-03-31 0:58 ` Kyle Moffett
2005-03-31 1:12 ` Nick Piggin [this message]
2005-03-31 1:27 ` Kyle Moffett
2005-03-29 14:22 ` Do not misuse Coverity please (Was: sound/oss/cs46xx.c: fix a check after use) Daniel Jacobowitz
2005-03-29 22:37 ` Kyle Moffett
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