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From: Linus Torvalds <torvalds@linux-foundation.org>
To: "J.A. Magallón" <jamagallon@ono.com>
Cc: Jan Engelhardt <jengelh@linux01.gwdg.de>,
	Jeff Garzik <jeff@garzik.org>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>
Subject: Re: somebody dropped a (warning) bomb
Date: Thu, 8 Feb 2007 13:42:47 -0800 (PST)	[thread overview]
Message-ID: <Pine.LNX.4.64.0702081338010.8424@woody.linux-foundation.org> (raw)
In-Reply-To: <20070208221317.5beedaeb@werewolf-wl>

[-- Attachment #1: Type: TEXT/PLAIN, Size: 1282 bytes --]



On Thu, 8 Feb 2007, J.A. Magallón wrote:
> 
> Perhaps the problem is that gcc warns you something like 'if you care
> anything about the sign behaviour of what you send to strlen() you're doomed'.

But you *cannot* care. That's the point. The warning is insane. For any 
function that takes "char *", you very fundamentally *cannot* care about 
the signedness of the argument, because doing so would be wrong. If you 
do care, you're already buggy.

> Ie, you declared the var unsigned, so you care about it. But I can do
> anything without any regard to the sign.

That makes no sense. 

First off, "strlen()" doesn't care about the sign of the buffer, so it's a 
bad example anyway. But take something that *can* care, namely "strcmp()", 
which can return different things depending on whether "char" is signed or 
not (is 0xff larger than 0x00? Depends on whether char is signed or 
not..).

But THE CALLER CANNOT AND MUST NOT CARE! Because the sign of "char" is 
implementation-defined, so if you call "strcmp()", you are already 
basically saying: I don't care (and I _cannot_ care) what sign you are 
using.

So having the compiler warn about it is insane. It's like warnign about 
the fact that it's Thursday today. It's not something the programmer cares 
about.

		Linus

  reply	other threads:[~2007-02-08 21:43 UTC|newest]

Thread overview: 68+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-02-08 15:00 Jeff Garzik
2007-02-08 16:33 ` Linus Torvalds
2007-02-08 18:42   ` Jan Engelhardt
2007-02-08 19:53     ` Linus Torvalds
2007-02-08 21:10       ` Jan Engelhardt
2007-02-08 21:37         ` Linus Torvalds
2007-02-08 23:12           ` David Rientjes
2007-02-08 23:37             ` Linus Torvalds
2007-02-09  0:24               ` David Rientjes
2007-02-09  0:42                 ` Linus Torvalds
2007-02-09  0:59                   ` Linus Torvalds
2007-02-09  0:59                   ` David Rientjes
2007-02-09  1:11                     ` Linus Torvalds
2007-02-09  1:18                       ` David Rientjes
2007-02-09 15:38                         ` Linus Torvalds
2007-02-09  3:27                   ` D. Hazelton
2007-02-09 19:54                     ` Pete Zaitcev
2007-02-09 12:34                   ` Jan Engelhardt
2007-02-09 13:16                     ` linux-os (Dick Johnson)
2007-02-09 17:45                       ` Jan Engelhardt
2007-02-09 20:29                         ` linux-os (Dick Johnson)
2007-02-09 22:05                           ` Jan Engelhardt
2007-02-09 22:58                             ` Martin Mares
2007-02-12 18:50                             ` linux-os (Dick Johnson)
2007-02-13 15:14                     ` Dick Streefland
2007-02-08 21:13       ` J.A. Magallón
2007-02-08 21:42         ` Linus Torvalds [this message]
2007-02-08 22:03           ` Linus Torvalds
2007-02-08 22:19             ` Willy Tarreau
2007-02-09  0:03             ` J.A. Magallón
2007-02-09  0:22               ` Linus Torvalds
2007-02-09 12:38             ` Sergei Organov
2007-02-09 15:58               ` Linus Torvalds
2007-02-12 11:12                 ` Sergei Organov
2007-02-12 16:26                   ` Linus Torvalds
2007-02-13 18:06                     ` Sergei Organov
2007-02-13 18:26                       ` Pekka Enberg
2007-02-13 19:14                         ` Sergei Organov
2007-02-13 19:43                           ` Pekka Enberg
2007-02-13 20:29                             ` Sergei Organov
2007-02-13 21:31                               ` Jeff Garzik
2007-02-13 23:21                               ` Linus Torvalds
2007-02-15 13:20                                 ` Sergei Organov
2007-02-15 15:57                                   ` Linus Torvalds
2007-02-15 18:53                                     ` Sergei Organov
2007-02-15 19:02                                       ` Linus Torvalds
2007-02-15 20:23                                         ` me, not " Oleg Verych
2007-02-16  4:26                                         ` Rene Herman
2007-02-19 11:58                                           ` Sergei Organov
2007-02-19 13:58                                         ` Sergei Organov
2007-02-15 22:32                                     ` Lennart Sorensen
2007-02-13 19:25                       ` Linus Torvalds
2007-02-13 19:59                         ` Sergei Organov
2007-02-13 20:24                           ` Linus Torvalds
2007-02-15 15:15                             ` Sergei Organov
2007-02-13 21:13                         ` Rob Landley
2007-02-13 22:21                       ` Olivier Galibert
2007-02-14 12:52                         ` Sergei Organov
2007-02-15 20:06                         ` Sergei Organov
2007-02-09 15:10     ` Sergei Organov
2007-02-08 16:35 ` Kumar Gala
     [not found] <7Mj5f-3oz-21@gated-at.bofh.it>
     [not found] ` <7MktH-5EW-35@gated-at.bofh.it>
     [not found]   ` <7Mmvy-vj-17@gated-at.bofh.it>
     [not found]     ` <7MnBC-2fk-13@gated-at.bofh.it>
     [not found]       ` <7MoQx-4p8-11@gated-at.bofh.it>
     [not found]         ` <7MpjE-50z-7@gated-at.bofh.it>
     [not found]           ` <7MpCS-5Fe-9@gated-at.bofh.it>
     [not found]             ` <7MDd7-17w-1@gated-at.bofh.it>
     [not found]               ` <7MGkB-62k-31@gated-at.bofh.it>
     [not found]                 ` <7NHoe-2Mb-37@gated-at.bofh.it>
     [not found]                   ` <7NMe9-1ZN-7@gated-at.bofh.it>
     [not found]                     ` <7Oagl-6bO-1@gated-at.bofh.it>
     [not found]                       ` <7ObvW-89N-23@gated-at.bofh.it>
     [not found]                         ` <7Oc8t-NS-1@gated-at.bofh.it>
2007-02-15 20:08                           ` Bodo Eggert
2007-02-16 11:21                             ` Sergei Organov
2007-02-16 14:51                               ` Bodo Eggert
2007-02-19 11:56                                 ` Sergei Organov
2007-02-16 12:46                             ` Sergei Organov
2007-02-16 17:40                               ` Bodo Eggert
2007-02-19 12:17                                 ` Sergei Organov

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