linux-kernel - Re: [PATCH] Don't compare unsigned variable for <0 in sys

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Date:	Tue, 28 Nov 2006 23:34:27 +0100
From:	"Jesper Juhl" <jesper.juhl@...il.com>
To:	"Linus Torvalds" <torvalds@...l.org>
Cc:	linux-kernel@...r.kernel.org, "Andrew Morton" <akpm@...l.org>,
	trivial@...nel.org
Subject: Re: [PATCH] Don't compare unsigned variable for <0 in sys_prctl()

On 28/11/06, Linus Torvalds <torvalds@...l.org> wrote:
>
>
> On Tue, 28 Nov 2006, Jesper Juhl wrote:
> >
> > In kernel/sys.c::sys_prctl() the argument named 'arg2' is very clearly
> > of type 'unsigned long', and when compiling with "gcc -W" gcc also warns :
> >   kernel/sys.c:2089: warning: comparison of unsigned expression < 0 is always false
> >
> > So this patch removes the test of "arg2 < 0".
>
> No, we don't do this.
>
> This is why we don't compile with "-W". Gcc is crap.
>
> The fact is, if it's unsigned, it's not something that the programmer
> should have to care about. We should write our code to be readable and
> obviously safe, and that means that
>
>         if (x < 0 || x > MAX)
>                 return -ERROR;
>
> is the _right_ way to do things, without having to carry stupid context
> around in our heads.
>
> If the compiler (whose _job_ it is to carry all that context and use it to
> generate good code) notices that the fact that "x" is unsignes means that
> one of the tests is unnecessary, that does not make it wrong.
>
> Gcc warns for a lot of wrong things. This is one of them.
>
> Friends don't let friends use "-W".
>
Hehe, ok, I'll stop cleaning this stuff up then.
Nice little hobby out the window there ;)

-- 
Jesper Juhl <jesper.juhl@...il.com>
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