linux-kernel - Re: somebody dropped a (warning) bomb

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Message-ID: <20070215223250.GO7584@csclub.uwaterloo.ca>
Date:	Thu, 15 Feb 2007 17:32:50 -0500
From:	lsorense@...lub.uwaterloo.ca (Lennart Sorensen)
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Sergei Organov <osv@...ad.com>,
	Pekka Enberg <penberg@...helsinki.fi>,
	"J.A. Magall??????n" <jamagallon@....com>,
	Jan Engelhardt <jengelh@...ux01.gwdg.de>,
	Jeff Garzik <jeff@...zik.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: somebody dropped a (warning) bomb

On Thu, Feb 15, 2007 at 07:57:05AM -0800, Linus Torvalds wrote:
> I agree that it's "unnecessary code", and in many ways exactly the same 
> thing. I just happen to believe that casts tend to be a lot more dangerous 
> than extraneous initializations. Casts have this nasty tendency of hiding 
> *other* problems too (ie you later change the thing you cast completely, 
> and now the compiler doesn't warn about a *real* bug, because the cast 
> will just silently force it to a wrong type).

Well one way you could cast it and still have the compiler tell you if
the type ever changes is doing something stupid like:

char* unsigned_char_star_to_char_star(unsigned char* in) {
	return (char*)in;
}

Then call your strlen with:
strlen(unsigned_char_star_to_char_star(my_unfortunate_unsigned_char_string)

If you ever changed the type the compiler would warn you again since the
convertion function doesn't accept anything other than unsigned char *
being passed in for "convertion".  Seems safer than a direct cast since
then you get no type checking anymore.

I hope it doesn't come to this though.  Hopefully gcc will change it's
behaviour back or give an option of --dontcomplainaboutcharstar :)

--
Len Sorensen
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