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From: "Dave Korn" <dk@artimi.com>
To: "'Andreas Schwab'" <schwab@suse.de>
Cc: "'Morten Welinder'" <terra@gnome.org>,
	<gcc@gcc.gnu.org>
Subject: RE: signed vs unsigned pointer warning
Date: Thu, 23 Sep 2004 12:29:00 -0000
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> -----Original Message-----
> From: Andreas Schwab 
> Sent: 22 September 2004 22:57
> To: Dave Korn
> Cc: 'Morten Welinder'; gcc
> Subject: Re: signed vs unsigned pointer warning
> 
> "Dave Korn" writes:
> 
> > Which I don't think you can, since you can't store negative numbers
> > in an unsigned type. 
> 
> Actually you can, due to the modulo behaviour of unsigned integers.
> 
> Andreas.


  Well, yes, it is physically possible, but it's a kind of type-punning, it
defies the aliasing rules, and we get into some very deeply
language-lawyerly issues here, but it's not a valid representation IIUIC and
therefore invokes undefined behaviour in many circumstances.


    cheers, 
      DaveK
-- 
Can't think of a witty .sigline today....