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From: Grant Coady <lkml@dodo.com.au>
To: Jan Engelhardt <jengelh@linux01.gwdg.de>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: xor as a lazy comparison
Date: Mon, 25 Jul 2005 06:07:50 +1000
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On Sun, 24 Jul 2005 18:40:25 +0200 (MEST), Jan Engelhardt <jengelh@linux01.gwdg.de> wrote:
>
>I have seen this in kernel/signal.c:check_kill_permission()
>
>            && (current->euid ^ t->suid) && (current->euid ^ t->uid)
>
>If current->euid and t->suid are the same, the xor returns 0, so these 
>statements are effectively the same as a !=
>
>	current->euid != t->suid ...
>
>Why ^ ?
To confuse you, coders with assembly or hardware background throw in 
equivalent bit operations to succinctly describe their visualisation 
of solution space...  Perhaps the writer _wanted_ you to pause and 
think?  Maybe the compiler produces better code?  Try it and see.

Grant.