Messages in this thread | | | From | Grant Coady <> | 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.
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