linux-kernel - Re: [RFC][PATCH] A generic boolean (version 6)

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Message-ID: <20060728202401.GA24439@lars.home.noschinski.de>
Date:	Fri, 28 Jul 2006 22:24:01 +0200
From:	Lars Noschinski <cebewee@....de>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	Nicholas Miell <nmiell@...cast.net>, ricknu-0@...dent.ltu.se,
	Arnd Bergmann <arnd.bergmann@...ibm.com>,
	linux-kernel@...r.kernel.org, Andrew Morton <akpm@...l.org>,
	Jeff Garzik <jeff@...zik.org>,
	Alexey Dobriyan <adobriyan@...il.com>,
	Vadim Lobanov <vlobanov@...akeasy.net>,
	Jan Engelhardt <jengelh@...ux01.gwdg.de>
Subject: Re: [RFC][PATCH] A generic boolean (version 6)

* Alan Cox <alan@...rguk.ukuu.org.uk> [2006-07-28 22:14]:
>Ar Iau, 2006-07-27 am 13:13 -0700, ysgrifennodd Nicholas Miell:
>> The compiler knows that "b = !!b;" is a no-op.
>
>b = !!b isn't a no-op.

For _Bool it should be:

>Try printf("%d", !!4);

printf("%d, %d", (_Bool)4, !!(_Bool)4);

prints "1, 1". From ISO/IEC 9899:1999:

When any scalar value is converted to _Bool, the result is 0 if the
value compares equal to 0; otherwise, the result is 1.


Greetings,
     Lars
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