linux-kernel - Re: [RFC][PATCH] A generic boolean (version 2)

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Date:	Sat, 22 Jul 2006 10:56:04 +0200 (MEST)
From:	Jan Engelhardt <jengelh@...ux01.gwdg.de>
To:	Michael Buesch <mb@...sch.de>
cc:	ricknu-0@...dent.ltu.se, 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>,
	Shorty Porty <getshorty_@...mail.com>,
	Peter Williams <pwil3058@...pond.net.au>
Subject: Re: [RFC][PATCH] A generic boolean (version 2)

>> >* u2 has been corrected to u1 (and also added it as __u1)
>> 
>> Do we really need this? Is not 'bool' enough?
>
>I would say we don't even _want_ this.
>A u1 variable will basically never be one bit wide.

Not without a compiler hack at least.

>Consider:
>
>struct device_control_buffer {
>	u1 device_is_fooing;
>	u32 foodata;
>} __attribute__((packed));
>
>This would not lead to the expected results.
>It's horribly broken, obfuscating and misleading.

And in fact, bitfields work different:

struct device {
	int device_is_fooing:1;
	u32 foodata;
};

but the result is likely the same.


Jan Engelhardt
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