linux-kernel - Re: [PATCH V2] sparse: Allow override of sizeof(bool) warning

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Message-ID: <dbc47544-a6f6-4ab4-80b0-25d93a1666e2@email.android.com>
Date:	Thu, 27 Feb 2014 07:10:25 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Borislav Petkov <bp@...en8.de>
CC:	Joe Perches <joe@...ches.com>, Ben Pfaff <blp@...ira.com>,
	Christopher Li <sparse@...isli.org>,
	Josh Triplett <josh@...htriplett.org>,
	linux-sparse@...r.kernel.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V2] sparse: Allow override of sizeof(bool) warning

Keep in mind, too, that for the kernel we don't care about the full C standard but a subset.  We rely on extrastandard behavior all over the place.  For all ABIs supported by the kernel, sizeof(_Book) == 1 and so everything is sane.


On February 27, 2014 12:25:29 AM PST, Borislav Petkov <bp@...en8.de> wrote:
>On Wed, Feb 26, 2014 at 07:42:37PM -0800, H. Peter Anvin wrote:
>> sizeof(_Bool), like for many other types, is ABI-dependent, but that
>> doesn't mean it is illegitimate.
>>
>> I don't think C99 says that it is invalid (which means C99 doesn't
>> permit is to be a packed bitmap.)
>
>Ok, but what can be said about the __pcpu_size_call() use case where we
>do sizeof(bool)? We have there accessors for sizes 1,2,4 and 8. Can we
>simply assume that the ABI will give us a size of bool which is one of
>those?
>
>What if sizeof(bool) is 3?
>
>Or, are we saying that sizeof(bool) will always be of some natural,
>native size like byte, short, int or long so we're good there?
>
>Thanks.

-- 
Sent from my mobile phone.  Please pardon brevity and lack of formatting.
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