linux-kernel - Re: double exclamation (!!) suckage in the kernel

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Message-ID: <20070525213213.GM4095@ftp.linux.org.uk>
Date:	Fri, 25 May 2007 22:32:13 +0100
From:	Al Viro <viro@....linux.org.uk>
To:	Satyam Sharma <satyam.sharma@...il.com>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: double exclamation (!!) suckage in the kernel

On Sat, May 26, 2007 at 02:26:11AM +0530, Satyam Sharma wrote:
> also be brave enough to take a C quiz here :-)
> 
> >        what type should x have for !!x to be a valid expression?
> 
> Any integer type (includes pointers)

Er, no...  Pointers are not integer types *and* you can use ! on any
scalar type (including floating ones, even though it's not particulary
useful there).

> >        what will be the type of result?
> 
> int (I guess boolean for C99?)

Actually, ! and comparisons still give int in C99 (and !x is defined as
(x == 0) in all situations).
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