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

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Message-ID: <a781481a0705251437k725b5218oab40ebe66dd661a8@mail.gmail.com>
Date:	Sat, 26 May 2007 03:07:15 +0530
From:	"Satyam Sharma" <satyam.sharma@...il.com>
To:	"Al Viro" <viro@....linux.org.uk>
Cc:	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>
Subject: Re: double exclamation (!!) suckage in the kernel

On 5/26/07, Al Viro <viro@....linux.org.uk> wrote:
> 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).

Yeah, I noticed this (with a sample program) just after the quiz ...

> > >        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).

Hmm, thanks for explaining this.

Satyam
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