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

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Message-ID: <a781481a0705251403s4d4bb918mcf735fceb8309e30@mail.gmail.com>
Date:	Sat, 26 May 2007 02:33:51 +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, Satyam Sharma <satyam.sharma@...il.com> wrote:
> On 5/26/07, Al Viro <viro@....linux.org.uk> wrote:
> >
> > That's a question for a quiz in introductory course on C:
>
> Ugh ... ok, I've embarrassed myself publicly already, so I'll
> also be brave enough to take a C quiz here :-)

Hmmm, and now I seem to have flunked ...

> >         what type should x have for !!x to be a valid expression?
>
> Any integer type (includes pointers)

gcc doesn't seem to mind a ! on a float either (does it do an implicit
cast to int first?). Can't think of too many situations where one would
want to do a ! on a float, actually, in any case ...

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