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

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Message-Id: <20070525.141421.73699719.davem@davemloft.net>
Date:	Fri, 25 May 2007 14:14:21 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	satyam.sharma@...il.com
Cc:	linux-kernel@...r.kernel.org
Subject: Re: double exclamation (!!) suckage in the kernel

From: "Satyam Sharma" <satyam.sharma@...il.com>
Date: Sat, 26 May 2007 01:53:59 +0530

WHat is with multiple people asking about "!!" all of a
sudden today?

> Are all these occurrences merely the debris of
> s/something/!notsomething/g kind of patches or is there some
> dark, unknown C / gcc wizardry I have absolutely no clue of?

"!!" is used in contexts where pointers might be being
tested as well as plain integers, the "!!" turns a pointer
into the equivalent integer boolean for testing.

NULL pointers become 0
non-NULL pointers become 1
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