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Re: [PATCH 1/3] ipc: avoid dereference of null pointer and quiet the GCC


From: Richard Braun
Subject: Re: [PATCH 1/3] ipc: avoid dereference of null pointer and quiet the GCC warning about uninitialized variable
Date: Wed, 18 Dec 2013 10:46:40 +0100
User-agent: Mutt/1.5.21 (2010-09-15)

On Wed, Dec 18, 2013 at 10:37:03AM +0100, Marin Ramesa wrote:
> Compiler needs to check both !a and !b. In order to evaluate !b it must 
> evaluate b. So when the code path is that when entry is a null pointer, 
> the evaluation of b results in a dereference of a null pointer.

No, that's wrong. The && and || operators are guaranteed to be evaluated
left-to-right, and yield if the first operand compares equal to 0. And
that's exactly why this check against NULL is done first.

-- 
Richard Braun



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