linux-kernel - Re: [PATCH] kernel/fork.c: use sizeof() instead of sizeof

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Date:	Tue, 2 Feb 2016 22:46:07 -0500
From:	Kevin Easton <kevin@...rana.org>
To:	Al Viro <viro@...IV.linux.org.uk>
Cc:	Aleksa Sarai <cyphar@...har.com>, xypron.glpk@....de,
	Tejun Heo <tj@...nel.org>, koct9i@...il.com,
	ebiederm@...ssion.com, Wei Tang <tangwei@...s.chinamobile.com>,
	linux-kernel@...r.kernel.org, oleg@...hat.com,
	josh@...htriplett.org, jason.low2@...com, peterz@...radead.org,
	Ingo Molnar <mingo@...nel.org>, akpm@...ux-foundation.org,
	kirill.shutemov@...ux.intel.com
Subject: Re: [PATCH] kernel/fork.c: use sizeof() instead of sizeof

On Tue, Feb 02, 2016 at 05:04:06PM +0000, Al Viro wrote:
 
> FWIW, the actual rules are
> 	unary-expression: postfix-expression |
> 			  ++ unary-expression |
> 			  -- unary-expression |
> 			  - cast-expression |
> 			  + cast-expression |
> 			  ! cast-expression |
> 			  ~ cast-expression |
> 			  * cast-expression |
> 			  & cast-expression |
> 			  sizeof unary-expression |
> 			  sizeof ( type-name )
> 	cast-expression: unary-expression |
> 			 ( type-name ) cast-expression
> Note that while e.g.
> 	++ ++ n
> is allowed by grammar, it runs afoul of the constraint for ++ argument, which
> must be a modifiable lvalue.  None of the operators above yield that, so
> the rules for ++ and -- might as well have been ++ postfix-expression and
> -- postfix-expression resp.

Unless I'm mistaken, * cast-expression yields an lvalue.

    - Kevin