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Message-ID: <1341873376.6118.56.camel@joe2Laptop>
Subject: Re: +
 checkpatch-add-check-for-use-of-sizeof-without-parenthesis.patch added to
 -mm tree
From: Joe Perches <joe@perches.com>
To: David Rientjes <rientjes@google.com>
Cc: linux-kernel@vger.kernel.org, mm-commits@vger.kernel.org,
        apw@canonical.com
Date: Mon, 09 Jul 2012 15:36:16 -0700
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On Mon, 2012-07-09 at 15:23 -0700, David Rientjes wrote:
> On Mon, 9 Jul 2012, akpm@linux-foundation.org wrote:
> 
> > From: Joe Perches <joe@perches.com>
> > Subject: checkpatch: Add acheck for use of sizeof without parenthesis
> > 
> > Kernel style uses parenthesis around sizeof.
> > 
> 
> Nack, there's a difference between "sizeof *task" and 
> "sizeof(struct task_struct)".  The former operates on a unary expression 
> and the latter operates on a type.  There are over 1000 occurrences in the 
> kernel where the sizeof operator, the former, is used on a unary 
> expression.

Huh?  Maybe I misunderstand you.

$ cat sizeof.c
#include <stdio.h>
#include <stdlib.h>
#include <strings.h>

struct foo {
	int bar[20];
	char *baz;
};

int main(int argc, char **argv)
{
	struct foo bar;
	struct foo *baz;

	printf("1: %zu\n", sizeof(struct foo));
	printf("2: %zu\n", sizeof bar);
	printf("3: %zu\n", sizeof *baz); 

	return 0;
}

$ gcc sizeof.c
$ ./a.out
1: 84
2: 84
3: 84

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