linux-kernel - Re: kernel.h: add ARRAY_AND_SIZE() macro to complement ARRAY

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Date:	Fri, 19 Sep 2008 10:54:26 +0400
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	Eric Miao <eric.y.miao@...il.com>
Cc:	Alexey Dobriyan <adobriyan@...il.com>,
	Ben Dooks <ben-linux@...ff.org>, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.arm.linux.org.uk
Subject: Re: kernel.h: add ARRAY_AND_SIZE() macro to complement
	ARRAY_SIZE().

[Eric Miao - Fri, Sep 19, 2008 at 02:38:21AM +0800]
| On Thu, Sep 18, 2008 at 11:06 PM, Alexey Dobriyan <adobriyan@...il.com> wrote:
| > On Thu, Sep 18, 2008 at 02:24:47PM +0100, Ben Dooks wrote:
| >> Move the ARRAY_AND_SIZE() macro from arch/arm/mach-pxa/generic.h
| >> to a more useful position in include/linux/kernel.h. This macro
| >> is very useful to registration functions that take an array and
| >> the number of array elements in it as consecutive arguments.
| >>
| >> The macro also should ensure that mistakes where the wrong array
| >> is used to the ARRAY_SIZE() macro is passed. It also makes it
| >> easier to avoid wrapping registration function arguments.
| >
| >> --- linux-2.6.27-rc6-quilt4.orig/include/linux/kernel.h
| >> +++ linux-2.6.27-rc6-quilt4/include/linux/kernel.h
| >> @@ -43,6 +43,7 @@ extern const char linux_proc_banner[];
| >>  #define IS_ALIGNED(x, a)             (((x) & ((typeof(x))(a) - 1)) == 0)
| >>
| >>  #define ARRAY_SIZE(arr) (sizeof(arr) / sizeof((arr)[0]) + __must_be_array(arr))
| >> +#define ARRAY_AND_SIZE(arr) (arr), ARRAY_SIZE(arr)
| >
| > Just like ARRAY_SIZE, it is misnamed.
| >
| 
| Any hint about the correct spelling?
| 
| > And it isn't obvious to what it expands. Hopefully arm people will
| > remove it. :-)
| 
| This is handy to use, saving several key strokes and making the line
| shorter. If it's not obvious to what it expands, there must be some
| fix for it?
| 

well, it seems it's not that good to use ARRAY_AND_SIZE at all.
Yes it's short but quite frankly - hiding number of args is not
that good.

example

	static void ssp_send_cmd(uint32_t *cmd, int num);

called as

	ssp_send_cmd(ARRAY_AND_SIZE(lcd_panel_on));

thanks it's not that spreaded across kernel.
Someday it could lead to ARRAY_AND_SIZE_CHECK_IF_EXIST_AND_PANIC :)

I hope you agree with me.

		- Cyrill -
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