Messages in this thread | | | Date | Fri, 19 Sep 2008 11:32:54 +0400 | From | Cyrill Gorcunov <> | Subject | Re: kernel.h: add ARRAY_AND_SIZE() macro to complement ARRAY_SIZE(). |
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[Eric Miao - Fri, Sep 19, 2008 at 03:22:13PM +0800] | On Fri, Sep 19, 2008 at 2:54 PM, Cyrill Gorcunov <gorcunov@gmail.com> wrote: | > [Eric Miao - Fri, Sep 19, 2008 at 02:38:21AM +0800] | > | On Thu, Sep 18, 2008 at 11:06 PM, Alexey Dobriyan <adobriyan@gmail.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 :) | | Probably that not gonna happen. | | without ARRAY_AND_SIZE: | | ssp_send_cmd(lcd_panel_on, ARRAY_SIZE(lcd_panel_on)); | | with: | | ssp_send_cmd(ARRAY_AND_SIZE(lcd_panel_on)); | | where you don't have to repeat the array name. I have to admit | that a macro expanding to something like an argument list instead | of a single variable or something is not a good idea. But, we are | using C, and there's no easy way just to pass the array itself, | otherwise one may come up with: | | ssp_send_cmd(lcd_panel_on); | | ssp_send_cmd(array a) | { | int size = a.length(); | | ........ | } | | I'm not trying to buy anyone anything, just illustrate this, and see | if anyone else is interested in doing so. |
Absolutely agreed with this (ie pass _one_ array name). Would be a good cleanup.
- Cyrill -
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