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SubjectRe: [PATCH v2] printk: help pr_debug and pr_devel to optimize out arguments
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Arnd Bergmann <arnd@arndb.de> writes:
> On Friday 04 December 2015 16:51:42 Aaron Conole wrote:
>> --- a/include/linux/printk.h
>> +++ b/include/linux/printk.h
>> @@ -106,13 +106,14 @@ struct va_format {
>>
>> /*
>> * Dummy printk for disabled debugging statements to use whilst maintaining
>> - * gcc's format and side-effect checking.
>> + * gcc's format checking.
>> */
>> -static inline __printf(1, 2)
>> -int no_printk(const char *fmt, ...)
>> -{
>> - return 0;
>> -}
>> +#define no_printk(fmt, ...) \
>> +do { \
>> + if (0) { \
>> + printk(fmt, ##__VA_ARGS__); \
>> + } \
>> +} while (0)
>>
>
> This change breaks compiling lib/842/, at least in some configurations:
>
> lib/842/842_decompress.c: In function '__do_index':
> lib/842/842_decompress.c:205:12422: error: implicit declaration of function 'no_printk'
>
> Using a gcc style vararg macro instead of the C99 style makes it work, but
> I don't know why the original version didn't work.
>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
>
> diff --git a/include/linux/printk.h b/include/linux/printk.h
> index cc3803a8f73e..4d1851a82254 100644
> --- a/include/linux/printk.h
> +++ b/include/linux/printk.h
> @@ -108,10 +108,10 @@ struct va_format {
> * Dummy printk for disabled debugging statements to use whilst maintaining
> * gcc's format checking.
> */
> -#define no_printk(fmt, ...) \
> +#define no_printk(arg ...) \
> do { \
> if (0) { \
> - printk(fmt, ##__VA_ARGS__); \
> + printk(arg); \
> } \
> } while (0)
>

Ugh. Sorry about this; I thought I had compiled everywhere but I guess not.


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