Re: [Xen-devel] [PATCH v3 3/3] x86/string: Clean up x86/string.h

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 15/05/17 15:22, Jan Beulich wrote:
>>>> On 15.05.17 at 15:08, <andrew.cooper3@xxxxxxxxxx> wrote:
>> On 15/05/17 11:19, Jan Beulich wrote:
>>>  >>> On 15.05.17 at 12:08, <JBeulich@xxxxxxxx> wrote:
>>>>>>> On 12.05.17 at 19:35, <andrew.cooper3@xxxxxxxxxx> wrote:
>>>>> --- a/xen/include/asm-x86/string.h
>>>>> +++ b/xen/include/asm-x86/string.h
>>>>> @@ -2,13 +2,23 @@
>>>>>  #define __X86_STRING_H__
>>>>>  
>>>>>  #define __HAVE_ARCH_MEMCPY
>>>>> -#define memcpy(t,f,n) (__builtin_memcpy((t),(f),(n)))
>>>>> +void *memcpy(void *dest, const void *src, size_t n);
>>>>> +#define memcpy(d, s, n) __builtin_memcpy(d, s, n)
>>>>>  
>>>>> -/* Some versions of gcc don't have this builtin. It's non-critical 
>>>>> anyway. 
>>>> */
>>>>>  #define __HAVE_ARCH_MEMMOVE
>>>>> -extern void *memmove(void *dest, const void *src, size_t n);
>>>>> +void *memmove(void *dest, const void *src, size_t n);
>>>>> +#define memmove(d, s, n) __builtin_memmove(d, s, n)
>>>>>  
>>>>>  #define __HAVE_ARCH_MEMSET
>>>>> -#define memset(s,c,n) (__builtin_memset((s),(c),(n)))
>>>>> +void *memset(void *dest, int c, size_t n);
>>>>> +#define memset(s, c, n) __builtin_memset(s, c, n)
>>>> Now that xen/string.h has the exact same declarations and
>>>> definitions already, why don't you simply delete the overrides
>>>> from here?
>>> Hmm, wait - I guess you need to keep them because of the custom
>>> implementation. That's awkward, there shouldn't be a need to have
>>> redundant declarations just because there are custom
>>> implementations. How about making __HAVE_ARCH_* serve both
>>> purposes, by allowing it to have different values (besides being
>>> defined or undefined)?
>> I don't understand how you would intend this new __HAVE_ARCH_* to work.
> E.g. __HAVE_ARCH_* = 2 meaning arch provides declaration and
> definition (i.e. generic header and source skip theirs), while
> __HAVE_ARCH_* = 1 meaning arch provides just a definition, but
> the generic declaration and macro (where applicable) are fine (i.e.
> only the generic source skips its piece of code).

I really don't thing its worth effort to make this change and diverge
from the Linux meaning.

It is not like these declarations are going to change often.

~Andrew

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