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

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> 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).

Jan


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