Re: [PATCH v9 04/11] public: xen.h: add definitions for UUID handling

[Julien Grall <julien.grall@linaro.org>]

Hi Jan,

On 11/10/17 09:54, Jan Beulich wrote:
>>>> On 11.10.17 at 01:24, <sstabellini@kernel.org> wrote:
>> On Tue, 10 Oct 2017, Volodymyr Babchuk wrote:
>>> --- a/xen/include/public/xen.h
>>> +++ b/xen/include/public/xen.h
>>> @@ -930,6 +930,39 @@ __DEFINE_XEN_GUEST_HANDLE(uint16, uint16_t);
>>>   __DEFINE_XEN_GUEST_HANDLE(uint32, uint32_t);
>>>   __DEFINE_XEN_GUEST_HANDLE(uint64, uint64_t);
>>>   
>>> +typedef struct {
>>> +    uint8_t a[16];
>>> +} xen_uuid_t;
>>> +
>>> +/*
>>> + * XEN_DEFINE_UUID(0x00112233, 0x4455, 0x6677, 0x8899,
>>> + *                 0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff)
>>> + * will construct UUID 00112233-4455-6677-8899-aabbccddeeff presented as
>>> + * {0x00, 0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77, 0x88,
>>> + * 0x99, 0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff};
>>> + *
>>> + * NB: This is compatible with Linux kernel and with libuuid, but it is not
>>> + * compatible with Microsoft, as they use mixed-endian encoding (some
>>> + * components are little-endian, some are big-endian).
>>> + */
>>> +#define XEN_DEFINE_UUID_(a, b, c, d, e1, e2, e3, e4, e5, e6)            \
>>> +    {{((a) >> 24) & 0xFF, ((a) >> 16) & 0xFF,                           \
>>> +      ((a) >>  8) & 0xFF, ((a) >>  0) & 0xFF,                           \
>>> +      ((b) >>  8) & 0xFF, ((b) >>  0) & 0xFF,                           \
>>> +      ((c) >>  8) & 0xFF, ((c) >>  0) & 0xFF,                           \
>>> +      ((d) >>  8) & 0xFF, ((d) >>  0) & 0xFF,                           \
>>> +                e1, e2, e3, e4, e5, e6}}
>>> +
>>> +/* Compound literals are supported in C99 and later. */
>>> +#if defined (__STDC_VERSION__) && __STDC_VERSION__ >= 199901L
>>> +#define XEN_DEFINE_UUID(a, b, c, d, e1, e2, e3, e4, e5, e6)             \
>>> +    ((xen_uuid_t)XEN_DEFINE_UUID_(a, b, c, d, e1, e2, e3, e4, e5, e6))
>>> +#else
>>> +#define XEN_DEFINE_UUID(a, b, c, d, e1, e2, e3, e4, e5, e6)             \
>>> +    XEN_DEFINE_UUID_(a, b, c, d, e1, e2, e3, e4, e5, e6)
>>> +
>>> +#endif /* defined (__STDC_VERSION__) && __STDC_VERSION__ >= 199901L */
>>> +
>>>   #endif /* !__ASSEMBLY__ */
>>>   
>>>   /* Default definitions for macros used by domctl/sysctl. */
>>
>> This looks good to me, but I would like to get Jan's opinion on this.
>> Ideally we would commit the series tomorrow before the code freeze.
> 
> While I can live with it being the way it is now, I've already
> indicated that I'd prefer __GNUC__ to also be checked for
> here. As that's a relaxation, it wouldn't be a problem to add
> later, I think (but I can't exclude I'm overlooking something,
> so it would feel better if it was done the intended final way
> from the beginning).

To be clear, you ask to do:

#if defined(__GNUC__) || (defined(__STDC_VERSION__) && __STDC_VERSION__ 
 >= 199901L)

am I correct?

Cheers,

-- 
Julien Grall

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
https://lists.xen.org/xen-devel