Re: [Xen-devel] [PATCH v8 04/11] public: xen.h: add definitions for UUID handling

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 10.10.17 at 19:03, <volodymyr_babchuk@xxxxxxxx> wrote:
> On 10.10.17 19:12, Jan Beulich wrote:
>>>>> On 10.10.17 at 17:52, <volodymyr_babchuk@xxxxxxxx> wrote:
>>> +    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
>> 
>> I didn't notice this earlier - why no check for __GNUC__?
> I have seen pattern "#if defined (__STDC_VERSION__) && __STDC_VERSION__ 

But if you check, all of the existing ones have
"#elif defined(__GNUC__)".

>  >= 199901" in various places in XEN, so I did it alike.
> Also, I'm using C99 feature, not gcc-only one.

I didn't ask you to replace the conditional, but to (possibly)
extend it.

Jan


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