Re: [Xen-devel] [PATCH] xen: add macro for defining variable length array in public headers

[Jan Beulich <jbeulich@xxxxxxxx>]

On 30.08.2019 16:29, Juergen Gross wrote:
> On 30.08.19 16:21, Jan Beulich wrote:
>> On 30.08.2019 10:32, Juergen Gross wrote:
>>> --- a/xen/include/public/xen.h
>>> +++ b/xen/include/public/xen.h
>>> @@ -53,6 +53,15 @@ DEFINE_XEN_GUEST_HANDLE(uint64_t);
>>>   DEFINE_XEN_GUEST_HANDLE(xen_pfn_t);
>>>   DEFINE_XEN_GUEST_HANDLE(xen_ulong_t);
>>>   
>>> +/* Define a variable length array (depends on compiler). */
>>> +#if defined(__STDC_VERSION__) && __STDC_VERSION__ >= 199901L
>>> +#define __XEN_VARLEN_ARRAY_SIZE
>>> +#elif defined(__GNUC__)
>>> +#define __XEN_VARLEN_ARRAY_SIZE  0
>>> +#else
>>> +#define __XEN_VARLEN_ARRAY_SIZE  1 /* variable size */
>>> +#endif
>>
>> To be in line with the intentions, the C90 standard, and io/ring.h
>> I'd suggest to use FLEX instead of VARLEN. Furthermore, especially
>> in a public header, two double leading underscores need to go away.
>>
>> And then, with FLEX in the name, SIZE isn't really appropriate
>> anymore. Therefore I see three possible names: XEN_FLEXIBLE_ARRAY,
>> XEN_FLEX_ARRAY_DIMENSION (possibly just _DIM at its end), or
>> XEN_FLEX_ARRAY_DESIGNATOR.
> 
> Okay to the "FLEX" part, but the "XEN_" prefix is not working due to
> compat header generation (that will result in COMPAT_ prefix in the
> compat headers).
> 
> So any other ideas for a sensible prefix?

Hmm, ugly. Perhaps all lower case then? Or have

#define COMPAT_FLEX_... XEN_FLEX_...

somewhere?

Jan

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