Re: [PATCH 3/3] docs/doxygen: doxygen documentation for grant_table.h

[Jan Beulich <jbeulich@xxxxxxxx>]

On 08.04.2021 13:02, Luca Fancellu wrote:
> 
> 
>> On 7 Apr 2021, at 22:26, Stefano Stabellini <sstabellini@xxxxxxxxxx> wrote:
>>
>> On Wed, 7 Apr 2021, Jan Beulich wrote:
>>> On 07.04.2021 10:42, Luca Fancellu wrote:
>>>> Just to be sure that we are in the same page, are you suggesting to modify 
>>>> the name
>>>> In this way?
>>>>
>>>> struct gnttab_cache_flush {
>>>> -    union {
>>>> +    union xen_gnttab_cache_flush_a {
>>>>        uint64_t dev_bus_addr;
>>>>        grant_ref_t ref;
>>>>    } a;
>>>>
>>>> Following this kind of pattern: xen_<upper struct name>_<member name> ?
>>>
>>> While in general I would be fine with this scheme, for field names like
>>> "a" or "u" it doesn't fit well imo.
>>
>> "a" is a bad name anyway, even for the member. We can take the
>> opportunity to find a better name. Almost anything would be better than
>> "a". Maybe "refaddr"?
>>
>>
>>> I'm also unconvinced this would be
>>> scalable to the case where there's further struct/union nesting.
>>
>> How many of these instances of multilevel nesting do we have? Luca might
>> know. Probably not many? They could be special-cased.
> 
> There are not many multilevel nesting instances of anonymous struct/union and 
> the maximum level of nesting I found in the public headers is 2:
> 
> union {
>       union/struct {
>               …
>       } <name>
> } <name>
> 
> I also see that in the majority of cases the unions have not meaningful names 
> like “a” or “u” as member name, instead struct names are fine,
> It could be fine to keep the meaningful name the same for the struct type 
> name and use the pattern for the non-meaningful ones as long
> as the names doesn’t create compilation errors?
> 
> Example:
> 
> struct upper_level {
>       union {
>               struct {
>               
>               } meaningful_name1;
>               struct {
>               
>               } meaningful_name2;
>       } u;
> };
> 
> becomes:
> 
> struct upper_level {
>       union upper_level_u {
>               struct meaningful_name1 {
>               
>               } meaningful_name1;
>               struct meaningful_name2 {
>               
>               } meaningful_name2;
>       } u;
> };

As you say - as long as there aren't any compilation issues. Two
top level struct-s could have identically named struct/union fields
without tag, in which case your approach outlined above will fail.
And even if there was no such case right now, the case would need
to be covered in whatever naming model was to be used (except, of
course, the one without any names).

Jan