RFR: 8227054: ServiceThread needs to know about all OopStorage objects

[coleen.phillimore at oracle.com]

On 8/20/19 5:10 PM, Kim Barrett wrote:
>> On Aug 20, 2019, at 3:42 PM, coleen.phillimore at oracle.com wrote:
>>
>>
>> The iterator code seems to have taken on a life of it's own, but the runtime changes still look good.
> Thanks.
>
>> Can you put some comment about why is there a singular iterator and what its purpose is?  Is there some implicit use I can't find?
>>
>> +  // Construct a singular iterator.  The only valid operations are
>> +  // destruction/copy/assignment.
>> +  Iterator() :
>> +    _index(singular_index),
>> +    _limit(singular_index)
>> +    DEBUG_ONLY(COMMA _category(singular)) {}
>> +
>>
> Does this help?
>
> -  // Construct a singular iterator.  The only valid operations are
> -  // destruction/copy/assignment.
> +  // Construct a singular iterator, not associated with any of the sets
> +  // (strong, weak, or all) of storage objects.  The only valid operations
> +  // are destruction/copy/assignment.
>
> Singular iterators exist so you can declare a variable and later assign to it.

Add this sentence to the comment and I'm fine.  I wanted the comment to 
say why it exists.

Thanks,
Coleen

> , for example
>
>      Iterator it;
>      if (need_strong) {
>        it = strong_iterator();
>      } else {
>        it = weak_iterator();
>      }
>      … use the iterator …
>
> The C++ standard uses the phrase “iterator with a singular value”; “singular iterator” is
> a common shorthand.
>