RFR: 8271513: support JavaThreadIteratorWithHandle replacement by new ThreadsList::Iterator

[David Holmes]

On Fri, 30 Jul 2021 19:19:49 GMT, Daniel D. Daugherty <dcubed at openjdk.org> wrote:

> A trivial fix to support JavaThreadIteratorWithHandle replacement by new ThreadsList::Iterator.
> 
> This fix was tested with Mach5 Tier[1-3].

Sorry Dan, while I like the use of the for-each loops very much I don't understand the details of the iterator declaration. I definitely do not classify this as a trivial change.

Thanks,
David

src/hotspot/share/runtime/threadSMR.hpp line 331:

> 329:   }
> 330: 
> 331:   using Iterator = ThreadsList::Iterator;

Is this like a typedef? I don't think I want to see plain "Iterator" and not know what the actual type is here.

src/hotspot/share/runtime/threadSMR.inline.hpp line 110:

> 108: }
> 109: 
> 110: ThreadsListHandle::Iterator ThreadsListHandle::begin() { return list()->begin(); }

I don't understand this - why is the return type not `ThreadsList::Iterator` as per the declaration in the hpp file? That `using` directive is apparently doing something more bizarre than I thought.

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PR: https://git.openjdk.java.net/jdk/pull/4948