RFR: 8291457: Clean up lifecycle of CDS dump-time data structures

[Coleen Phillimore]

On Wed, 3 Aug 2022 07:15:49 GMT, Ioi Lam <iklam at openjdk.org> wrote:

> I've rewritten the following data CDS structures to follow the [C++ rule-of-three](https://en.cppreference.com/w/cpp/language/rule_of_three) to improve their lifecycle handling and fix a memory leak. This is done to prepare for future CDS changes that make more allocations during archive creation.
> 
>> Rule of Three: If a class requires a user-defined destructor, a user-defined copy constructor, or a user-defined copy assignment operator, it almost certainly requires all three.
> 
> - DumpTimeClassInfo
> - DumpTimeClassInfo::DTLoaderConstraint
> - DumpTimeClassInfo::DTVerifierConstraint
> - DumpTimeLambdaProxyClassInfo
> 
> I implemented some of the assignment operators using the [copy-and-swap idiom](https://en.cppreference.com/w/cpp/language/copy_assignment) to handle `Symbol` refcounting. Thanks to @kimbarrett for the suggestion.

This looks a lot cleaner. I have a couple of questions.

src/hotspot/share/cds/dumpTimeClassInfo.cpp line 72:

> 70:       for (int i = 0; i < n; i++) {
> 71:         _loader_constraints->append(src._loader_constraints->at(i));
> 72:       }

Do you need the src copy after the copy constructor runs?  You could transfer ownership of the verifier and loader_constraints arrays if not.

src/hotspot/share/cds/dumpTimeClassInfo.cpp line 85:

> 83:   if (_loader_constraints != NULL) {
> 84:     delete _loader_constraints;
> 85:   }

So this delete operator in this destructor calls the destructors for all the elements of the _verifier_constraints, _verifier_constraint_flags and _loader_constraints elements, which decrements refcounts in them, right?

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PR: https://git.openjdk.org/jdk/pull/9722