RFR: 8322476: Remove GrowableArray C-Heap version, replace usages with GrowableArrayCHeap
Emanuel Peter
epeter at openjdk.org
Wed Dec 20 12:57:10 UTC 2023
[JDK-8247755](https://bugs.openjdk.org/browse/JDK-8247755) introduced the `GrowableArrayCHeap`. This duplicates the current C-Heap allocation capability in `GrowableArray`. I now remove that from `GrowableArray` and move all usages to `GrowableArrayCHeap`.
This has a few advantages:
- Clear separation between arena (and resource area) allocating array and C-heap allocating array.
- We can prevent assigning / copying between arrays of different allocation strategies already at compile time, and not only with asserts at runtime.
- We should not have multiple implementations of the same thing (C-Heap backed array).
- `GrowableArrayCHeap` is NONCOPYABLE. This is a nice restriction, we now know that C-Heap backed arrays do not get copied unknowingly.
**Bonus**
We can now restrict `GrowableArray` element type `E` to be `std::is_trivially_destructible<E>::value == true`. The idea is that arena / resource allocated arrays get abandoned, often without being even cleared. Hence, the elements in the array are never destructed. But if we only use elements that are trivially destructible, then it makes no difference if the destructors are ever called, or the elements simply abandoned.
For `GrowableArrayCHeap`, we expect that the user eventually calls the destructor for the array, which in turn calls the destructors of the remaining elements. Hence, it is up to the user to ensure the cleanup. And so we can allow non-trivial destructors.
**Testing**
Tier1-3 + stress testing: pending
-------------
Commit messages:
- fix comment about trivial elements
- check for trivial destructors
- improve comment
- add an explicit to constructor
- improve comments
- remove cheap internals from GrowableArray and fix verification
- remove constructors for GrowableArray with Cheap backing
- 8322476
Changes: https://git.openjdk.org/jdk/pull/17160/files
Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=17160&range=00
Issue: https://bugs.openjdk.org/browse/JDK-8322476
Stats: 774 lines in 127 files changed: 108 ins; 204 del; 462 mod
Patch: https://git.openjdk.org/jdk/pull/17160.diff
Fetch: git fetch https://git.openjdk.org/jdk.git pull/17160/head:pull/17160
PR: https://git.openjdk.org/jdk/pull/17160
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