RFR: 8284620: CodeBuffer may leak _overflow_arena

[Zhengyu Gu]

On Mon, 11 Apr 2022 06:43:12 GMT, Tobias Hartmann <thartmann at openjdk.org> wrote:

>> `CodeBuffer` is declared as `StackObj`, but it also has `ResourceObj` style `new operator`, to complicate thing further more, it has _overflow_arena that is C Heap allocated.
>> 
>> When Stack allocated `CodeBuffer` owns `_overflow_arena`, it works fine, because its destructor frees `_overflow_arena`. But if resource allocated `CodeBuffer` owns `_overflow_arena`, the arena is leaked, because its destructor is never called.
>> 
>> Test:
>> - [x] hotspot_compiler on Linux x86_64
>
> Looks reasonable to me. Another review would be good.

Thanks, @TobiHartmann

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PR: https://git.openjdk.java.net/jdk/pull/8172