8295012: Arena should not derive from CHeapObj<mtNone>

[kimbarrett]

Please review this change to the Arena class. Rather than deriving from
CHeapObj<mtNone> (which has the effect of preventing C-heap allocation for an
arena by asserting if such is attempted), instead have no allocation base
class so that new Arena(...) will fail to compile.

Testing: mach5 tier1

---

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Issue

• JDK-8295012: Arena should not derive from CHeapObj

Reviewers

• Stefan Karlsson (@stefank - Reviewer) ⚠️ Review applies to 828541f5
• David Holmes (@dholmes-ora - Reviewer) ⚠️ Review applies to 828541f5

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[mlbridge]

Webrevs

• 02: Full - Incremental (817072dd)
• 01: Full - Incremental (828541f5)
• 00: Full (1e64a3cd)

[dholmes-ora]

The allocation base class tells the reader that Arena has special allocation constraints, by removing this it is not apparent there are any such constraints. Can we at least add a comment?

I confess I've forgotten how not having an allocation base class prevents use of new Foo() ??

[stefank]

We have a link-time check in debug builds that fails the build if someone tries to use the global new operators.

[stefank]

What's the reason for keeping the new/delete operators in Arena, instead of inheriting from the newly introduced CHeapObjBase class?

[kimbarrett]

What's the reason for keeping the new/delete operators in Arena, instead of inheriting from the newly introduced CHeapObjBase class?

No good reason. I just forgot about them. I will make that change.

[openjdk]

@kimbarrett This change now passes all automated pre-integration checks.

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8295012: Arena should not derive from CHeapObj<mtNone>

Reviewed-by: stefank, dholmes

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At the time when this comment was updated there had been 1 new commit pushed to the master branch:

• ab8c136: 8292898: [vectorapi] Unify vector mask cast operation

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[dholmes-ora]

LGTM!

Thanks

[kimbarrett]

Thanks @stefank and @dholmes-ora for reviews.

[kimbarrett]

/integrate

[openjdk]

Going to push as commit 5ad126f.
Since your change was applied there has been 1 commit pushed to the master branch:

• ab8c136: 8292898: [vectorapi] Unify vector mask cast operation

Your commit was automatically rebased without conflicts.

[openjdk]

@kimbarrett Pushed as commit 5ad126f.

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