RFR: 8303489: Add a test to verify classes in vmStruct have unique vtables [v3]

[Alex Menkov]

On Thu, 2 Mar 2023 23:13:36 GMT, Alex Menkov <amenkov at openjdk.org> wrote:

>> In that case is it worth listing the "no vtable" classes that have a superclass? Are they somehow more interesting than those without a superclass?
>
> If superclass is set then it's the type which describes VM class (but some JM classes have super == null)
> Maybe the test should report all Types with CInt: false, CStr: false, JPrimitive: false, Oop: false, Ptr: false
> Looks like these entries correspond declare_toplevel_type/declare_type in vmStruct

Updated criteria to log classes without vtable

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PR: https://git.openjdk.org/jdk/pull/12820