RFR: 8320370: NMT: Change MallocMemorySnapshot to simplify code. [v2]

[Johan Sjölen]

On Tue, 21 Nov 2023 10:02:40 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

> > > Nice clean up!
> > > Just one question: I'm probably missing something here, but did we have to change from `ResourceObj` to `AnyObj` for this change to work?
> > 
> > 
> > Hi Gerard, no I think it is unnecessary to do this change to make it work (I haven't checked). I do think keeping it as `AnyObj` is a good idea however, as `MallocMemorySnapshot` is never resource allocated.
> 
> Why not make it a simple object then? Why derive from anything at all?
> 
> (Update: I am fine with the current state of the patch; up to you)

It's not clear to me what the rules are on this matter. To what degree are plain global classes allowed in HotSpot? I thought that they all need to inherit from `AnyObj`,`CHeapObj`, etc. Seems like we're more OK with internal (structs and classes within other classes) being "undecorated" with their allocation capabilities.

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PR Comment: https://git.openjdk.org/jdk/pull/16724#issuecomment-1820934602