RFR: 8252049: Native memory leak in ciMethodData ctor

[Vladimir Ivanov]

On Mon, 30 Nov 2020 13:41:23 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> src/hotspot/share/oops/methodData.cpp line 1208:
>> 
>>> 1206: MethodData::MethodData(ciMethodData& data)
>>> 1207:   : _extra_data_lock(Mutex::leaf, "unused") {
>>> 1208:   _extra_data_lock.~Mutex(); // release allocated resources before zeroing
>> 
>> So if _extra_data_lock was a pointer to Mutex, then this statement would be simply "delete _extra_data_lock;" instead, but we'd still have this copy constructor, right?
>
> Why isn't this a regular copy constructor taking MethodData, and pass this._orig instead and leave the zeroing in the caller?  I don't like that oops/methodData knows about ciMethodData.

If `_extra_data_lock` were a pointer, then `MethodData::MethodData` would just `_extra_data_lock(NULL)`.

Regarding where to put zeroing, I'm fine doing it either way. 

Just want to give a try the idea David and Kim proposed with separating the lock from MDO (w/ superclass trick).

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PR: https://git.openjdk.java.net/jdk/pull/1478