RFR: 8213481: [REDO] Fix incorrect copy constructors in hotspot

[Kim Barrett]

> On Nov 26, 2018, at 8:39 PM, David Holmes <david.holmes at oracle.com> wrote:
> 
> Hi Kim,
> 
> First thanks for the offline education on the nuances of copy constructors!

Happy to help.

> On 19/11/2018 4:14 pm, Kim Barrett wrote:
>> Please review this fix of the debug-only copy constructor and
>> assignment operator for ResourceObj, along with adding some missing
>> uses of the copy constructor.
>> The missing copy constructor uses were found by enabling -Wextra.
>> The ResourceObj debug-only copy constructor should behave exactly the
>> same as the corresponding default constructor.  That is, the setup for
>> checking the allocation state in the destructor and operator delete
>> should be the same whether in the normal or copy constructor.  That
>> previously wasn't true, resulting in assert failures.
> 
> That all seems fine to me.

Thanks.

>> The ResourceObj assignment operator also should not be assuming the
>> target of the assignment was stack/embeded allocated; that's just not
>> a valid assumption.  The corresponding assertion has been removed.
> 
> Isn't that enforcing a usage requirement of ResourceObj? C-heap/resource-area/arena allocated ResourceObj should only be used via pointers - assigning one to another makes no sense to me.

I don’t see any reason for such an artificial restriction, and think it might prevent reasonable uses.
I don’t have a specific use-case in mind, but the natural result is observed from doing the natural thing.