Do array class name symbols for unloaded array classes leak deliberately?

[coleen.phillimore at oracle.com]

Hi Thomas, Yes, this appears to be a bug.  It looks intentional but I 
can't remember why it would be, and didn't leave a comment.

Can you file a bug with your test case?

thanks,
Coleen

On 1/21/19 10:29 AM, Thomas Stüfe wrote:
> Hi all,
>
> Looking at ~ClassLoaderData(), I see that we never seem to decrease the
> refcount on Klass::_name for ArrayKlass* childs. We do this for
> InstanceKlass* childs (via ReleaseKlassClosure::do_klass() ->
> InstanceKlass::release_C_heap_structures(k)) but not for ArrayKlass*.
>
> This causes observable leaks: When I run a small test program where I load
> a number of generated classes, instance and array both, and then GC them,
> the array class symbol names leak:
>
> thomas at t450:/shared/projects/openjdk/jdk-jdk/output-fastdebug$ jjjcmd
> test3.Example2 VM.symboltable -verbose | grep myclass
> 26 65535: [Lmyclass_size_1_number_0;
> 26 65535: [Lmyclass_size_1_number_1;
> 26 65535: [Lmyclass_size_1_number_2;
>
> This seems to be always have been the case and it seems deliberate: the
> array class name is created as a permanent symbol :
>
> Klass* ObjArrayKlass::allocate_objArray_klass(ClassLoaderData* loader_data,
>                                                  int n, Klass*
> element_klass, TRAPS) {
>
> ...
>      name = SymbolTable::new_permanent_symbol(new_str, CHECK_0);
> ...
>
> }
>
> Why is that? Why do we remove class name symbols for instance classes, but
> leave them for arrays?
>
> Thanks & Kind Regards, Thomas