RFR (S) 8216302: StackTraceElement::fill_in can use cached Class.name

[Aleksey Shipilev]

On 1/8/19 3:15 AM, David Holmes wrote:
> It seems somewhat awkward to me to have two different code paths for initializing the
> java.lang.Class name field. Can this be restructured a little more (change Class.getName()) so that
> the VM always initializes "name" and then JVM_GetClassName could just call java_lang_Class::name,
> rather than duplicating the logic?

Mmm. I am afraid to do this eagerly because of more memory footprint and potential bootstrapping
issues. Also, I want to keep this open to implement a crazy footprint-reducing idea: nulling the
fields like Class.name to conserve footprint at expense of additional call to reinstate the value
afterwards.

> Specific comments:
> 
> src/hotspot/share/classfile/javaClasses.cpp
> 
> !     Klass* k = as_Klass(java_class);
> !     assert(k->is_klass(), "just checking");
> !     name = k->external_name();
> 
> as_Klass already has the requisite assertions so there was no reason to change this part of the
> code. I see that jvm.cpp already contains the same redundant logic.

Right. Ditched that change.

> Copyright years need updating.

Updated.

Also made the test more up-to-the-point, with clearing the Class.name cache explicitly.

New webrev:
  http://cr.openjdk.java.net/~shade/8216302/webrev.02/

Thanks,
-Aleksey