RFR (XS): 8017578 : Hotspot compilation error with latest Studio compiler

[David Chase]

bug:
in src/share/vm/adlc/forms.hpp, class Form needs a virtual destructor,
because it has polymorphic subtypes (that also lack virtual destructors).

fix:
make the destructor virtual

testing:
Reproduce bug with new compilers, verify that changes fixes it.
Jtreg locally (MacOSX)
compiler regression tests across platforms on JPRT.

webrev:
http://cr.openjdk.java.net/~drchase/8017578/webrev.00/

PROBLEM:

This is only the first hurdle.
After this is fixed, come errors of the form:

"/export/drchase/jdk8tl-full/hotspot/src/share/vm/oops/klass.hpp", line 452: Error: Initializing const volatile oop& requires an lvalue.
"/export/drchase/jdk8tl-full/hotspot/src/share/vm/oops/klass.hpp", line 452: Error: Formal argument o of type const volatile oop& in call to oop::oop(const volatile oop&) is being passed oop.
"/export/drchase/jdk8tl-full/hotspot/src/share/vm/runtime/handles.hpp", line 69: Error: Initializing const volatile oop& requires an lvalue.
"/export/drchase/jdk8tl-full/hotspot/src/share/vm/runtime/handles.hpp", line 69: Error: Formal argument o of type const volatile oop& in call to oop::oop(const volatile oop&) is being passed oop.
...
Compilation aborted, too many Error messages.

This is caused by:
...
#define CHECK_UNHANDLED_OOPS
...
in oopsHierarchy.hpp:
class oop {
...
  oop(const volatile oop& o)          { set_obj(o.obj()); }
  oop(const void* p)                  { set_obj(p); }

and in klass.hpp:
  virtual oop klass_holder() const      { return class_loader(); }

or in handles.hpp:
class Handle VALUE_OBJ_CLASS_SPEC {
 private:
  oop* _handle;

 protected:
  oop     obj() const                            { return _handle == NULL ? (oop)NULL : *_handle; }

Note that this code is all supposed to work when an oop is merely

typedef class oopDesc*                            oop;

Note that this is probably not a "compiler" bug anymore.

David