RFR: JDK-8211279: Verify missing object equals barriers

[Aleksey Shipilev]

On 10/03/2018 03:25 PM, Roman Kennke wrote:
> This addresses all the issues mentioned above:
> http://cr.openjdk.java.net/~rkennke/JDK-8211279/webrev.02/

I think this is a cute way to get things going.

*) I always get a bit uneasy seeing the casts to (void*) like here:

 413   static bool equals(oop o1, oop o2) { return (void*)o1 == (void*)o2; }

 ...but I think this comparison is well-defined in C++ with the semantics we want.

*) So, if CHECK_UNHANDLED_OOPS is not defined, this declaration is inaccessible, and asserts that
use it would fail to compile? I think this ifdef is not needed here, but rather it should be around
the asserts in oop::operator== and !=?

 133 #ifdef CHECK_UNHANDLED_OOPS
 134   virtual bool oop_equals_operator_allowed() { return true; }
 135 #endif
 136

...

  58 bool oop::operator==(const oop o) const {
  59   assert(BarrierSet::barrier_set()->oop_equals_operator_allowed(), "Not allowed");
  60   return obj() == o.obj();
  61 }

Thanks,
-Aleksey

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