RFR: 8272107: Removal of Unsafe::defineAnonymousClass left a dangling C++ class

[Ioi Lam]

On Tue, 10 Aug 2021 16:37:44 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> Please review this change to remove the now unused CPSlot class.  Uses of CPSlot have been replaced with Symbol*.  The change was tested by running JCK lang and VM tests, Mach5 tiers 1-2 on Linux, Mac OS, and WIndows and Macn5 tiers 3-5 on Linux x64.
>> 
>> Thanks, Harold
>
> src/hotspot/share/oops/constantPool.inline.hpp line 39:
> 
>> 37:   intptr_t adr = Atomic::load_acquire(obj_at_addr(which));
>> 38:   assert(adr != 0 || which == 0, "cp entry for klass should not be zero");
>> 39:   return (Symbol*)adr;
> 
> I think you can get rid of all slot_at* and replace them with symbol_at().  Since the symbols don't change after the constant pool is initialized, all this volatile isn't needed.  Used to be used to replace Symbol* with Klass* also.  @iklam can confirm.

`ConstantPool` objects are no modified after the class is linked, and linking is done single threaded. So there's no need to use the `Atomic::load_acquire` in the above code. I agree with Coleen that the above function can be replaced with symbol_at().

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PR: https://git.openjdk.java.net/jdk/pull/5070