RFR: 8308092: Replace NULL with nullptr in gc/x

[Stefan Karlsson]

On Tue, 16 May 2023 07:36:13 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> Replace NULL with nullptr in gc/x. We've already done this work for Generational ZGC, but left it for the Singlegen ZGC code.
>
> src/hotspot/share/gc/x/xBarrier.inline.hpp line 229:
> 
>> 227: //
>> 228: inline oop XBarrier::load_barrier_on_oop(oop o) {
>> 229:   return load_barrier_on_oop_field_preloaded((oop*)nullptr, o);
> 
> Casts should not be needed on `nullptr`.

They are needed to disambiguate the two overloaded functions that take `volatile oop*` and  `volatile narrowOop*` respectively.

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PR Review Comment: https://git.openjdk.org/jdk/pull/13984#discussion_r1194891740