Standard allocator methods per the semantics defined above. The deallocate and reallocate methods are @system because they may move memory around, leaving dangling pointers in user code.
Returns the global instance of this allocator type. The garbage collected allocator is thread-safe, therefore all of its methods and instance itself are shared.
The alignment is a static constant equal to platformAlignment, which ensures proper alignment for any D data type.
D's built-in garbage-collected allocator purified.
TODO remove and place with GCAllocator when https://github.com/dlang/phobos/pull/6432 has been merged.