The heap control switches – -H32 and -H64 –
determine whether dynamic allocation uses 32-bit or 64-bit memory.
They only affect compiler-generated allocations via __gnat_malloc;
explicit calls to malloc and related functions from the C
run-time library are unaffected.
-H32Allocate memory on 32-bit heap
-H64Allocate memory on 64-bit heap. This is the default
unless explicitly overridden by a 'Size clause on the access type.
These switches are only effective on VMS platforms.