Dynamic Allocation Control (GNAT User’s Guide for Native Platforms)

#### 4.5.2.5 Dynamic Allocation Control ¶

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.

`-H32`

  Allocate memory on 32-bit heap

`-H64`

  Allocate 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.