macro_rules! define_stack_allocator_traits {
    ($name : ident, global) => { ... };
    ($name : ident, $freelist_size : tt, stack) => { ... };
    ($name : ident, heap) => { ... };
    ($name : ident, $freelist_size : tt, malloc) => { ... };
    ($name : ident, $freelist_size : tt, calloc) => { ... };
    ($name : ident, generic) => { ... };
}