x                  The address of the area, quadword-
                       aligned (Alpha only) or octaword-aligned
                       (Integrity servers(ONLY)) . The address is
                       returned because the area may have to be moved
                       to a new address to reallocate enough space.
                       If the area was moved, the space previously
                       occupied is freed.
    NULL               Indicates that space cannot be reallocated
                       (for example, if there is not enough room).