At the moment, CircleOS does not provide any memory management. However, you can consider that a CircleOS application can manage its own memory allocation. CircleOS uses only the top of the RAM (and it shares the stack with the application). Thus, you can consider your own heap between the stack and your static variables that are linked at the address 0 (0x20000000).
In the future, we will have to implement a memory allocator for the 'resident applications'. But for the moment, we consider that only one application is running.