ControlMemory sets (writes) an address (used to access a Control object's memory) to the contents of memory.

If external is not NULL, the contents of external are set to an implementation-specific address that typically points to a different section or type of Control memory other than memory (e.g., to external or off-chip memory). These addresses (or addresses calculated from them) are passed as the src argument to mpiControlMemoryGet(...) and the dst argument to mpiControlMemorySet(...).