ncsim will consume an increasing ammount of memory when a function has an output port that return an associative array which was not initialized. My simulator version is 12.10-s011.
Below is a code example to reproduce the failure. The code is inside a class (uvm_object):
function void a_function(output bit ret_val[int]);
endfunction : get_cov
each time the call is done a small ammount of memory is allocated. I n my case I call this function several (millions of) times during simulation and then I can see the memory leaking.