#include "mpi.h" int MPI_Comm_free ( commp ) MPI_Comm *commp;
A null handle argument is an erroneous IN argument in MPI calls, unless an exception is explicitly stated in the text that defines the function. Such exception is allowed for handles to request objects in Wait and Test calls (sections Communication Completion and Multiple Completions ). Otherwise, a null handle can only be passed to a function that allocates a new object and returns a reference to it in the handle.