I just want to point out that casting away the const for low-level interfaces is really a non issue. Putting a const on the send buffer parameter in an MPI function prototype indicates a contract with the user that the MPI implementation will not change the contents of the buffer referenced from that function. As long as the MPI implementor knows that a routine called by the library will not modify the buffer it's OK to cast away the const. E.g., the POSIX standard tells you that writev must not change the contents of the buffer, so casting away const is fine. Sure, that means that the MPI implementor has to be more careful when casting away const to ensure that the function being called won't modify the buffer. But the whole point of the proposal is so that the _MPI_user_ doesn't need to do this and instead can count on the compiler to do the check. -d