Hi FT Folks, I encountered this oddity while doing some hacking today. Apparently, MPI_ERRORS_RETURN has a different signature from all other error handlers; it returns a value and all other error handlers (e.g. MPI_ERRORS_ARE_FATAL and user-defined error handlers) have void return: typedef void MPI_Comm_errhandler_function(MPI_Comm *, int *, ...); Because of this, MPI_Comm_call_errhandler effectively does not do anything when the error handler is set to MPI_ERRORS_RETURN. More specifically, the following code, return MPI_Comm_call_errhandler(my_comm, my_err_code); always returns success. To summarize the issues: (1) It is difficult or impossible to use the MPI error subsystem when the error handler is set to MPI_ERRORS_RETURN and (2) it is impossible for a user defined error handler to return an error code. These difficulties seem like they could be troublesome to users of FT that want to create higher level resilience/resilient libraries that interact with the MPI errors subsystem. Is what I have encountered a real issue or am I misunderstanding something? If it is a real issue, is it something we queue up for discussion at the upcoming F2F? Interested to hear your thoughts, ~Jim.