The following are defined C++ types, also included in the file mpi.h.
// Typedef MPI::AintThe rest of this annex uses the namespace notation because all the functions listed below are prototypes. The namespace notation is not used previously because the lists of constants and types above are not actual declarations.
// prototypes for user-defined functions
namespace MPI {
typedef void User_function(const void *invec, void* inoutvec, int len,
const Datatype& datatype);
};