pub unsafe extern "C" fn PMPI_Register_datarep(
datarep: *const i8,
read_conversion_fn: Option<unsafe extern "C" fn(_: *mut c_void, _: *mut ompi_datatype_t, _: i32, _: *mut c_void, _: i64, _: *mut c_void) -> i32>,
write_conversion_fn: Option<unsafe extern "C" fn(_: *mut c_void, _: *mut ompi_datatype_t, _: i32, _: *mut c_void, _: i64, _: *mut c_void) -> i32>,
dtype_file_extent_fn: Option<unsafe extern "C" fn(_: *mut ompi_datatype_t, _: *mut isize, _: *mut c_void) -> i32>,
extra_state: *mut c_void
) -> i32