Since dtype_file_extent_fn will also be called when the user calls
MPI_FILE_GET_TYPE_EXTENT (for user defined data representations),
I think we should either make no restrictions at all, or have
something like:
\MPI/ will only pass the following \mpiarg{datatype}s to
\func{dtype\_file\_extent\_fn}:
\begin{itemize}
\item a \mpiarg{datatype} passed to \func{MPI\_FILE\_GET\_TYPE\_EXTENT}
for a file with user defined data representation \mpiarg{datarep},
\item the \mpiarg{etype} used to set the view
for a file with user defined data representation \mpiarg{datarep}, or
\item an \MPI/ basic type used in the construction of either of the above.
\end{itemize}
- bill