This program demonstrates a bug that may cause a fault when using
MPI_Unpack together with a datatype containing a zero-size construct
like the MPI_Contiguous with count=0 in this case.

The following MPI implementations exhibit this bug:
 * mpich/3.4.3, 4.0, 4.0.1, 4.0.2
when configured with the YAKSA engine.

The underlying issue is that YAKSA is not prepared for zero-size
ranges while the MPI spec indirectly states these must be supported.

The bug is tracked at

<https://github.com/pmodels/mpich/issues/6234>

a fix is available in the file

config/checkpatch/mpich_zero_size_contiguous.patch

distributed with YAXT.
