MPI error when broadcasting strings

[austin-hoover]

I get an error when mpi broadcasting strings, but not arrays. The following script is adapted from here.

from orbit.core import orbit_mpi

mpi_comm = orbit_mpi.mpi_comm.MPI_COMM_WORLD
mpi_rank = orbit_mpi.MPI_Comm_rank(mpi_comm)
mpi_size = orbit_mpi.MPI_Comm_size(mpi_comm)

main_rank = 0

data = (1, 2, 3)
data_type = orbit_mpi.mpi_datatype.MPI_INT
data_new = orbit_mpi.MPI_Bcast(data, data_type, main_rank, mpi_comm)
print(f"rank={mpi_rank} data_new={data_new}")

data = (1.0, 2.0, 3.0)
data_type = orbit_mpi.mpi_datatype.MPI_DOUBLE
data_new = orbit_mpi.MPI_Bcast(data, data_type, main_rank, mpi_comm)
print(f"rank={mpi_rank} data_new={data_new}")

data = "test"
data_type = orbit_mpi.mpi_datatype.MPI_CHAR
data_new = orbit_mpi.MPI_Bcast(data, data_type, main_rank, mpi_comm)
print(f"rank={mpi_rank} data_new={data_new}")

The script fails on the third broadcast of the string "test".

(pyorbit-mpi) 46h@mac144229 MPI_Tests % mpirun -n 2 python test_mpi_bcast.py   
rank=0 data_new=(1, 2, 3)
rank=0 data_new=(1.0, 2.0, 3.0)
rank=1 data_new=(1, 2, 3)
rank=1 data_new=(1.0, 2.0, 3.0)
Traceback (most recent call last):
  File "/Users/46h/repo/pyorbit/examples/MPI_Tests/test_mpi_bcast.py", line 22, in <module>
Traceback (most recent call last):
  File "/Users/46h/repo/pyorbit/examples/MPI_Tests/test_mpi_bcast.py", line 22, in <module>
    data_new = orbit_mpi.MPI_Bcast(data, data_type, main_rank, mpi_comm)
    data_new = orbit_mpi.MPI_Bcast(data, data_type, main_rank, mpi_comm)
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
SystemError: PY_SSIZE_T_CLEAN macro must be defined for '#' formats
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
SystemError: PY_SSIZE_T_CLEAN macro must be defined for '#' formats

PyORBIT version = 3.0.2.dev2+gb0cf39f.d20250501

[austin-hoover]

https://docs.python.org/3/c-api/arg.html

Note On Python 3.12 and older, the macro PY_SSIZE_T_CLEAN must be defined before including Python.h to use all # variants of formats (s#, y#, etc.) explained below. This is not necessary on Python 3.13 and later.