Extending C++ IProcess in Python causes ref counting issues

[thomasms]

The following script shows the problem:

import peakingduck as pd


data = pd.core.NumericalData([2,3.4,5,123.,123.2,6453.42,3.5,345.34,23.4,524.542,89.3])

pm = pd.core.SimpleProcessManager()

# this causes problems, due to Python ref counting
# comment it out to find out
#pm.append(pd.core.SavitzkyGolaySmoother(3))

# this also causes issues
#sg = pd.core.SavitzkyGolaySmoother(3)
#pm.append(sg)
#del sg

# this is OK, since it is fro C++
pm.append(pd.core.MovingAverageSmoother(3))

# process the data
processeddata = pm.run(data).to_list()

print(processeddata)

Related to:

• shared_ptrs to Python-derived instances outlive the associated Python object pybind/pybind11#1546
• Ownership of python objects inheriting from C++ classes pybind/pybind11#1389
• Fix Python object lifetimes associated with shared_ptrs pybind/pybind11#1566
• Question about returning unique pointer in virtual function pybind/pybind11#673