Update (2020-12-22): Simplest reproduction can be seen in #1333
If a Python subclass of a pybind11 C++ class, with holder_type = shared_ptr<T>, has a shared_ptr<> that exists in C++ when its Python ref_count() goes to zero, Python will destroy the Python extension, and leave the C++ Alias type (e.g. PyBase, using PYBIND11_OVERLOAD*) functionality bare (and actually aliased / truncated affected by object slicing).
This could be prevented if a custom __del__, PyTypeObject::tp_del, or PyTypeObject::tp_dealloc is installed such that the instance could be resurrected if holder.use_count() > 1 for the given value-holder, and the ownership is released to C++.
(__del__ is the easiest, as Python explicitly mentions that you can increase the refcount of a destructing object and save it from death.)
This is related to #1132.
Update (2020-12-22): Simplest reproduction can be seen in #1333
If a Python subclass of a pybind11 C++ class, with
holder_type = shared_ptr<T>, has ashared_ptr<>that exists in C++ when its Pythonref_count()goes to zero, Python will destroy the Python extension, and leave the C++ Alias type (e.g.PyBase, usingPYBIND11_OVERLOAD*) functionality bare (and actuallyaliased / truncatedaffected by object slicing).This could be prevented if a custom
__del__,PyTypeObject::tp_del, orPyTypeObject::tp_deallocis installed such that the instance could be resurrected ifholder.use_count() > 1for the given value-holder, and the ownership is released to C++.(
__del__is the easiest, as Python explicitly mentions that you can increase the refcount of a destructing object and save it from death.)This is related to #1132.