Pure git merge --squash smart_holder (no manual interventions).

tests/test_class_sh_virtual_py_cpp_mix.cpp

@@ -0,0 +1,60 @@
+#include <pybind11/smart_holder.h>
+
+#include "pybind11_tests.h"
+
+#include <memory>
+
+namespace pybind11_tests {
+namespace class_sh_virtual_py_cpp_mix {
+
+class Base {
+public:
+    virtual ~Base() = default;
+    virtual int get() const { return 101; }
+
+    // Some compilers complain about implicitly defined versions of some of the following:
+    Base() = default;
+    Base(const Base &) = default;
+};
+
+class CppDerivedPlain : public Base {
+public:
+    int get() const override { return 202; }
+};
+
+class CppDerived : public Base {
+public:
+    int get() const override { return 212; }
+};
+
+int get_from_cpp_plainc_ptr(const Base *b) { return b->get() + 4000; }
+
+int get_from_cpp_unique_ptr(std::unique_ptr<Base> b) { return b->get() + 5000; }
+
+struct BaseVirtualOverrider : Base, py::trampoline_self_life_support {
+    using Base::Base;
+
+    int get() const override { PYBIND11_OVERRIDE(int, Base, get); }
+};
+
+struct CppDerivedVirtualOverrider : CppDerived, py::trampoline_self_life_support {
+    using CppDerived::CppDerived;
+
+    int get() const override { PYBIND11_OVERRIDE(int, CppDerived, get); }
+};
+
+} // namespace class_sh_virtual_py_cpp_mix
+} // namespace pybind11_tests
+
+using namespace pybind11_tests::class_sh_virtual_py_cpp_mix;
+
+TEST_SUBMODULE(class_sh_virtual_py_cpp_mix, m) {
+    py::classh<Base, BaseVirtualOverrider>(m, "Base").def(py::init<>()).def("get", &Base::get);
+
+    py::classh<CppDerivedPlain, Base>(m, "CppDerivedPlain").def(py::init<>());
+
+    py::classh<CppDerived, Base, CppDerivedVirtualOverrider>(m, "CppDerived").def(py::init<>());
+
+    m.def("get_from_cpp_plainc_ptr", get_from_cpp_plainc_ptr, py::arg("b"));
+    m.def("get_from_cpp_unique_ptr", get_from_cpp_unique_ptr, py::arg("b"));
+}