demonstrate premature delete using current pybind#2687

Author: rwgk

tests/CMakeLists.txt

@@ -115,6 +115,7 @@ set(PYBIND11_TEST_FILES
     test_opaque_types.cpp
     test_operator_overloading.cpp
     test_pickling.cpp
+    test_premature_delete.cpp
     test_pytypes.cpp
     test_sequences_and_iterators.cpp
     test_smart_ptr.cpp

tests/test_premature_delete.cpp

@@ -0,0 +1,69 @@
+#include "pybind11_tests.h"
+
+#include <iostream>
+#include <memory>
+
+namespace pybind11_tests {
+
+inline void to_cout(std::string text) { std::cout << text << std::endl; }
+
+class pointee { // NOT copyable.
+  public:
+    pointee() {
+      std::cout << "pointee(): " << this << std::endl;
+    }
+
+    int get_int() const {
+        to_cout("pointee::get_int()");
+        return 213;
+    }
+
+    ~pointee() { std::cout << "~pointee(): " << this << std::endl; }
+
+  private:
+    pointee(const pointee &) = delete;
+    pointee(pointee &&) = delete;
+    pointee &operator=(const pointee &) = delete;
+    pointee &operator=(pointee &&) = delete;
+};
+
+inline std::unique_ptr<pointee> make_unique_pointee() {
+    return std::unique_ptr<pointee>(new pointee);
+}
+
+class ptr_owner {
+  public:
+    explicit ptr_owner(std::unique_ptr<pointee> ptr) : ptr_(std::move(ptr)) {}
+
+    bool is_owner() const { return bool(ptr_); }
+
+    std::unique_ptr<pointee> give_up_ownership_via_unique_ptr() {
+        return std::move(ptr_);
+    }
+    std::shared_ptr<pointee> give_up_ownership_via_shared_ptr() {
+        return std::move(ptr_);
+    }
+
+  private:
+    std::unique_ptr<pointee> ptr_;
+};
+
+TEST_SUBMODULE(premature_delete, m) {
+    m.def("to_cout", to_cout);
+
+    py::class_<pointee>(m, "pointee")
+        .def(py::init<>())
+        .def("get_int", &pointee::get_int);
+
+    m.def("make_unique_pointee", make_unique_pointee);
+
+    py::class_<ptr_owner>(m, "ptr_owner")
+        .def(py::init<std::unique_ptr<pointee>>(), py::arg("ptr"))
+        .def("is_owner", &ptr_owner::is_owner)
+        .def("give_up_ownership_via_unique_ptr",
+             &ptr_owner::give_up_ownership_via_unique_ptr)
+        .def("give_up_ownership_via_shared_ptr",
+             &ptr_owner::give_up_ownership_via_shared_ptr);
+}
+
+} // namespace pybind11_tests

tests/test_premature_delete.py

@@ -0,0 +1,34 @@
+# -*- coding: utf-8 -*-
+import pytest
+
+from pybind11_tests import premature_delete as m
+
+
+def test_pointee_and_ptr_owner():
+    m.to_cout("")
+    obj = m.pointee()
+    assert obj.get_int() == 213
+    owner = m.ptr_owner(obj)
+    with pytest.raises(RuntimeError) as exc_info:
+        obj.get_int()
+    assert str(exc_info.value) == "Invalid object instance"
+    assert owner.is_owner()
+    m.to_cout("before give up")
+    if 1:  # Behavior is the same with 0 or 1 here.
+        reclaimed = owner.give_up_ownership_via_unique_ptr()
+    else:
+        reclaimed = owner.give_up_ownership_via_shared_ptr()
+    m.to_cout("after give up")
+    assert not owner.is_owner()
+    if 0:
+        # This is desired.
+        assert reclaimed.get_int() == 213
+    else:
+        # But obj is actually disowned.
+        with pytest.raises(RuntimeError) as exc_info:
+            obj.get_int()
+        assert str(exc_info.value) == "Invalid object instance"
+    m.to_cout("before del")
+    del reclaimed
+    m.to_cout("after del")
+    m.to_cout("")