Isolating shared_from_this tests from test_smart_ptr (minimal changes).

tests/test_class_sh_shared_from_this.cpp

@@ -0,0 +1,72 @@
+#include "pybind11_tests.h"
+#include "object.h"
+
+namespace test_class_sh_shared_from_this {
+
+class MyObject3 : public std::enable_shared_from_this<MyObject3> {
+public:
+    MyObject3(const MyObject3 &) = default;
+    MyObject3(int value) : value(value) { print_created(this, toString()); }
+    std::string toString() const { return "MyObject3[" + std::to_string(value) + "]"; }
+    virtual ~MyObject3() { print_destroyed(this); }
+private:
+    int value;
+};
+
+struct SharedFromThisRef {
+    struct B : std::enable_shared_from_this<B> {
+        B() { print_created(this); }
+        B(const B &) : std::enable_shared_from_this<B>() { print_copy_created(this); }
+        B(B &&) : std::enable_shared_from_this<B>() { print_move_created(this); }
+        ~B() { print_destroyed(this); }
+    };
+
+    B value = {};
+    std::shared_ptr<B> shared = std::make_shared<B>();
+};
+
+struct SharedFromThisVBase : std::enable_shared_from_this<SharedFromThisVBase> {
+    SharedFromThisVBase() = default;
+    SharedFromThisVBase(const SharedFromThisVBase &) = default;
+    virtual ~SharedFromThisVBase() = default;
+};
+
+struct SharedFromThisVirt : virtual SharedFromThisVBase {};
+
+} // namespace test_class_sh_shared_from_this
+
+using namespace test_class_sh_shared_from_this;
+
+PYBIND11_TYPE_CASTER_BASE_HOLDER(MyObject3, std::shared_ptr<MyObject3>)
+PYBIND11_TYPE_CASTER_BASE_HOLDER(SharedFromThisRef::B, std::shared_ptr<SharedFromThisRef::B>)
+PYBIND11_TYPE_CASTER_BASE_HOLDER(SharedFromThisRef, std::unique_ptr<SharedFromThisRef>)
+PYBIND11_TYPE_CASTER_BASE_HOLDER(SharedFromThisVirt, std::shared_ptr<SharedFromThisVirt>)
+
+TEST_SUBMODULE(class_sh_shared_from_this, m) {
+    py::class_<MyObject3, std::shared_ptr<MyObject3>>(m, "MyObject3")
+        .def(py::init<int>());
+    m.def("make_myobject3_1", []() { return new MyObject3(8); });
+    m.def("make_myobject3_2", []() { return std::make_shared<MyObject3>(9); });
+    m.def("print_myobject3_1", [](const MyObject3 *obj) { py::print(obj->toString()); });
+    m.def("print_myobject3_2", [](std::shared_ptr<MyObject3> obj) { py::print(obj->toString()); });
+    m.def("print_myobject3_3", [](const std::shared_ptr<MyObject3> &obj) { py::print(obj->toString()); });
+    m.def("print_myobject3_4", [](const std::shared_ptr<MyObject3> *obj) { py::print((*obj)->toString()); });
+
+    using B = SharedFromThisRef::B;
+    py::class_<B, std::shared_ptr<B>>(m, "B");
+    py::class_<SharedFromThisRef, std::unique_ptr<SharedFromThisRef>>(m, "SharedFromThisRef")
+        .def(py::init<>())
+        .def_readonly("bad_wp", &SharedFromThisRef::value)
+        .def_property_readonly("ref", [](const SharedFromThisRef &s) -> const B & { return *s.shared; })
+        .def_property_readonly("copy", [](const SharedFromThisRef &s) { return s.value; },
+                               py::return_value_policy::copy)
+        .def_readonly("holder_ref", &SharedFromThisRef::shared)
+        .def_property_readonly("holder_copy", [](const SharedFromThisRef &s) { return s.shared; },
+                               py::return_value_policy::copy)
+        .def("set_ref", [](SharedFromThisRef &, const B &) { return true; })
+        .def("set_holder", [](SharedFromThisRef &, std::shared_ptr<B>) { return true; });
+
+    static std::shared_ptr<SharedFromThisVirt> sft(new SharedFromThisVirt());
+    py::class_<SharedFromThisVirt, std::shared_ptr<SharedFromThisVirt>>(m, "SharedFromThisVirt")
+        .def_static("get", []() { return sft.get(); });
+}

tests/test_class_sh_shared_from_this.py

@@ -0,0 +1,76 @@
+# -*- coding: utf-8 -*-
+import pytest
+
+from pybind11_tests import class_sh_shared_from_this as m
+from pybind11_tests import ConstructorStats
+
+
+def test_smart_ptr(capture):
+    # Object3
+    for i, o in zip(
+        [9, 8, 9], [m.MyObject3(9), m.make_myobject3_1(), m.make_myobject3_2()]
+    ):
+        print(o)
+        with capture:
+            m.print_myobject3_1(o)
+            m.print_myobject3_2(o)
+            m.print_myobject3_3(o)
+            m.print_myobject3_4(o)
+        assert capture == "MyObject3[{i}]\n".format(i=i) * 4
+
+    cstats = ConstructorStats.get(m.MyObject3)
+    assert cstats.alive() == 1
+    o = None
+    assert cstats.alive() == 0
+    assert cstats.values() == ["MyObject3[9]", "MyObject3[8]", "MyObject3[9]"]
+    assert cstats.default_constructions == 0
+    assert cstats.copy_constructions == 0
+    # assert cstats.move_constructions >= 0 # Doesn't invoke any
+    assert cstats.copy_assignments == 0
+    assert cstats.move_assignments == 0
+
+
+def test_shared_ptr_from_this_and_references():
+    s = m.SharedFromThisRef()
+    stats = ConstructorStats.get(m.B)
+    assert stats.alive() == 2
+
+    ref = s.ref  # init_holder_helper(holder_ptr=false, owned=false, bad_wp=false)
+    assert stats.alive() == 2
+    assert s.set_ref(ref)
+    assert s.set_holder(
+        ref
+    )  # std::enable_shared_from_this can create a holder from a reference
+
+    bad_wp = s.bad_wp  # init_holder_helper(holder_ptr=false, owned=false, bad_wp=true)
+    assert stats.alive() == 2
+    assert s.set_ref(bad_wp)
+    with pytest.raises(RuntimeError) as excinfo:
+        assert s.set_holder(bad_wp)
+    assert "Unable to cast from non-held to held instance" in str(excinfo.value)
+
+    copy = s.copy  # init_holder_helper(holder_ptr=false, owned=true, bad_wp=false)
+    assert stats.alive() == 3
+    assert s.set_ref(copy)
+    assert s.set_holder(copy)
+
+    holder_ref = (
+        s.holder_ref
+    )  # init_holder_helper(holder_ptr=true, owned=false, bad_wp=false)
+    assert stats.alive() == 3
+    assert s.set_ref(holder_ref)
+    assert s.set_holder(holder_ref)
+
+    holder_copy = (
+        s.holder_copy
+    )  # init_holder_helper(holder_ptr=true, owned=true, bad_wp=false)
+    assert stats.alive() == 3
+    assert s.set_ref(holder_copy)
+    assert s.set_holder(holder_copy)
+
+    del ref, bad_wp, copy, holder_ref, holder_copy, s
+    assert stats.alive() == 0
+
+    z = m.SharedFromThisVirt.get()
+    y = m.SharedFromThisVirt.get()
+    assert y is z