From 01e437a2daa3b55f9dd126e768f08376b6bf844f Mon Sep 17 00:00:00 2001
From: "Ralf W. Grosse-Kunstleve" <rwgk@google.com>
Date: Thu, 19 Nov 2020 18:33:37 -0800
Subject: [PATCH] unique_ptr or shared_ptr return

---
 tests/test_unique_ptr_member.cpp | 57 ++++++++++++++++++++++++++------
 tests/test_unique_ptr_member.py  | 32 ++++++++++++++----
 2 files changed, 73 insertions(+), 16 deletions(-)

diff --git a/tests/test_unique_ptr_member.cpp b/tests/test_unique_ptr_member.cpp
index 96edf77c5..316dac44e 100644
--- a/tests/test_unique_ptr_member.cpp
+++ b/tests/test_unique_ptr_member.cpp
@@ -1,15 +1,23 @@
 #include "pybind11_tests.h"
 
+#include <iostream>
 #include <memory>
 
 namespace pybind11_tests {
 namespace unique_ptr_member {
 
+inline void to_cout(std::string text) { std::cout << text << std::endl; }
+
 class pointee { // NOT copyable.
   public:
     pointee() = default;
 
-    int get_int() const { return 213; }
+    int get_int() const {
+        to_cout("pointee::get_int()");
+        return 213;
+    }
+
+    ~pointee() { to_cout("~pointee()"); }
 
   private:
     pointee(const pointee &) = delete;
@@ -18,35 +26,64 @@ class pointee { // NOT copyable.
     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_;
 };
 
 // Just to have a minimal example of a typical C++ pattern.
 inline int cpp_pattern() {
-    auto obj = std::unique_ptr<pointee>(new pointee);
-    int result = (obj ? 10 : 0);
+    auto obj = make_unique_pointee();
+    int result = (obj ? 1 : 8);
+    obj->get_int();
     ptr_owner owner(std::move(obj));
-    result += (obj ? 1 : 0);
+    result = result * 10 + (obj ? 8 : 1);
+    result = result * 10 + (owner.is_owner() ? 1 : 8);
+    to_cout("before give up");
+    auto reclaimed = owner.give_up_ownership_via_shared_ptr();
+    to_cout("after give up");
+    result = result * 10 + (owner.is_owner() ? 8 : 1);
+    result = result * 10 + (reclaimed ? 1 : 8);
+    reclaimed.reset();
+    to_cout("after del");
+    result = result * 10 + (reclaimed ? 8 : 1);
     return result;
 }
 
 TEST_SUBMODULE(unique_ptr_member, m) {
-    m.def("cpp_pattern", cpp_pattern);
+    m.def("to_cout", to_cout);
 
-    py::class_<pointee>(m, "pointee")
+    py::class_<pointee, std::shared_ptr<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")
-#ifdef FEAT_UNIQUE_PTR_ARG
-        .def(py::init<std::unique_ptr<pointee>>(), py::arg("ptr"))
-#endif
-        ;
+        //.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);
+
+    m.def("cpp_pattern", cpp_pattern);
 }
 
 } // namespace unique_ptr_member
diff --git a/tests/test_unique_ptr_member.py b/tests/test_unique_ptr_member.py
index 121b8ef05..85b07f609 100644
--- a/tests/test_unique_ptr_member.py
+++ b/tests/test_unique_ptr_member.py
@@ -4,15 +4,35 @@ import pytest
 from pybind11_tests import unique_ptr_member as m
 
 
-def test_cpp_pattern():
-    res = m.cpp_pattern()
-    assert res == 10
+def test_make_unique_pointee():
+    m.to_cout("")
+    obj = m.make_unique_pointee()
+    assert obj.get_int() == 213
+    m.to_cout("")
 
 
 def test_pointee_and_ptr_owner():
+    m.to_cout("")
     obj = m.pointee()
     assert obj.get_int() == 213
-    m.ptr_owner(obj)
-    with pytest.raises(ValueError) as exc_info:
+    owner = m.ptr_owner(obj)
+    with pytest.raises(RuntimeError) as exc_info:
         obj.get_int()
-    assert str(exc_info.value).startswith("Missing value for wrapped C++ type ")
+    assert str(exc_info.value) == "Invalid object instance"
+    assert owner.is_owner()
+    m.to_cout("before give up")
+    reclaimed = owner.give_up_ownership_via_shared_ptr()
+    m.to_cout("after give up")
+    assert not owner.is_owner()
+    # assert reclaimed.get_int() == 213
+    del reclaimed
+    m.to_cout("after del")
+    m.to_cout("3")
+    m.to_cout("")
+
+
+def test_cpp_pattern():
+    m.to_cout("")
+    res = m.cpp_pattern()
+    assert res == 111111
+    m.to_cout("")