ext/pybind11/tests/test_stl.cpp - public/gem5 - Git at Google

 /*
     tests/test_stl.cpp -- STL type casters

     Copyright (c) 2017 Wenzel Jakob <wenzel.jakob@epfl.ch>

     All rights reserved. Use of this source code is governed by a
     BSD-style license that can be found in the LICENSE file.
 */

 #include "pybind11_tests.h"
 #include "constructor_stats.h"
 #include <pybind11/stl.h>

 #ifndef PYBIND11_HAS_FILESYSTEM_IS_OPTIONAL
 #define PYBIND11_HAS_FILESYSTEM_IS_OPTIONAL
 #endif
 #include <pybind11/stl/filesystem.h>

 #include <vector>
 #include <string>

 #if defined(PYBIND11_TEST_BOOST)
 #include <boost/optional.hpp>

 namespace pybind11 { namespace detail {
 template <typename T>
 struct type_caster<boost::optional<T>> : optional_caster<boost::optional<T>> {};

 template <>
 struct type_caster<boost::none_t> : void_caster<boost::none_t> {};
 }} // namespace pybind11::detail
 #endif

 // Test with `std::variant` in C++17 mode, or with `boost::variant` in C++11/14
 #if defined(PYBIND11_HAS_VARIANT)
 using std::variant;
 #elif defined(PYBIND11_TEST_BOOST) && (!defined(_MSC_VER) || _MSC_VER >= 1910)
 #  include <boost/variant.hpp>
 #  define PYBIND11_HAS_VARIANT 1
 using boost::variant;

 namespace pybind11 { namespace detail {
 template <typename... Ts>
 struct type_caster<boost::variant<Ts...>> : variant_caster<boost::variant<Ts...>> {};

 template <>
 struct visit_helper<boost::variant> {
     template <typename... Args>
     static auto call(Args &&...args) -> decltype(boost::apply_visitor(args...)) {
         return boost::apply_visitor(args...);
     }
 };
 }} // namespace pybind11::detail
 #endif

 PYBIND11_MAKE_OPAQUE(std::vector<std::string, std::allocator<std::string>>);

 /// Issue #528: templated constructor
 struct TplCtorClass {
     template <typename T>
     explicit TplCtorClass(const T &) {}
     bool operator==(const TplCtorClass &) const { return true; }
 };

 namespace std {
     template <>
     struct hash<TplCtorClass> { size_t operator()(const TplCtorClass &) const { return 0; } };
 } // namespace std


 template <template <typename> class OptionalImpl, typename T>
 struct OptionalHolder
 {
     // NOLINTNEXTLINE(modernize-use-equals-default): breaks GCC 4.8
     OptionalHolder() {};
     bool member_initialized() const {
         return member && member->initialized;
     }
     OptionalImpl<T> member = T{};
 };


 enum class EnumType {
   kSet = 42,
   kUnset = 85,
 };

 // This is used to test that return-by-ref and return-by-copy policies are
 // handled properly for optional types. This is a regression test for a dangling
 // reference issue. The issue seemed to require the enum value type to
 // reproduce - it didn't seem to happen if the value type is just an integer.
 template <template <typename> class OptionalImpl>
 class OptionalProperties {
 public:
     using OptionalEnumValue = OptionalImpl<EnumType>;

     OptionalProperties() : value(EnumType::kSet) {}
     ~OptionalProperties() {
         // Reset value to detect use-after-destruction.
         // This is set to a specific value rather than nullopt to ensure that
         // the memory that contains the value gets re-written.
         value = EnumType::kUnset;
     }

     OptionalEnumValue& access_by_ref() { return value; }
     OptionalEnumValue access_by_copy() { return value; }

 private:
     OptionalEnumValue value;
 };

 // This type mimics aspects of boost::optional from old versions of Boost,
 // which exposed a dangling reference bug in Pybind11. Recent versions of
 // boost::optional, as well as libstdc++'s std::optional, don't seem to be
 // affected by the same issue. This is meant to be a minimal implementation
 // required to reproduce the issue, not fully standard-compliant.
 // See issue #3330 for more details.
 template <typename T>
 class ReferenceSensitiveOptional {
 public:
     using value_type = T;

     ReferenceSensitiveOptional() = default;
     // NOLINTNEXTLINE(google-explicit-constructor)
     ReferenceSensitiveOptional(const T& value) : storage{value} {}
     // NOLINTNEXTLINE(google-explicit-constructor)
     ReferenceSensitiveOptional(T&& value) : storage{std::move(value)} {}
     ReferenceSensitiveOptional& operator=(const T& value) {
         storage = {value};
         return *this;
     }
     ReferenceSensitiveOptional& operator=(T&& value) {
         storage = {std::move(value)};
         return *this;
     }

     template <typename... Args>
     T& emplace(Args&&... args) {
         storage.clear();
         storage.emplace_back(std::forward<Args>(args)...);
         return storage.back();
     }

     const T& value() const noexcept {
         assert(!storage.empty());
         return storage[0];
     }

     const T& operator*() const noexcept {
         return value();
     }

     const T* operator->() const noexcept {
         return &value();
     }

     explicit operator bool() const noexcept {
         return !storage.empty();
     }

 private:
     std::vector<T> storage;
 };

 namespace pybind11 { namespace detail {
 template <typename T>
 struct type_caster<ReferenceSensitiveOptional<T>> : optional_caster<ReferenceSensitiveOptional<T>> {};
 } // namespace detail
 } // namespace pybind11


 TEST_SUBMODULE(stl, m) {
     // test_vector
     m.def("cast_vector", []() { return std::vector<int>{1}; });
     m.def("load_vector", [](const std::vector<int> &v) { return v.at(0) == 1 && v.at(1) == 2; });
     // `std::vector<bool>` is special because it returns proxy objects instead of references
     m.def("cast_bool_vector", []() { return std::vector<bool>{true, false}; });
     m.def("load_bool_vector", [](const std::vector<bool> &v) {
         return v.at(0) == true && v.at(1) == false;
     });
     // Unnumbered regression (caused by #936): pointers to stl containers aren't castable
     static std::vector<RValueCaster> lvv{2};
     m.def("cast_ptr_vector", []() { return &lvv; });

     // test_deque
     m.def("cast_deque", []() { return std::deque<int>{1}; });
     m.def("load_deque", [](const std::deque<int> &v) { return v.at(0) == 1 && v.at(1) == 2; });

     // test_array
     m.def("cast_array", []() { return std::array<int, 2> {{1 , 2}}; });
     m.def("load_array", [](const std::array<int, 2> &a) { return a[0] == 1 && a[1] == 2; });

     // test_valarray
     m.def("cast_valarray", []() { return std::valarray<int>{1, 4, 9}; });
     m.def("load_valarray", [](const std::valarray<int>& v) {
         return v.size() == 3 && v[0] == 1 && v[1] == 4 && v[2] == 9;
     });

     // test_map
     m.def("cast_map", []() { return std::map<std::string, std::string>{{"key", "value"}}; });
     m.def("load_map", [](const std::map<std::string, std::string> &map) {
         return map.at("key") == "value" && map.at("key2") == "value2";
     });

     // test_set
     m.def("cast_set", []() { return std::set<std::string>{"key1", "key2"}; });
     m.def("load_set", [](const std::set<std::string> &set) {
         return (set.count("key1") != 0u) && (set.count("key2") != 0u) && (set.count("key3") != 0u);
     });

     // test_recursive_casting
     m.def("cast_rv_vector", []() { return std::vector<RValueCaster>{2}; });
     m.def("cast_rv_array", []() { return std::array<RValueCaster, 3>(); });
     // NB: map and set keys are `const`, so while we technically do move them (as `const Type &&`),
     // casters don't typically do anything with that, which means they fall to the `const Type &`
     // caster.
     m.def("cast_rv_map", []() { return std::unordered_map<std::string, RValueCaster>{{"a", RValueCaster{}}}; });
     m.def("cast_rv_nested", []() {
         std::vector<std::array<std::list<std::unordered_map<std::string, RValueCaster>>, 2>> v;
         v.emplace_back(); // add an array
         v.back()[0].emplace_back(); // add a map to the array
         v.back()[0].back().emplace("b", RValueCaster{});
         v.back()[0].back().emplace("c", RValueCaster{});
         v.back()[1].emplace_back(); // add a map to the array
         v.back()[1].back().emplace("a", RValueCaster{});
         return v;
     });
     static std::array<RValueCaster, 2> lva;
     static std::unordered_map<std::string, RValueCaster> lvm{{"a", RValueCaster{}}, {"b", RValueCaster{}}};
     static std::unordered_map<std::string, std::vector<std::list<std::array<RValueCaster, 2>>>> lvn;
     lvn["a"].emplace_back(); // add a list
     lvn["a"].back().emplace_back(); // add an array
     lvn["a"].emplace_back(); // another list
     lvn["a"].back().emplace_back(); // add an array
     lvn["b"].emplace_back(); // add a list
     lvn["b"].back().emplace_back(); // add an array
     lvn["b"].back().emplace_back(); // add another array
     m.def("cast_lv_vector", []() -> const decltype(lvv) & { return lvv; });
     m.def("cast_lv_array", []() -> const decltype(lva) & { return lva; });
     m.def("cast_lv_map", []() -> const decltype(lvm) & { return lvm; });
     m.def("cast_lv_nested", []() -> const decltype(lvn) & { return lvn; });
     // #853:
     m.def("cast_unique_ptr_vector", []() {
         std::vector<std::unique_ptr<UserType>> v;
         v.emplace_back(new UserType{7});
         v.emplace_back(new UserType{42});
         return v;
     });

     pybind11::enum_<EnumType>(m, "EnumType")
         .value("kSet", EnumType::kSet)
         .value("kUnset", EnumType::kUnset);

     // test_move_out_container
     struct MoveOutContainer {
         struct Value { int value; };
         std::list<Value> move_list() const { return {{0}, {1}, {2}}; }
     };
     py::class_<MoveOutContainer::Value>(m, "MoveOutContainerValue")
         .def_readonly("value", &MoveOutContainer::Value::value);
     py::class_<MoveOutContainer>(m, "MoveOutContainer")
         .def(py::init<>())
         .def_property_readonly("move_list", &MoveOutContainer::move_list);

     // Class that can be move- and copy-constructed, but not assigned
     struct NoAssign {
         int value;

         explicit NoAssign(int value = 0) : value(value) { }
         NoAssign(const NoAssign &) = default;
         NoAssign(NoAssign &&) = default;

         NoAssign &operator=(const NoAssign &) = delete;
         NoAssign &operator=(NoAssign &&) = delete;
     };
     py::class_<NoAssign>(m, "NoAssign", "Class with no C++ assignment operators")
         .def(py::init<>())
         .def(py::init<int>());


     struct MoveOutDetector
     {
         MoveOutDetector() = default;
         MoveOutDetector(const MoveOutDetector&) = default;
         MoveOutDetector(MoveOutDetector&& other) noexcept
          : initialized(other.initialized) {
             // steal underlying resource
             other.initialized = false;
         }
         bool initialized = true;
     };
     py::class_<MoveOutDetector>(m, "MoveOutDetector", "Class with move tracking")
         .def(py::init<>())
         .def_readonly("initialized", &MoveOutDetector::initialized);


 #ifdef PYBIND11_HAS_OPTIONAL
     // test_optional
     m.attr("has_optional") = true;

     using opt_int = std::optional<int>;
     using opt_no_assign = std::optional<NoAssign>;
     m.def("double_or_zero", [](const opt_int& x) -> int {
         return x.value_or(0) * 2;
     });
     m.def("half_or_none", [](int x) -> opt_int { return x != 0 ? opt_int(x / 2) : opt_int(); });
     m.def("test_nullopt", [](opt_int x) {
         return x.value_or(42);
     }, py::arg_v("x", std::nullopt, "None"));
     m.def("test_no_assign", [](const opt_no_assign &x) {
         return x ? x->value : 42;
     }, py::arg_v("x", std::nullopt, "None"));

     m.def("nodefer_none_optional", [](std::optional<int>) { return true; });
     m.def("nodefer_none_optional", [](const py::none &) { return false; });

     using opt_holder = OptionalHolder<std::optional, MoveOutDetector>;
     py::class_<opt_holder>(m, "OptionalHolder", "Class with optional member")
         .def(py::init<>())
         .def_readonly("member", &opt_holder::member)
         .def("member_initialized", &opt_holder::member_initialized);

     using opt_props = OptionalProperties<std::optional>;
     pybind11::class_<opt_props>(m, "OptionalProperties")
         .def(pybind11::init<>())
         .def_property_readonly("access_by_ref", &opt_props::access_by_ref)
         .def_property_readonly("access_by_copy", &opt_props::access_by_copy);
 #endif

 #ifdef PYBIND11_HAS_EXP_OPTIONAL
     // test_exp_optional
     m.attr("has_exp_optional") = true;

     using exp_opt_int = std::experimental::optional<int>;
     using exp_opt_no_assign = std::experimental::optional<NoAssign>;
     m.def("double_or_zero_exp", [](const exp_opt_int& x) -> int {
         return x.value_or(0) * 2;
     });
     m.def("half_or_none_exp", [](int x) -> exp_opt_int {
         return x ? exp_opt_int(x / 2) : exp_opt_int();
     });
     m.def("test_nullopt_exp", [](exp_opt_int x) {
         return x.value_or(42);
     }, py::arg_v("x", std::experimental::nullopt, "None"));
     m.def("test_no_assign_exp", [](const exp_opt_no_assign &x) {
         return x ? x->value : 42;
     }, py::arg_v("x", std::experimental::nullopt, "None"));

     using opt_exp_holder = OptionalHolder<std::experimental::optional, MoveOutDetector>;
     py::class_<opt_exp_holder>(m, "OptionalExpHolder", "Class with optional member")
         .def(py::init<>())
         .def_readonly("member", &opt_exp_holder::member)
         .def("member_initialized", &opt_exp_holder::member_initialized);

     using opt_exp_props = OptionalProperties<std::experimental::optional>;
     pybind11::class_<opt_exp_props>(m, "OptionalExpProperties")
         .def(pybind11::init<>())
         .def_property_readonly("access_by_ref", &opt_exp_props::access_by_ref)
         .def_property_readonly("access_by_copy", &opt_exp_props::access_by_copy);
 #endif

 #if defined(PYBIND11_TEST_BOOST)
     // test_boost_optional
     m.attr("has_boost_optional") = true;

     using boost_opt_int = boost::optional<int>;
     using boost_opt_no_assign = boost::optional<NoAssign>;
     m.def("double_or_zero_boost", [](const boost_opt_int& x) -> int {
         return x.value_or(0) * 2;
     });
     m.def("half_or_none_boost", [](int x) -> boost_opt_int {
         return x != 0 ? boost_opt_int(x / 2) : boost_opt_int();
     });
     m.def("test_nullopt_boost", [](boost_opt_int x) {
         return x.value_or(42);
     }, py::arg_v("x", boost::none, "None"));
     m.def("test_no_assign_boost", [](const boost_opt_no_assign &x) {
         return x ? x->value : 42;
     }, py::arg_v("x", boost::none, "None"));

     using opt_boost_holder = OptionalHolder<boost::optional, MoveOutDetector>;
     py::class_<opt_boost_holder>(m, "OptionalBoostHolder", "Class with optional member")
         .def(py::init<>())
         .def_readonly("member", &opt_boost_holder::member)
         .def("member_initialized", &opt_boost_holder::member_initialized);

     using opt_boost_props = OptionalProperties<boost::optional>;
     pybind11::class_<opt_boost_props>(m, "OptionalBoostProperties")
         .def(pybind11::init<>())
         .def_property_readonly("access_by_ref", &opt_boost_props::access_by_ref)
         .def_property_readonly("access_by_copy", &opt_boost_props::access_by_copy);
 #endif

     // test_refsensitive_optional
     using refsensitive_opt_int = ReferenceSensitiveOptional<int>;
     using refsensitive_opt_no_assign = ReferenceSensitiveOptional<NoAssign>;
     m.def("double_or_zero_refsensitive", [](const refsensitive_opt_int& x) -> int {
         return (x ? x.value() : 0) * 2;
     });
     m.def("half_or_none_refsensitive", [](int x) -> refsensitive_opt_int {
         return x != 0 ? refsensitive_opt_int(x / 2) : refsensitive_opt_int();
     });
     // NOLINTNEXTLINE(performance-unnecessary-value-param)
     m.def("test_nullopt_refsensitive", [](refsensitive_opt_int x) {
         return x ? x.value() : 42;
     }, py::arg_v("x", refsensitive_opt_int(), "None"));
     m.def("test_no_assign_refsensitive", [](const refsensitive_opt_no_assign &x) {
         return x ? x->value : 42;
     }, py::arg_v("x", refsensitive_opt_no_assign(), "None"));

     using opt_refsensitive_holder = OptionalHolder<ReferenceSensitiveOptional, MoveOutDetector>;
     py::class_<opt_refsensitive_holder>(m, "OptionalRefSensitiveHolder", "Class with optional member")
         .def(py::init<>())
         .def_readonly("member", &opt_refsensitive_holder::member)
         .def("member_initialized", &opt_refsensitive_holder::member_initialized);

     using opt_refsensitive_props = OptionalProperties<ReferenceSensitiveOptional>;
     pybind11::class_<opt_refsensitive_props>(m, "OptionalRefSensitiveProperties")
         .def(pybind11::init<>())
         .def_property_readonly("access_by_ref", &opt_refsensitive_props::access_by_ref)
         .def_property_readonly("access_by_copy", &opt_refsensitive_props::access_by_copy);

 #ifdef PYBIND11_HAS_FILESYSTEM
     // test_fs_path
     m.attr("has_filesystem") = true;
     m.def("parent_path", [](const std::filesystem::path& p) { return p.parent_path(); });
 #endif

 #ifdef PYBIND11_HAS_VARIANT
     static_assert(std::is_same<py::detail::variant_caster_visitor::result_type, py::handle>::value,
                   "visitor::result_type is required by boost::variant in C++11 mode");

     struct visitor {
         using result_type = const char *;

         result_type operator()(int) { return "int"; }
         result_type operator()(const std::string &) { return "std::string"; }
         result_type operator()(double) { return "double"; }
         result_type operator()(std::nullptr_t) { return "std::nullptr_t"; }
     };

     // test_variant
     m.def("load_variant", [](const variant<int, std::string, double, std::nullptr_t> &v) {
         return py::detail::visit_helper<variant>::call(visitor(), v);
     });
     m.def("load_variant_2pass", [](variant<double, int> v) {
         return py::detail::visit_helper<variant>::call(visitor(), v);
     });
     m.def("cast_variant", []() {
         using V = variant<int, std::string>;
         return py::make_tuple(V(5), V("Hello"));
     });
 #endif

     // #528: templated constructor
     // (no python tests: the test here is that this compiles)
     m.def("tpl_ctor_vector", [](std::vector<TplCtorClass> &) {});
     m.def("tpl_ctor_map", [](std::unordered_map<TplCtorClass, TplCtorClass> &) {});
     m.def("tpl_ctor_set", [](std::unordered_set<TplCtorClass> &) {});
 #if defined(PYBIND11_HAS_OPTIONAL)
     m.def("tpl_constr_optional", [](std::optional<TplCtorClass> &) {});
 #endif
 #if defined(PYBIND11_HAS_EXP_OPTIONAL)
     m.def("tpl_constr_optional_exp", [](std::experimental::optional<TplCtorClass> &) {});
 #endif
 #if defined(PYBIND11_TEST_BOOST)
     m.def("tpl_constr_optional_boost", [](boost::optional<TplCtorClass> &) {});
 #endif

     // test_vec_of_reference_wrapper
     // #171: Can't return STL structures containing reference wrapper
     m.def("return_vec_of_reference_wrapper", [](std::reference_wrapper<UserType> p4) {
         static UserType p1{1}, p2{2}, p3{3};
         return std::vector<std::reference_wrapper<UserType>> {
             std::ref(p1), std::ref(p2), std::ref(p3), p4
         };
     });

     // test_stl_pass_by_pointer
     m.def("stl_pass_by_pointer", [](std::vector<int>* v) { return *v; }, "v"_a=nullptr);

     // #1258: pybind11/stl.h converts string to vector<string>
     m.def("func_with_string_or_vector_string_arg_overload",
           [](const std::vector<std::string> &) { return 1; });
     m.def("func_with_string_or_vector_string_arg_overload",
           [](const std::list<std::string> &) { return 2; });
     m.def("func_with_string_or_vector_string_arg_overload", [](const std::string &) { return 3; });

     class Placeholder {
     public:
         Placeholder() { print_created(this); }
         Placeholder(const Placeholder &) = delete;
         ~Placeholder() { print_destroyed(this); }
     };
     py::class_<Placeholder>(m, "Placeholder");

     /// test_stl_vector_ownership
     m.def("test_stl_ownership",
           []() {
               std::vector<Placeholder *> result;
               result.push_back(new Placeholder());
               return result;
           },
           py::return_value_policy::take_ownership);

     m.def("array_cast_sequence", [](std::array<int, 3> x) { return x; });

     /// test_issue_1561
     struct Issue1561Inner { std::string data; };
     struct Issue1561Outer { std::vector<Issue1561Inner> list; };

     py::class_<Issue1561Inner>(m, "Issue1561Inner")
         .def(py::init<std::string>())
         .def_readwrite("data", &Issue1561Inner::data);

     py::class_<Issue1561Outer>(m, "Issue1561Outer")
         .def(py::init<>())
         .def_readwrite("list", &Issue1561Outer::list);

     m.def(
         "return_vector_bool_raw_ptr",
         []() { return new std::vector<bool>(4513); },
         // Without explicitly specifying `take_ownership`, this function leaks.
         py::return_value_policy::take_ownership);
 }
	/*
	tests/test_stl.cpp -- STL type casters

	Copyright (c) 2017 Wenzel Jakob <wenzel.jakob@epfl.ch>

	All rights reserved. Use of this source code is governed by a
	BSD-style license that can be found in the LICENSE file.
	*/

	#include "pybind11_tests.h"
	#include "constructor_stats.h"
	#include <pybind11/stl.h>

	#ifndef PYBIND11_HAS_FILESYSTEM_IS_OPTIONAL
	#define PYBIND11_HAS_FILESYSTEM_IS_OPTIONAL
	#endif
	#include <pybind11/stl/filesystem.h>

	#include <vector>
	#include <string>

	#if defined(PYBIND11_TEST_BOOST)
	#include <boost/optional.hpp>

	namespace pybind11 { namespace detail {
	template <typename T>
	struct type_caster<boost::optional<T>> : optional_caster<boost::optional<T>> {};

	template <>
	struct type_caster<boost::none_t> : void_caster<boost::none_t> {};
	}} // namespace pybind11::detail
	#endif

	// Test with `std::variant` in C++17 mode, or with `boost::variant` in C++11/14
	#if defined(PYBIND11_HAS_VARIANT)
	using std::variant;
	#elif defined(PYBIND11_TEST_BOOST) && (!defined(_MSC_VER) \|\| _MSC_VER >= 1910)
	# include <boost/variant.hpp>
	# define PYBIND11_HAS_VARIANT 1
	using boost::variant;

	namespace pybind11 { namespace detail {
	template <typename... Ts>
	struct type_caster<boost::variant<Ts...>> : variant_caster<boost::variant<Ts...>> {};

	template <>
	struct visit_helper<boost::variant> {
	template <typename... Args>
	static auto call(Args &&...args) -> decltype(boost::apply_visitor(args...)) {
	return boost::apply_visitor(args...);
	}
	};
	}} // namespace pybind11::detail
	#endif

	PYBIND11_MAKE_OPAQUE(std::vector<std::string, std::allocator<std::string>>);

	/// Issue #528: templated constructor
	struct TplCtorClass {
	template <typename T>
	explicit TplCtorClass(const T &) {}
	bool operator==(const TplCtorClass &) const { return true; }
	};

	namespace std {
	template <>
	struct hash<TplCtorClass> { size_t operator()(const TplCtorClass &) const { return 0; } };
	} // namespace std


	template <template <typename> class OptionalImpl, typename T>
	struct OptionalHolder
	{
	// NOLINTNEXTLINE(modernize-use-equals-default): breaks GCC 4.8
	OptionalHolder() {};
	bool member_initialized() const {
	return member && member->initialized;
	}
	OptionalImpl<T> member = T{};
	};


	enum class EnumType {
	kSet = 42,
	kUnset = 85,
	};

	// This is used to test that return-by-ref and return-by-copy policies are
	// handled properly for optional types. This is a regression test for a dangling
	// reference issue. The issue seemed to require the enum value type to
	// reproduce - it didn't seem to happen if the value type is just an integer.
	template <template <typename> class OptionalImpl>
	class OptionalProperties {
	public:
	using OptionalEnumValue = OptionalImpl<EnumType>;

	OptionalProperties() : value(EnumType::kSet) {}
	~OptionalProperties() {
	// Reset value to detect use-after-destruction.
	// This is set to a specific value rather than nullopt to ensure that
	// the memory that contains the value gets re-written.
	value = EnumType::kUnset;
	}

	OptionalEnumValue& access_by_ref() { return value; }
	OptionalEnumValue access_by_copy() { return value; }

	private:
	OptionalEnumValue value;
	};

	// This type mimics aspects of boost::optional from old versions of Boost,
	// which exposed a dangling reference bug in Pybind11. Recent versions of
	// boost::optional, as well as libstdc++'s std::optional, don't seem to be
	// affected by the same issue. This is meant to be a minimal implementation
	// required to reproduce the issue, not fully standard-compliant.
	// See issue #3330 for more details.
	template <typename T>
	class ReferenceSensitiveOptional {
	public:
	using value_type = T;

	ReferenceSensitiveOptional() = default;
	// NOLINTNEXTLINE(google-explicit-constructor)
	ReferenceSensitiveOptional(const T& value) : storage{value} {}
	// NOLINTNEXTLINE(google-explicit-constructor)
	ReferenceSensitiveOptional(T&& value) : storage{std::move(value)} {}
	ReferenceSensitiveOptional& operator=(const T& value) {
	storage = {value};
	return *this;
	}
	ReferenceSensitiveOptional& operator=(T&& value) {
	storage = {std::move(value)};
	return *this;
	}

	template <typename... Args>
	T& emplace(Args&&... args) {
	storage.clear();
	storage.emplace_back(std::forward<Args>(args)...);
	return storage.back();
	}

	const T& value() const noexcept {
	assert(!storage.empty());
	return storage[0];
	}

	const T& operator*() const noexcept {
	return value();
	}

	const T* operator->() const noexcept {
	return &value();
	}

	explicit operator bool() const noexcept {
	return !storage.empty();
	}

	private:
	std::vector<T> storage;
	};

	namespace pybind11 { namespace detail {
	template <typename T>
	struct type_caster<ReferenceSensitiveOptional<T>> : optional_caster<ReferenceSensitiveOptional<T>> {};
	} // namespace detail
	} // namespace pybind11


	TEST_SUBMODULE(stl, m) {
	// test_vector
	m.def("cast_vector", []() { return std::vector<int>{1}; });
	m.def("load_vector", [](const std::vector<int> &v) { return v.at(0) == 1 && v.at(1) == 2; });
	// `std::vector<bool>` is special because it returns proxy objects instead of references
	m.def("cast_bool_vector", []() { return std::vector<bool>{true, false}; });
	m.def("load_bool_vector", [](const std::vector<bool> &v) {
	return v.at(0) == true && v.at(1) == false;
	});
	// Unnumbered regression (caused by #936): pointers to stl containers aren't castable
	static std::vector<RValueCaster> lvv{2};
	m.def("cast_ptr_vector", []() { return &lvv; });

	// test_deque
	m.def("cast_deque", []() { return std::deque<int>{1}; });
	m.def("load_deque", [](const std::deque<int> &v) { return v.at(0) == 1 && v.at(1) == 2; });

	// test_array
	m.def("cast_array", []() { return std::array<int, 2> {{1 , 2}}; });
	m.def("load_array", [](const std::array<int, 2> &a) { return a[0] == 1 && a[1] == 2; });

	// test_valarray
	m.def("cast_valarray", []() { return std::valarray<int>{1, 4, 9}; });
	m.def("load_valarray", [](const std::valarray<int>& v) {
	return v.size() == 3 && v[0] == 1 && v[1] == 4 && v[2] == 9;
	});

	// test_map
	m.def("cast_map", []() { return std::map<std::string, std::string>{{"key", "value"}}; });
	m.def("load_map", [](const std::map<std::string, std::string> &map) {
	return map.at("key") == "value" && map.at("key2") == "value2";
	});

	// test_set
	m.def("cast_set", []() { return std::set<std::string>{"key1", "key2"}; });
	m.def("load_set", [](const std::set<std::string> &set) {
	return (set.count("key1") != 0u) && (set.count("key2") != 0u) && (set.count("key3") != 0u);
	});

	// test_recursive_casting
	m.def("cast_rv_vector", []() { return std::vector<RValueCaster>{2}; });
	m.def("cast_rv_array", []() { return std::array<RValueCaster, 3>(); });
	// NB: map and set keys are `const`, so while we technically do move them (as `const Type &&`),
	// casters don't typically do anything with that, which means they fall to the `const Type &`
	// caster.
	m.def("cast_rv_map", []() { return std::unordered_map<std::string, RValueCaster>{{"a", RValueCaster{}}}; });
	m.def("cast_rv_nested", []() {
	std::vector<std::array<std::list<std::unordered_map<std::string, RValueCaster>>, 2>> v;
	v.emplace_back(); // add an array
	v.back()[0].emplace_back(); // add a map to the array
	v.back()[0].back().emplace("b", RValueCaster{});
	v.back()[0].back().emplace("c", RValueCaster{});
	v.back()[1].emplace_back(); // add a map to the array
	v.back()[1].back().emplace("a", RValueCaster{});
	return v;
	});
	static std::array<RValueCaster, 2> lva;
	static std::unordered_map<std::string, RValueCaster> lvm{{"a", RValueCaster{}}, {"b", RValueCaster{}}};
	static std::unordered_map<std::string, std::vector<std::list<std::array<RValueCaster, 2>>>> lvn;
	lvn["a"].emplace_back(); // add a list
	lvn["a"].back().emplace_back(); // add an array
	lvn["a"].emplace_back(); // another list
	lvn["a"].back().emplace_back(); // add an array
	lvn["b"].emplace_back(); // add a list
	lvn["b"].back().emplace_back(); // add an array
	lvn["b"].back().emplace_back(); // add another array
	m.def("cast_lv_vector", []() -> const decltype(lvv) & { return lvv; });
	m.def("cast_lv_array", []() -> const decltype(lva) & { return lva; });
	m.def("cast_lv_map", []() -> const decltype(lvm) & { return lvm; });
	m.def("cast_lv_nested", []() -> const decltype(lvn) & { return lvn; });
	// #853:
	m.def("cast_unique_ptr_vector", []() {
	std::vector<std::unique_ptr<UserType>> v;
	v.emplace_back(new UserType{7});
	v.emplace_back(new UserType{42});
	return v;
	});

	pybind11::enum_<EnumType>(m, "EnumType")
	.value("kSet", EnumType::kSet)
	.value("kUnset", EnumType::kUnset);

	// test_move_out_container
	struct MoveOutContainer {
	struct Value { int value; };
	std::list<Value> move_list() const { return {{0}, {1}, {2}}; }
	};
	py::class_<MoveOutContainer::Value>(m, "MoveOutContainerValue")
	.def_readonly("value", &MoveOutContainer::Value::value);
	py::class_<MoveOutContainer>(m, "MoveOutContainer")
	.def(py::init<>())
	.def_property_readonly("move_list", &MoveOutContainer::move_list);

	// Class that can be move- and copy-constructed, but not assigned
	struct NoAssign {
	int value;

	explicit NoAssign(int value = 0) : value(value) { }
	NoAssign(const NoAssign &) = default;
	NoAssign(NoAssign &&) = default;

	NoAssign &operator=(const NoAssign &) = delete;
	NoAssign &operator=(NoAssign &&) = delete;
	};
	py::class_<NoAssign>(m, "NoAssign", "Class with no C++ assignment operators")
	.def(py::init<>())
	.def(py::init<int>());


	struct MoveOutDetector
	{
	MoveOutDetector() = default;
	MoveOutDetector(const MoveOutDetector&) = default;
	MoveOutDetector(MoveOutDetector&& other) noexcept
	: initialized(other.initialized) {
	// steal underlying resource
	other.initialized = false;
	}
	bool initialized = true;
	};
	py::class_<MoveOutDetector>(m, "MoveOutDetector", "Class with move tracking")
	.def(py::init<>())
	.def_readonly("initialized", &MoveOutDetector::initialized);


	#ifdef PYBIND11_HAS_OPTIONAL
	// test_optional
	m.attr("has_optional") = true;

	using opt_int = std::optional<int>;
	using opt_no_assign = std::optional<NoAssign>;
	m.def("double_or_zero", [](const opt_int& x) -> int {
	return x.value_or(0) * 2;
	});
	m.def("half_or_none", [](int x) -> opt_int { return x != 0 ? opt_int(x / 2) : opt_int(); });
	m.def("test_nullopt", [](opt_int x) {
	return x.value_or(42);
	}, py::arg_v("x", std::nullopt, "None"));
	m.def("test_no_assign", [](const opt_no_assign &x) {
	return x ? x->value : 42;
	}, py::arg_v("x", std::nullopt, "None"));

	m.def("nodefer_none_optional", [](std::optional<int>) { return true; });
	m.def("nodefer_none_optional", [](const py::none &) { return false; });

	using opt_holder = OptionalHolder<std::optional, MoveOutDetector>;
	py::class_<opt_holder>(m, "OptionalHolder", "Class with optional member")
	.def(py::init<>())
	.def_readonly("member", &opt_holder::member)
	.def("member_initialized", &opt_holder::member_initialized);

	using opt_props = OptionalProperties<std::optional>;
	pybind11::class_<opt_props>(m, "OptionalProperties")
	.def(pybind11::init<>())
	.def_property_readonly("access_by_ref", &opt_props::access_by_ref)
	.def_property_readonly("access_by_copy", &opt_props::access_by_copy);
	#endif

	#ifdef PYBIND11_HAS_EXP_OPTIONAL
	// test_exp_optional
	m.attr("has_exp_optional") = true;

	using exp_opt_int = std::experimental::optional<int>;
	using exp_opt_no_assign = std::experimental::optional<NoAssign>;
	m.def("double_or_zero_exp", [](const exp_opt_int& x) -> int {
	return x.value_or(0) * 2;
	});
	m.def("half_or_none_exp", [](int x) -> exp_opt_int {
	return x ? exp_opt_int(x / 2) : exp_opt_int();
	});
	m.def("test_nullopt_exp", [](exp_opt_int x) {
	return x.value_or(42);
	}, py::arg_v("x", std::experimental::nullopt, "None"));
	m.def("test_no_assign_exp", [](const exp_opt_no_assign &x) {
	return x ? x->value : 42;
	}, py::arg_v("x", std::experimental::nullopt, "None"));

	using opt_exp_holder = OptionalHolder<std::experimental::optional, MoveOutDetector>;
	py::class_<opt_exp_holder>(m, "OptionalExpHolder", "Class with optional member")
	.def(py::init<>())
	.def_readonly("member", &opt_exp_holder::member)
	.def("member_initialized", &opt_exp_holder::member_initialized);

	using opt_exp_props = OptionalProperties<std::experimental::optional>;
	pybind11::class_<opt_exp_props>(m, "OptionalExpProperties")
	.def(pybind11::init<>())
	.def_property_readonly("access_by_ref", &opt_exp_props::access_by_ref)
	.def_property_readonly("access_by_copy", &opt_exp_props::access_by_copy);
	#endif

	#if defined(PYBIND11_TEST_BOOST)
	// test_boost_optional
	m.attr("has_boost_optional") = true;

	using boost_opt_int = boost::optional<int>;
	using boost_opt_no_assign = boost::optional<NoAssign>;
	m.def("double_or_zero_boost", [](const boost_opt_int& x) -> int {
	return x.value_or(0) * 2;
	});
	m.def("half_or_none_boost", [](int x) -> boost_opt_int {
	return x != 0 ? boost_opt_int(x / 2) : boost_opt_int();
	});
	m.def("test_nullopt_boost", [](boost_opt_int x) {
	return x.value_or(42);
	}, py::arg_v("x", boost::none, "None"));
	m.def("test_no_assign_boost", [](const boost_opt_no_assign &x) {
	return x ? x->value : 42;
	}, py::arg_v("x", boost::none, "None"));

	using opt_boost_holder = OptionalHolder<boost::optional, MoveOutDetector>;
	py::class_<opt_boost_holder>(m, "OptionalBoostHolder", "Class with optional member")
	.def(py::init<>())
	.def_readonly("member", &opt_boost_holder::member)
	.def("member_initialized", &opt_boost_holder::member_initialized);

	using opt_boost_props = OptionalProperties<boost::optional>;
	pybind11::class_<opt_boost_props>(m, "OptionalBoostProperties")
	.def(pybind11::init<>())
	.def_property_readonly("access_by_ref", &opt_boost_props::access_by_ref)
	.def_property_readonly("access_by_copy", &opt_boost_props::access_by_copy);
	#endif

	// test_refsensitive_optional
	using refsensitive_opt_int = ReferenceSensitiveOptional<int>;
	using refsensitive_opt_no_assign = ReferenceSensitiveOptional<NoAssign>;
	m.def("double_or_zero_refsensitive", [](const refsensitive_opt_int& x) -> int {
	return (x ? x.value() : 0) * 2;
	});
	m.def("half_or_none_refsensitive", [](int x) -> refsensitive_opt_int {
	return x != 0 ? refsensitive_opt_int(x / 2) : refsensitive_opt_int();
	});
	// NOLINTNEXTLINE(performance-unnecessary-value-param)
	m.def("test_nullopt_refsensitive", [](refsensitive_opt_int x) {
	return x ? x.value() : 42;
	}, py::arg_v("x", refsensitive_opt_int(), "None"));
	m.def("test_no_assign_refsensitive", [](const refsensitive_opt_no_assign &x) {
	return x ? x->value : 42;
	}, py::arg_v("x", refsensitive_opt_no_assign(), "None"));

	using opt_refsensitive_holder = OptionalHolder<ReferenceSensitiveOptional, MoveOutDetector>;
	py::class_<opt_refsensitive_holder>(m, "OptionalRefSensitiveHolder", "Class with optional member")
	.def(py::init<>())
	.def_readonly("member", &opt_refsensitive_holder::member)
	.def("member_initialized", &opt_refsensitive_holder::member_initialized);

	using opt_refsensitive_props = OptionalProperties<ReferenceSensitiveOptional>;
	pybind11::class_<opt_refsensitive_props>(m, "OptionalRefSensitiveProperties")
	.def(pybind11::init<>())
	.def_property_readonly("access_by_ref", &opt_refsensitive_props::access_by_ref)
	.def_property_readonly("access_by_copy", &opt_refsensitive_props::access_by_copy);

	#ifdef PYBIND11_HAS_FILESYSTEM
	// test_fs_path
	m.attr("has_filesystem") = true;
	m.def("parent_path", [](const std::filesystem::path& p) { return p.parent_path(); });
	#endif

	#ifdef PYBIND11_HAS_VARIANT
	static_assert(std::is_same<py::detail::variant_caster_visitor::result_type, py::handle>::value,
	"visitor::result_type is required by boost::variant in C++11 mode");

	struct visitor {
	using result_type = const char *;

	result_type operator()(int) { return "int"; }
	result_type operator()(const std::string &) { return "std::string"; }
	result_type operator()(double) { return "double"; }
	result_type operator()(std::nullptr_t) { return "std::nullptr_t"; }
	};

	// test_variant
	m.def("load_variant", [](const variant<int, std::string, double, std::nullptr_t> &v) {
	return py::detail::visit_helper<variant>::call(visitor(), v);
	});
	m.def("load_variant_2pass", [](variant<double, int> v) {
	return py::detail::visit_helper<variant>::call(visitor(), v);
	});
	m.def("cast_variant", []() {
	using V = variant<int, std::string>;
	return py::make_tuple(V(5), V("Hello"));
	});
	#endif

	// #528: templated constructor
	// (no python tests: the test here is that this compiles)
	m.def("tpl_ctor_vector", [](std::vector<TplCtorClass> &) {});
	m.def("tpl_ctor_map", [](std::unordered_map<TplCtorClass, TplCtorClass> &) {});
	m.def("tpl_ctor_set", [](std::unordered_set<TplCtorClass> &) {});
	#if defined(PYBIND11_HAS_OPTIONAL)
	m.def("tpl_constr_optional", [](std::optional<TplCtorClass> &) {});
	#endif
	#if defined(PYBIND11_HAS_EXP_OPTIONAL)
	m.def("tpl_constr_optional_exp", [](std::experimental::optional<TplCtorClass> &) {});
	#endif
	#if defined(PYBIND11_TEST_BOOST)
	m.def("tpl_constr_optional_boost", [](boost::optional<TplCtorClass> &) {});
	#endif

	// test_vec_of_reference_wrapper
	// #171: Can't return STL structures containing reference wrapper
	m.def("return_vec_of_reference_wrapper", [](std::reference_wrapper<UserType> p4) {
	static UserType p1{1}, p2{2}, p3{3};
	return std::vector<std::reference_wrapper<UserType>> {
	std::ref(p1), std::ref(p2), std::ref(p3), p4
	};
	});

	// test_stl_pass_by_pointer
	m.def("stl_pass_by_pointer", [](std::vector<int>* v) { return *v; }, "v"_a=nullptr);

	// #1258: pybind11/stl.h converts string to vector<string>
	m.def("func_with_string_or_vector_string_arg_overload",
	[](const std::vector<std::string> &) { return 1; });
	m.def("func_with_string_or_vector_string_arg_overload",
	[](const std::list<std::string> &) { return 2; });
	m.def("func_with_string_or_vector_string_arg_overload", [](const std::string &) { return 3; });

	class Placeholder {
	public:
	Placeholder() { print_created(this); }
	Placeholder(const Placeholder &) = delete;
	~Placeholder() { print_destroyed(this); }
	};
	py::class_<Placeholder>(m, "Placeholder");

	/// test_stl_vector_ownership
	m.def("test_stl_ownership",
	[]() {
	std::vector<Placeholder *> result;
	result.push_back(new Placeholder());
	return result;
	},
	py::return_value_policy::take_ownership);

	m.def("array_cast_sequence", [](std::array<int, 3> x) { return x; });

	/// test_issue_1561
	struct Issue1561Inner { std::string data; };
	struct Issue1561Outer { std::vector<Issue1561Inner> list; };

	py::class_<Issue1561Inner>(m, "Issue1561Inner")
	.def(py::init<std::string>())
	.def_readwrite("data", &Issue1561Inner::data);

	py::class_<Issue1561Outer>(m, "Issue1561Outer")
	.def(py::init<>())
	.def_readwrite("list", &Issue1561Outer::list);

	m.def(
	"return_vector_bool_raw_ptr",
	[]() { return new std::vector<bool>(4513); },
	// Without explicitly specifying `take_ownership`, this function leaks.
	py::return_value_policy::take_ownership);
	}