tests/test_with_catch/test_interpreter.cpp

#include <pybind11/critical_section.h>
#include <pybind11/embed.h>
#include <pybind11/pybind11.h>
#include <pybind11/stl_bind.h>

// Silence MSVC C++17 deprecation warning from Catch regarding std::uncaught_exceptions (up to
// catch 2.0.1; this should be fixed in the next catch release after 2.0.1).
PYBIND11_WARNING_DISABLE_MSVC(4996)

#include "catch_skip.h"

#include <catch.hpp>
#include <cstdlib>
#include <fstream>
#include <functional>
#include <thread>
#include <utility>

namespace py = pybind11;
using namespace py::literals;

struct ImplicitReturnItem {
    explicit ImplicitReturnItem(int value) : value(value) {}
    int value;
};
struct ImplicitReturnValues : std::vector<std::shared_ptr<ImplicitReturnItem>> {
    using std::vector<std::shared_ptr<ImplicitReturnItem>>::vector;
    static int instances;
    struct Counter {
        Counter() { ++instances; }
        Counter(const Counter &) { ++instances; }
        ~Counter() { --instances; }
    } counter;
};
int ImplicitReturnValues::instances = 0;
PYBIND11_MAKE_OPAQUE(ImplicitReturnValues)

struct ImplicitReturnProvider {
    virtual ~ImplicitReturnProvider() = default;
    virtual ImplicitReturnValues values() = 0;
    virtual const ImplicitReturnValues &reference() = 0;
    virtual ImplicitReturnValues *pointer() = 0;
#ifdef PYBIND11_HAS_STRING_VIEW
    virtual std::u16string_view view() = 0;
#endif
};

struct PyImplicitReturnProvider : ImplicitReturnProvider {
    ImplicitReturnValues values() override {
        PYBIND11_OVERRIDE_PURE(ImplicitReturnValues, ImplicitReturnProvider, values, );
    }
    const ImplicitReturnValues &reference() override {
        PYBIND11_OVERRIDE_PURE(const ImplicitReturnValues &, ImplicitReturnProvider, reference, );
    }
    ImplicitReturnValues *pointer() override {
        PYBIND11_OVERRIDE_PURE(ImplicitReturnValues *, ImplicitReturnProvider, pointer, );
    }
#ifdef PYBIND11_HAS_STRING_VIEW
    std::u16string_view view() override {
        PYBIND11_OVERRIDE_PURE(std::u16string_view, ImplicitReturnProvider, view, );
    }
#endif
};

PYBIND11_EMBEDDED_MODULE(implicit_return_module, m, py::multiple_interpreters::not_supported()) {
    py::class_<ImplicitReturnItem, std::shared_ptr<ImplicitReturnItem>>(m, "Item").def(
        py::init<int>());
    py::bind_vector<ImplicitReturnValues>(m, "Values");
    py::implicitly_convertible<py::list, ImplicitReturnValues>();
    py::class_<ImplicitReturnProvider, PyImplicitReturnProvider>(m, "Provider").def(py::init<>());
}

TEST_CASE("Implicit conversions in native trampoline returns") {
    py::dict locals;
    py::exec(R"(
        from implicit_return_module import Item, Provider
        class PythonProvider(Provider):
            def __init__(self):
                super().__init__()
                self.result = [Item(17), Item(-4), Item(99)]
                self.fresh = False
            def values(self):
                return list(self.result) if self.fresh else self.result
            def reference(self):
                return self.result
            def pointer(self):
                return self.result
            def view(self):
                return "hello"
        provider = PythonProvider()
    )",
             locals);
    py::object provider = locals["provider"];
    auto *cpp_provider = provider.cast<ImplicitReturnProvider *>();

    SECTION("Copy from a retained Python return value") { provider.attr("fresh") = false; }
    SECTION("Move from a temporary Python return value") { provider.attr("fresh") = true; }

    REQUIRE(ImplicitReturnValues::instances == 0);
    // An enclosing bound call already owns its conversion temporaries. They must
    // not be destroyed earlier by a nested return-conversion frame.
    auto bound_call = py::cpp_function([&]() {
        auto result = cpp_provider->values();
        return ImplicitReturnValues::instances;
    });
    REQUIRE(bound_call().cast<int>() == 2);
    REQUIRE(ImplicitReturnValues::instances == 0);

    // A short-lived return-conversion frame cannot support a borrowed result.
    REQUIRE_THROWS_AS(cpp_provider->reference(), py::cast_error);
    REQUIRE_THROWS_AS(cpp_provider->pointer(), py::cast_error);
#ifdef PYBIND11_HAS_STRING_VIEW
    REQUIRE_THROWS_AS(cpp_provider->view(), py::cast_error);
#endif

    // Calling from native C++ is essential: a bound function would already provide
    // a loader frame and hide the missing life support during return conversion.
    for (int i = 0; i < 3; ++i) {
        auto result = cpp_provider->values();
        REQUIRE(ImplicitReturnValues::instances == 1);
        REQUIRE(result.size() == 3);
        REQUIRE(result[0]->value == 17);
        REQUIRE(result[1]->value == -4);
        REQUIRE(result[2]->value == 99);
    }
    REQUIRE_THROWS_AS(cpp_provider->reference(), py::cast_error);

    auto retained = cpp_provider->values();
    provider.attr("result").attr("clear")();
    REQUIRE(retained[0]->value == 17);
    REQUIRE(retained[1]->value == -4);
    REQUIRE(retained[2]->value == 99);

    provider.attr("result") = py::make_tuple("invalid");
    REQUIRE_THROWS_AS(cpp_provider->values(), py::cast_error);
}

size_t get_sys_path_size() {
    auto sys_path = py::module::import("sys").attr("path");
    return py::len(sys_path);
}

bool has_state_dict_internals_obj() {
    py::dict state = py::detail::get_python_state_dict();
    return state.contains(PYBIND11_INTERNALS_ID);
}

uintptr_t get_details_as_uintptr() {
    return reinterpret_cast<uintptr_t>(py::detail::get_internals_pp_manager().get_pp()->get());
}

class Widget {
public:
    explicit Widget(std::string message) : message(std::move(message)) {}
    virtual ~Widget() = default;

    std::string the_message() const { return message; }
    virtual int the_answer() const = 0;
    virtual std::string argv0() const = 0;

private:
    std::string message;
};

class PyWidget final : public Widget {
    using Widget::Widget;

    int the_answer() const override { PYBIND11_OVERRIDE_PURE(int, Widget, the_answer, ); }
    std::string argv0() const override { PYBIND11_OVERRIDE_PURE(std::string, Widget, argv0, ); }
};

class test_override_cache_helper {

public:
    virtual int func() { return 0; }

    test_override_cache_helper() = default;
    virtual ~test_override_cache_helper() = default;
    // Non-copyable
    test_override_cache_helper &operator=(test_override_cache_helper const &Right) = delete;
    test_override_cache_helper(test_override_cache_helper const &Copy) = delete;
};

class test_override_cache_helper_trampoline : public test_override_cache_helper {
    int func() override { PYBIND11_OVERRIDE(int, test_override_cache_helper, func, ); }
};

PYBIND11_EMBEDDED_MODULE(widget_module, m, py::multiple_interpreters::per_interpreter_gil()) {
    py::class_<Widget, PyWidget>(m, "Widget")
        .def(py::init<std::string>())
        .def_property_readonly("the_message", &Widget::the_message);

    m.def("add", [](int i, int j) { return i + j; });

    auto sub = m.def_submodule("sub");
    sub.def("add", [](int i, int j) { return i + j; });
}

PYBIND11_EMBEDDED_MODULE(trampoline_module, m, py::multiple_interpreters::not_supported()) {
    py::class_<test_override_cache_helper,
               test_override_cache_helper_trampoline,
               std::shared_ptr<test_override_cache_helper>>(m, "test_override_cache_helper")
        .def(py::init_alias<>())
        .def("func", &test_override_cache_helper::func);
}

enum class SomeEnum { value1, value2 }; // Added in PR #6015

PYBIND11_EMBEDDED_MODULE(enum_module, m, py::multiple_interpreters::per_interpreter_gil()) {
    py::enum_<SomeEnum>(m, "SomeEnum")
        .value("value1", SomeEnum::value1)
        .value("value2", SomeEnum::value2);
}

PYBIND11_EMBEDDED_MODULE(throw_exception, , py::multiple_interpreters::not_supported()) {
    throw std::runtime_error("C++ Error");
}

PYBIND11_EMBEDDED_MODULE(throw_error_already_set, , py::multiple_interpreters::not_supported()) {
    auto d = py::dict();
    d["missing"].cast<py::object>();
}

static int internals_init_module_executions = 0;

PYBIND11_EMBEDDED_MODULE(internals_init_module,
                         m,
                         py::mod_gil_not_used(),
                         py::multiple_interpreters::per_interpreter_gil()) {
    ++internals_init_module_executions;
    m.def("answer", []() { return 42; });
}

TEST_CASE("PYTHONPATH is used to update sys.path") {
    // The setup for this TEST_CASE is in catch.cpp!
    auto sys_path = py::str(py::module_::import("sys").attr("path")).cast<std::string>();
    REQUIRE_THAT(
        sys_path,
        Catch::Matchers::Contains("pybind11_test_with_catch_PYTHONPATH_2099743835476552"));
}

TEST_CASE("Pass classes and data between modules defined in C++ and Python") {
    auto module_ = py::module_::import("test_interpreter");
    REQUIRE(py::hasattr(module_, "DerivedWidget"));

    auto locals = py::dict("hello"_a = "Hello, World!", "x"_a = 5, **module_.attr("__dict__"));
    py::exec(R"(
        widget = DerivedWidget("{} - {}".format(hello, x))
        message = widget.the_message
    )",
             py::globals(),
             locals);
    REQUIRE(locals["message"].cast<std::string>() == "Hello, World! - 5");

    auto py_widget = module_.attr("DerivedWidget")("The question");
    auto message = py_widget.attr("the_message");
    REQUIRE(message.cast<std::string>() == "The question");

    const auto &cpp_widget = py_widget.cast<const Widget &>();
    REQUIRE(cpp_widget.the_answer() == 42);
}

TEST_CASE("Override cache") {
    auto module_ = py::module_::import("test_trampoline");
    REQUIRE(py::hasattr(module_, "func"));
    REQUIRE(py::hasattr(module_, "func2"));

    auto locals = py::dict(**module_.attr("__dict__"));

    int i = 0;
    for (; i < 1500; ++i) {
        std::shared_ptr<test_override_cache_helper> p_obj;
        std::shared_ptr<test_override_cache_helper> p_obj2;

        py::object loc_inst = locals["func"]();
        p_obj = py::cast<std::shared_ptr<test_override_cache_helper>>(loc_inst);

        int ret = p_obj->func();

        REQUIRE(ret == 42);

        loc_inst = locals["func2"]();

        p_obj2 = py::cast<std::shared_ptr<test_override_cache_helper>>(loc_inst);

        p_obj2->func();
    }
}

TEST_CASE("Import error handling") {
    REQUIRE_NOTHROW(py::module_::import("widget_module"));
    REQUIRE_THROWS_WITH(py::module_::import("throw_exception"), "ImportError: C++ Error");
    REQUIRE_THROWS_WITH(py::module_::import("throw_error_already_set"),
                        Catch::Contains("ImportError: initialization failed"));

    auto locals = py::dict("is_keyerror"_a = false, "message"_a = "not set");
    py::exec(R"(
        try:
            import throw_error_already_set
        except ImportError as e:
            is_keyerror = type(e.__cause__) == KeyError
            message = str(e.__cause__)
    )",
             py::globals(),
             locals);
    REQUIRE(locals["is_keyerror"].cast<bool>() == true);
    REQUIRE(locals["message"].cast<std::string>() == "'missing'");
}

TEST_CASE("There can be only one interpreter") {
    static_assert(std::is_move_constructible<py::scoped_interpreter>::value, "");
    static_assert(!std::is_move_assignable<py::scoped_interpreter>::value, "");
    static_assert(!std::is_copy_constructible<py::scoped_interpreter>::value, "");
    static_assert(!std::is_copy_assignable<py::scoped_interpreter>::value, "");

    REQUIRE_THROWS_WITH(py::initialize_interpreter(), "The interpreter is already running");
    REQUIRE_THROWS_WITH(py::scoped_interpreter(), "The interpreter is already running");

    py::finalize_interpreter();
    REQUIRE_NOTHROW(py::scoped_interpreter());
    {
        auto pyi1 = py::scoped_interpreter();
        auto pyi2 = std::move(pyi1);
    }
    py::initialize_interpreter();
}

TEST_CASE("Custom PyConfig") {
    py::finalize_interpreter();
    PyConfig config;
    PyConfig_InitPythonConfig(&config);
    REQUIRE_NOTHROW(py::scoped_interpreter{&config});
    {
        py::scoped_interpreter p{&config};
        REQUIRE(py::module_::import("widget_module").attr("add")(1, 41).cast<int>() == 42);
    }
    py::initialize_interpreter();
}

TEST_CASE("scoped_interpreter with PyConfig_InitIsolatedConfig and argv") {
    std::vector<std::string> path;
    for (auto p : py::module::import("sys").attr("path")) {
        path.emplace_back(py::str(p));
    }

    py::finalize_interpreter();
    {
        PyConfig config;
        PyConfig_InitIsolatedConfig(&config);
        char *argv[] = {strdup("a.out")};
        py::scoped_interpreter argv_scope{&config, 1, argv, true};
        std::free(argv[0]);
        // Because this config is isolated, setting the path during init will not work, we have to
        // set it manually.  If we don't set it, then we can't import "test_interpreter"
        for (auto &&p : path) {
            py::list(py::module::import("sys").attr("path")).append(p);
        }
        try {
            auto module = py::module::import("test_interpreter");
            auto py_widget = module.attr("DerivedWidget")("The question");
            const auto &cpp_widget = py_widget.cast<const Widget &>();
            REQUIRE(cpp_widget.argv0() == "a.out");
        } catch (py::error_already_set &e) {
            // catch here so that the exception doesn't escape the interpreter that owns it
            FAIL(e.what());
        }
    }
    py::initialize_interpreter();
}

TEST_CASE("scoped_interpreter with PyConfig_InitPythonConfig and argv") {
    py::finalize_interpreter();
    {
        PyConfig config;
        PyConfig_InitPythonConfig(&config);

        // `initialize_interpreter() overrides the default value for config.parse_argv (`1`) by
        // changing it to `0`. This test exercises `scoped_interpreter` with the default config.
        char *argv[] = {strdup("a.out"), strdup("arg1")};
        py::scoped_interpreter argv_scope(&config, 2, argv);
        std::free(argv[0]);
        std::free(argv[1]);
        auto module = py::module::import("test_interpreter");
        auto py_widget = module.attr("DerivedWidget")("The question");
        const auto &cpp_widget = py_widget.cast<const Widget &>();
        REQUIRE(cpp_widget.argv0() == "arg1");
    }
    py::initialize_interpreter();
}

TEST_CASE("Add program dir to path without PyConfig") {
    py::finalize_interpreter();
    size_t path_size_add_program_dir_to_path_false = 0;
    {
        py::scoped_interpreter scoped_interp{true, 0, nullptr, false};
        path_size_add_program_dir_to_path_false = get_sys_path_size();
    }
    {
        py::scoped_interpreter scoped_interp{};
        REQUIRE(get_sys_path_size() == path_size_add_program_dir_to_path_false + 1);
    }
    py::initialize_interpreter();
}

TEST_CASE("Add program dir to path using PyConfig") {
    py::finalize_interpreter();
    size_t path_size_add_program_dir_to_path_false = 0;
    {
        PyConfig config;
        PyConfig_InitPythonConfig(&config);
        py::scoped_interpreter scoped_interp{&config, 0, nullptr, false};
        path_size_add_program_dir_to_path_false = get_sys_path_size();
    }
    {
        PyConfig config;
        PyConfig_InitPythonConfig(&config);
        py::scoped_interpreter scoped_interp{&config};
        REQUIRE(get_sys_path_size() == path_size_add_program_dir_to_path_false + 1);
    }
    py::initialize_interpreter();
}

TEST_CASE("Internals are initialized when a module executes", "[internals_init]") {
    // Use a fresh interpreter so that another module cannot have populated its internals.
    py::finalize_interpreter();
    py::initialize_interpreter();
    internals_init_module_executions = 0;
    REQUIRE_FALSE(has_state_dict_internals_obj());
    REQUIRE(py::detail::get_local_internals_capsule() == nullptr);

    auto *definition = PyInit_internals_init_module();
    REQUIRE(definition != nullptr);
    REQUIRE_FALSE(has_state_dict_internals_obj());
    REQUIRE(py::detail::get_local_internals_capsule() == nullptr);

    auto spec = py::module_::import("importlib.util")
                    .attr("spec_from_loader")("internals_init_module", py::none());
    auto *module_def = reinterpret_cast<PyModuleDef *>(definition);
    auto module
        = py::reinterpret_steal<py::module_>(PyModule_FromDefAndSpec(module_def, spec.ptr()));
    REQUIRE(module);
    module.attr("__spec__") = spec;
    REQUIRE_FALSE(has_state_dict_internals_obj());
    REQUIRE(py::detail::get_local_internals_capsule() == nullptr);
    REQUIRE(internals_init_module_executions == 0);

    REQUIRE(PyModule_ExecDef(module.ptr(), module_def) == 0);
    REQUIRE(has_state_dict_internals_obj());
    REQUIRE(py::detail::get_local_internals_capsule() != nullptr);
    REQUIRE(internals_init_module_executions == 1);
    REQUIRE(module.attr("answer")().cast<int>() == 42);
}

TEST_CASE("Restart the interpreter", "[internals_init]") {
    // Verify pre-restart state.
    REQUIRE(py::module_::import("widget_module").attr("add")(1, 2).cast<int>() == 3);
    REQUIRE(has_state_dict_internals_obj());
    REQUIRE(py::module_::import("external_module").attr("A")(123).attr("value").cast<int>()
            == 123);

    // local and foreign module internals should point to the same internals:
    REQUIRE(get_details_as_uintptr()
            == py::module_::import("external_module").attr("internals_at")().cast<uintptr_t>());

    // Restart the interpreter.
    py::finalize_interpreter();
    REQUIRE(Py_IsInitialized() == 0);

    py::initialize_interpreter();
    REQUIRE(Py_IsInitialized() == 1);

    // Internals are deleted after a restart.
    REQUIRE_FALSE(has_state_dict_internals_obj());
    REQUIRE(get_details_as_uintptr() == 0);
    pybind11::detail::get_internals();
    REQUIRE(has_state_dict_internals_obj());
    REQUIRE(get_details_as_uintptr() != 0);
    REQUIRE(get_details_as_uintptr()
            == py::module_::import("external_module").attr("internals_at")().cast<uintptr_t>());
    REQUIRE(py::module_::import("external_module").attr("A")(321).attr("value").cast<int>()
            == 321);

    // Make sure that an interpreter with no get_internals() created until finalize still gets the
    // internals destroyed
    py::finalize_interpreter();
    py::initialize_interpreter();
    bool ran = false;
    py::module_::import("__main__").attr("internals_destroy_test")
        = py::capsule(&ran, [](void *ran) {
              py::detail::get_internals();
              REQUIRE(has_state_dict_internals_obj());
              *static_cast<bool *>(ran) = true;
          });
    REQUIRE_FALSE(has_state_dict_internals_obj());
    REQUIRE_FALSE(ran);
    py::finalize_interpreter();
    REQUIRE(ran);
    py::initialize_interpreter();
    REQUIRE_FALSE(has_state_dict_internals_obj());
    REQUIRE(get_details_as_uintptr() == 0);

    // C++ modules can be reloaded.
    auto cpp_module = py::module_::import("widget_module");
    REQUIRE(cpp_module.attr("add")(1, 2).cast<int>() == 3);

    // Also verify submodules work
    REQUIRE(cpp_module.attr("sub").attr("add")(1, 41).cast<int>() == 42);

    // C++ type information is reloaded and can be used in python modules.
    auto py_module = py::module_::import("test_interpreter");
    auto py_widget = py_module.attr("DerivedWidget")("Hello after restart");
    REQUIRE(py_widget.attr("the_message").cast<std::string>() == "Hello after restart");
}

TEST_CASE("Enum module survives restart") { // Added in PR #6015
    // Regression test for gh-5976: py::enum_ uses def_property_static, which
    // calls process_attributes::init after initialize_generic's strdup loop,
    // leaving arg names as string literals. Without the fix, destruct() would
    // call free() on those literals during interpreter finalization.
    PYBIND11_CATCH2_SKIP_IF(PY_MAJOR_VERSION == 3 && PY_MINOR_VERSION == 12,
                            "Pre-existing crash in enum cleanup during finalize on Python 3.12");

    auto enum_mod = py::module_::import("enum_module");
    REQUIRE(enum_mod.attr("SomeEnum").attr("value1").attr("name").cast<std::string>() == "value1");

    py::finalize_interpreter();
    py::initialize_interpreter();

    enum_mod = py::module_::import("enum_module");
    REQUIRE(enum_mod.attr("SomeEnum").attr("value2").attr("name").cast<std::string>() == "value2");
}

TEST_CASE("Execution frame") {
    // When the interpreter is embedded, there is no execution frame, but `py::exec`
    // should still function by using reasonable globals: `__main__.__dict__`.
    py::exec("var = dict(number=42)");
    REQUIRE(py::globals()["var"]["number"].cast<int>() == 42);
}

TEST_CASE("Threads") {
    // Restart interpreter to ensure threads are not initialized
    py::finalize_interpreter();
    py::initialize_interpreter();

    constexpr auto num_threads = 10;
    auto locals = py::dict("count"_a = 0);

    {
        py::gil_scoped_release gil_release{};
#if defined(Py_GIL_DISABLED) && PY_VERSION_HEX < 0x030E0000
        std::mutex mutex;
#endif

        auto threads = std::vector<std::thread>();
        for (auto i = 0; i < num_threads; ++i) {
            threads.emplace_back([&]() {
                py::gil_scoped_acquire gil{};
#ifdef Py_GIL_DISABLED
#    if PY_VERSION_HEX < 0x030E0000
                // This will not run with the GIL, so it won't deadlock. That's
                // because of how we run our tests. Be more careful of
                // deadlocks if the "free-threaded" GIL could be enabled (at
                // runtime).
                std::lock_guard<std::mutex> lock(mutex);
#    else
                // CPython's thread-safe API in no-GIL mode.
                py::scoped_critical_section lock(locals);
#    endif
#endif
                locals["count"] = locals["count"].cast<int>() + 1;
            });
        }

        for (auto &thread : threads) {
            thread.join();
        }
    }

    REQUIRE(locals["count"].cast<int>() == num_threads);
}

// Scope exit utility https://stackoverflow.com/a/36644501/7255855
struct scope_exit {
    std::function<void()> f_;
    explicit scope_exit(std::function<void()> f) noexcept : f_(std::move(f)) {}
    ~scope_exit() {
        if (f_) {
            f_();
        }
    }
};

TEST_CASE("Reload module from file") {
    // Disable generation of cached bytecode (.pyc files) for this test, otherwise
    // Python might pick up an old version from the cache instead of the new versions
    // of the .py files generated below
    auto sys = py::module_::import("sys");
    bool dont_write_bytecode = sys.attr("dont_write_bytecode").cast<bool>();
    sys.attr("dont_write_bytecode") = true;
    // Reset the value at scope exit
    scope_exit reset_dont_write_bytecode(
        [&]() { sys.attr("dont_write_bytecode") = dont_write_bytecode; });

    std::string module_name = "test_module_reload";
    std::string module_file = module_name + ".py";

    // Create the module .py file
    std::ofstream test_module(module_file);
    test_module << "def test():\n";
    test_module << "    return 1\n";
    test_module.close();
    // Delete the file at scope exit
    scope_exit delete_module_file([&]() { std::remove(module_file.c_str()); });

    // Import the module from file
    auto module_ = py::module_::import(module_name.c_str());
    int result = module_.attr("test")().cast<int>();
    REQUIRE(result == 1);

    // Update the module .py file with a small change
    test_module.open(module_file);
    test_module << "def test():\n";
    test_module << "    return 2\n";
    test_module.close();

    // Reload the module
    module_.reload();
    result = module_.attr("test")().cast<int>();
    REQUIRE(result == 2);
}

TEST_CASE("sys.argv gets initialized properly") {
    py::finalize_interpreter();
    {
        py::scoped_interpreter default_scope;
        auto module = py::module::import("test_interpreter");
        auto py_widget = module.attr("DerivedWidget")("The question");
        const auto &cpp_widget = py_widget.cast<const Widget &>();
        REQUIRE(cpp_widget.argv0().empty());
    }

    {
        char *argv[] = {strdup("a.out")};
        py::scoped_interpreter argv_scope(true, 1, argv);
        std::free(argv[0]);
        auto module = py::module::import("test_interpreter");
        auto py_widget = module.attr("DerivedWidget")("The question");
        const auto &cpp_widget = py_widget.cast<const Widget &>();
        REQUIRE(cpp_widget.argv0() == "a.out");
    }
    py::initialize_interpreter();
}

TEST_CASE("make_iterator can be called before then after finalizing an interpreter") {
    // Reproduction of issue #2101 (https://github.com/pybind/pybind11/issues/2101)
    py::finalize_interpreter();

    std::vector<int> container;
    {
        pybind11::scoped_interpreter g;
        auto iter = pybind11::make_iterator(container.begin(), container.end());
    }

    REQUIRE_NOTHROW([&]() {
        pybind11::scoped_interpreter g;
        auto iter = pybind11::make_iterator(container.begin(), container.end());
    }());

    py::initialize_interpreter();
}

#ifdef PYBIND11_HAS_STRING_VIEW
TEST_CASE("Casting to a string_view outside a bound function") {
    // Regression for PR #6092: view casters add the source to loader_life_support, but
    // outside a bound function there is no frame. The caller owns the source's lifetime
    // here, so the cast must succeed rather than throw.
    py::str unicode("hello");
    py::bytes bytes_obj("world", 5);
    auto bytearray_obj
        = py::reinterpret_steal<py::object>(PyByteArray_FromStringAndSize("bytes", 5));

    REQUIRE(py::cast<std::string_view>(unicode) == "hello");
    REQUIRE(py::cast<std::string_view>(bytes_obj) == "world");
    REQUIRE(py::cast<std::string_view>(bytearray_obj) == "bytes");

    // Wide string views require an encoded temporary. With no loader life-support
    // frame, returning a view into that temporary must fail.
    REQUIRE_THROWS_AS(py::cast<std::u16string_view>(unicode), py::cast_error);
    REQUIRE_THROWS_AS(py::cast<std::u32string_view>(unicode), py::cast_error);

    // Bound-function dispatch provides a frame that keeps both temporaries alive.
    auto accepts_wide_views
        = py::cpp_function([](std::u16string_view value16, std::u32string_view value32) {
              return value16 == std::u16string_view(u"hello")
                     && value32 == std::u32string_view(U"hello");
          });
    REQUIRE(accepts_wide_views(unicode, unicode).cast<bool>());
}
#endif