Merge branch 'master' into v2.10

include/pybind11/eigen/tensor.h

+/*
+    pybind11/eigen/tensor.h: Transparent conversion for Eigen tensors
+
+    All rights reserved. Use of this source code is governed by a
+    BSD-style license that can be found in the LICENSE file.
+*/
+
+#pragma once
+
+#include "../numpy.h"
+
+#if defined(__GNUC__) && !defined(__clang__) && !defined(__INTEL_COMPILER)
+static_assert(__GNUC__ > 5, "Eigen Tensor support in pybind11 requires GCC > 5.0");
+#endif
+
+// Disable warnings for Eigen
+PYBIND11_WARNING_PUSH
+PYBIND11_WARNING_DISABLE_MSVC(4554)
+PYBIND11_WARNING_DISABLE_MSVC(4127)
+PYBIND11_WARNING_DISABLE_GCC("-Wmaybe-uninitialized")
+
+#include <unsupported/Eigen/CXX11/Tensor>
+
+PYBIND11_WARNING_POP
+
+static_assert(EIGEN_VERSION_AT_LEAST(3, 3, 0),
+              "Eigen Tensor support in pybind11 requires Eigen >= 3.3.0");
+
+PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+
+PYBIND11_WARNING_DISABLE_MSVC(4127)
+
+PYBIND11_NAMESPACE_BEGIN(detail)
+
+inline bool is_tensor_aligned(const void *data) {
+    return (reinterpret_cast<std::size_t>(data) % EIGEN_DEFAULT_ALIGN_BYTES) == 0;
+}
+
+template <typename T>
+constexpr int compute_array_flag_from_tensor() {
+    static_assert((static_cast<int>(T::Layout) == static_cast<int>(Eigen::RowMajor))
+                      || (static_cast<int>(T::Layout) == static_cast<int>(Eigen::ColMajor)),
+                  "Layout must be row or column major");
+    return (static_cast<int>(T::Layout) == static_cast<int>(Eigen::RowMajor)) ? array::c_style
+                                                                              : array::f_style;
+}
+
+template <typename T>
+struct eigen_tensor_helper {};
+
+template <typename Scalar_, int NumIndices_, int Options_, typename IndexType>
+struct eigen_tensor_helper<Eigen::Tensor<Scalar_, NumIndices_, Options_, IndexType>> {
+    using Type = Eigen::Tensor<Scalar_, NumIndices_, Options_, IndexType>;
+    using ValidType = void;
+
+    static Eigen::DSizes<typename Type::Index, Type::NumIndices> get_shape(const Type &f) {
+        return f.dimensions();
+    }
+
+    static constexpr bool
+    is_correct_shape(const Eigen::DSizes<typename Type::Index, Type::NumIndices> & /*shape*/) {
+        return true;
+    }
+
+    template <typename T>
+    struct helper {};
+
+    template <size_t... Is>
+    struct helper<index_sequence<Is...>> {
+        static constexpr auto value = concat(const_name(((void) Is, "?"))...);
+    };
+
+    static constexpr auto dimensions_descriptor
+        = helper<decltype(make_index_sequence<Type::NumIndices>())>::value;
+
+    template <typename... Args>
+    static Type *alloc(Args &&...args) {
+        return new Type(std::forward<Args>(args)...);
+    }
+
+    static void free(Type *tensor) { delete tensor; }
+};
+
+template <typename Scalar_, typename std::ptrdiff_t... Indices, int Options_, typename IndexType>
+struct eigen_tensor_helper<
+    Eigen::TensorFixedSize<Scalar_, Eigen::Sizes<Indices...>, Options_, IndexType>> {
+    using Type = Eigen::TensorFixedSize<Scalar_, Eigen::Sizes<Indices...>, Options_, IndexType>;
+    using ValidType = void;
+
+    static constexpr Eigen::DSizes<typename Type::Index, Type::NumIndices>
+    get_shape(const Type & /*f*/) {
+        return get_shape();
+    }
+
+    static constexpr Eigen::DSizes<typename Type::Index, Type::NumIndices> get_shape() {
+        return Eigen::DSizes<typename Type::Index, Type::NumIndices>(Indices...);
+    }
+
+    static bool
+    is_correct_shape(const Eigen::DSizes<typename Type::Index, Type::NumIndices> &shape) {
+        return get_shape() == shape;
+    }
+
+    static constexpr auto dimensions_descriptor = concat(const_name<Indices>()...);
+
+    template <typename... Args>
+    static Type *alloc(Args &&...args) {
+        Eigen::aligned_allocator<Type> allocator;
+        return ::new (allocator.allocate(1)) Type(std::forward<Args>(args)...);
+    }
+
+    static void free(Type *tensor) {
+        Eigen::aligned_allocator<Type> allocator;
+        tensor->~Type();
+        allocator.deallocate(tensor, 1);
+    }
+};
+
+template <typename Type, bool ShowDetails, bool NeedsWriteable = false>
+struct get_tensor_descriptor {
+    static constexpr auto details
+        = const_name<NeedsWriteable>(", flags.writeable", "")
+          + const_name<static_cast<int>(Type::Layout) == static_cast<int>(Eigen::RowMajor)>(
+              ", flags.c_contiguous", ", flags.f_contiguous");
+    static constexpr auto value
+        = const_name("numpy.ndarray[") + npy_format_descriptor<typename Type::Scalar>::name
+          + const_name("[") + eigen_tensor_helper<remove_cv_t<Type>>::dimensions_descriptor
+          + const_name("]") + const_name<ShowDetails>(details, const_name("")) + const_name("]");
+};
+
+// When EIGEN_AVOID_STL_ARRAY is defined, Eigen::DSizes<T, 0> does not have the begin() member
+// function. Falling back to a simple loop works around this issue.
+//
+// We need to disable the type-limits warning for the inner loop when size = 0.
+
+PYBIND11_WARNING_PUSH
+PYBIND11_WARNING_DISABLE_GCC("-Wtype-limits")
+
+template <typename T, int size>
+std::vector<T> convert_dsizes_to_vector(const Eigen::DSizes<T, size> &arr) {
+    std::vector<T> result(size);
+
+    for (size_t i = 0; i < size; i++) {
+        result[i] = arr[i];
+    }
+
+    return result;
+}
+
+template <typename T, int size>
+Eigen::DSizes<T, size> get_shape_for_array(const array &arr) {
+    Eigen::DSizes<T, size> result;
+    const T *shape = arr.shape();
+    for (size_t i = 0; i < size; i++) {
+        result[i] = shape[i];
+    }
+
+    return result;
+}
+
+PYBIND11_WARNING_POP
+
+template <typename Type>
+struct type_caster<Type, typename eigen_tensor_helper<Type>::ValidType> {
+    using Helper = eigen_tensor_helper<Type>;
+    static constexpr auto temp_name = get_tensor_descriptor<Type, false>::value;
+    PYBIND11_TYPE_CASTER(Type, temp_name);
+
+    bool load(handle src, bool convert) {
+        if (!convert) {
+            if (!isinstance<array>(src)) {
+                return false;
+            }
+            array temp = array::ensure(src);
+            if (!temp) {
+                return false;
+            }
+
+            if (!convert && !temp.dtype().is(dtype::of<typename Type::Scalar>())) {
+                return false;
+            }
+        }
+
+        array_t<typename Type::Scalar, compute_array_flag_from_tensor<Type>()> arr(
+            reinterpret_borrow<object>(src));
+
+        if (arr.ndim() != Type::NumIndices) {
+            return false;
+        }
+        auto shape = get_shape_for_array<typename Type::Index, Type::NumIndices>(arr);
+
+        if (!Helper::is_correct_shape(shape)) {
+            return false;
+        }
+
+#if EIGEN_VERSION_AT_LEAST(3, 4, 0)
+        auto data_pointer = arr.data();
+#else
+        // Handle Eigen bug
+        auto data_pointer = const_cast<typename Type::Scalar *>(arr.data());
+#endif
+
+        if (is_tensor_aligned(arr.data())) {
+            value = Eigen::TensorMap<const Type, Eigen::Aligned>(data_pointer, shape);
+        } else {
+            value = Eigen::TensorMap<const Type>(data_pointer, shape);
+        }
+
+        return true;
+    }
+
+    static handle cast(Type &&src, return_value_policy policy, handle parent) {
+        if (policy == return_value_policy::reference
+            || policy == return_value_policy::reference_internal) {
+            pybind11_fail("Cannot use a reference return value policy for an rvalue");
+        }
+        return cast_impl(&src, return_value_policy::move, parent);
+    }
+
+    static handle cast(const Type &&src, return_value_policy policy, handle parent) {
+        if (policy == return_value_policy::reference
+            || policy == return_value_policy::reference_internal) {
+            pybind11_fail("Cannot use a reference return value policy for an rvalue");
+        }
+        return cast_impl(&src, return_value_policy::move, parent);
+    }
+
+    static handle cast(Type &src, return_value_policy policy, handle parent) {
+        if (policy == return_value_policy::automatic
+            || policy == return_value_policy::automatic_reference) {
+            policy = return_value_policy::copy;
+        }
+        return cast_impl(&src, policy, parent);
+    }
+
+    static handle cast(const Type &src, return_value_policy policy, handle parent) {
+        if (policy == return_value_policy::automatic
+            || policy == return_value_policy::automatic_reference) {
+            policy = return_value_policy::copy;
+        }
+        return cast(&src, policy, parent);
+    }
+
+    static handle cast(Type *src, return_value_policy policy, handle parent) {
+        if (policy == return_value_policy::automatic) {
+            policy = return_value_policy::take_ownership;
+        } else if (policy == return_value_policy::automatic_reference) {
+            policy = return_value_policy::reference;
+        }
+        return cast_impl(src, policy, parent);
+    }
+
+    static handle cast(const Type *src, return_value_policy policy, handle parent) {
+        if (policy == return_value_policy::automatic) {
+            policy = return_value_policy::take_ownership;
+        } else if (policy == return_value_policy::automatic_reference) {
+            policy = return_value_policy::reference;
+        }
+        return cast_impl(src, policy, parent);
+    }
+
+    template <typename C>
+    static handle cast_impl(C *src, return_value_policy policy, handle parent) {
+        object parent_object;
+        bool writeable = false;
+        switch (policy) {
+            case return_value_policy::move:
+                if (std::is_const<C>::value) {
+                    pybind11_fail("Cannot move from a constant reference");
+                }
+
+                src = Helper::alloc(std::move(*src));
+
+                parent_object
+                    = capsule(src, [](void *ptr) { Helper::free(reinterpret_cast<Type *>(ptr)); });
+                writeable = true;
+                break;
+
+            case return_value_policy::take_ownership:
+                if (std::is_const<C>::value) {
+                    // This cast is ugly, and might be UB in some cases, but we don't have an
+                    // alternative here as we must free that memory
+                    Helper::free(const_cast<Type *>(src));
+                    pybind11_fail("Cannot take ownership of a const reference");
+                }
+
+                parent_object
+                    = capsule(src, [](void *ptr) { Helper::free(reinterpret_cast<Type *>(ptr)); });
+                writeable = true;
+                break;
+
+            case return_value_policy::copy:
+                writeable = true;
+                break;
+
+            case return_value_policy::reference:
+                parent_object = none();
+                writeable = !std::is_const<C>::value;
+                break;
+
+            case return_value_policy::reference_internal:
+                // Default should do the right thing
+                if (!parent) {
+                    pybind11_fail("Cannot use reference internal when there is no parent");
+                }
+                parent_object = reinterpret_borrow<object>(parent);
+                writeable = !std::is_const<C>::value;
+                break;
+
+            default:
+                pybind11_fail("pybind11 bug in eigen.h, please file a bug report");
+        }
+
+        auto result = array_t<typename Type::Scalar, compute_array_flag_from_tensor<Type>()>(
+            convert_dsizes_to_vector(Helper::get_shape(*src)), src->data(), parent_object);
+
+        if (!writeable) {
+            array_proxy(result.ptr())->flags &= ~detail::npy_api::NPY_ARRAY_WRITEABLE_;
+        }
+
+        return result.release();
+    }
+};
+
+template <typename StoragePointerType,
+          bool needs_writeable,
+          enable_if_t<!needs_writeable, bool> = true>
+StoragePointerType get_array_data_for_type(array &arr) {
+#if EIGEN_VERSION_AT_LEAST(3, 4, 0)
+    return reinterpret_cast<StoragePointerType>(arr.data());
+#else
+    // Handle Eigen bug
+    return reinterpret_cast<StoragePointerType>(const_cast<void *>(arr.data()));
+#endif
+}
+
+template <typename StoragePointerType,
+          bool needs_writeable,
+          enable_if_t<needs_writeable, bool> = true>
+StoragePointerType get_array_data_for_type(array &arr) {
+    return reinterpret_cast<StoragePointerType>(arr.mutable_data());
+}
+
+template <typename T, typename = void>
+struct get_storage_pointer_type;
+
+template <typename MapType>
+struct get_storage_pointer_type<MapType, void_t<typename MapType::StoragePointerType>> {
+    using SPT = typename MapType::StoragePointerType;
+};
+
+template <typename MapType>
+struct get_storage_pointer_type<MapType, void_t<typename MapType::PointerArgType>> {
+    using SPT = typename MapType::PointerArgType;
+};
+
+template <typename Type, int Options>
+struct type_caster<Eigen::TensorMap<Type, Options>,
+                   typename eigen_tensor_helper<remove_cv_t<Type>>::ValidType> {
+    using MapType = Eigen::TensorMap<Type, Options>;
+    using Helper = eigen_tensor_helper<remove_cv_t<Type>>;
+
+    bool load(handle src, bool /*convert*/) {
+        // Note that we have a lot more checks here as we want to make sure to avoid copies
+        if (!isinstance<array>(src)) {
+            return false;
+        }
+        auto arr = reinterpret_borrow<array>(src);
+        if ((arr.flags() & compute_array_flag_from_tensor<Type>()) == 0) {
+            return false;
+        }
+
+        if (!arr.dtype().is(dtype::of<typename Type::Scalar>())) {
+            return false;
+        }
+
+        if (arr.ndim() != Type::NumIndices) {
+            return false;
+        }
+
+        constexpr bool is_aligned = (Options & Eigen::Aligned) != 0;
+
+        if (is_aligned && !is_tensor_aligned(arr.data())) {
+            return false;
+        }
+
+        auto shape = get_shape_for_array<typename Type::Index, Type::NumIndices>(arr);
+
+        if (!Helper::is_correct_shape(shape)) {
+            return false;
+        }
+
+        if (needs_writeable && !arr.writeable()) {
+            return false;
+        }
+
+        auto result = get_array_data_for_type<typename get_storage_pointer_type<MapType>::SPT,
+                                              needs_writeable>(arr);
+
+        value.reset(new MapType(std::move(result), std::move(shape)));
+
+        return true;
+    }
+
+    static handle cast(MapType &&src, return_value_policy policy, handle parent) {
+        return cast_impl(&src, policy, parent);
+    }
+
+    static handle cast(const MapType &&src, return_value_policy policy, handle parent) {
+        return cast_impl(&src, policy, parent);
+    }
+
+    static handle cast(MapType &src, return_value_policy policy, handle parent) {
+        if (policy == return_value_policy::automatic
+            || policy == return_value_policy::automatic_reference) {
+            policy = return_value_policy::copy;
+        }
+        return cast_impl(&src, policy, parent);
+    }
+
+    static handle cast(const MapType &src, return_value_policy policy, handle parent) {
+        if (policy == return_value_policy::automatic
+            || policy == return_value_policy::automatic_reference) {
+            policy = return_value_policy::copy;
+        }
+        return cast(&src, policy, parent);
+    }
+
+    static handle cast(MapType *src, return_value_policy policy, handle parent) {
+        if (policy == return_value_policy::automatic) {
+            policy = return_value_policy::take_ownership;
+        } else if (policy == return_value_policy::automatic_reference) {
+            policy = return_value_policy::reference;
+        }
+        return cast_impl(src, policy, parent);
+    }
+
+    static handle cast(const MapType *src, return_value_policy policy, handle parent) {
+        if (policy == return_value_policy::automatic) {
+            policy = return_value_policy::take_ownership;
+        } else if (policy == return_value_policy::automatic_reference) {
+            policy = return_value_policy::reference;
+        }
+        return cast_impl(src, policy, parent);
+    }
+
+    template <typename C>
+    static handle cast_impl(C *src, return_value_policy policy, handle parent) {
+        object parent_object;
+        constexpr bool writeable = !std::is_const<C>::value;
+        switch (policy) {
+            case return_value_policy::reference:
+                parent_object = none();
+                break;
+
+            case return_value_policy::reference_internal:
+                // Default should do the right thing
+                if (!parent) {
+                    pybind11_fail("Cannot use reference internal when there is no parent");
+                }
+                parent_object = reinterpret_borrow<object>(parent);
+                break;
+
+            case return_value_policy::take_ownership:
+                delete src;
+                // fallthrough
+            default:
+                // move, take_ownership don't make any sense for a ref/map:
+                pybind11_fail("Invalid return_value_policy for Eigen Map type, must be either "
+                              "reference or reference_internal");
+        }
+
+        auto result = array_t<typename Type::Scalar, compute_array_flag_from_tensor<Type>()>(
+            convert_dsizes_to_vector(Helper::get_shape(*src)),
+            src->data(),
+            std::move(parent_object));
+
+        if (!writeable) {
+            array_proxy(result.ptr())->flags &= ~detail::npy_api::NPY_ARRAY_WRITEABLE_;
+        }
+
+        return result.release();
+    }
+
+#if EIGEN_VERSION_AT_LEAST(3, 4, 0)
+
+    static constexpr bool needs_writeable = !std::is_const<typename std::remove_pointer<
+        typename get_storage_pointer_type<MapType>::SPT>::type>::value;
+#else
+    // Handle Eigen bug
+    static constexpr bool needs_writeable = !std::is_const<Type>::value;
+#endif
+
+protected:
+    // TODO: Move to std::optional once std::optional has more support
+    std::unique_ptr<MapType> value;
+
+public:
+    static constexpr auto name = get_tensor_descriptor<Type, true, needs_writeable>::value;
+    explicit operator MapType *() { return value.get(); }
+    explicit operator MapType &() { return *value; }
+    explicit operator MapType &&() && { return std::move(*value); }
+
+    template <typename T_>
+    using cast_op_type = ::pybind11::detail::movable_cast_op_type<T_>;
+};
+
+PYBIND11_NAMESPACE_END(detail)
+PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)

include/pybind11/embed.h

@@ -86,38 +86,26 @@ inline wchar_t *widen_chars(const char *safe_arg) {
     return widened_arg;
 }
 
-PYBIND11_NAMESPACE_END(detail)
-
-/** \rst
-    Initialize the Python interpreter. No other pybind11 or CPython API functions can be
-    called before this is done; with the exception of `PYBIND11_EMBEDDED_MODULE`. The
-    optional `init_signal_handlers` parameter can be used to skip the registration of
-    signal handlers (see the `Python documentation`_ for details). Calling this function
-    again after the interpreter has already been initialized is a fatal error.
-
-    If initializing the Python interpreter fails, then the program is terminated.  (This
-    is controlled by the CPython runtime and is an exception to pybind11's normal behavior
-    of throwing exceptions on errors.)
-
-    The remaining optional parameters, `argc`, `argv`, and `add_program_dir_to_path` are
-    used to populate ``sys.argv`` and ``sys.path``.
-    See the |PySys_SetArgvEx documentation|_ for details.
-
-    .. _Python documentation: https://docs.python.org/3/c-api/init.html#c.Py_InitializeEx
-    .. |PySys_SetArgvEx documentation| replace:: ``PySys_SetArgvEx`` documentation
-    .. _PySys_SetArgvEx documentation: https://docs.python.org/3/c-api/init.html#c.PySys_SetArgvEx
- \endrst */
-inline void initialize_interpreter(bool init_signal_handlers = true,
-                                   int argc = 0,
-                                   const char *const *argv = nullptr,
-                                   bool add_program_dir_to_path = true) {
+inline void precheck_interpreter() {
     if (Py_IsInitialized() != 0) {
         pybind11_fail("The interpreter is already running");
     }
+}
 
-#if PY_VERSION_HEX < 0x030B0000
+#if !defined(PYBIND11_PYCONFIG_SUPPORT_PY_VERSION_HEX)
+#    define PYBIND11_PYCONFIG_SUPPORT_PY_VERSION_HEX (0x03080000)
+#endif
 
+#if PY_VERSION_HEX < PYBIND11_PYCONFIG_SUPPORT_PY_VERSION_HEX
+inline void initialize_interpreter_pre_pyconfig(bool init_signal_handlers,
+                                                int argc,
+                                                const char *const *argv,
+                                                bool add_program_dir_to_path) {
+    detail::precheck_interpreter();
     Py_InitializeEx(init_signal_handlers ? 1 : 0);
+#    if defined(WITH_THREAD) && PY_VERSION_HEX < 0x03070000
+    PyEval_InitThreads();
+#    endif
 
     // Before it was special-cased in python 3.8, passing an empty or null argv
     // caused a segfault, so we have to reimplement the special case ourselves.
@@ -147,26 +135,30 @@ inline void initialize_interpreter(bool init_signal_handlers = true,
     auto *pysys_argv = widened_argv.get();
 
     PySys_SetArgvEx(argc, pysys_argv, static_cast<int>(add_program_dir_to_path));
-#else
-    PyConfig config;
-    PyConfig_InitIsolatedConfig(&config);
-    config.isolated = 0;
-    config.use_environment = 1;
-    config.install_signal_handlers = init_signal_handlers ? 1 : 0;
+}
+#endif
 
-    PyStatus status = PyConfig_SetBytesArgv(&config, argc, const_cast<char *const *>(argv));
-    if (PyStatus_Exception(status)) {
+PYBIND11_NAMESPACE_END(detail)
+
+#if PY_VERSION_HEX >= PYBIND11_PYCONFIG_SUPPORT_PY_VERSION_HEX
+inline void initialize_interpreter(PyConfig *config,
+                                   int argc = 0,
+                                   const char *const *argv = nullptr,
+                                   bool add_program_dir_to_path = true) {
+    detail::precheck_interpreter();
+    PyStatus status = PyConfig_SetBytesArgv(config, argc, const_cast<char *const *>(argv));
+    if (PyStatus_Exception(status) != 0) {
         // A failure here indicates a character-encoding failure or the python
         // interpreter out of memory. Give up.
-        PyConfig_Clear(&config);
-        throw std::runtime_error(PyStatus_IsError(status) ? status.err_msg
-                                                          : "Failed to prepare CPython");
+        PyConfig_Clear(config);
+        throw std::runtime_error(PyStatus_IsError(status) != 0 ? status.err_msg
+                                                               : "Failed to prepare CPython");
     }
-    status = Py_InitializeFromConfig(&config);
-    PyConfig_Clear(&config);
-    if (PyStatus_Exception(status)) {
-        throw std::runtime_error(PyStatus_IsError(status) ? status.err_msg
-                                                          : "Failed to init CPython");
+    status = Py_InitializeFromConfig(config);
+    if (PyStatus_Exception(status) != 0) {
+        PyConfig_Clear(config);
+        throw std::runtime_error(PyStatus_IsError(status) != 0 ? status.err_msg
+                                                               : "Failed to init CPython");
     }
     if (add_program_dir_to_path) {
         PyRun_SimpleString("import sys, os.path; "
@@ -174,6 +166,43 @@ inline void initialize_interpreter(bool init_signal_handlers = true,
                            "os.path.abspath(os.path.dirname(sys.argv[0])) "
                            "if sys.argv and os.path.exists(sys.argv[0]) else '')");
     }
+    PyConfig_Clear(config);
+}
+#endif
+
+/** \rst
+    Initialize the Python interpreter. No other pybind11 or CPython API functions can be
+    called before this is done; with the exception of `PYBIND11_EMBEDDED_MODULE`. The
+    optional `init_signal_handlers` parameter can be used to skip the registration of
+    signal handlers (see the `Python documentation`_ for details). Calling this function
+    again after the interpreter has already been initialized is a fatal error.
+
+    If initializing the Python interpreter fails, then the program is terminated.  (This
+    is controlled by the CPython runtime and is an exception to pybind11's normal behavior
+    of throwing exceptions on errors.)
+
+    The remaining optional parameters, `argc`, `argv`, and `add_program_dir_to_path` are
+    used to populate ``sys.argv`` and ``sys.path``.
+    See the |PySys_SetArgvEx documentation|_ for details.
+
+    .. _Python documentation: https://docs.python.org/3/c-api/init.html#c.Py_InitializeEx
+    .. |PySys_SetArgvEx documentation| replace:: ``PySys_SetArgvEx`` documentation
+    .. _PySys_SetArgvEx documentation: https://docs.python.org/3/c-api/init.html#c.PySys_SetArgvEx
+ \endrst */
+inline void initialize_interpreter(bool init_signal_handlers = true,
+                                   int argc = 0,
+                                   const char *const *argv = nullptr,
+                                   bool add_program_dir_to_path = true) {
+#if PY_VERSION_HEX < PYBIND11_PYCONFIG_SUPPORT_PY_VERSION_HEX
+    detail::initialize_interpreter_pre_pyconfig(
+        init_signal_handlers, argc, argv, add_program_dir_to_path);
+#else
+    PyConfig config;
+    PyConfig_InitIsolatedConfig(&config);
+    config.isolated = 0;
+    config.use_environment = 1;
+    config.install_signal_handlers = init_signal_handlers ? 1 : 0;
+    initialize_interpreter(&config, argc, argv, add_program_dir_to_path);
 #endif
 }
 
@@ -261,6 +290,15 @@ public:
         initialize_interpreter(init_signal_handlers, argc, argv, add_program_dir_to_path);
     }
 
+#if PY_VERSION_HEX >= PYBIND11_PYCONFIG_SUPPORT_PY_VERSION_HEX
+    explicit scoped_interpreter(PyConfig *config,
+                                int argc = 0,
+                                const char *const *argv = nullptr,
+                                bool add_program_dir_to_path = true) {
+        initialize_interpreter(config, argc, argv, add_program_dir_to_path);
+    }
+#endif
+
     scoped_interpreter(const scoped_interpreter &) = delete;
     scoped_interpreter(scoped_interpreter &&other) noexcept { other.is_valid = false; }
     scoped_interpreter &operator=(const scoped_interpreter &) = delete;

include/pybind11/functional.h

@@ -48,9 +48,16 @@ public:
          */
         if (auto cfunc = func.cpp_function()) {
             auto *cfunc_self = PyCFunction_GET_SELF(cfunc.ptr());
-            if (isinstance<capsule>(cfunc_self)) {
+            if (cfunc_self == nullptr) {
+                PyErr_Clear();
+            } else if (isinstance<capsule>(cfunc_self)) {
                 auto c = reinterpret_borrow<capsule>(cfunc_self);
-                auto *rec = (function_record *) c;
+
+                function_record *rec = nullptr;
+                // Check that we can safely reinterpret the capsule into a function_record
+                if (detail::is_function_record_capsule(c)) {
+                    rec = c.get_pointer<function_record>();
+                }
 
                 while (rec != nullptr) {
                     if (rec->is_stateless

include/pybind11/numpy.h

@@ -36,6 +36,8 @@ static_assert(std::is_signed<Py_intptr_t>::value, "Py_intptr_t must be signed");
 
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 
+PYBIND11_WARNING_DISABLE_MSVC(4127)
+
 class array; // Forward declaration
 
 PYBIND11_NAMESPACE_BEGIN(detail)
@@ -875,7 +877,7 @@ public:
      */
     template <typename T, ssize_t Dims = -1>
     detail::unchecked_mutable_reference<T, Dims> mutable_unchecked() & {
-        if (PYBIND11_SILENCE_MSVC_C4127(Dims >= 0) && ndim() != Dims) {
+        if (Dims >= 0 && ndim() != Dims) {
             throw std::domain_error("array has incorrect number of dimensions: "
                                     + std::to_string(ndim()) + "; expected "
                                     + std::to_string(Dims));
@@ -893,7 +895,7 @@ public:
      */
     template <typename T, ssize_t Dims = -1>
     detail::unchecked_reference<T, Dims> unchecked() const & {
-        if (PYBIND11_SILENCE_MSVC_C4127(Dims >= 0) && ndim() != Dims) {
+        if (Dims >= 0 && ndim() != Dims) {
             throw std::domain_error("array has incorrect number of dimensions: "
                                     + std::to_string(ndim()) + "; expected "
                                     + std::to_string(Dims));
@@ -1469,7 +1471,7 @@ private:
         }
 
 // Extract name, offset and format descriptor for a struct field
-#    define PYBIND11_FIELD_DESCRIPTOR(T, Field) PYBIND11_FIELD_DESCRIPTOR_EX(T, Field, #    Field)
+#    define PYBIND11_FIELD_DESCRIPTOR(T, Field) PYBIND11_FIELD_DESCRIPTOR_EX(T, Field, #Field)
 
 // The main idea of this macro is borrowed from https://github.com/swansontec/map-macro
 // (C) William Swanson, Paul Fultz
@@ -1865,9 +1867,10 @@ private:
         }
 
         auto result = returned_array::create(trivial, shape);
+
+        PYBIND11_WARNING_PUSH
 #ifdef PYBIND11_DETECTED_CLANG_WITH_MISLEADING_CALL_STD_MOVE_EXPLICITLY_WARNING
-#    pragma clang diagnostic push
-#    pragma clang diagnostic ignored "-Wreturn-std-move"
+        PYBIND11_WARNING_DISABLE_CLANG("-Wreturn-std-move")
 #endif
 
         if (size == 0) {
@@ -1883,9 +1886,7 @@ private:
         }
 
         return result;
-#ifdef PYBIND11_DETECTED_CLANG_WITH_MISLEADING_CALL_STD_MOVE_EXPLICITLY_WARNING
-#    pragma clang diagnostic pop
-#endif
+        PYBIND11_WARNING_POP
     }
 
     template <size_t... Index, size_t... VIndex, size_t... BIndex>

include/pybind11/options.h

@@ -47,6 +47,16 @@ public:
         return *this;
     }
 
+    options &disable_enum_members_docstring() & {
+        global_state().show_enum_members_docstring = false;
+        return *this;
+    }
+
+    options &enable_enum_members_docstring() & {
+        global_state().show_enum_members_docstring = true;
+        return *this;
+    }
+
     // Getter methods (return the global state):
 
     static bool show_user_defined_docstrings() {
@@ -55,6 +65,10 @@ public:
 
     static bool show_function_signatures() { return global_state().show_function_signatures; }
 
+    static bool show_enum_members_docstring() {
+        return global_state().show_enum_members_docstring;
+    }
+
     // This type is not meant to be allocated on the heap.
     void *operator new(size_t) = delete;
 
@@ -63,6 +77,8 @@ private:
         bool show_user_defined_docstrings = true; //< Include user-supplied texts in docstrings.
         bool show_function_signatures = true;     //< Include auto-generated function signatures
                                                   //  in docstrings.
+        bool show_enum_members_docstring = true;  //< Include auto-generated member list in enum
+                                                  //  docstrings.
     };
 
     static state &global_state() {

include/pybind11/pybind11.h

@@ -35,6 +35,8 @@
 #    include <cxxabi.h>
 #endif
 
+PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+
 /* https://stackoverflow.com/questions/46798456/handling-gccs-noexcept-type-warning
    This warning is about ABI compatibility, not code health.
    It is only actually needed in a couple places, but apparently GCC 7 "generates this warning if
@@ -43,11 +45,10 @@
    No other GCC version generates this warning.
  */
 #if defined(__GNUC__) && __GNUC__ == 7
-#    pragma GCC diagnostic push
-#    pragma GCC diagnostic ignored "-Wnoexcept-type"
+PYBIND11_WARNING_DISABLE_GCC("-Wnoexcept-type")
 #endif
 
-PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+PYBIND11_WARNING_DISABLE_MSVC(4127)
 
 PYBIND11_NAMESPACE_BEGIN(detail)
 
@@ -177,22 +178,22 @@ protected:
         auto *rec = unique_rec.get();
 
         /* Store the capture object directly in the function record if there is enough space */
-        if (PYBIND11_SILENCE_MSVC_C4127(sizeof(capture) <= sizeof(rec->data))) {
+        if (sizeof(capture) <= sizeof(rec->data)) {
             /* Without these pragmas, GCC warns that there might not be
                enough space to use the placement new operator. However, the
                'if' statement above ensures that this is the case. */
-#if defined(__GNUG__) && __GNUC__ >= 6 && !defined(__clang__) && !defined(__INTEL_COMPILER)
-#    pragma GCC diagnostic push
-#    pragma GCC diagnostic ignored "-Wplacement-new"
+            PYBIND11_WARNING_PUSH
+
+#if defined(__GNUG__) && __GNUC__ >= 6
+            PYBIND11_WARNING_DISABLE_GCC("-Wplacement-new")
 #endif
+
             new ((capture *) &rec->data) capture{std::forward<Func>(f)};
-#if defined(__GNUG__) && __GNUC__ >= 6 && !defined(__clang__) && !defined(__INTEL_COMPILER)
-#    pragma GCC diagnostic pop
-#endif
-#if defined(__GNUG__) && !PYBIND11_HAS_STD_LAUNDER && !defined(__INTEL_COMPILER)
-#    pragma GCC diagnostic push
-#    pragma GCC diagnostic ignored "-Wstrict-aliasing"
+
+#if !PYBIND11_HAS_STD_LAUNDER
+            PYBIND11_WARNING_DISABLE_GCC("-Wstrict-aliasing")
 #endif
+
             // UB without std::launder, but without breaking ABI and/or
             // a significant refactoring it's "impossible" to solve.
             if (!std::is_trivially_destructible<capture>::value) {
@@ -202,9 +203,7 @@ protected:
                     data->~capture();
                 };
             }
-#if defined(__GNUG__) && !PYBIND11_HAS_STD_LAUNDER && !defined(__INTEL_COMPILER)
-#    pragma GCC diagnostic pop
-#endif
+            PYBIND11_WARNING_POP
         } else {
             rec->data[0] = new capture{std::forward<Func>(f)};
             rec->free_data = [](function_record *r) { delete ((capture *) r->data[0]); };
@@ -468,13 +467,20 @@ protected:
         if (rec->sibling) {
             if (PyCFunction_Check(rec->sibling.ptr())) {
                 auto *self = PyCFunction_GET_SELF(rec->sibling.ptr());
-                capsule rec_capsule = isinstance<capsule>(self) ? reinterpret_borrow<capsule>(self)
-                                                                : capsule(self);
-                chain = (detail::function_record *) rec_capsule;
-                /* Never append a method to an overload chain of a parent class;
-                   instead, hide the parent's overloads in this case */
-                if (!chain->scope.is(rec->scope)) {
+                if (!isinstance<capsule>(self)) {
                     chain = nullptr;
+                } else {
+                    auto rec_capsule = reinterpret_borrow<capsule>(self);
+                    if (detail::is_function_record_capsule(rec_capsule)) {
+                        chain = rec_capsule.get_pointer<detail::function_record>();
+                        /* Never append a method to an overload chain of a parent class;
+                           instead, hide the parent's overloads in this case */
+                        if (!chain->scope.is(rec->scope)) {
+                            chain = nullptr;
+                        }
+                    } else {
+                        chain = nullptr;
+                    }
                 }
             }
             // Don't trigger for things like the default __init__, which are wrapper_descriptors
@@ -496,6 +502,7 @@ protected:
 
             capsule rec_capsule(unique_rec.release(),
                                 [](void *ptr) { destruct((detail::function_record *) ptr); });
+            rec_capsule.set_name(detail::get_function_record_capsule_name());
             guarded_strdup.release();
 
             object scope_module;
@@ -661,10 +668,13 @@ protected:
     /// Main dispatch logic for calls to functions bound using pybind11
     static PyObject *dispatcher(PyObject *self, PyObject *args_in, PyObject *kwargs_in) {
         using namespace detail;
+        assert(isinstance<capsule>(self));
 
         /* Iterator over the list of potentially admissible overloads */
-        const function_record *overloads = (function_record *) PyCapsule_GetPointer(self, nullptr),
+        const function_record *overloads = reinterpret_cast<function_record *>(
+                                  PyCapsule_GetPointer(self, get_function_record_capsule_name())),
                               *it = overloads;
+        assert(overloads != nullptr);
 
         /* Need to know how many arguments + keyword arguments there are to pick the right
            overload */
@@ -1416,9 +1426,9 @@ template <typename T, enable_if_t<has_operator_delete<T>::value, int> = 0>
 void call_operator_delete(T *p, size_t, size_t) {
     T::operator delete(p);
 }
-template <
-    typename T,
-    enable_if_t<!has_operator_delete<T>::value && has_operator_delete_size<T>::value, int> = 0>
+template <typename T,
+          enable_if_t<!has_operator_delete<T>::value && has_operator_delete_size<T>::value, int>
+          = 0>
 void call_operator_delete(T *p, size_t s, size_t) {
     T::operator delete(p, s);
 }
@@ -1830,8 +1840,7 @@ private:
         if (holder_ptr) {
             init_holder_from_existing(v_h, holder_ptr, std::is_copy_constructible<holder_type>());
             v_h.set_holder_constructed();
-        } else if (PYBIND11_SILENCE_MSVC_C4127(detail::always_construct_holder<holder_type>::value)
-                   || inst->owned) {
+        } else if (detail::always_construct_holder<holder_type>::value || inst->owned) {
             new (std::addressof(v_h.holder<holder_type>())) holder_type(v_h.value_ptr<type>());
             v_h.set_holder_constructed();
         }
@@ -1871,9 +1880,22 @@ private:
 
     static detail::function_record *get_function_record(handle h) {
         h = detail::get_function(h);
-        return h ? (detail::function_record *) reinterpret_borrow<capsule>(
-                   PyCFunction_GET_SELF(h.ptr()))
-                 : nullptr;
+        if (!h) {
+            return nullptr;
+        }
+
+        handle func_self = PyCFunction_GET_SELF(h.ptr());
+        if (!func_self) {
+            throw error_already_set();
+        }
+        if (!isinstance<capsule>(func_self)) {
+            return nullptr;
+        }
+        auto cap = reinterpret_borrow<capsule>(func_self);
+        if (!detail::is_function_record_capsule(cap)) {
+            return nullptr;
+        }
+        return cap.get_pointer<detail::function_record>();
     }
 };
 
@@ -1950,29 +1972,35 @@ struct enum_base {
             name("name"),
             is_method(m_base));
 
-        m_base.attr("__doc__") = static_property(
-            cpp_function(
-                [](handle arg) -> std::string {
-                    std::string docstring;
-                    dict entries = arg.attr("__entries");
-                    if (((PyTypeObject *) arg.ptr())->tp_doc) {
-                        docstring += std::string(((PyTypeObject *) arg.ptr())->tp_doc) + "\n\n";
-                    }
-                    docstring += "Members:";
-                    for (auto kv : entries) {
-                        auto key = std::string(pybind11::str(kv.first));
-                        auto comment = kv.second[int_(1)];
-                        docstring += "\n\n  " + key;
-                        if (!comment.is_none()) {
-                            docstring += " : " + (std::string) pybind11::str(comment);
+        if (options::show_enum_members_docstring()) {
+            m_base.attr("__doc__") = static_property(
+                cpp_function(
+                    [](handle arg) -> std::string {
+                        std::string docstring;
+                        dict entries = arg.attr("__entries");
+                        if (((PyTypeObject *) arg.ptr())->tp_doc) {
+                            docstring += std::string(
+                                reinterpret_cast<PyTypeObject *>(arg.ptr())->tp_doc);
+                            docstring += "\n\n";
                         }
-                    }
-                    return docstring;
-                },
-                name("__doc__")),
-            none(),
-            none(),
-            "");
+                        docstring += "Members:";
+                        for (auto kv : entries) {
+                            auto key = std::string(pybind11::str(kv.first));
+                            auto comment = kv.second[int_(1)];
+                            docstring += "\n\n  ";
+                            docstring += key;
+                            if (!comment.is_none()) {
+                                docstring += " : ";
+                                docstring += pybind11::str(comment).cast<std::string>();
+                            }
+                        }
+                        return docstring;
+                    },
+                    name("__doc__")),
+                none(),
+                none(),
+                "");
+        }
 
         m_base.attr("__members__") = static_property(cpp_function(
                                                          [](handle arg) -> dict {
@@ -2852,7 +2880,3 @@ inline function get_overload(const T *this_ptr, const char *name) {
     PYBIND11_OVERRIDE_PURE(PYBIND11_TYPE(ret_type), PYBIND11_TYPE(cname), fn, __VA_ARGS__);
 
 PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)
-
-#if defined(__GNUC__) && __GNUC__ == 7
-#    pragma GCC diagnostic pop // -Wnoexcept-type
-#endif

include/pybind11/pytypes.h

@@ -33,6 +33,8 @@
 
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 
+PYBIND11_WARNING_DISABLE_MSVC(4127)
+
 /* A few forward declarations */
 class handle;
 class object;
@@ -230,7 +232,8 @@ public:
         detail::enable_if_t<detail::all_of<detail::none_of<std::is_base_of<handle, T>,
                                                            detail::is_pyobj_ptr_or_nullptr_t<T>>,
                                            std::is_convertible<T, PyObject *>>::value,
-                            int> = 0>
+                            int>
+        = 0>
     // NOLINTNEXTLINE(google-explicit-constructor)
     handle(T &obj) : m_ptr(obj) {}
 
@@ -246,6 +249,11 @@ public:
     const handle &inc_ref() const & {
 #ifdef PYBIND11_HANDLE_REF_DEBUG
         inc_ref_counter(1);
+#endif
+#if defined(PYBIND11_ASSERT_GIL_HELD_INCREF_DECREF)
+        if (m_ptr != nullptr && !PyGILState_Check()) {
+            throw std::runtime_error("pybind11::handle::inc_ref() PyGILState_Check() failure.");
+        }
 #endif
         Py_XINCREF(m_ptr);
         return *this;
@@ -257,6 +265,11 @@ public:
         this function automatically. Returns a reference to itself.
     \endrst */
     const handle &dec_ref() const & {
+#if defined(PYBIND11_ASSERT_GIL_HELD_INCREF_DECREF)
+        if (m_ptr != nullptr && !PyGILState_Check()) {
+            throw std::runtime_error("pybind11::handle::dec_ref() PyGILState_Check() failure.");
+        }
+#endif
         Py_XDECREF(m_ptr);
         return *this;
     }
@@ -623,12 +636,6 @@ inline std::string error_string() {
 
 PYBIND11_NAMESPACE_END(detail)
 
-#if defined(_MSC_VER)
-#    pragma warning(push)
-#    pragma warning(disable : 4275 4251)
-//     warning C4275: An exported class was derived from a class that wasn't exported.
-//     Can be ignored when derived from a STL class.
-#endif
 /// Fetch and hold an error which was already set in Python.  An instance of this is typically
 /// thrown to propagate python-side errors back through C++ which can either be caught manually or
 /// else falls back to the function dispatcher (which then raises the captured error back to
@@ -688,9 +695,6 @@ private:
     ///          crashes (undefined behavior) if the Python interpreter is finalizing.
     static void m_fetched_error_deleter(detail::error_fetch_and_normalize *raw_ptr);
 };
-#if defined(_MSC_VER)
-#    pragma warning(pop)
-#endif
 
 /// Replaces the current Python error indicator with the chosen error, performing a
 /// 'raise from' to indicate that the chosen error was caused by the original error.
@@ -893,10 +897,8 @@ object object_or_cast(T &&o);
 // Match a PyObject*, which we want to convert directly to handle via its converting constructor
 inline handle object_or_cast(PyObject *ptr) { return ptr; }
 
-#if defined(_MSC_VER) && _MSC_VER < 1920
-#    pragma warning(push)
-#    pragma warning(disable : 4522) // warning C4522: multiple assignment operators specified
-#endif
+PYBIND11_WARNING_PUSH
+PYBIND11_WARNING_DISABLE_MSVC(4522) // warning C4522: multiple assignment operators specified
 template <typename Policy>
 class accessor : public object_api<accessor<Policy>> {
     using key_type = typename Policy::key_type;
@@ -960,9 +962,7 @@ private:
     key_type key;
     mutable object cache;
 };
-#if defined(_MSC_VER) && _MSC_VER < 1920
-#    pragma warning(pop)
-#endif
+PYBIND11_WARNING_POP
 
 PYBIND11_NAMESPACE_BEGIN(accessor_policies)
 struct obj_attr {
@@ -1702,7 +1702,7 @@ PYBIND11_NAMESPACE_BEGIN(detail)
 // unsigned type: (A)-1 != (B)-1 when A and B are unsigned types of different sizes).
 template <typename Unsigned>
 Unsigned as_unsigned(PyObject *o) {
-    if (PYBIND11_SILENCE_MSVC_C4127(sizeof(Unsigned) <= sizeof(unsigned long))) {
+    if (sizeof(Unsigned) <= sizeof(unsigned long)) {
         unsigned long v = PyLong_AsUnsignedLong(o);
         return v == (unsigned long) -1 && PyErr_Occurred() ? (Unsigned) -1 : (Unsigned) v;
     }
@@ -1719,7 +1719,7 @@ public:
     template <typename T, detail::enable_if_t<std::is_integral<T>::value, int> = 0>
     // NOLINTNEXTLINE(google-explicit-constructor)
     int_(T value) {
-        if (PYBIND11_SILENCE_MSVC_C4127(sizeof(T) <= sizeof(long))) {
+        if (sizeof(T) <= sizeof(long)) {
             if (std::is_signed<T>::value) {
                 m_ptr = PyLong_FromLong((long) value);
             } else {

include/pybind11/stl_bind.h

@@ -10,10 +10,13 @@
 #pragma once
 
 #include "detail/common.h"
+#include "detail/type_caster_base.h"
+#include "cast.h"
 #include "operators.h"
 
 #include <algorithm>
 #include <sstream>
+#include <type_traits>
 
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 PYBIND11_NAMESPACE_BEGIN(detail)
@@ -636,18 +639,52 @@ auto map_if_insertion_operator(Class_ &cl, std::string const &name)
         "Return the canonical string representation of this map.");
 }
 
-template <typename Map>
+template <typename KeyType>
 struct keys_view {
-    Map &map;
+    virtual size_t len() = 0;
+    virtual iterator iter() = 0;
+    virtual bool contains(const KeyType &k) = 0;
+    virtual bool contains(const object &k) = 0;
+    virtual ~keys_view() = default;
 };
 
-template <typename Map>
+template <typename MappedType>
 struct values_view {
-    Map &map;
+    virtual size_t len() = 0;
+    virtual iterator iter() = 0;
+    virtual ~values_view() = default;
 };
 
-template <typename Map>
+template <typename KeyType, typename MappedType>
 struct items_view {
+    virtual size_t len() = 0;
+    virtual iterator iter() = 0;
+    virtual ~items_view() = default;
+};
+
+template <typename Map, typename KeysView>
+struct KeysViewImpl : public KeysView {
+    explicit KeysViewImpl(Map &map) : map(map) {}
+    size_t len() override { return map.size(); }
+    iterator iter() override { return make_key_iterator(map.begin(), map.end()); }
+    bool contains(const typename Map::key_type &k) override { return map.find(k) != map.end(); }
+    bool contains(const object &) override { return false; }
+    Map &map;
+};
+
+template <typename Map, typename ValuesView>
+struct ValuesViewImpl : public ValuesView {
+    explicit ValuesViewImpl(Map &map) : map(map) {}
+    size_t len() override { return map.size(); }
+    iterator iter() override { return make_value_iterator(map.begin(), map.end()); }
+    Map &map;
+};
+
+template <typename Map, typename ItemsView>
+struct ItemsViewImpl : public ItemsView {
+    explicit ItemsViewImpl(Map &map) : map(map) {}
+    size_t len() override { return map.size(); }
+    iterator iter() override { return make_iterator(map.begin(), map.end()); }
     Map &map;
 };
 
@@ -657,9 +694,11 @@ template <typename Map, typename holder_type = std::unique_ptr<Map>, typename...
 class_<Map, holder_type> bind_map(handle scope, const std::string &name, Args &&...args) {
     using KeyType = typename Map::key_type;
     using MappedType = typename Map::mapped_type;
-    using KeysView = detail::keys_view<Map>;
-    using ValuesView = detail::values_view<Map>;
-    using ItemsView = detail::items_view<Map>;
+    using StrippedKeyType = detail::remove_cvref_t<KeyType>;
+    using StrippedMappedType = detail::remove_cvref_t<MappedType>;
+    using KeysView = detail::keys_view<StrippedKeyType>;
+    using ValuesView = detail::values_view<StrippedMappedType>;
+    using ItemsView = detail::items_view<StrippedKeyType, StrippedMappedType>;
     using Class_ = class_<Map, holder_type>;
 
     // If either type is a non-module-local bound type then make the map binding non-local as well;
@@ -673,12 +712,57 @@ class_<Map, holder_type> bind_map(handle scope, const std::string &name, Args &&
     }
 
     Class_ cl(scope, name.c_str(), pybind11::module_local(local), std::forward<Args>(args)...);
-    class_<KeysView> keys_view(
-        scope, ("KeysView[" + name + "]").c_str(), pybind11::module_local(local));
-    class_<ValuesView> values_view(
-        scope, ("ValuesView[" + name + "]").c_str(), pybind11::module_local(local));
-    class_<ItemsView> items_view(
-        scope, ("ItemsView[" + name + "]").c_str(), pybind11::module_local(local));
+    static constexpr auto key_type_descr = detail::make_caster<KeyType>::name;
+    static constexpr auto mapped_type_descr = detail::make_caster<MappedType>::name;
+    std::string key_type_name(key_type_descr.text), mapped_type_name(mapped_type_descr.text);
+
+    // If key type isn't properly wrapped, fall back to C++ names
+    if (key_type_name == "%") {
+        key_type_name = detail::type_info_description(typeid(KeyType));
+    }
+    // Similarly for value type:
+    if (mapped_type_name == "%") {
+        mapped_type_name = detail::type_info_description(typeid(MappedType));
+    }
+
+    // Wrap KeysView[KeyType] if it wasn't already wrapped
+    if (!detail::get_type_info(typeid(KeysView))) {
+        class_<KeysView> keys_view(
+            scope, ("KeysView[" + key_type_name + "]").c_str(), pybind11::module_local(local));
+        keys_view.def("__len__", &KeysView::len);
+        keys_view.def("__iter__",
+                      &KeysView::iter,
+                      keep_alive<0, 1>() /* Essential: keep view alive while iterator exists */
+        );
+        keys_view.def("__contains__",
+                      static_cast<bool (KeysView::*)(const KeyType &)>(&KeysView::contains));
+        // Fallback for when the object is not of the key type
+        keys_view.def("__contains__",
+                      static_cast<bool (KeysView::*)(const object &)>(&KeysView::contains));
+    }
+    // Similarly for ValuesView:
+    if (!detail::get_type_info(typeid(ValuesView))) {
+        class_<ValuesView> values_view(scope,
+                                       ("ValuesView[" + mapped_type_name + "]").c_str(),
+                                       pybind11::module_local(local));
+        values_view.def("__len__", &ValuesView::len);
+        values_view.def("__iter__",
+                        &ValuesView::iter,
+                        keep_alive<0, 1>() /* Essential: keep view alive while iterator exists */
+        );
+    }
+    // Similarly for ItemsView:
+    if (!detail::get_type_info(typeid(ItemsView))) {
+        class_<ItemsView> items_view(
+            scope,
+            ("ItemsView[" + key_type_name + ", ").append(mapped_type_name + "]").c_str(),
+            pybind11::module_local(local));
+        items_view.def("__len__", &ItemsView::len);
+        items_view.def("__iter__",
+                       &ItemsView::iter,
+                       keep_alive<0, 1>() /* Essential: keep view alive while iterator exists */
+        );
+    }
 
     cl.def(init<>());
 
@@ -698,19 +782,25 @@ class_<Map, holder_type> bind_map(handle scope, const std::string &name, Args &&
 
     cl.def(
         "keys",
-        [](Map &m) { return KeysView{m}; },
+        [](Map &m) {
+            return std::unique_ptr<KeysView>(new detail::KeysViewImpl<Map, KeysView>(m));
+        },
         keep_alive<0, 1>() /* Essential: keep map alive while view exists */
     );
 
     cl.def(
         "values",
-        [](Map &m) { return ValuesView{m}; },
+        [](Map &m) {
+            return std::unique_ptr<ValuesView>(new detail::ValuesViewImpl<Map, ValuesView>(m));
+        },
         keep_alive<0, 1>() /* Essential: keep map alive while view exists */
     );
 
     cl.def(
         "items",
-        [](Map &m) { return ItemsView{m}; },
+        [](Map &m) {
+            return std::unique_ptr<ItemsView>(new detail::ItemsViewImpl<Map, ItemsView>(m));
+        },
         keep_alive<0, 1>() /* Essential: keep map alive while view exists */
     );
 
@@ -749,36 +839,6 @@ class_<Map, holder_type> bind_map(handle scope, const std::string &name, Args &&
 
     cl.def("__len__", &Map::size);
 
-    keys_view.def("__len__", [](KeysView &view) { return view.map.size(); });
-    keys_view.def(
-        "__iter__",
-        [](KeysView &view) { return make_key_iterator(view.map.begin(), view.map.end()); },
-        keep_alive<0, 1>() /* Essential: keep view alive while iterator exists */
-    );
-    keys_view.def("__contains__", [](KeysView &view, const KeyType &k) -> bool {
-        auto it = view.map.find(k);
-        if (it == view.map.end()) {
-            return false;
-        }
-        return true;
-    });
-    // Fallback for when the object is not of the key type
-    keys_view.def("__contains__", [](KeysView &, const object &) -> bool { return false; });
-
-    values_view.def("__len__", [](ValuesView &view) { return view.map.size(); });
-    values_view.def(
-        "__iter__",
-        [](ValuesView &view) { return make_value_iterator(view.map.begin(), view.map.end()); },
-        keep_alive<0, 1>() /* Essential: keep view alive while iterator exists */
-    );
-
-    items_view.def("__len__", [](ItemsView &view) { return view.map.size(); });
-    items_view.def(
-        "__iter__",
-        [](ItemsView &view) { return make_iterator(view.map.begin(), view.map.end()); },
-        keep_alive<0, 1>() /* Essential: keep view alive while iterator exists */
-    );
-
     return cl;
 }
 

pybind11/_version.py

@@ -8,5 +8,5 @@ def _to_int(s: str) -> Union[int, str]:
         return s
 
 
-__version__ = "2.10.1"
+__version__ = "2.10.2"
 version_info = tuple(_to_int(s) for s in __version__.split("."))

setup.cfg

@@ -46,5 +46,5 @@ zip_safe = False
 max-line-length = 120
 show_source = True
 exclude = .git, __pycache__, build, dist, docs, tools, venv
-extend-ignore = E203, E722, B903, B950
-extend-select = B9
+extend-ignore = E203, E722
+extend-select = B902, B904

tests/CMakeLists.txt

@@ -128,7 +128,8 @@ set(PYBIND11_TEST_FILES
     test_custom_type_casters
     test_custom_type_setup
     test_docstring_options
-    test_eigen
+    test_eigen_matrix
+    test_eigen_tensor
     test_enum
     test_eval
     test_exceptions
@@ -233,7 +234,10 @@ list(GET PYBIND11_EIGEN_VERSION_AND_HASH 1 PYBIND11_EIGEN_VERSION_HASH)
 # Check if Eigen is available; if not, remove from PYBIND11_TEST_FILES (but
 # keep it in PYBIND11_PYTEST_FILES, so that we get the "eigen is not installed"
 # skip message).
-list(FIND PYBIND11_TEST_FILES test_eigen.cpp PYBIND11_TEST_FILES_EIGEN_I)
+list(FIND PYBIND11_TEST_FILES test_eigen_matrix.cpp PYBIND11_TEST_FILES_EIGEN_I)
+if(PYBIND11_TEST_FILES_EIGEN_I EQUAL -1)
+  list(FIND PYBIND11_TEST_FILES test_eigen_tensor.cpp PYBIND11_TEST_FILES_EIGEN_I)
+endif()
 if(PYBIND11_TEST_FILES_EIGEN_I GREATER -1)
   # Try loading via newer Eigen's Eigen3Config first (bypassing tools/FindEigen3.cmake).
   # Eigen 3.3.1+ exports a cmake 3.0+ target for handling dependency requirements, but also
@@ -288,13 +292,34 @@ if(PYBIND11_TEST_FILES_EIGEN_I GREATER -1)
       set(EIGEN3_VERSION ${EIGEN3_VERSION_STRING})
     endif()
     message(STATUS "Building tests with Eigen v${EIGEN3_VERSION}")
+
+    if(NOT (CMAKE_CXX_COMPILER_ID STREQUAL "GNU" AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS 5.0))
+      tests_extra_targets("test_eigen_tensor.py" "eigen_tensor_avoid_stl_array")
+    endif()
+
   else()
-    list(REMOVE_AT PYBIND11_TEST_FILES ${PYBIND11_TEST_FILES_EIGEN_I})
+    list(FIND PYBIND11_TEST_FILES test_eigen_matrix.cpp PYBIND11_TEST_FILES_EIGEN_I)
+    if(PYBIND11_TEST_FILES_EIGEN_I GREATER -1)
+      list(REMOVE_AT PYBIND11_TEST_FILES ${PYBIND11_TEST_FILES_EIGEN_I})
+    endif()
+
+    list(FIND PYBIND11_TEST_FILES test_eigen_tensor.cpp PYBIND11_TEST_FILES_EIGEN_I)
+    if(PYBIND11_TEST_FILES_EIGEN_I GREATER -1)
+      list(REMOVE_AT PYBIND11_TEST_FILES ${PYBIND11_TEST_FILES_EIGEN_I})
+    endif()
     message(
       STATUS "Building tests WITHOUT Eigen, use -DDOWNLOAD_EIGEN=ON on CMake 3.11+ to download")
   endif()
 endif()
 
+# Some code doesn't support gcc 4
+if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU" AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS 5.0)
+  list(FIND PYBIND11_TEST_FILES test_eigen_tensor.cpp PYBIND11_TEST_FILES_EIGEN_I)
+  if(PYBIND11_TEST_FILES_EIGEN_I GREATER -1)
+    list(REMOVE_AT PYBIND11_TEST_FILES ${PYBIND11_TEST_FILES_EIGEN_I})
+  endif()
+endif()
+
 # Optional dependency for some tests (boost::variant is only supported with version >= 1.56)
 find_package(Boost 1.56)
 

tests/conftest.py

@@ -7,6 +7,8 @@ Adds docstring and exceptions message sanitizers.
 import contextlib
 import difflib
 import gc
+import multiprocessing
+import os
 import re
 import textwrap
 
@@ -15,6 +17,22 @@ import pytest
 # Early diagnostic for failed imports
 import pybind11_tests
 
+
+@pytest.fixture(scope="session", autouse=True)
+def always_forkserver_on_unix():
+    if os.name == "nt":
+        return
+
+    # Full background: https://github.com/pybind/pybind11/issues/4105#issuecomment-1301004592
+    # In a nutshell: fork() after starting threads == flakiness in the form of deadlocks.
+    # It is actually a well-known pitfall, unfortunately without guard rails.
+    # "forkserver" is more performant than "spawn" (~9s vs ~13s for tests/test_gil_scoped.py,
+    # visit the issuecomment link above for details).
+    # Windows does not have fork() and the associated pitfall, therefore it is best left
+    # running with defaults.
+    multiprocessing.set_start_method("forkserver")
+
+
 _long_marker = re.compile(r"([0-9])L")
 _hexadecimal = re.compile(r"0x[0-9a-fA-F]+")
 

tests/eigen_tensor_avoid_stl_array.cpp

+/*
+    tests/eigen_tensor.cpp -- automatic conversion of Eigen Tensor
+
+    All rights reserved. Use of this source code is governed by a
+    BSD-style license that can be found in the LICENSE file.
+*/
+
+#ifndef EIGEN_AVOID_STL_ARRAY
+#    define EIGEN_AVOID_STL_ARRAY
+#endif
+
+#include "test_eigen_tensor.inl"
+
+PYBIND11_MODULE(eigen_tensor_avoid_stl_array, m) { eigen_tensor_test::test_module(m); }

tests/extra_python_package/test_files.py

@@ -55,6 +55,11 @@ detail_headers = {
     "include/pybind11/detail/typeid.h",
 }
 
+eigen_headers = {
+    "include/pybind11/eigen/matrix.h",
+    "include/pybind11/eigen/tensor.h",
+}
+
 stl_headers = {
     "include/pybind11/stl/filesystem.h",
 }
@@ -82,7 +87,7 @@ py_files = {
     "setup_helpers.py",
 }
 
-headers = main_headers | detail_headers | stl_headers
+headers = main_headers | detail_headers | eigen_headers | stl_headers
 src_files = headers | cmake_files | pkgconfig_files
 all_files = src_files | py_files
 
@@ -92,6 +97,7 @@ sdist_files = {
     "pybind11/include",
     "pybind11/include/pybind11",
     "pybind11/include/pybind11/detail",
+    "pybind11/include/pybind11/eigen",
     "pybind11/include/pybind11/stl",
     "pybind11/share",
     "pybind11/share/cmake",

tests/test_builtin_casters.cpp

@@ -73,6 +73,9 @@ PYBIND11_NAMESPACE_END(detail)
 PYBIND11_NAMESPACE_END(pybind11)
 
 TEST_SUBMODULE(builtin_casters, m) {
+    PYBIND11_WARNING_PUSH
+    PYBIND11_WARNING_DISABLE_MSVC(4127)
+
     // test_simple_string
     m.def("string_roundtrip", [](const char *s) { return s; });
 
@@ -86,7 +89,7 @@ TEST_SUBMODULE(builtin_casters, m) {
     std::wstring wstr;
     wstr.push_back(0x61);   // a
     wstr.push_back(0x2e18); // ⸘
-    if (PYBIND11_SILENCE_MSVC_C4127(sizeof(wchar_t) == 2)) {
+    if (sizeof(wchar_t) == 2) {
         wstr.push_back(mathbfA16_1);
         wstr.push_back(mathbfA16_2);
     } // 𝐀, utf16
@@ -113,7 +116,7 @@ TEST_SUBMODULE(builtin_casters, m) {
     // Under Python 2.7, invalid unicode UTF-32 characters didn't appear to trigger
     // UnicodeDecodeError
     m.def("bad_utf32_string", [=]() { return std::u32string({a32, char32_t(0xd800), z32}); });
-    if (PYBIND11_SILENCE_MSVC_C4127(sizeof(wchar_t) == 2)) {
+    if (sizeof(wchar_t) == 2) {
         m.def("bad_wchar_string", [=]() {
             return std::wstring({wchar_t(0x61), wchar_t(0xd800)});
         });
@@ -384,4 +387,6 @@ TEST_SUBMODULE(builtin_casters, m) {
     m.def("takes_const_ref", [](const ConstRefCasted &x) { return x.tag; });
     m.def("takes_const_ref_wrap",
           [](std::reference_wrapper<const ConstRefCasted> x) { return x.get().tag; });
+
+    PYBIND11_WARNING_POP
 }

tests/test_callbacks.cpp

@@ -240,4 +240,41 @@ TEST_SUBMODULE(callbacks, m) {
             f();
         }
     });
+
+    auto *custom_def = []() {
+        static PyMethodDef def;
+        def.ml_name = "example_name";
+        def.ml_doc = "Example doc";
+        def.ml_meth = [](PyObject *, PyObject *args) -> PyObject * {
+            if (PyTuple_Size(args) != 1) {
+                throw std::runtime_error("Invalid number of arguments for example_name");
+            }
+            PyObject *first = PyTuple_GetItem(args, 0);
+            if (!PyLong_Check(first)) {
+                throw std::runtime_error("Invalid argument to example_name");
+            }
+            auto result = py::cast(PyLong_AsLong(first) * 9);
+            return result.release().ptr();
+        };
+        def.ml_flags = METH_VARARGS;
+        return &def;
+    }();
+
+    // rec_capsule with name that has the same value (but not pointer) as our internal one
+    // This capsule should be detected by our code as foreign and not inspected as the pointers
+    // shouldn't match
+    constexpr const char *rec_capsule_name
+        = pybind11::detail::internals_function_record_capsule_name;
+    py::capsule rec_capsule(std::malloc(1), [](void *data) { std::free(data); });
+    rec_capsule.set_name(rec_capsule_name);
+    m.add_object("custom_function", PyCFunction_New(custom_def, rec_capsule.ptr()));
+
+    // This test requires a new ABI version to pass
+#if PYBIND11_INTERNALS_VERSION > 4
+    // rec_capsule with nullptr name
+    py::capsule rec_capsule2(std::malloc(1), [](void *data) { std::free(data); });
+    m.add_object("custom_function2", PyCFunction_New(custom_def, rec_capsule2.ptr()));
+#else
+    m.add_object("custom_function2", py::none());
+#endif
 }

tests/test_callbacks.py

@@ -193,3 +193,16 @@ def test_callback_num_times():
     if len(rates) > 1:
         print("Min    Mean   Max")
         print(f"{min(rates):6.3f} {sum(rates) / len(rates):6.3f} {max(rates):6.3f}")
+
+
+def test_custom_func():
+    assert m.custom_function(4) == 36
+    assert m.roundtrip(m.custom_function)(4) == 36
+
+
+@pytest.mark.skipif(
+    m.custom_function2 is None, reason="Current PYBIND11_INTERNALS_VERSION too low"
+)
+def test_custom_func2():
+    assert m.custom_function2(3) == 27
+    assert m.roundtrip(m.custom_function2)(3) == 27

tests/test_class.cpp

@@ -22,10 +22,8 @@
 
 #include <utility>
 
-#if defined(_MSC_VER)
-#    pragma warning(disable : 4324)
+PYBIND11_WARNING_DISABLE_MSVC(4324)
 //     warning C4324: structure was padded due to alignment specifier
-#endif
 
 // test_brace_initialization
 struct NoBraceInitialization {

tests/test_constants_and_functions.cpp

@@ -52,15 +52,12 @@ int f1(int x) noexcept { return x + 1; }
 #endif
 int f2(int x) noexcept(true) { return x + 2; }
 int f3(int x) noexcept(false) { return x + 3; }
-#if defined(__GNUG__) && !defined(__INTEL_COMPILER)
-#    pragma GCC diagnostic push
-#    pragma GCC diagnostic ignored "-Wdeprecated"
-#endif
+PYBIND11_WARNING_PUSH
+PYBIND11_WARNING_DISABLE_GCC("-Wdeprecated")
+PYBIND11_WARNING_DISABLE_CLANG("-Wdeprecated")
 // NOLINTNEXTLINE(modernize-use-noexcept)
 int f4(int x) throw() { return x + 4; } // Deprecated equivalent to noexcept(true)
-#if defined(__GNUG__) && !defined(__INTEL_COMPILER)
-#    pragma GCC diagnostic pop
-#endif
+PYBIND11_WARNING_POP
 struct C {
     int m1(int x) noexcept { return x - 1; }
     int m2(int x) const noexcept { return x - 2; }
@@ -68,17 +65,14 @@ struct C {
     int m4(int x) const noexcept(true) { return x - 4; }
     int m5(int x) noexcept(false) { return x - 5; }
     int m6(int x) const noexcept(false) { return x - 6; }
-#if defined(__GNUG__) && !defined(__INTEL_COMPILER)
-#    pragma GCC diagnostic push
-#    pragma GCC diagnostic ignored "-Wdeprecated"
-#endif
+    PYBIND11_WARNING_PUSH
+    PYBIND11_WARNING_DISABLE_GCC("-Wdeprecated")
+    PYBIND11_WARNING_DISABLE_CLANG("-Wdeprecated")
     // NOLINTNEXTLINE(modernize-use-noexcept)
     int m7(int x) throw() { return x - 7; }
     // NOLINTNEXTLINE(modernize-use-noexcept)
     int m8(int x) const throw() { return x - 8; }
-#if defined(__GNUG__) && !defined(__INTEL_COMPILER)
-#    pragma GCC diagnostic pop
-#endif
+    PYBIND11_WARNING_POP
 };
 } // namespace test_exc_sp
 
@@ -126,14 +120,12 @@ TEST_SUBMODULE(constants_and_functions, m) {
         .def("m8", &C::m8);
     m.def("f1", f1);
     m.def("f2", f2);
-#if defined(__INTEL_COMPILER)
-#    pragma warning push
-#    pragma warning disable 878 // incompatible exception specifications
-#endif
+
+    PYBIND11_WARNING_PUSH
+    PYBIND11_WARNING_DISABLE_INTEL(878) // incompatible exception specifications
     m.def("f3", f3);
-#if defined(__INTEL_COMPILER)
-#    pragma warning pop
-#endif
+    PYBIND11_WARNING_POP
+
     m.def("f4", f4);
 
     // test_function_record_leaks

tests/test_docstring_options.cpp

@@ -85,4 +85,57 @@ TEST_SUBMODULE(docstring_options, m) {
                           &DocstringTestFoo::setValue,
                           "This is a property docstring");
     }
+
+    {
+        enum class DocstringTestEnum1 { Member1, Member2 };
+
+        py::enum_<DocstringTestEnum1>(m, "DocstringTestEnum1", "Enum docstring")
+            .value("Member1", DocstringTestEnum1::Member1)
+            .value("Member2", DocstringTestEnum1::Member2);
+    }
+
+    {
+        py::options options;
+        options.enable_enum_members_docstring();
+
+        enum class DocstringTestEnum2 { Member1, Member2 };
+
+        py::enum_<DocstringTestEnum2>(m, "DocstringTestEnum2", "Enum docstring")
+            .value("Member1", DocstringTestEnum2::Member1)
+            .value("Member2", DocstringTestEnum2::Member2);
+    }
+
+    {
+        py::options options;
+        options.disable_enum_members_docstring();
+
+        enum class DocstringTestEnum3 { Member1, Member2 };
+
+        py::enum_<DocstringTestEnum3>(m, "DocstringTestEnum3", "Enum docstring")
+            .value("Member1", DocstringTestEnum3::Member1)
+            .value("Member2", DocstringTestEnum3::Member2);
+    }
+
+    {
+        py::options options;
+        options.disable_user_defined_docstrings();
+
+        enum class DocstringTestEnum4 { Member1, Member2 };
+
+        py::enum_<DocstringTestEnum4>(m, "DocstringTestEnum4", "Enum docstring")
+            .value("Member1", DocstringTestEnum4::Member1)
+            .value("Member2", DocstringTestEnum4::Member2);
+    }
+
+    {
+        py::options options;
+        options.disable_user_defined_docstrings();
+        options.disable_enum_members_docstring();
+
+        enum class DocstringTestEnum5 { Member1, Member2 };
+
+        py::enum_<DocstringTestEnum5>(m, "DocstringTestEnum5", "Enum docstring")
+            .value("Member1", DocstringTestEnum5::Member1)
+            .value("Member2", DocstringTestEnum5::Member2);
+    }
 }