File indexing completed on 2025-02-23 05:15:01

 /*
     pybind11/detail/init.h: init factory function implementation and support code.
 
     Copyright (c) 2017 Jason Rhinelander <jason@imaginary.ca>
 
     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 "class.h"
 
 PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
 PYBIND11_NAMESPACE_BEGIN(detail)
 
 template <>
 class type_caster<value_and_holder> {
 public:
     bool load(handle h, bool) {
         value = reinterpret_cast<value_and_holder *>(h.ptr());
         return true;
     }
 
     template <typename> using cast_op_type = value_and_holder &;
     explicit operator value_and_holder &() { return *value; }
     static constexpr auto name = const_name<value_and_holder>();
 
 private:
     value_and_holder *value = nullptr;
 };
 
 PYBIND11_NAMESPACE_BEGIN(initimpl)
 
 inline void no_nullptr(void *ptr) {
     if (!ptr) throw type_error("pybind11::init(): factory function returned nullptr");
 }
 
 // Implementing functions for all forms of py::init<...> and py::init(...)
 template <typename Class> using Cpp = typename Class::type;
 template <typename Class> using Alias = typename Class::type_alias;
 template <typename Class> using Holder = typename Class::holder_type;
 
 template <typename Class> using is_alias_constructible = std::is_constructible<Alias<Class>, Cpp<Class> &&>;
 
 // Takes a Cpp pointer and returns true if it actually is a polymorphic Alias instance.
 template <typename Class, enable_if_t<Class::has_alias, int> = 0>
 bool is_alias(Cpp<Class> *ptr) {
     return dynamic_cast<Alias<Class> *>(ptr) != nullptr;
 }
 // Failing fallback version of the above for a no-alias class (always returns false)
 template <typename /*Class*/>
 constexpr bool is_alias(void *) { return false; }
 
 // Constructs and returns a new object; if the given arguments don't map to a constructor, we fall
 // back to brace aggregate initiailization so that for aggregate initialization can be used with
 // py::init, e.g.  `py::init<int, int>` to initialize a `struct T { int a; int b; }`.  For
 // non-aggregate types, we need to use an ordinary T(...) constructor (invoking as `T{...}` usually
 // works, but will not do the expected thing when `T` has an `initializer_list<T>` constructor).
 template <typename Class, typename... Args, detail::enable_if_t<std::is_constructible<Class, Args...>::value, int> = 0>
 inline Class *construct_or_initialize(Args &&...args) { return new Class(std::forward<Args>(args)...); }
 template <typename Class, typename... Args, detail::enable_if_t<!std::is_constructible<Class, Args...>::value, int> = 0>
 inline Class *construct_or_initialize(Args &&...args) { return new Class{std::forward<Args>(args)...}; }
 
 // Attempts to constructs an alias using a `Alias(Cpp &&)` constructor.  This allows types with
 // an alias to provide only a single Cpp factory function as long as the Alias can be
 // constructed from an rvalue reference of the base Cpp type.  This means that Alias classes
 // can, when appropriate, simply define a `Alias(Cpp &&)` constructor rather than needing to
 // inherit all the base class constructors.
 template <typename Class>
 void construct_alias_from_cpp(std::true_type /*is_alias_constructible*/,
                               value_and_holder &v_h, Cpp<Class> &&base) {
     v_h.value_ptr() = new Alias<Class>(std::move(base));
 }
 template <typename Class>
 [[noreturn]] void construct_alias_from_cpp(std::false_type /*!is_alias_constructible*/,
                                            value_and_holder &, Cpp<Class> &&) {
     throw type_error("pybind11::init(): unable to convert returned instance to required "
                      "alias class: no `Alias<Class>(Class &&)` constructor available");
 }
 
 // Error-generating fallback for factories that don't match one of the below construction
 // mechanisms.
 template <typename Class>
 void construct(...) {
     static_assert(!std::is_same<Class, Class>::value /* always false */,
             "pybind11::init(): init function must return a compatible pointer, "
             "holder, or value");
 }
 
 // Pointer return v1: the factory function returns a class pointer for a registered class.
 // If we don't need an alias (because this class doesn't have one, or because the final type is
 // inherited on the Python side) we can simply take over ownership.  Otherwise we need to try to
 // construct an Alias from the returned base instance.
 template <typename Class>
 void construct(value_and_holder &v_h, Cpp<Class> *ptr, bool need_alias) {
     PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(need_alias);
     no_nullptr(ptr);
     if (PYBIND11_SILENCE_MSVC_C4127(Class::has_alias) && need_alias && !is_alias<Class>(ptr)) {
         // We're going to try to construct an alias by moving the cpp type.  Whether or not
         // that succeeds, we still need to destroy the original cpp pointer (either the
         // moved away leftover, if the alias construction works, or the value itself if we
         // throw an error), but we can't just call `delete ptr`: it might have a special
         // deleter, or might be shared_from_this.  So we construct a holder around it as if
         // it was a normal instance, then steal the holder away into a local variable; thus
         // the holder and destruction happens when we leave the C++ scope, and the holder
         // class gets to handle the destruction however it likes.
         v_h.value_ptr() = ptr;
         v_h.set_instance_registered(true); // To prevent init_instance from registering it
         v_h.type->init_instance(v_h.inst, nullptr); // Set up the holder
         Holder<Class> temp_holder(std::move(v_h.holder<Holder<Class>>())); // Steal the holder
         v_h.type->dealloc(v_h); // Destroys the moved-out holder remains, resets value ptr to null
         v_h.set_instance_registered(false);
 
         construct_alias_from_cpp<Class>(is_alias_constructible<Class>{}, v_h, std::move(*ptr));
     } else {
         // Otherwise the type isn't inherited, so we don't need an Alias
         v_h.value_ptr() = ptr;
     }
 }
 
 // Pointer return v2: a factory that always returns an alias instance ptr.  We simply take over
 // ownership of the pointer.
 template <typename Class, enable_if_t<Class::has_alias, int> = 0>
 void construct(value_and_holder &v_h, Alias<Class> *alias_ptr, bool) {
     no_nullptr(alias_ptr);
     v_h.value_ptr() = static_cast<Cpp<Class> *>(alias_ptr);
 }
 
 // Holder return: copy its pointer, and move or copy the returned holder into the new instance's
 // holder.  This also handles types like std::shared_ptr<T> and std::unique_ptr<T> where T is a
 // derived type (through those holder's implicit conversion from derived class holder constructors).
 template <typename Class>
 void construct(value_and_holder &v_h, Holder<Class> holder, bool need_alias) {
     PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(need_alias);
     auto *ptr = holder_helper<Holder<Class>>::get(holder);
     no_nullptr(ptr);
     // If we need an alias, check that the held pointer is actually an alias instance
     if (PYBIND11_SILENCE_MSVC_C4127(Class::has_alias) && need_alias && !is_alias<Class>(ptr))
         throw type_error("pybind11::init(): construction failed: returned holder-wrapped instance "
                          "is not an alias instance");
 
     v_h.value_ptr() = ptr;
     v_h.type->init_instance(v_h.inst, &holder);
 }
 
 // return-by-value version 1: returning a cpp class by value.  If the class has an alias and an
 // alias is required the alias must have an `Alias(Cpp &&)` constructor so that we can construct
 // the alias from the base when needed (i.e. because of Python-side inheritance).  When we don't
 // need it, we simply move-construct the cpp value into a new instance.
 template <typename Class>
 void construct(value_and_holder &v_h, Cpp<Class> &&result, bool need_alias) {
     PYBIND11_WORKAROUND_INCORRECT_MSVC_C4100(need_alias);
     static_assert(std::is_move_constructible<Cpp<Class>>::value,
         "pybind11::init() return-by-value factory function requires a movable class");
     if (PYBIND11_SILENCE_MSVC_C4127(Class::has_alias) && need_alias)
         construct_alias_from_cpp<Class>(is_alias_constructible<Class>{}, v_h, std::move(result));
     else
         v_h.value_ptr() = new Cpp<Class>(std::move(result));
 }
 
 // return-by-value version 2: returning a value of the alias type itself.  We move-construct an
 // Alias instance (even if no the python-side inheritance is involved).  The is intended for
 // cases where Alias initialization is always desired.
 template <typename Class>
 void construct(value_and_holder &v_h, Alias<Class> &&result, bool) {
     static_assert(std::is_move_constructible<Alias<Class>>::value,
         "pybind11::init() return-by-alias-value factory function requires a movable alias class");
     v_h.value_ptr() = new Alias<Class>(std::move(result));
 }
 
 // Implementing class for py::init<...>()
 template <typename... Args>
 struct constructor {
     template <typename Class, typename... Extra, enable_if_t<!Class::has_alias, int> = 0>
     static void execute(Class &cl, const Extra&... extra) {
         cl.def("__init__", [](value_and_holder &v_h, Args... args) {
             v_h.value_ptr() = construct_or_initialize<Cpp<Class>>(std::forward<Args>(args)...);
         }, is_new_style_constructor(), extra...);
     }
 
     template <typename Class, typename... Extra,
               enable_if_t<Class::has_alias &&
                           std::is_constructible<Cpp<Class>, Args...>::value, int> = 0>
     static void execute(Class &cl, const Extra&... extra) {
         cl.def("__init__", [](value_and_holder &v_h, Args... args) {
             if (Py_TYPE(v_h.inst) == v_h.type->type)
                 v_h.value_ptr() = construct_or_initialize<Cpp<Class>>(std::forward<Args>(args)...);
             else
                 v_h.value_ptr() = construct_or_initialize<Alias<Class>>(std::forward<Args>(args)...);
         }, is_new_style_constructor(), extra...);
     }
 
     template <typename Class, typename... Extra,
               enable_if_t<Class::has_alias &&
                           !std::is_constructible<Cpp<Class>, Args...>::value, int> = 0>
     static void execute(Class &cl, const Extra&... extra) {
         cl.def("__init__", [](value_and_holder &v_h, Args... args) {
             v_h.value_ptr() = construct_or_initialize<Alias<Class>>(std::forward<Args>(args)...);
         }, is_new_style_constructor(), extra...);
     }
 };
 
 // Implementing class for py::init_alias<...>()
 template <typename... Args> struct alias_constructor {
     template <typename Class, typename... Extra,
               enable_if_t<Class::has_alias && std::is_constructible<Alias<Class>, Args...>::value, int> = 0>
     static void execute(Class &cl, const Extra&... extra) {
         cl.def("__init__", [](value_and_holder &v_h, Args... args) {
             v_h.value_ptr() = construct_or_initialize<Alias<Class>>(std::forward<Args>(args)...);
         }, is_new_style_constructor(), extra...);
     }
 };
 
 // Implementation class for py::init(Func) and py::init(Func, AliasFunc)
 template <typename CFunc, typename AFunc = void_type (*)(),
           typename = function_signature_t<CFunc>, typename = function_signature_t<AFunc>>
 struct factory;
 
 // Specialization for py::init(Func)
 template <typename Func, typename Return, typename... Args>
 struct factory<Func, void_type (*)(), Return(Args...)> {
     remove_reference_t<Func> class_factory;
 
     // NOLINTNEXTLINE(google-explicit-constructor)
     factory(Func &&f) : class_factory(std::forward<Func>(f)) {}
 
     // The given class either has no alias or has no separate alias factory;
     // this always constructs the class itself.  If the class is registered with an alias
     // type and an alias instance is needed (i.e. because the final type is a Python class
     // inheriting from the C++ type) the returned value needs to either already be an alias
     // instance, or the alias needs to be constructible from a `Class &&` argument.
     template <typename Class, typename... Extra>
     void execute(Class &cl, const Extra &...extra) && {
         #if defined(PYBIND11_CPP14)
         cl.def("__init__", [func = std::move(class_factory)]
         #else
         auto &func = class_factory;
         cl.def("__init__", [func]
         #endif
         (value_and_holder &v_h, Args... args) {
             construct<Class>(v_h, func(std::forward<Args>(args)...),
                              Py_TYPE(v_h.inst) != v_h.type->type);
         }, is_new_style_constructor(), extra...);
     }
 };
 
 // Specialization for py::init(Func, AliasFunc)
 template <typename CFunc, typename AFunc,
           typename CReturn, typename... CArgs, typename AReturn, typename... AArgs>
 struct factory<CFunc, AFunc, CReturn(CArgs...), AReturn(AArgs...)> {
     static_assert(sizeof...(CArgs) == sizeof...(AArgs),
                   "pybind11::init(class_factory, alias_factory): class and alias factories "
                   "must have identical argument signatures");
     static_assert(all_of<std::is_same<CArgs, AArgs>...>::value,
                   "pybind11::init(class_factory, alias_factory): class and alias factories "
                   "must have identical argument signatures");
 
     remove_reference_t<CFunc> class_factory;
     remove_reference_t<AFunc> alias_factory;
 
     factory(CFunc &&c, AFunc &&a)
         : class_factory(std::forward<CFunc>(c)), alias_factory(std::forward<AFunc>(a)) { }
 
     // The class factory is called when the `self` type passed to `__init__` is the direct
     // class (i.e. not inherited), the alias factory when `self` is a Python-side subtype.
     template <typename Class, typename... Extra>
     void execute(Class &cl, const Extra&... extra) && {
         static_assert(Class::has_alias, "The two-argument version of `py::init()` can "
                                         "only be used if the class has an alias");
         #if defined(PYBIND11_CPP14)
         cl.def("__init__", [class_func = std::move(class_factory), alias_func = std::move(alias_factory)]
         #else
         auto &class_func = class_factory;
         auto &alias_func = alias_factory;
         cl.def("__init__", [class_func, alias_func]
         #endif
         (value_and_holder &v_h, CArgs... args) {
             if (Py_TYPE(v_h.inst) == v_h.type->type)
                 // If the instance type equals the registered type we don't have inheritance, so
                 // don't need the alias and can construct using the class function:
                 construct<Class>(v_h, class_func(std::forward<CArgs>(args)...), false);
             else
                 construct<Class>(v_h, alias_func(std::forward<CArgs>(args)...), true);
         }, is_new_style_constructor(), extra...);
     }
 };
 
 /// Set just the C++ state. Same as `__init__`.
 template <typename Class, typename T>
 void setstate(value_and_holder &v_h, T &&result, bool need_alias) {
     construct<Class>(v_h, std::forward<T>(result), need_alias);
 }
 
 /// Set both the C++ and Python states
 template <typename Class, typename T, typename O,
           enable_if_t<std::is_convertible<O, handle>::value, int> = 0>
 void setstate(value_and_holder &v_h, std::pair<T, O> &&result, bool need_alias) {
     construct<Class>(v_h, std::move(result.first), need_alias);
     auto d = handle(result.second);
     if (PyDict_Check(d.ptr()) && PyDict_Size(d.ptr()) == 0) {
         // Skipping setattr below, to not force use of py::dynamic_attr() for Class unnecessarily.
         // See PR #2972 for details.
         return;
     }
     setattr((PyObject *) v_h.inst, "__dict__", d);
 }
 
 /// Implementation for py::pickle(GetState, SetState)
 template <typename Get, typename Set,
           typename = function_signature_t<Get>, typename = function_signature_t<Set>>
 struct pickle_factory;
 
 template <typename Get, typename Set,
           typename RetState, typename Self, typename NewInstance, typename ArgState>
 struct pickle_factory<Get, Set, RetState(Self), NewInstance(ArgState)> {
     static_assert(std::is_same<intrinsic_t<RetState>, intrinsic_t<ArgState>>::value,
                   "The type returned by `__getstate__` must be the same "
                   "as the argument accepted by `__setstate__`");
 
     remove_reference_t<Get> get;
     remove_reference_t<Set> set;
 
     pickle_factory(Get get, Set set)
         : get(std::forward<Get>(get)), set(std::forward<Set>(set)) { }
 
     template <typename Class, typename... Extra>
     void execute(Class &cl, const Extra &...extra) && {
         cl.def("__getstate__", std::move(get));
 
 #if defined(PYBIND11_CPP14)
         cl.def("__setstate__", [func = std::move(set)]
 #else
         auto &func = set;
         cl.def("__setstate__", [func]
 #endif
         (value_and_holder &v_h, ArgState state) {
             setstate<Class>(v_h, func(std::forward<ArgState>(state)),
                             Py_TYPE(v_h.inst) != v_h.type->type);
         }, is_new_style_constructor(), extra...);
     }
 };
 
 PYBIND11_NAMESPACE_END(initimpl)
 PYBIND11_NAMESPACE_END(detail)
 PYBIND11_NAMESPACE_END(pybind11)