/* 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" NAMESPACE_BEGIN(PYBIND11_NAMESPACE) 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 &; operator value_and_holder &() { return *value; } static PYBIND11_DESCR name() { return type_descr(_<value_and_holder>()); } private: value_and_holder *value = nullptr; }; 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) { no_nullptr(ptr); if (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) { auto *ptr = holder_helper<Holder<Class>>::get(holder); // If we need an alias, check that the held pointer is actually an alias instance if (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) { static_assert(std::is_move_constructible<Cpp<Class>>::value, "pybind11::init() return-by-value factory function requires a movable class"); if (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; 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); setattr((PyObject *) v_h.inst, "__dict__", result.second); } /// 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...); } }; NAMESPACE_END(initimpl) NAMESPACE_END(detail) NAMESPACE_END(pybind11)