ext/pybind11/tests/test_virtual_functions.cpp - amd/gem5 - Git at Google

 /*
     tests/test_virtual_functions.cpp -- overriding virtual functions from Python

     Copyright (c) 2016 Wenzel Jakob <wenzel.jakob@epfl.ch>

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

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

 /* This is an example class that we'll want to be able to extend from Python */
 class ExampleVirt  {
 public:
     ExampleVirt(int state) : state(state) { print_created(this, state); }
     ExampleVirt(const ExampleVirt &e) : state(e.state) { print_copy_created(this); }
     ExampleVirt(ExampleVirt &&e) : state(e.state) { print_move_created(this); e.state = 0; }
     ~ExampleVirt() { print_destroyed(this); }

     virtual int run(int value) {
         py::print("Original implementation of "
                   "ExampleVirt::run(state={}, value={}, str1={}, str2={})"_s.format(state, value, get_string1(), *get_string2()));
         return state + value;
     }

     virtual bool run_bool() = 0;
     virtual void pure_virtual() = 0;

     // Returning a reference/pointer to a type converted from python (numbers, strings, etc.) is a
     // bit trickier, because the actual int& or std::string& or whatever only exists temporarily, so
     // we have to handle it specially in the trampoline class (see below).
     virtual const std::string &get_string1() { return str1; }
     virtual const std::string *get_string2() { return &str2; }

 private:
     int state;
     const std::string str1{"default1"}, str2{"default2"};
 };

 /* This is a wrapper class that must be generated */
 class PyExampleVirt : public ExampleVirt {
 public:
     using ExampleVirt::ExampleVirt; /* Inherit constructors */

     int run(int value) override {
         /* Generate wrapping code that enables native function overloading */
         PYBIND11_OVERLOAD(
             int,         /* Return type */
             ExampleVirt, /* Parent class */
             run,         /* Name of function */
             value        /* Argument(s) */
         );
     }

     bool run_bool() override {
         PYBIND11_OVERLOAD_PURE(
             bool,         /* Return type */
             ExampleVirt,  /* Parent class */
             run_bool,     /* Name of function */
                           /* This function has no arguments. The trailing comma
                              in the previous line is needed for some compilers */
         );
     }

     void pure_virtual() override {
         PYBIND11_OVERLOAD_PURE(
             void,         /* Return type */
             ExampleVirt,  /* Parent class */
             pure_virtual, /* Name of function */
                           /* This function has no arguments. The trailing comma
                              in the previous line is needed for some compilers */
         );
     }

     // We can return reference types for compatibility with C++ virtual interfaces that do so, but
     // note they have some significant limitations (see the documentation).
     const std::string &get_string1() override {
         PYBIND11_OVERLOAD(
             const std::string &, /* Return type */
             ExampleVirt,         /* Parent class */
             get_string1,         /* Name of function */
                                  /* (no arguments) */
         );
     }

     const std::string *get_string2() override {
         PYBIND11_OVERLOAD(
             const std::string *, /* Return type */
             ExampleVirt,         /* Parent class */
             get_string2,         /* Name of function */
                                  /* (no arguments) */
         );
     }

 };

 class NonCopyable {
 public:
     NonCopyable(int a, int b) : value{new int(a*b)} { print_created(this, a, b); }
     NonCopyable(NonCopyable &&o) { value = std::move(o.value); print_move_created(this); }
     NonCopyable(const NonCopyable &) = delete;
     NonCopyable() = delete;
     void operator=(const NonCopyable &) = delete;
     void operator=(NonCopyable &&) = delete;
     std::string get_value() const {
         if (value) return std::to_string(*value); else return "(null)";
     }
     ~NonCopyable() { print_destroyed(this); }

 private:
     std::unique_ptr<int> value;
 };

 // This is like the above, but is both copy and movable.  In effect this means it should get moved
 // when it is not referenced elsewhere, but copied if it is still referenced.
 class Movable {
 public:
     Movable(int a, int b) : value{a+b} { print_created(this, a, b); }
     Movable(const Movable &m) { value = m.value; print_copy_created(this); }
     Movable(Movable &&m) { value = std::move(m.value); print_move_created(this); }
     std::string get_value() const { return std::to_string(value); }
     ~Movable() { print_destroyed(this); }
 private:
     int value;
 };

 class NCVirt {
 public:
     virtual NonCopyable get_noncopyable(int a, int b) { return NonCopyable(a, b); }
     virtual Movable get_movable(int a, int b) = 0;

     std::string print_nc(int a, int b) { return get_noncopyable(a, b).get_value(); }
     std::string print_movable(int a, int b) { return get_movable(a, b).get_value(); }
 };
 class NCVirtTrampoline : public NCVirt {
 #if !defined(__INTEL_COMPILER)
     NonCopyable get_noncopyable(int a, int b) override {
         PYBIND11_OVERLOAD(NonCopyable, NCVirt, get_noncopyable, a, b);
     }
 #endif
     Movable get_movable(int a, int b) override {
         PYBIND11_OVERLOAD_PURE(Movable, NCVirt, get_movable, a, b);
     }
 };

 struct Base {
     /* for some reason MSVC2015 can't compile this if the function is pure virtual */
     virtual std::string dispatch() const { return {}; };
     virtual ~Base() = default;
 };

 struct DispatchIssue : Base {
     virtual std::string dispatch() const {
         PYBIND11_OVERLOAD_PURE(std::string, Base, dispatch, /* no arguments */);
     }
 };

 // Forward declaration (so that we can put the main tests here; the inherited virtual approaches are
 // rather long).
 void initialize_inherited_virtuals(py::module &m);

 TEST_SUBMODULE(virtual_functions, m) {
     // test_override
     py::class_<ExampleVirt, PyExampleVirt>(m, "ExampleVirt")
         .def(py::init<int>())
         /* Reference original class in function definitions */
         .def("run", &ExampleVirt::run)
         .def("run_bool", &ExampleVirt::run_bool)
         .def("pure_virtual", &ExampleVirt::pure_virtual);

     py::class_<NonCopyable>(m, "NonCopyable")
         .def(py::init<int, int>());

     py::class_<Movable>(m, "Movable")
         .def(py::init<int, int>());

     // test_move_support
 #if !defined(__INTEL_COMPILER)
     py::class_<NCVirt, NCVirtTrampoline>(m, "NCVirt")
         .def(py::init<>())
         .def("get_noncopyable", &NCVirt::get_noncopyable)
         .def("get_movable", &NCVirt::get_movable)
         .def("print_nc", &NCVirt::print_nc)
         .def("print_movable", &NCVirt::print_movable);
 #endif

     m.def("runExampleVirt", [](ExampleVirt *ex, int value) { return ex->run(value); });
     m.def("runExampleVirtBool", [](ExampleVirt* ex) { return ex->run_bool(); });
     m.def("runExampleVirtVirtual", [](ExampleVirt *ex) { ex->pure_virtual(); });

     m.def("cstats_debug", &ConstructorStats::get<ExampleVirt>);
     initialize_inherited_virtuals(m);

     // test_alias_delay_initialization1
     // don't invoke Python dispatch classes by default when instantiating C++ classes
     // that were not extended on the Python side
     struct A {
         virtual ~A() {}
         virtual void f() { py::print("A.f()"); }
     };

     struct PyA : A {
         PyA() { py::print("PyA.PyA()"); }
         ~PyA() { py::print("PyA.~PyA()"); }

         void f() override {
             py::print("PyA.f()");
             PYBIND11_OVERLOAD(void, A, f);
         }
     };

     py::class_<A, PyA>(m, "A")
         .def(py::init<>())
         .def("f", &A::f);

     m.def("call_f", [](A *a) { a->f(); });

     // test_alias_delay_initialization2
     // ... unless we explicitly request it, as in this example:
     struct A2 {
         virtual ~A2() {}
         virtual void f() { py::print("A2.f()"); }
     };

     struct PyA2 : A2 {
         PyA2() { py::print("PyA2.PyA2()"); }
         ~PyA2() { py::print("PyA2.~PyA2()"); }
         void f() override {
             py::print("PyA2.f()");
             PYBIND11_OVERLOAD(void, A2, f);
         }
     };

     py::class_<A2, PyA2>(m, "A2")
         .def(py::init_alias<>())
         .def(py::init([](int) { return new PyA2(); }))
         .def("f", &A2::f);

     m.def("call_f", [](A2 *a2) { a2->f(); });

     // test_dispatch_issue
     // #159: virtual function dispatch has problems with similar-named functions
     py::class_<Base, DispatchIssue>(m, "DispatchIssue")
         .def(py::init<>())
         .def("dispatch", &Base::dispatch);

     m.def("dispatch_issue_go", [](const Base * b) { return b->dispatch(); });

     // test_override_ref
     // #392/397: overridding reference-returning functions
     class OverrideTest {
     public:
         struct A { std::string value = "hi"; };
         std::string v;
         A a;
         explicit OverrideTest(const std::string &v) : v{v} {}
         virtual std::string str_value() { return v; }
         virtual std::string &str_ref() { return v; }
         virtual A A_value() { return a; }
         virtual A &A_ref() { return a; }
         virtual ~OverrideTest() = default;
     };

     class PyOverrideTest : public OverrideTest {
     public:
         using OverrideTest::OverrideTest;
         std::string str_value() override { PYBIND11_OVERLOAD(std::string, OverrideTest, str_value); }
         // Not allowed (uncommenting should hit a static_assert failure): we can't get a reference
         // to a python numeric value, since we only copy values in the numeric type caster:
 //      std::string &str_ref() override { PYBIND11_OVERLOAD(std::string &, OverrideTest, str_ref); }
         // But we can work around it like this:
     private:
         std::string _tmp;
         std::string str_ref_helper() { PYBIND11_OVERLOAD(std::string, OverrideTest, str_ref); }
     public:
         std::string &str_ref() override { return _tmp = str_ref_helper(); }

         A A_value() override { PYBIND11_OVERLOAD(A, OverrideTest, A_value); }
         A &A_ref() override { PYBIND11_OVERLOAD(A &, OverrideTest, A_ref); }
     };

     py::class_<OverrideTest::A>(m, "OverrideTest_A")
         .def_readwrite("value", &OverrideTest::A::value);
     py::class_<OverrideTest, PyOverrideTest>(m, "OverrideTest")
         .def(py::init<const std::string &>())
         .def("str_value", &OverrideTest::str_value)
 //      .def("str_ref", &OverrideTest::str_ref)
         .def("A_value", &OverrideTest::A_value)
         .def("A_ref", &OverrideTest::A_ref);
 }


 // Inheriting virtual methods.  We do two versions here: the repeat-everything version and the
 // templated trampoline versions mentioned in docs/advanced.rst.
 //
 // These base classes are exactly the same, but we technically need distinct
 // classes for this example code because we need to be able to bind them
 // properly (pybind11, sensibly, doesn't allow us to bind the same C++ class to
 // multiple python classes).
 class A_Repeat {
 #define A_METHODS \
 public: \
     virtual int unlucky_number() = 0; \
     virtual std::string say_something(unsigned times) { \
         std::string s = ""; \
         for (unsigned i = 0; i < times; ++i) \
             s += "hi"; \
         return s; \
     } \
     std::string say_everything() { \
         return say_something(1) + " " + std::to_string(unlucky_number()); \
     }
 A_METHODS
     virtual ~A_Repeat() = default;
 };
 class B_Repeat : public A_Repeat {
 #define B_METHODS \
 public: \
     int unlucky_number() override { return 13; } \
     std::string say_something(unsigned times) override { \
         return "B says hi " + std::to_string(times) + " times"; \
     } \
     virtual double lucky_number() { return 7.0; }
 B_METHODS
 };
 class C_Repeat : public B_Repeat {
 #define C_METHODS \
 public: \
     int unlucky_number() override { return 4444; } \
     double lucky_number() override { return 888; }
 C_METHODS
 };
 class D_Repeat : public C_Repeat {
 #define D_METHODS // Nothing overridden.
 D_METHODS
 };

 // Base classes for templated inheritance trampolines.  Identical to the repeat-everything version:
 class A_Tpl { A_METHODS; virtual ~A_Tpl() = default; };
 class B_Tpl : public A_Tpl { B_METHODS };
 class C_Tpl : public B_Tpl { C_METHODS };
 class D_Tpl : public C_Tpl { D_METHODS };


 // Inheritance approach 1: each trampoline gets every virtual method (11 in total)
 class PyA_Repeat : public A_Repeat {
 public:
     using A_Repeat::A_Repeat;
     int unlucky_number() override { PYBIND11_OVERLOAD_PURE(int, A_Repeat, unlucky_number, ); }
     std::string say_something(unsigned times) override { PYBIND11_OVERLOAD(std::string, A_Repeat, say_something, times); }
 };
 class PyB_Repeat : public B_Repeat {
 public:
     using B_Repeat::B_Repeat;
     int unlucky_number() override { PYBIND11_OVERLOAD(int, B_Repeat, unlucky_number, ); }
     std::string say_something(unsigned times) override { PYBIND11_OVERLOAD(std::string, B_Repeat, say_something, times); }
     double lucky_number() override { PYBIND11_OVERLOAD(double, B_Repeat, lucky_number, ); }
 };
 class PyC_Repeat : public C_Repeat {
 public:
     using C_Repeat::C_Repeat;
     int unlucky_number() override { PYBIND11_OVERLOAD(int, C_Repeat, unlucky_number, ); }
     std::string say_something(unsigned times) override { PYBIND11_OVERLOAD(std::string, C_Repeat, say_something, times); }
     double lucky_number() override { PYBIND11_OVERLOAD(double, C_Repeat, lucky_number, ); }
 };
 class PyD_Repeat : public D_Repeat {
 public:
     using D_Repeat::D_Repeat;
     int unlucky_number() override { PYBIND11_OVERLOAD(int, D_Repeat, unlucky_number, ); }
     std::string say_something(unsigned times) override { PYBIND11_OVERLOAD(std::string, D_Repeat, say_something, times); }
     double lucky_number() override { PYBIND11_OVERLOAD(double, D_Repeat, lucky_number, ); }
 };

 // Inheritance approach 2: templated trampoline classes.
 //
 // Advantages:
 // - we have only 2 (template) class and 4 method declarations (one per virtual method, plus one for
 //   any override of a pure virtual method), versus 4 classes and 6 methods (MI) or 4 classes and 11
 //   methods (repeat).
 // - Compared to MI, we also don't have to change the non-trampoline inheritance to virtual, and can
 //   properly inherit constructors.
 //
 // Disadvantage:
 // - the compiler must still generate and compile 14 different methods (more, even, than the 11
 //   required for the repeat approach) instead of the 6 required for MI.  (If there was no pure
 //   method (or no pure method override), the number would drop down to the same 11 as the repeat
 //   approach).
 template <class Base = A_Tpl>
 class PyA_Tpl : public Base {
 public:
     using Base::Base; // Inherit constructors
     int unlucky_number() override { PYBIND11_OVERLOAD_PURE(int, Base, unlucky_number, ); }
     std::string say_something(unsigned times) override { PYBIND11_OVERLOAD(std::string, Base, say_something, times); }
 };
 template <class Base = B_Tpl>
 class PyB_Tpl : public PyA_Tpl<Base> {
 public:
     using PyA_Tpl<Base>::PyA_Tpl; // Inherit constructors (via PyA_Tpl's inherited constructors)
     int unlucky_number() override { PYBIND11_OVERLOAD(int, Base, unlucky_number, ); }
     double lucky_number() override { PYBIND11_OVERLOAD(double, Base, lucky_number, ); }
 };
 // Since C_Tpl and D_Tpl don't declare any new virtual methods, we don't actually need these (we can
 // use PyB_Tpl<C_Tpl> and PyB_Tpl<D_Tpl> for the trampoline classes instead):
 /*
 template <class Base = C_Tpl> class PyC_Tpl : public PyB_Tpl<Base> {
 public:
     using PyB_Tpl<Base>::PyB_Tpl;
 };
 template <class Base = D_Tpl> class PyD_Tpl : public PyC_Tpl<Base> {
 public:
     using PyC_Tpl<Base>::PyC_Tpl;
 };
 */


 void initialize_inherited_virtuals(py::module &m) {
     // test_inherited_virtuals

     // Method 1: repeat
     py::class_<A_Repeat, PyA_Repeat>(m, "A_Repeat")
         .def(py::init<>())
         .def("unlucky_number", &A_Repeat::unlucky_number)
         .def("say_something", &A_Repeat::say_something)
         .def("say_everything", &A_Repeat::say_everything);
     py::class_<B_Repeat, A_Repeat, PyB_Repeat>(m, "B_Repeat")
         .def(py::init<>())
         .def("lucky_number", &B_Repeat::lucky_number);
     py::class_<C_Repeat, B_Repeat, PyC_Repeat>(m, "C_Repeat")
         .def(py::init<>());
     py::class_<D_Repeat, C_Repeat, PyD_Repeat>(m, "D_Repeat")
         .def(py::init<>());

     // test_
     // Method 2: Templated trampolines
     py::class_<A_Tpl, PyA_Tpl<>>(m, "A_Tpl")
         .def(py::init<>())
         .def("unlucky_number", &A_Tpl::unlucky_number)
         .def("say_something", &A_Tpl::say_something)
         .def("say_everything", &A_Tpl::say_everything);
     py::class_<B_Tpl, A_Tpl, PyB_Tpl<>>(m, "B_Tpl")
         .def(py::init<>())
         .def("lucky_number", &B_Tpl::lucky_number);
     py::class_<C_Tpl, B_Tpl, PyB_Tpl<C_Tpl>>(m, "C_Tpl")
         .def(py::init<>());
     py::class_<D_Tpl, C_Tpl, PyB_Tpl<D_Tpl>>(m, "D_Tpl")
         .def(py::init<>());

 };
	/*
	tests/test_virtual_functions.cpp -- overriding virtual functions from Python

	Copyright (c) 2016 Wenzel Jakob <wenzel.jakob@epfl.ch>

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

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

	/* This is an example class that we'll want to be able to extend from Python */
	class ExampleVirt {
	public:
	ExampleVirt(int state) : state(state) { print_created(this, state); }
	ExampleVirt(const ExampleVirt &e) : state(e.state) { print_copy_created(this); }
	ExampleVirt(ExampleVirt &&e) : state(e.state) { print_move_created(this); e.state = 0; }
	~ExampleVirt() { print_destroyed(this); }

	virtual int run(int value) {
	py::print("Original implementation of "
	"ExampleVirt::run(state={}, value={}, str1={}, str2={})"_s.format(state, value, get_string1(), *get_string2()));
	return state + value;
	}

	virtual bool run_bool() = 0;
	virtual void pure_virtual() = 0;

	// Returning a reference/pointer to a type converted from python (numbers, strings, etc.) is a
	// bit trickier, because the actual int& or std::string& or whatever only exists temporarily, so
	// we have to handle it specially in the trampoline class (see below).
	virtual const std::string &get_string1() { return str1; }
	virtual const std::string *get_string2() { return &str2; }

	private:
	int state;
	const std::string str1{"default1"}, str2{"default2"};
	};

	/* This is a wrapper class that must be generated */
	class PyExampleVirt : public ExampleVirt {
	public:
	using ExampleVirt::ExampleVirt; /* Inherit constructors */

	int run(int value) override {
	/* Generate wrapping code that enables native function overloading */
	PYBIND11_OVERLOAD(
	int, /* Return type */
	ExampleVirt, /* Parent class */
	run, /* Name of function */
	value /* Argument(s) */
	);
	}

	bool run_bool() override {
	PYBIND11_OVERLOAD_PURE(
	bool, /* Return type */
	ExampleVirt, /* Parent class */
	run_bool, /* Name of function */
	/* This function has no arguments. The trailing comma
	in the previous line is needed for some compilers */
	);
	}

	void pure_virtual() override {
	PYBIND11_OVERLOAD_PURE(
	void, /* Return type */
	ExampleVirt, /* Parent class */
	pure_virtual, /* Name of function */
	/* This function has no arguments. The trailing comma
	in the previous line is needed for some compilers */
	);
	}

	// We can return reference types for compatibility with C++ virtual interfaces that do so, but
	// note they have some significant limitations (see the documentation).
	const std::string &get_string1() override {
	PYBIND11_OVERLOAD(
	const std::string &, /* Return type */
	ExampleVirt, /* Parent class */
	get_string1, /* Name of function */
	/* (no arguments) */
	);
	}

	const std::string *get_string2() override {
	PYBIND11_OVERLOAD(
	const std::string , / Return type */
	ExampleVirt, /* Parent class */
	get_string2, /* Name of function */
	/* (no arguments) */
	);
	}

	};

	class NonCopyable {
	public:
	NonCopyable(int a, int b) : value{new int(a*b)} { print_created(this, a, b); }
	NonCopyable(NonCopyable &&o) { value = std::move(o.value); print_move_created(this); }
	NonCopyable(const NonCopyable &) = delete;
	NonCopyable() = delete;
	void operator=(const NonCopyable &) = delete;
	void operator=(NonCopyable &&) = delete;
	std::string get_value() const {
	if (value) return std::to_string(*value); else return "(null)";
	}
	~NonCopyable() { print_destroyed(this); }

	private:
	std::unique_ptr<int> value;
	};

	// This is like the above, but is both copy and movable. In effect this means it should get moved
	// when it is not referenced elsewhere, but copied if it is still referenced.
	class Movable {
	public:
	Movable(int a, int b) : value{a+b} { print_created(this, a, b); }
	Movable(const Movable &m) { value = m.value; print_copy_created(this); }
	Movable(Movable &&m) { value = std::move(m.value); print_move_created(this); }
	std::string get_value() const { return std::to_string(value); }
	~Movable() { print_destroyed(this); }
	private:
	int value;
	};

	class NCVirt {
	public:
	virtual NonCopyable get_noncopyable(int a, int b) { return NonCopyable(a, b); }
	virtual Movable get_movable(int a, int b) = 0;

	std::string print_nc(int a, int b) { return get_noncopyable(a, b).get_value(); }
	std::string print_movable(int a, int b) { return get_movable(a, b).get_value(); }
	};
	class NCVirtTrampoline : public NCVirt {
	#if !defined(__INTEL_COMPILER)
	NonCopyable get_noncopyable(int a, int b) override {
	PYBIND11_OVERLOAD(NonCopyable, NCVirt, get_noncopyable, a, b);
	}
	#endif
	Movable get_movable(int a, int b) override {
	PYBIND11_OVERLOAD_PURE(Movable, NCVirt, get_movable, a, b);
	}
	};

	struct Base {
	/* for some reason MSVC2015 can't compile this if the function is pure virtual */
	virtual std::string dispatch() const { return {}; };
	virtual ~Base() = default;
	};

	struct DispatchIssue : Base {
	virtual std::string dispatch() const {
	PYBIND11_OVERLOAD_PURE(std::string, Base, dispatch, /* no arguments */);
	}
	};

	// Forward declaration (so that we can put the main tests here; the inherited virtual approaches are
	// rather long).
	void initialize_inherited_virtuals(py::module &m);

	TEST_SUBMODULE(virtual_functions, m) {
	// test_override
	py::class_<ExampleVirt, PyExampleVirt>(m, "ExampleVirt")
	.def(py::init<int>())
	/* Reference original class in function definitions */
	.def("run", &ExampleVirt::run)
	.def("run_bool", &ExampleVirt::run_bool)
	.def("pure_virtual", &ExampleVirt::pure_virtual);

	py::class_<NonCopyable>(m, "NonCopyable")
	.def(py::init<int, int>());

	py::class_<Movable>(m, "Movable")
	.def(py::init<int, int>());

	// test_move_support
	#if !defined(__INTEL_COMPILER)
	py::class_<NCVirt, NCVirtTrampoline>(m, "NCVirt")
	.def(py::init<>())
	.def("get_noncopyable", &NCVirt::get_noncopyable)
	.def("get_movable", &NCVirt::get_movable)
	.def("print_nc", &NCVirt::print_nc)
	.def("print_movable", &NCVirt::print_movable);
	#endif

	m.def("runExampleVirt", [](ExampleVirt *ex, int value) { return ex->run(value); });
	m.def("runExampleVirtBool", [](ExampleVirt* ex) { return ex->run_bool(); });
	m.def("runExampleVirtVirtual", [](ExampleVirt *ex) { ex->pure_virtual(); });

	m.def("cstats_debug", &ConstructorStats::get<ExampleVirt>);
	initialize_inherited_virtuals(m);

	// test_alias_delay_initialization1
	// don't invoke Python dispatch classes by default when instantiating C++ classes
	// that were not extended on the Python side
	struct A {
	virtual ~A() {}
	virtual void f() { py::print("A.f()"); }
	};

	struct PyA : A {
	PyA() { py::print("PyA.PyA()"); }
	~PyA() { py::print("PyA.~PyA()"); }

	void f() override {
	py::print("PyA.f()");
	PYBIND11_OVERLOAD(void, A, f);
	}
	};

	py::class_<A, PyA>(m, "A")
	.def(py::init<>())
	.def("f", &A::f);

	m.def("call_f", [](A *a) { a->f(); });

	// test_alias_delay_initialization2
	// ... unless we explicitly request it, as in this example:
	struct A2 {
	virtual ~A2() {}
	virtual void f() { py::print("A2.f()"); }
	};

	struct PyA2 : A2 {
	PyA2() { py::print("PyA2.PyA2()"); }
	~PyA2() { py::print("PyA2.~PyA2()"); }
	void f() override {
	py::print("PyA2.f()");
	PYBIND11_OVERLOAD(void, A2, f);
	}
	};

	py::class_<A2, PyA2>(m, "A2")
	.def(py::init_alias<>())
	.def(py::init([](int) { return new PyA2(); }))
	.def("f", &A2::f);

	m.def("call_f", [](A2 *a2) { a2->f(); });

	// test_dispatch_issue
	// #159: virtual function dispatch has problems with similar-named functions
	py::class_<Base, DispatchIssue>(m, "DispatchIssue")
	.def(py::init<>())
	.def("dispatch", &Base::dispatch);

	m.def("dispatch_issue_go", [](const Base * b) { return b->dispatch(); });

	// test_override_ref
	// #392/397: overridding reference-returning functions
	class OverrideTest {
	public:
	struct A { std::string value = "hi"; };
	std::string v;
	A a;
	explicit OverrideTest(const std::string &v) : v{v} {}
	virtual std::string str_value() { return v; }
	virtual std::string &str_ref() { return v; }
	virtual A A_value() { return a; }
	virtual A &A_ref() { return a; }
	virtual ~OverrideTest() = default;
	};

	class PyOverrideTest : public OverrideTest {
	public:
	using OverrideTest::OverrideTest;
	std::string str_value() override { PYBIND11_OVERLOAD(std::string, OverrideTest, str_value); }
	// Not allowed (uncommenting should hit a static_assert failure): we can't get a reference
	// to a python numeric value, since we only copy values in the numeric type caster:
	// std::string &str_ref() override { PYBIND11_OVERLOAD(std::string &, OverrideTest, str_ref); }
	// But we can work around it like this:
	private:
	std::string _tmp;
	std::string str_ref_helper() { PYBIND11_OVERLOAD(std::string, OverrideTest, str_ref); }
	public:
	std::string &str_ref() override { return _tmp = str_ref_helper(); }

	A A_value() override { PYBIND11_OVERLOAD(A, OverrideTest, A_value); }
	A &A_ref() override { PYBIND11_OVERLOAD(A &, OverrideTest, A_ref); }
	};

	py::class_<OverrideTest::A>(m, "OverrideTest_A")
	.def_readwrite("value", &OverrideTest::A::value);
	py::class_<OverrideTest, PyOverrideTest>(m, "OverrideTest")
	.def(py::init<const std::string &>())
	.def("str_value", &OverrideTest::str_value)
	// .def("str_ref", &OverrideTest::str_ref)
	.def("A_value", &OverrideTest::A_value)
	.def("A_ref", &OverrideTest::A_ref);
	}


	// Inheriting virtual methods. We do two versions here: the repeat-everything version and the
	// templated trampoline versions mentioned in docs/advanced.rst.
	//
	// These base classes are exactly the same, but we technically need distinct
	// classes for this example code because we need to be able to bind them
	// properly (pybind11, sensibly, doesn't allow us to bind the same C++ class to
	// multiple python classes).
	class A_Repeat {
	#define A_METHODS \
	public: \
	virtual int unlucky_number() = 0; \
	virtual std::string say_something(unsigned times) { \
	std::string s = ""; \
	for (unsigned i = 0; i < times; ++i) \
	s += "hi"; \
	return s; \
	} \
	std::string say_everything() { \
	return say_something(1) + " " + std::to_string(unlucky_number()); \
	}
	A_METHODS
	virtual ~A_Repeat() = default;
	};
	class B_Repeat : public A_Repeat {
	#define B_METHODS \
	public: \
	int unlucky_number() override { return 13; } \
	std::string say_something(unsigned times) override { \
	return "B says hi " + std::to_string(times) + " times"; \
	} \
	virtual double lucky_number() { return 7.0; }
	B_METHODS
	};
	class C_Repeat : public B_Repeat {
	#define C_METHODS \
	public: \
	int unlucky_number() override { return 4444; } \
	double lucky_number() override { return 888; }
	C_METHODS
	};
	class D_Repeat : public C_Repeat {
	#define D_METHODS // Nothing overridden.
	D_METHODS
	};

	// Base classes for templated inheritance trampolines. Identical to the repeat-everything version:
	class A_Tpl { A_METHODS; virtual ~A_Tpl() = default; };
	class B_Tpl : public A_Tpl { B_METHODS };
	class C_Tpl : public B_Tpl { C_METHODS };
	class D_Tpl : public C_Tpl { D_METHODS };


	// Inheritance approach 1: each trampoline gets every virtual method (11 in total)
	class PyA_Repeat : public A_Repeat {
	public:
	using A_Repeat::A_Repeat;
	int unlucky_number() override { PYBIND11_OVERLOAD_PURE(int, A_Repeat, unlucky_number, ); }
	std::string say_something(unsigned times) override { PYBIND11_OVERLOAD(std::string, A_Repeat, say_something, times); }
	};
	class PyB_Repeat : public B_Repeat {
	public:
	using B_Repeat::B_Repeat;
	int unlucky_number() override { PYBIND11_OVERLOAD(int, B_Repeat, unlucky_number, ); }
	std::string say_something(unsigned times) override { PYBIND11_OVERLOAD(std::string, B_Repeat, say_something, times); }
	double lucky_number() override { PYBIND11_OVERLOAD(double, B_Repeat, lucky_number, ); }
	};
	class PyC_Repeat : public C_Repeat {
	public:
	using C_Repeat::C_Repeat;
	int unlucky_number() override { PYBIND11_OVERLOAD(int, C_Repeat, unlucky_number, ); }
	std::string say_something(unsigned times) override { PYBIND11_OVERLOAD(std::string, C_Repeat, say_something, times); }
	double lucky_number() override { PYBIND11_OVERLOAD(double, C_Repeat, lucky_number, ); }
	};
	class PyD_Repeat : public D_Repeat {
	public:
	using D_Repeat::D_Repeat;
	int unlucky_number() override { PYBIND11_OVERLOAD(int, D_Repeat, unlucky_number, ); }
	std::string say_something(unsigned times) override { PYBIND11_OVERLOAD(std::string, D_Repeat, say_something, times); }
	double lucky_number() override { PYBIND11_OVERLOAD(double, D_Repeat, lucky_number, ); }
	};

	// Inheritance approach 2: templated trampoline classes.
	//
	// Advantages:
	// - we have only 2 (template) class and 4 method declarations (one per virtual method, plus one for
	// any override of a pure virtual method), versus 4 classes and 6 methods (MI) or 4 classes and 11
	// methods (repeat).
	// - Compared to MI, we also don't have to change the non-trampoline inheritance to virtual, and can
	// properly inherit constructors.
	//
	// Disadvantage:
	// - the compiler must still generate and compile 14 different methods (more, even, than the 11
	// required for the repeat approach) instead of the 6 required for MI. (If there was no pure
	// method (or no pure method override), the number would drop down to the same 11 as the repeat
	// approach).
	template <class Base = A_Tpl>
	class PyA_Tpl : public Base {
	public:
	using Base::Base; // Inherit constructors
	int unlucky_number() override { PYBIND11_OVERLOAD_PURE(int, Base, unlucky_number, ); }
	std::string say_something(unsigned times) override { PYBIND11_OVERLOAD(std::string, Base, say_something, times); }
	};
	template <class Base = B_Tpl>
	class PyB_Tpl : public PyA_Tpl<Base> {
	public:
	using PyA_Tpl<Base>::PyA_Tpl; // Inherit constructors (via PyA_Tpl's inherited constructors)
	int unlucky_number() override { PYBIND11_OVERLOAD(int, Base, unlucky_number, ); }
	double lucky_number() override { PYBIND11_OVERLOAD(double, Base, lucky_number, ); }
	};
	// Since C_Tpl and D_Tpl don't declare any new virtual methods, we don't actually need these (we can
	// use PyB_Tpl<C_Tpl> and PyB_Tpl<D_Tpl> for the trampoline classes instead):
	/*
	template <class Base = C_Tpl> class PyC_Tpl : public PyB_Tpl<Base> {
	public:
	using PyB_Tpl<Base>::PyB_Tpl;
	};
	template <class Base = D_Tpl> class PyD_Tpl : public PyC_Tpl<Base> {
	public:
	using PyC_Tpl<Base>::PyC_Tpl;
	};
	*/


	void initialize_inherited_virtuals(py::module &m) {
	// test_inherited_virtuals

	// Method 1: repeat
	py::class_<A_Repeat, PyA_Repeat>(m, "A_Repeat")
	.def(py::init<>())
	.def("unlucky_number", &A_Repeat::unlucky_number)
	.def("say_something", &A_Repeat::say_something)
	.def("say_everything", &A_Repeat::say_everything);
	py::class_<B_Repeat, A_Repeat, PyB_Repeat>(m, "B_Repeat")
	.def(py::init<>())
	.def("lucky_number", &B_Repeat::lucky_number);
	py::class_<C_Repeat, B_Repeat, PyC_Repeat>(m, "C_Repeat")
	.def(py::init<>());
	py::class_<D_Repeat, C_Repeat, PyD_Repeat>(m, "D_Repeat")
	.def(py::init<>());

	// test_
	// Method 2: Templated trampolines
	py::class_<A_Tpl, PyA_Tpl<>>(m, "A_Tpl")
	.def(py::init<>())
	.def("unlucky_number", &A_Tpl::unlucky_number)
	.def("say_something", &A_Tpl::say_something)
	.def("say_everything", &A_Tpl::say_everything);
	py::class_<B_Tpl, A_Tpl, PyB_Tpl<>>(m, "B_Tpl")
	.def(py::init<>())
	.def("lucky_number", &B_Tpl::lucky_number);
	py::class_<C_Tpl, B_Tpl, PyB_Tpl<C_Tpl>>(m, "C_Tpl")
	.def(py::init<>());
	py::class_<D_Tpl, C_Tpl, PyB_Tpl<D_Tpl>>(m, "D_Tpl")
	.def(py::init<>());

	};