1// <any> -*- C++ -*-
2
3// Copyright (C) 2014-2024 Free Software Foundation, Inc.
4//
5// This file is part of the GNU ISO C++ Library. This library is free
6// software; you can redistribute it and/or modify it under the
7// terms of the GNU General Public License as published by the
8// Free Software Foundation; either version 3, or (at your option)
9// any later version.
10
11// This library is distributed in the hope that it will be useful,
12// but WITHOUT ANY WARRANTY; without even the implied warranty of
13// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14// GNU General Public License for more details.
15
16// Under Section 7 of GPL version 3, you are granted additional
17// permissions described in the GCC Runtime Library Exception, version
18// 3.1, as published by the Free Software Foundation.
19
20// You should have received a copy of the GNU General Public License and
21// a copy of the GCC Runtime Library Exception along with this program;
22// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23// <http://www.gnu.org/licenses/>.
24
25/** @file include/any
26 * This is a Standard C++ Library header.
27 */
28
29#ifndef _GLIBCXX_ANY
30#define _GLIBCXX_ANY 1
31
32#pragma GCC system_header
33
34#define __glibcxx_want_any
35#include <bits/version.h>
36
37#ifdef __cpp_lib_any // C++ >= 17
38
39#include <initializer_list>
40#include <typeinfo>
41#include <new>
42#include <type_traits>
43#include <bits/utility.h> // in_place_type_t
44
45namespace std _GLIBCXX_VISIBILITY(default)
46{
47_GLIBCXX_BEGIN_NAMESPACE_VERSION
48
49 /**
50 * @addtogroup utilities
51 * @{
52 */
53
54 /**
55 * @brief Exception class thrown by a failed @c any_cast
56 * @ingroup exceptions
57 */
58 class bad_any_cast : public bad_cast
59 {
60 public:
61 virtual const char* what() const noexcept { return "bad any_cast"; }
62 };
63
64 [[gnu::noreturn]] inline void __throw_bad_any_cast()
65 {
66#if __cpp_exceptions
67 throw bad_any_cast{};
68#else
69 __builtin_abort();
70#endif
71 }
72
73 /**
74 * @brief A type-safe container of any type.
75 *
76 * An `any` object's state is either empty or it stores a contained object
77 * of CopyConstructible type.
78 *
79 * @since C++17
80 */
81 class any
82 {
83 // Holds either pointer to a heap object or the contained object itself.
84 union _Storage
85 {
86 constexpr _Storage() : _M_ptr{nullptr} {}
87
88 // Prevent trivial copies of this type, buffer might hold a non-POD.
89 _Storage(const _Storage&) = delete;
90 _Storage& operator=(const _Storage&) = delete;
91
92 void* _M_ptr;
93 aligned_storage<sizeof(_M_ptr), alignof(void*)>::type _M_buffer;
94 };
95
96 template<typename _Tp, typename _Safe = is_nothrow_move_constructible<_Tp>,
97 bool _Fits = (sizeof(_Tp) <= sizeof(_Storage))
98 && (alignof(_Tp) <= alignof(_Storage))>
99 using _Internal = std::integral_constant<bool, _Safe::value && _Fits>;
100
101 template<typename _Tp>
102 struct _Manager_internal; // uses small-object optimization
103
104 template<typename _Tp>
105 struct _Manager_external; // creates contained object on the heap
106
107 template<typename _Tp>
108 using _Manager = __conditional_t<_Internal<_Tp>::value,
109 _Manager_internal<_Tp>,
110 _Manager_external<_Tp>>;
111
112 template<typename _Tp, typename _VTp = decay_t<_Tp>>
113 using _Decay_if_not_any = enable_if_t<!is_same_v<_VTp, any>, _VTp>;
114
115 /// Emplace with an object created from @p __args as the contained object.
116 template <typename _Tp, typename... _Args,
117 typename _Mgr = _Manager<_Tp>>
118 void __do_emplace(_Args&&... __args)
119 {
120 reset();
121 _Mgr::_S_create(_M_storage, std::forward<_Args>(__args)...);
122 _M_manager = &_Mgr::_S_manage;
123 }
124
125 /// Emplace with an object created from @p __il and @p __args as
126 /// the contained object.
127 template <typename _Tp, typename _Up, typename... _Args,
128 typename _Mgr = _Manager<_Tp>>
129 void __do_emplace(initializer_list<_Up> __il, _Args&&... __args)
130 {
131 reset();
132 _Mgr::_S_create(_M_storage, __il, std::forward<_Args>(__args)...);
133 _M_manager = &_Mgr::_S_manage;
134 }
135
136 template <typename _Res, typename _Tp, typename... _Args>
137 using __any_constructible
138 = enable_if<__and_<is_copy_constructible<_Tp>,
139 is_constructible<_Tp, _Args...>>::value,
140 _Res>;
141
142 template <typename _Tp, typename... _Args>
143 using __any_constructible_t
144 = typename __any_constructible<bool, _Tp, _Args...>::type;
145
146 template<typename _VTp, typename... _Args>
147 using __emplace_t
148 = typename __any_constructible<_VTp&, _VTp, _Args...>::type;
149
150 public:
151 // construct/destruct
152
153 /// Default constructor, creates an empty object.
154 constexpr any() noexcept : _M_manager(nullptr) { }
155
156 /// Copy constructor, copies the state of @p __other
157 any(const any& __other)
158 {
159 if (!__other.has_value())
160 _M_manager = nullptr;
161 else
162 {
163 _Arg __arg;
164 __arg._M_any = this;
165 __other._M_manager(_Op_clone, &__other, &__arg);
166 }
167 }
168
169 /**
170 * @brief Move constructor, transfer the state from @p __other
171 *
172 * @post @c !__other.has_value() (this postcondition is a GNU extension)
173 */
174 any(any&& __other) noexcept
175 {
176 if (!__other.has_value())
177 _M_manager = nullptr;
178 else
179 {
180 _Arg __arg;
181 __arg._M_any = this;
182 __other._M_manager(_Op_xfer, &__other, &__arg);
183 }
184 }
185
186 /// Construct with a copy of @p __value as the contained object.
187 template <typename _Tp, typename _VTp = _Decay_if_not_any<_Tp>,
188 typename _Mgr = _Manager<_VTp>,
189 enable_if_t<is_copy_constructible_v<_VTp>
190 && !__is_in_place_type_v<_VTp>, bool> = true>
191 any(_Tp&& __value)
192 : _M_manager(&_Mgr::_S_manage)
193 {
194 _Mgr::_S_create(_M_storage, std::forward<_Tp>(__value));
195 }
196
197 /// Construct with an object created from @p __args as the contained object.
198 template <typename _Tp, typename... _Args, typename _VTp = decay_t<_Tp>,
199 typename _Mgr = _Manager<_VTp>,
200 __any_constructible_t<_VTp, _Args&&...> = false>
201 explicit
202 any(in_place_type_t<_Tp>, _Args&&... __args)
203 : _M_manager(&_Mgr::_S_manage)
204 {
205 _Mgr::_S_create(_M_storage, std::forward<_Args>(__args)...);
206 }
207
208 /// Construct with an object created from @p __il and @p __args as
209 /// the contained object.
210 template <typename _Tp, typename _Up, typename... _Args,
211 typename _VTp = decay_t<_Tp>, typename _Mgr = _Manager<_VTp>,
212 __any_constructible_t<_VTp, initializer_list<_Up>&,
213 _Args&&...> = false>
214 explicit
215 any(in_place_type_t<_Tp>, initializer_list<_Up> __il, _Args&&... __args)
216 : _M_manager(&_Mgr::_S_manage)
217 {
218 _Mgr::_S_create(_M_storage, __il, std::forward<_Args>(__args)...);
219 }
220
221 /// Destructor, calls @c reset()
222 ~any() { reset(); }
223
224 // assignments
225
226 /// Copy the state of another object.
227 any&
228 operator=(const any& __rhs)
229 {
230 *this = any(__rhs);
231 return *this;
232 }
233
234 /**
235 * @brief Move assignment operator
236 *
237 * @post @c !__rhs.has_value() (not guaranteed for other implementations)
238 */
239 any&
240 operator=(any&& __rhs) noexcept
241 {
242 if (!__rhs.has_value())
243 reset();
244 else if (this != &__rhs)
245 {
246 reset();
247 _Arg __arg;
248 __arg._M_any = this;
249 __rhs._M_manager(_Op_xfer, &__rhs, &__arg);
250 }
251 return *this;
252 }
253
254 /// Store a copy of @p __rhs as the contained object.
255 template<typename _Tp>
256 enable_if_t<is_copy_constructible<_Decay_if_not_any<_Tp>>::value, any&>
257 operator=(_Tp&& __rhs)
258 {
259 *this = any(std::forward<_Tp>(__rhs));
260 return *this;
261 }
262
263 /// Emplace with an object created from @p __args as the contained object.
264 template <typename _Tp, typename... _Args>
265 __emplace_t<decay_t<_Tp>, _Args...>
266 emplace(_Args&&... __args)
267 {
268 using _VTp = decay_t<_Tp>;
269 __do_emplace<_VTp>(std::forward<_Args>(__args)...);
270 return *any::_Manager<_VTp>::_S_access(_M_storage);
271 }
272
273 /// Emplace with an object created from @p __il and @p __args as
274 /// the contained object.
275 template <typename _Tp, typename _Up, typename... _Args>
276 __emplace_t<decay_t<_Tp>, initializer_list<_Up>&, _Args&&...>
277 emplace(initializer_list<_Up> __il, _Args&&... __args)
278 {
279 using _VTp = decay_t<_Tp>;
280 __do_emplace<_VTp, _Up>(__il, std::forward<_Args>(__args)...);
281 return *any::_Manager<_VTp>::_S_access(_M_storage);
282 }
283
284 // modifiers
285
286 /// If not empty, destroy the contained object.
287 void reset() noexcept
288 {
289 if (has_value())
290 {
291 _M_manager(_Op_destroy, this, nullptr);
292 _M_manager = nullptr;
293 }
294 }
295
296 /// Exchange state with another object.
297 void swap(any& __rhs) noexcept
298 {
299 if (!has_value() && !__rhs.has_value())
300 return;
301
302 if (has_value() && __rhs.has_value())
303 {
304 if (this == &__rhs)
305 return;
306
307 any __tmp;
308 _Arg __arg;
309 __arg._M_any = &__tmp;
310 __rhs._M_manager(_Op_xfer, &__rhs, &__arg);
311 __arg._M_any = &__rhs;
312 _M_manager(_Op_xfer, this, &__arg);
313 __arg._M_any = this;
314 __tmp._M_manager(_Op_xfer, &__tmp, &__arg);
315 }
316 else
317 {
318 any* __empty = !has_value() ? this : &__rhs;
319 any* __full = !has_value() ? &__rhs : this;
320 _Arg __arg;
321 __arg._M_any = __empty;
322 __full->_M_manager(_Op_xfer, __full, &__arg);
323 }
324 }
325
326 // observers
327
328 /// Reports whether there is a contained object or not.
329 bool has_value() const noexcept { return _M_manager != nullptr; }
330
331#if __cpp_rtti
332 /// The @c typeid of the contained object, or @c typeid(void) if empty.
333 const type_info& type() const noexcept
334 {
335 if (!has_value())
336 return typeid(void);
337 _Arg __arg;
338 _M_manager(_Op_get_type_info, this, &__arg);
339 return *__arg._M_typeinfo;
340 }
341#endif
342
343 /// @cond undocumented
344 template<typename _Tp>
345 static constexpr bool __is_valid_cast()
346 { return __or_<is_reference<_Tp>, is_copy_constructible<_Tp>>::value; }
347 /// @endcond
348
349 private:
350 enum _Op {
351 _Op_access, _Op_get_type_info, _Op_clone, _Op_destroy, _Op_xfer
352 };
353
354 union _Arg
355 {
356 void* _M_obj;
357 const std::type_info* _M_typeinfo;
358 any* _M_any;
359 };
360
361 void (*_M_manager)(_Op, const any*, _Arg*);
362 _Storage _M_storage;
363
364 /// @cond undocumented
365 template<typename _Tp>
366 friend void* __any_caster(const any* __any);
367 /// @endcond
368
369 // Manage in-place contained object.
370 template<typename _Tp>
371 struct _Manager_internal
372 {
373 static void
374 _S_manage(_Op __which, const any* __anyp, _Arg* __arg);
375
376 template<typename _Up>
377 static void
378 _S_create(_Storage& __storage, _Up&& __value)
379 {
380 void* __addr = &__storage._M_buffer;
381 ::new (__addr) _Tp(std::forward<_Up>(__value));
382 }
383
384 template<typename... _Args>
385 static void
386 _S_create(_Storage& __storage, _Args&&... __args)
387 {
388 void* __addr = &__storage._M_buffer;
389 ::new (__addr) _Tp(std::forward<_Args>(__args)...);
390 }
391
392 static _Tp*
393 _S_access(const _Storage& __storage)
394 {
395 // The contained object is in __storage._M_buffer
396 const void* __addr = &__storage._M_buffer;
397 return static_cast<_Tp*>(const_cast<void*>(__addr));
398 }
399 };
400
401 // Manage external contained object.
402 template<typename _Tp>
403 struct _Manager_external
404 {
405 static void
406 _S_manage(_Op __which, const any* __anyp, _Arg* __arg);
407
408 template<typename _Up>
409 static void
410 _S_create(_Storage& __storage, _Up&& __value)
411 {
412 __storage._M_ptr = new _Tp(std::forward<_Up>(__value));
413 }
414 template<typename... _Args>
415 static void
416 _S_create(_Storage& __storage, _Args&&... __args)
417 {
418 __storage._M_ptr = new _Tp(std::forward<_Args>(__args)...);
419 }
420 static _Tp*
421 _S_access(const _Storage& __storage)
422 {
423 // The contained object is in *__storage._M_ptr
424 return static_cast<_Tp*>(__storage._M_ptr);
425 }
426 };
427 };
428
429 /// Exchange the states of two @c any objects.
430 inline void swap(any& __x, any& __y) noexcept { __x.swap(rhs&: __y); }
431
432 /// Create an `any` holding a `_Tp` constructed from `__args...`.
433 template <typename _Tp, typename... _Args>
434 inline
435 enable_if_t<is_constructible_v<any, in_place_type_t<_Tp>, _Args...>, any>
436 make_any(_Args&&... __args)
437 {
438 return any(in_place_type<_Tp>, std::forward<_Args>(__args)...);
439 }
440
441 /// Create an `any` holding a `_Tp` constructed from `__il` and `__args...`.
442 template <typename _Tp, typename _Up, typename... _Args>
443 inline
444 enable_if_t<is_constructible_v<any, in_place_type_t<_Tp>,
445 initializer_list<_Up>&, _Args...>, any>
446 make_any(initializer_list<_Up> __il, _Args&&... __args)
447 {
448 return any(in_place_type<_Tp>, __il, std::forward<_Args>(__args)...);
449 }
450
451 /**
452 * @brief Access the contained object.
453 *
454 * @tparam _ValueType A const-reference or CopyConstructible type.
455 * @param __any The object to access.
456 * @return The contained object.
457 * @throw bad_any_cast If <code>
458 * __any.type() != typeid(remove_reference_t<_ValueType>)
459 * </code>
460 */
461 template<typename _ValueType>
462 inline _ValueType any_cast(const any& __any)
463 {
464 using _Up = __remove_cvref_t<_ValueType>;
465 static_assert(any::__is_valid_cast<_ValueType>(),
466 "Template argument must be a reference or CopyConstructible type");
467 static_assert(is_constructible_v<_ValueType, const _Up&>,
468 "Template argument must be constructible from a const value.");
469 auto __p = any_cast<_Up>(&__any);
470 if (__p)
471 return static_cast<_ValueType>(*__p);
472 __throw_bad_any_cast();
473 }
474
475 /**
476 * @brief Access the contained object.
477 *
478 * @tparam _ValueType A reference or CopyConstructible type.
479 * @param __any The object to access.
480 * @return The contained object.
481 * @throw bad_any_cast If <code>
482 * __any.type() != typeid(remove_reference_t<_ValueType>)
483 * </code>
484 *
485 * @{
486 */
487 template<typename _ValueType>
488 inline _ValueType any_cast(any& __any)
489 {
490 using _Up = __remove_cvref_t<_ValueType>;
491 static_assert(any::__is_valid_cast<_ValueType>(),
492 "Template argument must be a reference or CopyConstructible type");
493 static_assert(is_constructible_v<_ValueType, _Up&>,
494 "Template argument must be constructible from an lvalue.");
495 auto __p = any_cast<_Up>(&__any);
496 if (__p)
497 return static_cast<_ValueType>(*__p);
498 __throw_bad_any_cast();
499 }
500
501 template<typename _ValueType>
502 inline _ValueType any_cast(any&& __any)
503 {
504 using _Up = __remove_cvref_t<_ValueType>;
505 static_assert(any::__is_valid_cast<_ValueType>(),
506 "Template argument must be a reference or CopyConstructible type");
507 static_assert(is_constructible_v<_ValueType, _Up>,
508 "Template argument must be constructible from an rvalue.");
509 auto __p = any_cast<_Up>(&__any);
510 if (__p)
511 return static_cast<_ValueType>(std::move(*__p));
512 __throw_bad_any_cast();
513 }
514 /// @}
515
516 /// @cond undocumented
517 template<typename _Tp>
518 void* __any_caster(const any* __any)
519 {
520 // any_cast<T> returns non-null if __any->type() == typeid(T) and
521 // typeid(T) ignores cv-qualifiers so remove them:
522 using _Up = remove_cv_t<_Tp>;
523 // The contained value has a decayed type, so if decay_t<U> is not U,
524 // then it's not possible to have a contained value of type U:
525 if constexpr (!is_same_v<decay_t<_Up>, _Up>)
526 return nullptr;
527 // Only copy constructible types can be used for contained values:
528 else if constexpr (!is_copy_constructible_v<_Up>)
529 return nullptr;
530 // First try comparing function addresses, which works without RTTI
531 else if (__any->_M_manager == &any::_Manager<_Up>::_S_manage
532#if __cpp_rtti
533 || __any->type() == typeid(_Tp)
534#endif
535 )
536 {
537 return any::_Manager<_Up>::_S_access(__any->_M_storage);
538 }
539 return nullptr;
540 }
541 /// @endcond
542
543 /**
544 * @brief Access the contained object.
545 *
546 * @tparam _ValueType The type of the contained object.
547 * @param __any A pointer to the object to access.
548 * @return The address of the contained object if <code>
549 * __any != nullptr && __any.type() == typeid(_ValueType)
550 * </code>, otherwise a null pointer.
551 *
552 * @{
553 */
554 template<typename _ValueType>
555 inline const _ValueType* any_cast(const any* __any) noexcept
556 {
557 // _GLIBCXX_RESOLVE_LIB_DEFECTS
558 // 3305. any_cast<void>
559 static_assert(!is_void_v<_ValueType>);
560
561 // As an optimization, don't bother instantiating __any_caster for
562 // function types, since std::any can only hold objects.
563 if constexpr (is_object_v<_ValueType>)
564 if (__any)
565 return static_cast<_ValueType*>(__any_caster<_ValueType>(__any));
566 return nullptr;
567 }
568
569 template<typename _ValueType>
570 inline _ValueType* any_cast(any* __any) noexcept
571 {
572 static_assert(!is_void_v<_ValueType>);
573
574 if constexpr (is_object_v<_ValueType>)
575 if (__any)
576 return static_cast<_ValueType*>(__any_caster<_ValueType>(__any));
577 return nullptr;
578 }
579 /// @}
580
581 template<typename _Tp>
582 void
583 any::_Manager_internal<_Tp>::
584 _S_manage(_Op __which, const any* __any, _Arg* __arg)
585 {
586 // The contained object is in _M_storage._M_buffer
587 auto __ptr = reinterpret_cast<const _Tp*>(&__any->_M_storage._M_buffer);
588 switch (__which)
589 {
590 case _Op_access:
591 __arg->_M_obj = const_cast<_Tp*>(__ptr);
592 break;
593 case _Op_get_type_info:
594#if __cpp_rtti
595 __arg->_M_typeinfo = &typeid(_Tp);
596#endif
597 break;
598 case _Op_clone:
599 ::new(&__arg->_M_any->_M_storage._M_buffer) _Tp(*__ptr);
600 __arg->_M_any->_M_manager = __any->_M_manager;
601 break;
602 case _Op_destroy:
603 __ptr->~_Tp();
604 break;
605 case _Op_xfer:
606 ::new(&__arg->_M_any->_M_storage._M_buffer) _Tp
607 (std::move(*const_cast<_Tp*>(__ptr)));
608 __ptr->~_Tp();
609 __arg->_M_any->_M_manager = __any->_M_manager;
610 const_cast<any*>(__any)->_M_manager = nullptr;
611 break;
612 }
613 }
614
615 template<typename _Tp>
616 void
617 any::_Manager_external<_Tp>::
618 _S_manage(_Op __which, const any* __any, _Arg* __arg)
619 {
620 // The contained object is *_M_storage._M_ptr
621 auto __ptr = static_cast<const _Tp*>(__any->_M_storage._M_ptr);
622 switch (__which)
623 {
624 case _Op_access:
625 __arg->_M_obj = const_cast<_Tp*>(__ptr);
626 break;
627 case _Op_get_type_info:
628#if __cpp_rtti
629 __arg->_M_typeinfo = &typeid(_Tp);
630#endif
631 break;
632 case _Op_clone:
633 __arg->_M_any->_M_storage._M_ptr = new _Tp(*__ptr);
634 __arg->_M_any->_M_manager = __any->_M_manager;
635 break;
636 case _Op_destroy:
637 delete __ptr;
638 break;
639 case _Op_xfer:
640 __arg->_M_any->_M_storage._M_ptr = __any->_M_storage._M_ptr;
641 __arg->_M_any->_M_manager = __any->_M_manager;
642 const_cast<any*>(__any)->_M_manager = nullptr;
643 break;
644 }
645 }
646
647 /// @}
648
649 namespace __detail::__variant
650 {
651 template<typename> struct _Never_valueless_alt; // see <variant>
652
653 // Provide the strong exception-safety guarantee when emplacing an
654 // any into a variant.
655 template<>
656 struct _Never_valueless_alt<std::any>
657 : std::true_type
658 { };
659 } // namespace __detail::__variant
660
661_GLIBCXX_END_NAMESPACE_VERSION
662} // namespace std
663
664#endif // __cpp_lib_any
665#endif // _GLIBCXX_ANY
666