source: Daodan/MSYS2/mingw32/include/c++/11.2.0/any@ 1181

Last change on this file since 1181 was 1166, checked in by rossy, 3 years ago

Daodan: Replace MinGW build env with an up-to-date MSYS2 env
File size: 17.8 KB
Line 
1// <any> -*- C++ -*-
2
3// Copyright (C) 2014-2021 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#if __cplusplus >= 201703L
35
36#include <typeinfo>
37#include <new>
38#include <utility>
39#include <type_traits>
40
41namespace std _GLIBCXX_VISIBILITY(default)
42{
43_GLIBCXX_BEGIN_NAMESPACE_VERSION
44
45 /**
46 * @addtogroup utilities
47 * @{
48 */
49
50 /**
51 * @brief Exception class thrown by a failed @c any_cast
52 * @ingroup exceptions
53 */
54 class bad_any_cast : public bad_cast
55 {
56 public:
57 virtual const char* what() const noexcept { return "bad any_cast"; }
58 };
59
60 [[gnu::noreturn]] inline void __throw_bad_any_cast()
61 {
62#if __cpp_exceptions
63 throw bad_any_cast{};
64#else
65 __builtin_abort();
66#endif
67 }
68
69#define __cpp_lib_any 201606L
70
71 /**
72 * @brief A type-safe container of any type.
73 *
74 * An @c any object's state is either empty or it stores a contained object
75 * of CopyConstructible type.
76 */
77 class any
78 {
79 // Holds either pointer to a heap object or the contained object itself.
80 union _Storage
81 {
82 constexpr _Storage() : _M_ptr{nullptr} {}
83
84 // Prevent trivial copies of this type, buffer might hold a non-POD.
85 _Storage(const _Storage&) = delete;
86 _Storage& operator=(const _Storage&) = delete;
87
88 void* _M_ptr;
89 aligned_storage<sizeof(_M_ptr), alignof(void*)>::type _M_buffer;
90 };
91
92 template<typename _Tp, typename _Safe = is_nothrow_move_constructible<_Tp>,
93 bool _Fits = (sizeof(_Tp) <= sizeof(_Storage))
94 && (alignof(_Tp) <= alignof(_Storage))>
95 using _Internal = std::integral_constant<bool, _Safe::value && _Fits>;
96
97 template<typename _Tp>
98 struct _Manager_internal; // uses small-object optimization
99
100 template<typename _Tp>
101 struct _Manager_external; // creates contained object on the heap
102
103 template<typename _Tp>
104 using _Manager = conditional_t<_Internal<_Tp>::value,
105 _Manager_internal<_Tp>,
106 _Manager_external<_Tp>>;
107
108 template<typename _Tp, typename _VTp = decay_t<_Tp>>
109 using _Decay_if_not_any = enable_if_t<!is_same_v<_VTp, any>, _VTp>;
110
111 /// Emplace with an object created from @p __args as the contained object.
112 template <typename _Tp, typename... _Args,
113 typename _Mgr = _Manager<_Tp>>
114 void __do_emplace(_Args&&... __args)
115 {
116 reset();
117 _Mgr::_S_create(_M_storage, std::forward<_Args>(__args)...);
118 _M_manager = &_Mgr::_S_manage;
119 }
120
121 /// Emplace with an object created from @p __il and @p __args as
122 /// the contained object.
123 template <typename _Tp, typename _Up, typename... _Args,
124 typename _Mgr = _Manager<_Tp>>
125 void __do_emplace(initializer_list<_Up> __il, _Args&&... __args)
126 {
127 reset();
128 _Mgr::_S_create(_M_storage, __il, std::forward<_Args>(__args)...);
129 _M_manager = &_Mgr::_S_manage;
130 }
131
132 template <typename _Res, typename _Tp, typename... _Args>
133 using __any_constructible
134 = enable_if<__and_<is_copy_constructible<_Tp>,
135 is_constructible<_Tp, _Args...>>::value,
136 _Res>;
137
138 template <typename _Tp, typename... _Args>
139 using __any_constructible_t
140 = typename __any_constructible<bool, _Tp, _Args...>::type;
141
142 template<typename _VTp, typename... _Args>
143 using __emplace_t
144 = typename __any_constructible<_VTp&, _VTp, _Args...>::type;
145
146 public:
147 // construct/destruct
148
149 /// Default constructor, creates an empty object.
150 constexpr any() noexcept : _M_manager(nullptr) { }
151
152 /// Copy constructor, copies the state of @p __other
153 any(const any& __other)
154 {
155 if (!__other.has_value())
156 _M_manager = nullptr;
157 else
158 {
159 _Arg __arg;
160 __arg._M_any = this;
161 __other._M_manager(_Op_clone, &__other, &__arg);
162 }
163 }
164
165 /**
166 * @brief Move constructor, transfer the state from @p __other
167 *
168 * @post @c !__other.has_value() (this postcondition is a GNU extension)
169 */
170 any(any&& __other) noexcept
171 {
172 if (!__other.has_value())
173 _M_manager = nullptr;
174 else
175 {
176 _Arg __arg;
177 __arg._M_any = this;
178 __other._M_manager(_Op_xfer, &__other, &__arg);
179 }
180 }
181
182 /// Construct with a copy of @p __value as the contained object.
183 template <typename _Tp, typename _VTp = _Decay_if_not_any<_Tp>,
184 typename _Mgr = _Manager<_VTp>,
185 enable_if_t<is_copy_constructible<_VTp>::value
186 && !__is_in_place_type<_VTp>::value, bool> = true>
187 any(_Tp&& __value)
188 : _M_manager(&_Mgr::_S_manage)
189 {
190 _Mgr::_S_create(_M_storage, std::forward<_Tp>(__value));
191 }
192
193 /// Construct with an object created from @p __args as the contained object.
194 template <typename _Tp, typename... _Args, typename _VTp = decay_t<_Tp>,
195 typename _Mgr = _Manager<_VTp>,
196 __any_constructible_t<_VTp, _Args&&...> = false>
197 explicit
198 any(in_place_type_t<_Tp>, _Args&&... __args)
199 : _M_manager(&_Mgr::_S_manage)
200 {
201 _Mgr::_S_create(_M_storage, std::forward<_Args>(__args)...);
202 }
203
204 /// Construct with an object created from @p __il and @p __args as
205 /// the contained object.
206 template <typename _Tp, typename _Up, typename... _Args,
207 typename _VTp = decay_t<_Tp>, typename _Mgr = _Manager<_VTp>,
208 __any_constructible_t<_VTp, initializer_list<_Up>&,
209 _Args&&...> = false>
210 explicit
211 any(in_place_type_t<_Tp>, initializer_list<_Up> __il, _Args&&... __args)
212 : _M_manager(&_Mgr::_S_manage)
213 {
214 _Mgr::_S_create(_M_storage, __il, std::forward<_Args>(__args)...);
215 }
216
217 /// Destructor, calls @c reset()
218 ~any() { reset(); }
219
220 // assignments
221
222 /// Copy the state of another object.
223 any&
224 operator=(const any& __rhs)
225 {
226 *this = any(__rhs);
227 return *this;
228 }
229
230 /**
231 * @brief Move assignment operator
232 *
233 * @post @c !__rhs.has_value() (not guaranteed for other implementations)
234 */
235 any&
236 operator=(any&& __rhs) noexcept
237 {
238 if (!__rhs.has_value())
239 reset();
240 else if (this != &__rhs)
241 {
242 reset();
243 _Arg __arg;
244 __arg._M_any = this;
245 __rhs._M_manager(_Op_xfer, &__rhs, &__arg);
246 }
247 return *this;
248 }
249
250 /// Store a copy of @p __rhs as the contained object.
251 template<typename _Tp>
252 enable_if_t<is_copy_constructible<_Decay_if_not_any<_Tp>>::value, any&>
253 operator=(_Tp&& __rhs)
254 {
255 *this = any(std::forward<_Tp>(__rhs));
256 return *this;
257 }
258
259 /// Emplace with an object created from @p __args as the contained object.
260 template <typename _Tp, typename... _Args>
261 __emplace_t<decay_t<_Tp>, _Args...>
262 emplace(_Args&&... __args)
263 {
264 using _VTp = decay_t<_Tp>;
265 __do_emplace<_VTp>(std::forward<_Args>(__args)...);
266 any::_Arg __arg;
267 this->_M_manager(any::_Op_access, this, &__arg);
268 return *static_cast<_VTp*>(__arg._M_obj);
269 }
270
271 /// Emplace with an object created from @p __il and @p __args as
272 /// the contained object.
273 template <typename _Tp, typename _Up, typename... _Args>
274 __emplace_t<decay_t<_Tp>, initializer_list<_Up>&, _Args&&...>
275 emplace(initializer_list<_Up> __il, _Args&&... __args)
276 {
277 using _VTp = decay_t<_Tp>;
278 __do_emplace<_VTp, _Up>(__il, std::forward<_Args>(__args)...);
279 any::_Arg __arg;
280 this->_M_manager(any::_Op_access, this, &__arg);
281 return *static_cast<_VTp*>(__arg._M_obj);
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 template<typename _Tp>
344 static constexpr bool __is_valid_cast()
345 { return __or_<is_reference<_Tp>, is_copy_constructible<_Tp>>::value; }
346
347 private:
348 enum _Op {
349 _Op_access, _Op_get_type_info, _Op_clone, _Op_destroy, _Op_xfer
350 };
351
352 union _Arg
353 {
354 void* _M_obj;
355 const std::type_info* _M_typeinfo;
356 any* _M_any;
357 };
358
359 void (*_M_manager)(_Op, const any*, _Arg*);
360 _Storage _M_storage;
361
362 template<typename _Tp>
363 friend void* __any_caster(const any* __any);
364
365 // Manage in-place contained object.
366 template<typename _Tp>
367 struct _Manager_internal
368 {
369 static void
370 _S_manage(_Op __which, const any* __anyp, _Arg* __arg);
371
372 template<typename _Up>
373 static void
374 _S_create(_Storage& __storage, _Up&& __value)
375 {
376 void* __addr = &__storage._M_buffer;
377 ::new (__addr) _Tp(std::forward<_Up>(__value));
378 }
379
380 template<typename... _Args>
381 static void
382 _S_create(_Storage& __storage, _Args&&... __args)
383 {
384 void* __addr = &__storage._M_buffer;
385 ::new (__addr) _Tp(std::forward<_Args>(__args)...);
386 }
387 };
388
389 // Manage external contained object.
390 template<typename _Tp>
391 struct _Manager_external
392 {
393 static void
394 _S_manage(_Op __which, const any* __anyp, _Arg* __arg);
395
396 template<typename _Up>
397 static void
398 _S_create(_Storage& __storage, _Up&& __value)
399 {
400 __storage._M_ptr = new _Tp(std::forward<_Up>(__value));
401 }
402 template<typename... _Args>
403 static void
404 _S_create(_Storage& __storage, _Args&&... __args)
405 {
406 __storage._M_ptr = new _Tp(std::forward<_Args>(__args)...);
407 }
408 };
409 };
410
411 /// Exchange the states of two @c any objects.
412 inline void swap(any& __x, any& __y) noexcept { __x.swap(__y); }
413
414 /// Create an any holding a @c _Tp constructed from @c __args.
415 template <typename _Tp, typename... _Args>
416 any make_any(_Args&&... __args)
417 {
418 return any(in_place_type<_Tp>, std::forward<_Args>(__args)...);
419 }
420
421 /// Create an any holding a @c _Tp constructed from @c __il and @c __args.
422 template <typename _Tp, typename _Up, typename... _Args>
423 any make_any(initializer_list<_Up> __il, _Args&&... __args)
424 {
425 return any(in_place_type<_Tp>, __il, std::forward<_Args>(__args)...);
426 }
427
428 /**
429 * @brief Access the contained object.
430 *
431 * @tparam _ValueType A const-reference or CopyConstructible type.
432 * @param __any The object to access.
433 * @return The contained object.
434 * @throw bad_any_cast If <code>
435 * __any.type() != typeid(remove_reference_t<_ValueType>)
436 * </code>
437 */
438 template<typename _ValueType>
439 inline _ValueType any_cast(const any& __any)
440 {
441 using _Up = __remove_cvref_t<_ValueType>;
442 static_assert(any::__is_valid_cast<_ValueType>(),
443 "Template argument must be a reference or CopyConstructible type");
444 static_assert(is_constructible_v<_ValueType, const _Up&>,
445 "Template argument must be constructible from a const value.");
446 auto __p = any_cast<_Up>(&__any);
447 if (__p)
448 return static_cast<_ValueType>(*__p);
449 __throw_bad_any_cast();
450 }
451
452 /**
453 * @brief Access the contained object.
454 *
455 * @tparam _ValueType A reference or CopyConstructible type.
456 * @param __any The object to access.
457 * @return The contained object.
458 * @throw bad_any_cast If <code>
459 * __any.type() != typeid(remove_reference_t<_ValueType>)
460 * </code>
461 *
462 * @{
463 */
464 template<typename _ValueType>
465 inline _ValueType any_cast(any& __any)
466 {
467 using _Up = __remove_cvref_t<_ValueType>;
468 static_assert(any::__is_valid_cast<_ValueType>(),
469 "Template argument must be a reference or CopyConstructible type");
470 static_assert(is_constructible_v<_ValueType, _Up&>,
471 "Template argument must be constructible from an lvalue.");
472 auto __p = any_cast<_Up>(&__any);
473 if (__p)
474 return static_cast<_ValueType>(*__p);
475 __throw_bad_any_cast();
476 }
477
478 template<typename _ValueType>
479 inline _ValueType any_cast(any&& __any)
480 {
481 using _Up = __remove_cvref_t<_ValueType>;
482 static_assert(any::__is_valid_cast<_ValueType>(),
483 "Template argument must be a reference or CopyConstructible type");
484 static_assert(is_constructible_v<_ValueType, _Up>,
485 "Template argument must be constructible from an rvalue.");
486 auto __p = any_cast<_Up>(&__any);
487 if (__p)
488 return static_cast<_ValueType>(std::move(*__p));
489 __throw_bad_any_cast();
490 }
491 /// @}
492
493 /// @cond undocumented
494 template<typename _Tp>
495 void* __any_caster(const any* __any)
496 {
497 // any_cast<T> returns non-null if __any->type() == typeid(T) and
498 // typeid(T) ignores cv-qualifiers so remove them:
499 using _Up = remove_cv_t<_Tp>;
500 // The contained value has a decayed type, so if decay_t<U> is not U,
501 // then it's not possible to have a contained value of type U:
502 if constexpr (!is_same_v<decay_t<_Up>, _Up>)
503 return nullptr;
504 // Only copy constructible types can be used for contained values:
505 else if constexpr (!is_copy_constructible_v<_Up>)
506 return nullptr;
507 // First try comparing function addresses, which works without RTTI
508 else if (__any->_M_manager == &any::_Manager<_Up>::_S_manage
509#if __cpp_rtti
510 || __any->type() == typeid(_Tp)
511#endif
512 )
513 {
514 any::_Arg __arg;
515 __any->_M_manager(any::_Op_access, __any, &__arg);
516 return __arg._M_obj;
517 }
518 return nullptr;
519 }
520 /// @endcond
521
522 /**
523 * @brief Access the contained object.
524 *
525 * @tparam _ValueType The type of the contained object.
526 * @param __any A pointer to the object to access.
527 * @return The address of the contained object if <code>
528 * __any != nullptr && __any.type() == typeid(_ValueType)
529 * </code>, otherwise a null pointer.
530 *
531 * @{
532 */
533 template<typename _ValueType>
534 inline const _ValueType* any_cast(const any* __any) noexcept
535 {
536 if constexpr (is_object_v<_ValueType>)
537 if (__any)
538 return static_cast<_ValueType*>(__any_caster<_ValueType>(__any));
539 return nullptr;
540 }
541
542 template<typename _ValueType>
543 inline _ValueType* any_cast(any* __any) noexcept
544 {
545 if constexpr (is_object_v<_ValueType>)
546 if (__any)
547 return static_cast<_ValueType*>(__any_caster<_ValueType>(__any));
548 return nullptr;
549 }
550 /// @}
551
552 template<typename _Tp>
553 void
554 any::_Manager_internal<_Tp>::
555 _S_manage(_Op __which, const any* __any, _Arg* __arg)
556 {
557 // The contained object is in _M_storage._M_buffer
558 auto __ptr = reinterpret_cast<const _Tp*>(&__any->_M_storage._M_buffer);
559 switch (__which)
560 {
561 case _Op_access:
562 __arg->_M_obj = const_cast<_Tp*>(__ptr);
563 break;
564 case _Op_get_type_info:
565#if __cpp_rtti
566 __arg->_M_typeinfo = &typeid(_Tp);
567#endif
568 break;
569 case _Op_clone:
570 ::new(&__arg->_M_any->_M_storage._M_buffer) _Tp(*__ptr);
571 __arg->_M_any->_M_manager = __any->_M_manager;
572 break;
573 case _Op_destroy:
574 __ptr->~_Tp();
575 break;
576 case _Op_xfer:
577 ::new(&__arg->_M_any->_M_storage._M_buffer) _Tp
578 (std::move(*const_cast<_Tp*>(__ptr)));
579 __ptr->~_Tp();
580 __arg->_M_any->_M_manager = __any->_M_manager;
581 const_cast<any*>(__any)->_M_manager = nullptr;
582 break;
583 }
584 }
585
586 template<typename _Tp>
587 void
588 any::_Manager_external<_Tp>::
589 _S_manage(_Op __which, const any* __any, _Arg* __arg)
590 {
591 // The contained object is *_M_storage._M_ptr
592 auto __ptr = static_cast<const _Tp*>(__any->_M_storage._M_ptr);
593 switch (__which)
594 {
595 case _Op_access:
596 __arg->_M_obj = const_cast<_Tp*>(__ptr);
597 break;
598 case _Op_get_type_info:
599#if __cpp_rtti
600 __arg->_M_typeinfo = &typeid(_Tp);
601#endif
602 break;
603 case _Op_clone:
604 __arg->_M_any->_M_storage._M_ptr = new _Tp(*__ptr);
605 __arg->_M_any->_M_manager = __any->_M_manager;
606 break;
607 case _Op_destroy:
608 delete __ptr;
609 break;
610 case _Op_xfer:
611 __arg->_M_any->_M_storage._M_ptr = __any->_M_storage._M_ptr;
612 __arg->_M_any->_M_manager = __any->_M_manager;
613 const_cast<any*>(__any)->_M_manager = nullptr;
614 break;
615 }
616 }
617
618 /// @}
619
620 namespace __detail::__variant
621 {
622 template<typename> struct _Never_valueless_alt; // see <variant>
623
624 // Provide the strong exception-safety guarantee when emplacing an
625 // any into a variant.
626 template<>
627 struct _Never_valueless_alt<std::any>
628 : std::true_type
629 { };
630 } // namespace __detail::__variant
631
632_GLIBCXX_END_NAMESPACE_VERSION
633} // namespace std
634
635#endif // C++17
636#endif // _GLIBCXX_ANY
Note: See TracBrowser for help on using the repository browser.