1// <any> -*- C++ -*- 2 3// Copyright (C) 2014-2020 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 return *any::_Manager<_VTp>::_S_access(_M_storage); 267 } 268 269 /// Emplace with an object created from @p __il and @p __args as 270 /// the contained object. 271 template <typename _Tp, typename _Up, typename... _Args> 272 __emplace_t<decay_t<_Tp>, initializer_list<_Up>&, _Args&&...> 273 emplace(initializer_list<_Up> __il, _Args&&... __args) 274 { 275 using _VTp = decay_t<_Tp>; 276 __do_emplace<_VTp, _Up>(__il, std::forward<_Args>(__args)...); 277 return *any::_Manager<_VTp>::_S_access(_M_storage); 278 } 279 280 // modifiers 281 282 /// If not empty, destroy the contained object. 283 void reset() noexcept 284 { 285 if (has_value()) 286 { 287 _M_manager(_Op_destroy, this, nullptr); 288 _M_manager = nullptr; 289 } 290 } 291 292 /// Exchange state with another object. 293 void swap(any& __rhs) noexcept 294 { 295 if (!has_value() && !__rhs.has_value()) 296 return; 297 298 if (has_value() && __rhs.has_value()) 299 { 300 if (this == &__rhs) 301 return; 302 303 any __tmp; 304 _Arg __arg; 305 __arg._M_any = &__tmp; 306 __rhs._M_manager(_Op_xfer, &__rhs, &__arg); 307 __arg._M_any = &__rhs; 308 _M_manager(_Op_xfer, this, &__arg); 309 __arg._M_any = this; 310 __tmp._M_manager(_Op_xfer, &__tmp, &__arg); 311 } 312 else 313 { 314 any* __empty = !has_value() ? this : &__rhs; 315 any* __full = !has_value() ? &__rhs : this; 316 _Arg __arg; 317 __arg._M_any = __empty; 318 __full->_M_manager(_Op_xfer, __full, &__arg); 319 } 320 } 321 322 // observers 323 324 /// Reports whether there is a contained object or not. 325 bool has_value() const noexcept { return _M_manager != nullptr; } 326 327#if __cpp_rtti 328 /// The @c typeid of the contained object, or @c typeid(void) if empty. 329 const type_info& type() const noexcept 330 { 331 if (!has_value()) 332 return typeid(void); 333 _Arg __arg; 334 _M_manager(_Op_get_type_info, this, &__arg); 335 return *__arg._M_typeinfo; 336 } 337#endif 338 339 template<typename _Tp> 340 static constexpr bool __is_valid_cast() 341 { return __or_<is_reference<_Tp>, is_copy_constructible<_Tp>>::value; } 342 343 private: 344 enum _Op { 345 _Op_access, _Op_get_type_info, _Op_clone, _Op_destroy, _Op_xfer 346 }; 347 348 union _Arg 349 { 350 void* _M_obj; 351 const std::type_info* _M_typeinfo; 352 any* _M_any; 353 }; 354 355 void (*_M_manager)(_Op, const any*, _Arg*); 356 _Storage _M_storage; 357 358 template<typename _Tp> 359 friend void* __any_caster(const any* __any); 360 361 // Manage in-place contained object. 362 template<typename _Tp> 363 struct _Manager_internal 364 { 365 static void 366 _S_manage(_Op __which, const any* __anyp, _Arg* __arg); 367 368 template<typename _Up> 369 static void 370 _S_create(_Storage& __storage, _Up&& __value) 371 { 372 void* __addr = &__storage._M_buffer; 373 ::new (__addr) _Tp(std::forward<_Up>(__value)); 374 } 375 376 template<typename... _Args> 377 static void 378 _S_create(_Storage& __storage, _Args&&... __args) 379 { 380 void* __addr = &__storage._M_buffer; 381 ::new (__addr) _Tp(std::forward<_Args>(__args)...); 382 } 383 384 static _Tp* 385 _S_access(const _Storage& __storage) 386 { 387 // The contained object is in __storage._M_buffer 388 const void* __addr = &__storage._M_buffer; 389 return static_cast<_Tp*>(const_cast<void*>(__addr)); 390 } 391 }; 392 393 // Manage external contained object. 394 template<typename _Tp> 395 struct _Manager_external 396 { 397 static void 398 _S_manage(_Op __which, const any* __anyp, _Arg* __arg); 399 400 template<typename _Up> 401 static void 402 _S_create(_Storage& __storage, _Up&& __value) 403 { 404 __storage._M_ptr = new _Tp(std::forward<_Up>(__value)); 405 } 406 template<typename... _Args> 407 static void 408 _S_create(_Storage& __storage, _Args&&... __args) 409 { 410 __storage._M_ptr = new _Tp(std::forward<_Args>(__args)...); 411 } 412 static _Tp* 413 _S_access(const _Storage& __storage) 414 { 415 // The contained object is in *__storage._M_ptr 416 return static_cast<_Tp*>(__storage._M_ptr); 417 } 418 }; 419 }; 420 421 /// Exchange the states of two @c any objects. 422 inline void swap(any& __x, any& __y) noexcept { __x.swap(__y); } 423 424 /// Create an `any` holding a `_Tp` constructed from `__args...`. 425 template <typename _Tp, typename... _Args> 426 inline 427 enable_if_t<is_constructible_v<any, in_place_type_t<_Tp>, _Args...>, any> 428 make_any(_Args&&... __args) 429 { 430 return any(in_place_type<_Tp>, std::forward<_Args>(__args)...); 431 } 432 433 /// Create an `any` holding a `_Tp` constructed from `__il` and `__args...`. 434 template <typename _Tp, typename _Up, typename... _Args> 435 inline 436 enable_if_t<is_constructible_v<any, in_place_type_t<_Tp>, 437 initializer_list<_Up>&, _Args...>, any> 438 make_any(initializer_list<_Up> __il, _Args&&... __args) 439 { 440 return any(in_place_type<_Tp>, __il, std::forward<_Args>(__args)...); 441 } 442 443 /** 444 * @brief Access the contained object. 445 * 446 * @tparam _ValueType A const-reference or CopyConstructible type. 447 * @param __any The object to access. 448 * @return The contained object. 449 * @throw bad_any_cast If <code> 450 * __any.type() != typeid(remove_reference_t<_ValueType>) 451 * </code> 452 */ 453 template<typename _ValueType> 454 inline _ValueType any_cast(const any& __any) 455 { 456 using _Up = __remove_cvref_t<_ValueType>; 457 static_assert(any::__is_valid_cast<_ValueType>(), 458 "Template argument must be a reference or CopyConstructible type"); 459 static_assert(is_constructible_v<_ValueType, const _Up&>, 460 "Template argument must be constructible from a const value."); 461 auto __p = any_cast<_Up>(&__any); 462 if (__p) 463 return static_cast<_ValueType>(*__p); 464 __throw_bad_any_cast(); 465 } 466 467 /** 468 * @brief Access the contained object. 469 * 470 * @tparam _ValueType A reference or CopyConstructible type. 471 * @param __any The object to access. 472 * @return The contained object. 473 * @throw bad_any_cast If <code> 474 * __any.type() != typeid(remove_reference_t<_ValueType>) 475 * </code> 476 * 477 * @{ 478 */ 479 template<typename _ValueType> 480 inline _ValueType any_cast(any& __any) 481 { 482 using _Up = __remove_cvref_t<_ValueType>; 483 static_assert(any::__is_valid_cast<_ValueType>(), 484 "Template argument must be a reference or CopyConstructible type"); 485 static_assert(is_constructible_v<_ValueType, _Up&>, 486 "Template argument must be constructible from an lvalue."); 487 auto __p = any_cast<_Up>(&__any); 488 if (__p) 489 return static_cast<_ValueType>(*__p); 490 __throw_bad_any_cast(); 491 } 492 493 template<typename _ValueType> 494 inline _ValueType any_cast(any&& __any) 495 { 496 using _Up = __remove_cvref_t<_ValueType>; 497 static_assert(any::__is_valid_cast<_ValueType>(), 498 "Template argument must be a reference or CopyConstructible type"); 499 static_assert(is_constructible_v<_ValueType, _Up>, 500 "Template argument must be constructible from an rvalue."); 501 auto __p = any_cast<_Up>(&__any); 502 if (__p) 503 return static_cast<_ValueType>(std::move(*__p)); 504 __throw_bad_any_cast(); 505 } 506 /// @} 507 508 /// @cond undocumented 509 template<typename _Tp> 510 void* __any_caster(const any* __any) 511 { 512 // any_cast<T> returns non-null if __any->type() == typeid(T) and 513 // typeid(T) ignores cv-qualifiers so remove them: 514 using _Up = remove_cv_t<_Tp>; 515 // The contained value has a decayed type, so if decay_t<U> is not U, 516 // then it's not possible to have a contained value of type U: 517 if constexpr (!is_same_v<decay_t<_Up>, _Up>) 518 return nullptr; 519 // Only copy constructible types can be used for contained values: 520 else if constexpr (!is_copy_constructible_v<_Up>) 521 return nullptr; 522 // First try comparing function addresses, which works without RTTI 523 else if (__any->_M_manager == &any::_Manager<_Up>::_S_manage 524#if __cpp_rtti 525 || __any->type() == typeid(_Tp) 526#endif 527 ) 528 { 529 return any::_Manager<_Up>::_S_access(__any->_M_storage); 530 } 531 return nullptr; 532 } 533 /// @endcond 534 535 /** 536 * @brief Access the contained object. 537 * 538 * @tparam _ValueType The type of the contained object. 539 * @param __any A pointer to the object to access. 540 * @return The address of the contained object if <code> 541 * __any != nullptr && __any.type() == typeid(_ValueType) 542 * </code>, otherwise a null pointer. 543 * 544 * @{ 545 */ 546 template<typename _ValueType> 547 inline const _ValueType* any_cast(const any* __any) noexcept 548 { 549 if constexpr (is_object_v<_ValueType>) 550 if (__any) 551 return static_cast<_ValueType*>(__any_caster<_ValueType>(__any)); 552 return nullptr; 553 } 554 555 template<typename _ValueType> 556 inline _ValueType* any_cast(any* __any) noexcept 557 { 558 if constexpr (is_object_v<_ValueType>) 559 if (__any) 560 return static_cast<_ValueType*>(__any_caster<_ValueType>(__any)); 561 return nullptr; 562 } 563 /// @} 564 565 template<typename _Tp> 566 void 567 any::_Manager_internal<_Tp>:: 568 _S_manage(_Op __which, const any* __any, _Arg* __arg) 569 { 570 // The contained object is in _M_storage._M_buffer 571 auto __ptr = reinterpret_cast<const _Tp*>(&__any->_M_storage._M_buffer); 572 switch (__which) 573 { 574 case _Op_access: 575 __arg->_M_obj = const_cast<_Tp*>(__ptr); 576 break; 577 case _Op_get_type_info: 578#if __cpp_rtti 579 __arg->_M_typeinfo = &typeid(_Tp); 580#endif 581 break; 582 case _Op_clone: 583 ::new(&__arg->_M_any->_M_storage._M_buffer) _Tp(*__ptr); 584 __arg->_M_any->_M_manager = __any->_M_manager; 585 break; 586 case _Op_destroy: 587 __ptr->~_Tp(); 588 break; 589 case _Op_xfer: 590 ::new(&__arg->_M_any->_M_storage._M_buffer) _Tp 591 (std::move(*const_cast<_Tp*>(__ptr))); 592 __ptr->~_Tp(); 593 __arg->_M_any->_M_manager = __any->_M_manager; 594 const_cast<any*>(__any)->_M_manager = nullptr; 595 break; 596 } 597 } 598 599 template<typename _Tp> 600 void 601 any::_Manager_external<_Tp>:: 602 _S_manage(_Op __which, const any* __any, _Arg* __arg) 603 { 604 // The contained object is *_M_storage._M_ptr 605 auto __ptr = static_cast<const _Tp*>(__any->_M_storage._M_ptr); 606 switch (__which) 607 { 608 case _Op_access: 609 __arg->_M_obj = const_cast<_Tp*>(__ptr); 610 break; 611 case _Op_get_type_info: 612#if __cpp_rtti 613 __arg->_M_typeinfo = &typeid(_Tp); 614#endif 615 break; 616 case _Op_clone: 617 __arg->_M_any->_M_storage._M_ptr = new _Tp(*__ptr); 618 __arg->_M_any->_M_manager = __any->_M_manager; 619 break; 620 case _Op_destroy: 621 delete __ptr; 622 break; 623 case _Op_xfer: 624 __arg->_M_any->_M_storage._M_ptr = __any->_M_storage._M_ptr; 625 __arg->_M_any->_M_manager = __any->_M_manager; 626 const_cast<any*>(__any)->_M_manager = nullptr; 627 break; 628 } 629 } 630 631 /// @} 632 633 namespace __detail::__variant 634 { 635 template<typename> struct _Never_valueless_alt; // see <variant> 636 637 // Provide the strong exception-safety guarantee when emplacing an 638 // any into a variant. 639 template<> 640 struct _Never_valueless_alt<std::any> 641 : std::true_type 642 { }; 643 } // namespace __detail::__variant 644 645_GLIBCXX_END_NAMESPACE_VERSION 646} // namespace std 647 648#endif // C++17 649#endif // _GLIBCXX_ANY 650