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The C and C++ Include Header Files
/usr/include/c++/11/any
$ cat -n /usr/include/c++/11/any 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 41 namespace 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 `any` object's state is either empty or it stores a contained object 75 * of CopyConstructible type. 76 * 77 * @since C++17 78 */ 79 class any 80 { 81 // Holds either pointer to a heap object or the contained object itself. 82 union _Storage 83 { 84 constexpr _Storage() : _M_ptr{nullptr} {} 85 86 // Prevent trivial copies of this type, buffer might hold a non-POD. 87 _Storage(const _Storage&) = delete; 88 _Storage& operator=(const _Storage&) = delete; 89 90 void* _M_ptr; 91 aligned_storage<sizeof(_M_ptr), alignof(void*)>::type _M_buffer; 92 }; 93 94 template<typename _Tp, typename _Safe = is_nothrow_move_constructible<_Tp>, 95 bool _Fits = (sizeof(_Tp) <= sizeof(_Storage)) 96 && (alignof(_Tp) <= alignof(_Storage))> 97 using _Internal = std::integral_constant<bool, _Safe::value && _Fits>; 98 99 template<typename _Tp> 100 struct _Manager_internal; // uses small-object optimization 101 102 template<typename _Tp> 103 struct _Manager_external; // creates contained object on the heap 104 105 template<typename _Tp> 106 using _Manager = conditional_t<_Internal<_Tp>::value, 107 _Manager_internal<_Tp>, 108 _Manager_external<_Tp>>; 109 110 template<typename _Tp, typename _VTp = decay_t<_Tp>> 111 using _Decay_if_not_any = enable_if_t<!is_same_v<_VTp, any>, _VTp>; 112 113 /// Emplace with an object created from @p __args as the contained object. 114 template <typename _Tp, typename... _Args, 115 typename _Mgr = _Manager<_Tp>> 116 void __do_emplace(_Args&&... __args) 117 { 118 reset(); 119 _Mgr::_S_create(_M_storage, std::forward<_Args>(__args)...); 120 _M_manager = &_Mgr::_S_manage; 121 } 122 123 /// Emplace with an object created from @p __il and @p __args as 124 /// the contained object. 125 template <typename _Tp, typename _Up, typename... _Args, 126 typename _Mgr = _Manager<_Tp>> 127 void __do_emplace(initializer_list<_Up> __il, _Args&&... __args) 128 { 129 reset(); 130 _Mgr::_S_create(_M_storage, __il, std::forward<_Args>(__args)...); 131 _M_manager = &_Mgr::_S_manage; 132 } 133 134 template <typename _Res, typename _Tp, typename... _Args> 135 using __any_constructible 136 = enable_if<__and_<is_copy_constructible<_Tp>, 137 is_constructible<_Tp, _Args...>>::value, 138 _Res>; 139 140 template <typename _Tp, typename... _Args> 141 using __any_constructible_t 142 = typename __any_constructible<bool, _Tp, _Args...>::type; 143 144 template<typename _VTp, typename... _Args> 145 using __emplace_t 146 = typename __any_constructible<_VTp&, _VTp, _Args...>::type; 147 148 public: 149 // construct/destruct 150 151 /// Default constructor, creates an empty object. 152 constexpr any() noexcept : _M_manager(nullptr) { } 153 154 /// Copy constructor, copies the state of @p __other 155 any(const any& __other) 156 { 157 if (!__other.has_value()) 158 _M_manager = nullptr; 159 else 160 { 161 _Arg __arg; 162 __arg._M_any = this; 163 __other._M_manager(_Op_clone, &__other, &__arg); 164 } 165 } 166 167 /** 168 * @brief Move constructor, transfer the state from @p __other 169 * 170 * @post @c !__other.has_value() (this postcondition is a GNU extension) 171 */ 172 any(any&& __other) noexcept 173 { 174 if (!__other.has_value()) 175 _M_manager = nullptr; 176 else 177 { 178 _Arg __arg; 179 __arg._M_any = this; 180 __other._M_manager(_Op_xfer, &__other, &__arg); 181 } 182 } 183 184 /// Construct with a copy of @p __value as the contained object. 185 template <typename _Tp, typename _VTp = _Decay_if_not_any<_Tp>, 186 typename _Mgr = _Manager<_VTp>, 187 enable_if_t<is_copy_constructible_v<_VTp> 188 && !__is_in_place_type_v<_VTp>, bool> = true> 189 any(_Tp&& __value) 190 : _M_manager(&_Mgr::_S_manage) 191 { 192 _Mgr::_S_create(_M_storage, std::forward<_Tp>(__value)); 193 } 194 195 /// Construct with an object created from @p __args as the contained object. 196 template <typename _Tp, typename... _Args, typename _VTp = decay_t<_Tp>, 197 typename _Mgr = _Manager<_VTp>, 198 __any_constructible_t<_VTp, _Args&&...> = false> 199 explicit 200 any(in_place_type_t<_Tp>, _Args&&... __args) 201 : _M_manager(&_Mgr::_S_manage) 202 { 203 _Mgr::_S_create(_M_storage, std::forward<_Args>(__args)...); 204 } 205 206 /// Construct with an object created from @p __il and @p __args as 207 /// the contained object. 208 template <typename _Tp, typename _Up, typename... _Args, 209 typename _VTp = decay_t<_Tp>, typename _Mgr = _Manager<_VTp>, 210 __any_constructible_t<_VTp, initializer_list<_Up>&, 211 _Args&&...> = false> 212 explicit 213 any(in_place_type_t<_Tp>, initializer_list<_Up> __il, _Args&&... __args) 214 : _M_manager(&_Mgr::_S_manage) 215 { 216 _Mgr::_S_create(_M_storage, __il, std::forward<_Args>(__args)...); 217 } 218 219 /// Destructor, calls @c reset() 220 ~any() { reset(); } 221 222 // assignments 223 224 /// Copy the state of another object. 225 any& 226 operator=(const any& __rhs) 227 { 228 *this = any(__rhs); 229 return *this; 230 } 231 232 /** 233 * @brief Move assignment operator 234 * 235 * @post @c !__rhs.has_value() (not guaranteed for other implementations) 236 */ 237 any& 238 operator=(any&& __rhs) noexcept 239 { 240 if (!__rhs.has_value()) 241 reset(); 242 else if (this != &__rhs) 243 { 244 reset(); 245 _Arg __arg; 246 __arg._M_any = this; 247 __rhs._M_manager(_Op_xfer, &__rhs, &__arg); 248 } 249 return *this; 250 } 251 252 /// Store a copy of @p __rhs as the contained object. 253 template<typename _Tp> 254 enable_if_t<is_copy_constructible<_Decay_if_not_any<_Tp>>::value, any&> 255 operator=(_Tp&& __rhs) 256 { 257 *this = any(std::forward<_Tp>(__rhs)); 258 return *this; 259 } 260 261 /// Emplace with an object created from @p __args as the contained object. 262 template <typename _Tp, typename... _Args> 263 __emplace_t<decay_t<_Tp>, _Args...> 264 emplace(_Args&&... __args) 265 { 266 using _VTp = decay_t<_Tp>; 267 __do_emplace<_VTp>(std::forward<_Args>(__args)...); 268 return *any::_Manager<_VTp>::_S_access(_M_storage); 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 return *any::_Manager<_VTp>::_S_access(_M_storage); 280 } 281 282 // modifiers 283 284 /// If not empty, destroy the contained object. 285 void reset() noexcept 286 { 287 if (has_value()) 288 { 289 _M_manager(_Op_destroy, this, nullptr); 290 _M_manager = nullptr; 291 } 292 } 293 294 /// Exchange state with another object. 295 void swap(any& __rhs) noexcept 296 { 297 if (!has_value() && !__rhs.has_value()) 298 return; 299 300 if (has_value() && __rhs.has_value()) 301 { 302 if (this == &__rhs) 303 return; 304 305 any __tmp; 306 _Arg __arg; 307 __arg._M_any = &__tmp; 308 __rhs._M_manager(_Op_xfer, &__rhs, &__arg); 309 __arg._M_any = &__rhs; 310 _M_manager(_Op_xfer, this, &__arg); 311 __arg._M_any = this; 312 __tmp._M_manager(_Op_xfer, &__tmp, &__arg); 313 } 314 else 315 { 316 any* __empty = !has_value() ? this : &__rhs; 317 any* __full = !has_value() ? &__rhs : this; 318 _Arg __arg; 319 __arg._M_any = __empty; 320 __full->_M_manager(_Op_xfer, __full, &__arg); 321 } 322 } 323 324 // observers 325 326 /// Reports whether there is a contained object or not. 327 bool has_value() const noexcept { return _M_manager != nullptr; } 328 329 #if __cpp_rtti 330 /// The @c typeid of the contained object, or @c typeid(void) if empty. 331 const type_info& type() const noexcept 332 { 333 if (!has_value()) 334 return typeid(void); 335 _Arg __arg; 336 _M_manager(_Op_get_type_info, this, &__arg); 337 return *__arg._M_typeinfo; 338 } 339 #endif 340 341 /// @cond undocumented 342 template<typename _Tp> 343 static constexpr bool __is_valid_cast() 344 { return __or_<is_reference<_Tp>, is_copy_constructible<_Tp>>::value; } 345 /// @endcond 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 /// @cond undocumented 363 template<typename _Tp> 364 friend void* __any_caster(const any* __any); 365 /// @endcond 366 367 // Manage in-place contained object. 368 template<typename _Tp> 369 struct _Manager_internal 370 { 371 static void 372 _S_manage(_Op __which, const any* __anyp, _Arg* __arg); 373 374 template<typename _Up> 375 static void 376 _S_create(_Storage& __storage, _Up&& __value) 377 { 378 void* __addr = &__storage._M_buffer; 379 ::new (__addr) _Tp(std::forward<_Up>(__value)); 380 } 381 382 template<typename... _Args> 383 static void 384 _S_create(_Storage& __storage, _Args&&... __args) 385 { 386 void* __addr = &__storage._M_buffer; 387 ::new (__addr) _Tp(std::forward<_Args>(__args)...); 388 } 389 390 static _Tp* 391 _S_access(const _Storage& __storage) 392 { 393 // The contained object is in __storage._M_buffer 394 const void* __addr = &__storage._M_buffer; 395 return static_cast<_Tp*>(const_cast<void*>(__addr)); 396 } 397 }; 398 399 // Manage external contained object. 400 template<typename _Tp> 401 struct _Manager_external 402 { 403 static void 404 _S_manage(_Op __which, const any* __anyp, _Arg* __arg); 405 406 template<typename _Up> 407 static void 408 _S_create(_Storage& __storage, _Up&& __value) 409 { 410 __storage._M_ptr = new _Tp(std::forward<_Up>(__value)); 411 } 412 template<typename... _Args> 413 static void 414 _S_create(_Storage& __storage, _Args&&... __args) 415 { 416 __storage._M_ptr = new _Tp(std::forward<_Args>(__args)...); 417 } 418 static _Tp* 419 _S_access(const _Storage& __storage) 420 { 421 // The contained object is in *__storage._M_ptr 422 return static_cast<_Tp*>(__storage._M_ptr); 423 } 424 }; 425 }; 426 427 /// Exchange the states of two @c any objects. 428 inline void swap(any& __x, any& __y) noexcept { __x.swap(__y); } 429 430 /// Create an `any` holding a `_Tp` constructed from `__args...`. 431 template <typename _Tp, typename... _Args> 432 inline 433 enable_if_t<is_constructible_v<any, in_place_type_t<_Tp>, _Args...>, any> 434 make_any(_Args&&... __args) 435 { 436 return any(in_place_type<_Tp>, std::forward<_Args>(__args)...); 437 } 438 439 /// Create an `any` holding a `_Tp` constructed from `__il` and `__args...`. 440 template <typename _Tp, typename _Up, typename... _Args> 441 inline 442 enable_if_t<is_constructible_v<any, in_place_type_t<_Tp>, 443 initializer_list<_Up>&, _Args...>, any> 444 make_any(initializer_list<_Up> __il, _Args&&... __args) 445 { 446 return any(in_place_type<_Tp>, __il, std::forward<_Args>(__args)...); 447 } 448 449 /** 450 * @brief Access the contained object. 451 * 452 * @tparam _ValueType A const-reference or CopyConstructible type. 453 * @param __any The object to access. 454 * @return The contained object. 455 * @throw bad_any_cast If <code> 456 * __any.type() != typeid(remove_reference_t<_ValueType>) 457 * </code> 458 */ 459 template<typename _ValueType> 460 inline _ValueType any_cast(const any& __any) 461 { 462 using _Up = __remove_cvref_t<_ValueType>; 463 static_assert(any::__is_valid_cast<_ValueType>(), 464 "Template argument must be a reference or CopyConstructible type"); 465 static_assert(is_constructible_v<_ValueType, const _Up&>, 466 "Template argument must be constructible from a const value."); 467 auto __p = any_cast<_Up>(&__any); 468 if (__p) 469 return static_cast<_ValueType>(*__p); 470 __throw_bad_any_cast(); 471 } 472 473 /** 474 * @brief Access the contained object. 475 * 476 * @tparam _ValueType A reference or CopyConstructible type. 477 * @param __any The object to access. 478 * @return The contained object. 479 * @throw bad_any_cast If <code> 480 * __any.type() != typeid(remove_reference_t<_ValueType>) 481 * </code> 482 * 483 * @{ 484 */ 485 template<typename _ValueType> 486 inline _ValueType any_cast(any& __any) 487 { 488 using _Up = __remove_cvref_t<_ValueType>; 489 static_assert(any::__is_valid_cast<_ValueType>(), 490 "Template argument must be a reference or CopyConstructible type"); 491 static_assert(is_constructible_v<_ValueType, _Up&>, 492 "Template argument must be constructible from an lvalue."); 493 auto __p = any_cast<_Up>(&__any); 494 if (__p) 495 return static_cast<_ValueType>(*__p); 496 __throw_bad_any_cast(); 497 } 498 499 template<typename _ValueType> 500 inline _ValueType any_cast(any&& __any) 501 { 502 using _Up = __remove_cvref_t<_ValueType>; 503 static_assert(any::__is_valid_cast<_ValueType>(), 504 "Template argument must be a reference or CopyConstructible type"); 505 static_assert(is_constructible_v<_ValueType, _Up>, 506 "Template argument must be constructible from an rvalue."); 507 auto __p = any_cast<_Up>(&__any); 508 if (__p) 509 return static_cast<_ValueType>(std::move(*__p)); 510 __throw_bad_any_cast(); 511 } 512 /// @} 513 514 /// @cond undocumented 515 template<typename _Tp> 516 void* __any_caster(const any* __any) 517 { 518 // any_cast<T> returns non-null if __any->type() == typeid(T) and 519 // typeid(T) ignores cv-qualifiers so remove them: 520 using _Up = remove_cv_t<_Tp>; 521 // The contained value has a decayed type, so if decay_t<U> is not U, 522 // then it's not possible to have a contained value of type U: 523 if constexpr (!is_same_v<decay_t<_Up>, _Up>) 524 return nullptr; 525 // Only copy constructible types can be used for contained values: 526 else if constexpr (!is_copy_constructible_v<_Up>) 527 return nullptr; 528 // First try comparing function addresses, which works without RTTI 529 else if (__any->_M_manager == &any::_Manager<_Up>::_S_manage 530 #if __cpp_rtti 531 || __any->type() == typeid(_Tp) 532 #endif 533 ) 534 { 535 return any::_Manager<_Up>::_S_access(__any->_M_storage); 536 } 537 return nullptr; 538 } 539 /// @endcond 540 541 /** 542 * @brief Access the contained object. 543 * 544 * @tparam _ValueType The type of the contained object. 545 * @param __any A pointer to the object to access. 546 * @return The address of the contained object if <code> 547 * __any != nullptr && __any.type() == typeid(_ValueType) 548 * </code>, otherwise a null pointer. 549 * 550 * @{ 551 */ 552 template<typename _ValueType> 553 inline const _ValueType* any_cast(const any* __any) noexcept 554 { 555 if constexpr (is_object_v<_ValueType>) 556 if (__any) 557 return static_cast<_ValueType*>(__any_caster<_ValueType>(__any)); 558 return nullptr; 559 } 560 561 template<typename _ValueType> 562 inline _ValueType* any_cast(any* __any) noexcept 563 { 564 if constexpr (is_object_v<_ValueType>) 565 if (__any) 566 return static_cast<_ValueType*>(__any_caster<_ValueType>(__any)); 567 return nullptr; 568 } 569 /// @} 570 571 template<typename _Tp> 572 void 573 any::_Manager_internal<_Tp>:: 574 _S_manage(_Op __which, const any* __any, _Arg* __arg) 575 { 576 // The contained object is in _M_storage._M_buffer 577 auto __ptr = reinterpret_cast<const _Tp*>(&__any->_M_storage._M_buffer); 578 switch (__which) 579 { 580 case _Op_access: 581 __arg->_M_obj = const_cast<_Tp*>(__ptr); 582 break; 583 case _Op_get_type_info: 584 #if __cpp_rtti 585 __arg->_M_typeinfo = &typeid(_Tp); 586 #endif 587 break; 588 case _Op_clone: 589 ::new(&__arg->_M_any->_M_storage._M_buffer) _Tp(*__ptr); 590 __arg->_M_any->_M_manager = __any->_M_manager; 591 break; 592 case _Op_destroy: 593 __ptr->~_Tp(); 594 break; 595 case _Op_xfer: 596 ::new(&__arg->_M_any->_M_storage._M_buffer) _Tp 597 (std::move(*const_cast<_Tp*>(__ptr))); 598 __ptr->~_Tp(); 599 __arg->_M_any->_M_manager = __any->_M_manager; 600 const_cast<any*>(__any)->_M_manager = nullptr; 601 break; 602 } 603 } 604 605 template<typename _Tp> 606 void 607 any::_Manager_external<_Tp>:: 608 _S_manage(_Op __which, const any* __any, _Arg* __arg) 609 { 610 // The contained object is *_M_storage._M_ptr 611 auto __ptr = static_cast<const _Tp*>(__any->_M_storage._M_ptr); 612 switch (__which) 613 { 614 case _Op_access: 615 __arg->_M_obj = const_cast<_Tp*>(__ptr); 616 break; 617 case _Op_get_type_info: 618 #if __cpp_rtti 619 __arg->_M_typeinfo = &typeid(_Tp); 620 #endif 621 break; 622 case _Op_clone: 623 __arg->_M_any->_M_storage._M_ptr = new _Tp(*__ptr); 624 __arg->_M_any->_M_manager = __any->_M_manager; 625 break; 626 case _Op_destroy: 627 delete __ptr; 628 break; 629 case _Op_xfer: 630 __arg->_M_any->_M_storage._M_ptr = __any->_M_storage._M_ptr; 631 __arg->_M_any->_M_manager = __any->_M_manager; 632 const_cast<any*>(__any)->_M_manager = nullptr; 633 break; 634 } 635 } 636 637 /// @} 638 639 namespace __detail::__variant 640 { 641 template<typename> struct _Never_valueless_alt; // see <variant> 642 643 // Provide the strong exception-safety guarantee when emplacing an 644 // any into a variant. 645 template<> 646 struct _Never_valueless_alt<std::any> 647 : std::true_type 648 { }; 649 } // namespace __detail::__variant 650 651 _GLIBCXX_END_NAMESPACE_VERSION 652 } // namespace std 653 654 #endif // C++17 655 #endif // _GLIBCXX_ANY
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