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The C and C++ Include Header Files
/usr/include/c++/13/any
$ cat -n /usr/include/c++/13/any 1 // <any> -*- C++ -*- 2 3 // Copyright (C) 2014-2023 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 <initializer_list> 37 #include <typeinfo> 38 #include <new> 39 #include <type_traits> 40 #include <bits/utility.h> // in_place_type_t 41 42 namespace std _GLIBCXX_VISIBILITY(default) 43 { 44 _GLIBCXX_BEGIN_NAMESPACE_VERSION 45 46 /** 47 * @addtogroup utilities 48 * @{ 49 */ 50 51 /** 52 * @brief Exception class thrown by a failed @c any_cast 53 * @ingroup exceptions 54 */ 55 class bad_any_cast : public bad_cast 56 { 57 public: 58 virtual const char* what() const noexcept { return "bad any_cast"; } 59 }; 60 61 [[gnu::noreturn]] inline void __throw_bad_any_cast() 62 { 63 #if __cpp_exceptions 64 throw bad_any_cast{}; 65 #else 66 __builtin_abort(); 67 #endif 68 } 69 70 #define __cpp_lib_any 201606L 71 72 /** 73 * @brief A type-safe container of any type. 74 * 75 * An `any` object's state is either empty or it stores a contained object 76 * of CopyConstructible type. 77 * 78 * @since C++17 79 */ 80 class any 81 { 82 // Holds either pointer to a heap object or the contained object itself. 83 union _Storage 84 { 85 constexpr _Storage() : _M_ptr{nullptr} {} 86 87 // Prevent trivial copies of this type, buffer might hold a non-POD. 88 _Storage(const _Storage&) = delete; 89 _Storage& operator=(const _Storage&) = delete; 90 91 void* _M_ptr; 92 aligned_storage<sizeof(_M_ptr), alignof(void*)>::type _M_buffer; 93 }; 94 95 template<typename _Tp, typename _Safe = is_nothrow_move_constructible<_Tp>, 96 bool _Fits = (sizeof(_Tp) <= sizeof(_Storage)) 97 && (alignof(_Tp) <= alignof(_Storage))> 98 using _Internal = std::integral_constant<bool, _Safe::value && _Fits>; 99 100 template<typename _Tp> 101 struct _Manager_internal; // uses small-object optimization 102 103 template<typename _Tp> 104 struct _Manager_external; // creates contained object on the heap 105 106 template<typename _Tp> 107 using _Manager = __conditional_t<_Internal<_Tp>::value, 108 _Manager_internal<_Tp>, 109 _Manager_external<_Tp>>; 110 111 template<typename _Tp, typename _VTp = decay_t<_Tp>> 112 using _Decay_if_not_any = enable_if_t<!is_same_v<_VTp, any>, _VTp>; 113 114 /// Emplace with an object created from @p __args as the contained object. 115 template <typename _Tp, typename... _Args, 116 typename _Mgr = _Manager<_Tp>> 117 void __do_emplace(_Args&&... __args) 118 { 119 reset(); 120 _Mgr::_S_create(_M_storage, std::forward<_Args>(__args)...); 121 _M_manager = &_Mgr::_S_manage; 122 } 123 124 /// Emplace with an object created from @p __il and @p __args as 125 /// the contained object. 126 template <typename _Tp, typename _Up, typename... _Args, 127 typename _Mgr = _Manager<_Tp>> 128 void __do_emplace(initializer_list<_Up> __il, _Args&&... __args) 129 { 130 reset(); 131 _Mgr::_S_create(_M_storage, __il, std::forward<_Args>(__args)...); 132 _M_manager = &_Mgr::_S_manage; 133 } 134 135 template <typename _Res, typename _Tp, typename... _Args> 136 using __any_constructible 137 = enable_if<__and_<is_copy_constructible<_Tp>, 138 is_constructible<_Tp, _Args...>>::value, 139 _Res>; 140 141 template <typename _Tp, typename... _Args> 142 using __any_constructible_t 143 = typename __any_constructible<bool, _Tp, _Args...>::type; 144 145 template<typename _VTp, typename... _Args> 146 using __emplace_t 147 = typename __any_constructible<_VTp&, _VTp, _Args...>::type; 148 149 public: 150 // construct/destruct 151 152 /// Default constructor, creates an empty object. 153 constexpr any() noexcept : _M_manager(nullptr) { } 154 155 /// Copy constructor, copies the state of @p __other 156 any(const any& __other) 157 { 158 if (!__other.has_value()) 159 _M_manager = nullptr; 160 else 161 { 162 _Arg __arg; 163 __arg._M_any = this; 164 __other._M_manager(_Op_clone, &__other, &__arg); 165 } 166 } 167 168 /** 169 * @brief Move constructor, transfer the state from @p __other 170 * 171 * @post @c !__other.has_value() (this postcondition is a GNU extension) 172 */ 173 any(any&& __other) noexcept 174 { 175 if (!__other.has_value()) 176 _M_manager = nullptr; 177 else 178 { 179 _Arg __arg; 180 __arg._M_any = this; 181 __other._M_manager(_Op_xfer, &__other, &__arg); 182 } 183 } 184 185 /// Construct with a copy of @p __value as the contained object. 186 template <typename _Tp, typename _VTp = _Decay_if_not_any<_Tp>, 187 typename _Mgr = _Manager<_VTp>, 188 enable_if_t<is_copy_constructible_v<_VTp> 189 && !__is_in_place_type_v<_VTp>, bool> = true> 190 any(_Tp&& __value) 191 : _M_manager(&_Mgr::_S_manage) 192 { 193 _Mgr::_S_create(_M_storage, std::forward<_Tp>(__value)); 194 } 195 196 /// Construct with an object created from @p __args as the contained object. 197 template <typename _Tp, typename... _Args, typename _VTp = decay_t<_Tp>, 198 typename _Mgr = _Manager<_VTp>, 199 __any_constructible_t<_VTp, _Args&&...> = false> 200 explicit 201 any(in_place_type_t<_Tp>, _Args&&... __args) 202 : _M_manager(&_Mgr::_S_manage) 203 { 204 _Mgr::_S_create(_M_storage, std::forward<_Args>(__args)...); 205 } 206 207 /// Construct with an object created from @p __il and @p __args as 208 /// the contained object. 209 template <typename _Tp, typename _Up, typename... _Args, 210 typename _VTp = decay_t<_Tp>, typename _Mgr = _Manager<_VTp>, 211 __any_constructible_t<_VTp, initializer_list<_Up>&, 212 _Args&&...> = false> 213 explicit 214 any(in_place_type_t<_Tp>, initializer_list<_Up> __il, _Args&&... __args) 215 : _M_manager(&_Mgr::_S_manage) 216 { 217 _Mgr::_S_create(_M_storage, __il, std::forward<_Args>(__args)...); 218 } 219 220 /// Destructor, calls @c reset() 221 ~any() { reset(); } 222 223 // assignments 224 225 /// Copy the state of another object. 226 any& 227 operator=(const any& __rhs) 228 { 229 *this = any(__rhs); 230 return *this; 231 } 232 233 /** 234 * @brief Move assignment operator 235 * 236 * @post @c !__rhs.has_value() (not guaranteed for other implementations) 237 */ 238 any& 239 operator=(any&& __rhs) noexcept 240 { 241 if (!__rhs.has_value()) 242 reset(); 243 else if (this != &__rhs) 244 { 245 reset(); 246 _Arg __arg; 247 __arg._M_any = this; 248 __rhs._M_manager(_Op_xfer, &__rhs, &__arg); 249 } 250 return *this; 251 } 252 253 /// Store a copy of @p __rhs as the contained object. 254 template<typename _Tp> 255 enable_if_t<is_copy_constructible<_Decay_if_not_any<_Tp>>::value, any&> 256 operator=(_Tp&& __rhs) 257 { 258 *this = any(std::forward<_Tp>(__rhs)); 259 return *this; 260 } 261 262 /// Emplace with an object created from @p __args as the contained object. 263 template <typename _Tp, typename... _Args> 264 __emplace_t<decay_t<_Tp>, _Args...> 265 emplace(_Args&&... __args) 266 { 267 using _VTp = decay_t<_Tp>; 268 __do_emplace<_VTp>(std::forward<_Args>(__args)...); 269 return *any::_Manager<_VTp>::_S_access(_M_storage); 270 } 271 272 /// Emplace with an object created from @p __il and @p __args as 273 /// the contained object. 274 template <typename _Tp, typename _Up, typename... _Args> 275 __emplace_t<decay_t<_Tp>, initializer_list<_Up>&, _Args&&...> 276 emplace(initializer_list<_Up> __il, _Args&&... __args) 277 { 278 using _VTp = decay_t<_Tp>; 279 __do_emplace<_VTp, _Up>(__il, std::forward<_Args>(__args)...); 280 return *any::_Manager<_VTp>::_S_access(_M_storage); 281 } 282 283 // modifiers 284 285 /// If not empty, destroy the contained object. 286 void reset() noexcept 287 { 288 if (has_value()) 289 { 290 _M_manager(_Op_destroy, this, nullptr); 291 _M_manager = nullptr; 292 } 293 } 294 295 /// Exchange state with another object. 296 void swap(any& __rhs) noexcept 297 { 298 if (!has_value() && !__rhs.has_value()) 299 return; 300 301 if (has_value() && __rhs.has_value()) 302 { 303 if (this == &__rhs) 304 return; 305 306 any __tmp; 307 _Arg __arg; 308 __arg._M_any = &__tmp; 309 __rhs._M_manager(_Op_xfer, &__rhs, &__arg); 310 __arg._M_any = &__rhs; 311 _M_manager(_Op_xfer, this, &__arg); 312 __arg._M_any = this; 313 __tmp._M_manager(_Op_xfer, &__tmp, &__arg); 314 } 315 else 316 { 317 any* __empty = !has_value() ? this : &__rhs; 318 any* __full = !has_value() ? &__rhs : this; 319 _Arg __arg; 320 __arg._M_any = __empty; 321 __full->_M_manager(_Op_xfer, __full, &__arg); 322 } 323 } 324 325 // observers 326 327 /// Reports whether there is a contained object or not. 328 bool has_value() const noexcept { return _M_manager != nullptr; } 329 330 #if __cpp_rtti 331 /// The @c typeid of the contained object, or @c typeid(void) if empty. 332 const type_info& type() const noexcept 333 { 334 if (!has_value()) 335 return typeid(void); 336 _Arg __arg; 337 _M_manager(_Op_get_type_info, this, &__arg); 338 return *__arg._M_typeinfo; 339 } 340 #endif 341 342 /// @cond undocumented 343 template<typename _Tp> 344 static constexpr bool __is_valid_cast() 345 { return __or_<is_reference<_Tp>, is_copy_constructible<_Tp>>::value; } 346 /// @endcond 347 348 private: 349 enum _Op { 350 _Op_access, _Op_get_type_info, _Op_clone, _Op_destroy, _Op_xfer 351 }; 352 353 union _Arg 354 { 355 void* _M_obj; 356 const std::type_info* _M_typeinfo; 357 any* _M_any; 358 }; 359 360 void (*_M_manager)(_Op, const any*, _Arg*); 361 _Storage _M_storage; 362 363 /// @cond undocumented 364 template<typename _Tp> 365 friend void* __any_caster(const any* __any); 366 /// @endcond 367 368 // Manage in-place contained object. 369 template<typename _Tp> 370 struct _Manager_internal 371 { 372 static void 373 _S_manage(_Op __which, const any* __anyp, _Arg* __arg); 374 375 template<typename _Up> 376 static void 377 _S_create(_Storage& __storage, _Up&& __value) 378 { 379 void* __addr = &__storage._M_buffer; 380 ::new (__addr) _Tp(std::forward<_Up>(__value)); 381 } 382 383 template<typename... _Args> 384 static void 385 _S_create(_Storage& __storage, _Args&&... __args) 386 { 387 void* __addr = &__storage._M_buffer; 388 ::new (__addr) _Tp(std::forward<_Args>(__args)...); 389 } 390 391 static _Tp* 392 _S_access(const _Storage& __storage) 393 { 394 // The contained object is in __storage._M_buffer 395 const void* __addr = &__storage._M_buffer; 396 return static_cast<_Tp*>(const_cast<void*>(__addr)); 397 } 398 }; 399 400 // Manage external contained object. 401 template<typename _Tp> 402 struct _Manager_external 403 { 404 static void 405 _S_manage(_Op __which, const any* __anyp, _Arg* __arg); 406 407 template<typename _Up> 408 static void 409 _S_create(_Storage& __storage, _Up&& __value) 410 { 411 __storage._M_ptr = new _Tp(std::forward<_Up>(__value)); 412 } 413 template<typename... _Args> 414 static void 415 _S_create(_Storage& __storage, _Args&&... __args) 416 { 417 __storage._M_ptr = new _Tp(std::forward<_Args>(__args)...); 418 } 419 static _Tp* 420 _S_access(const _Storage& __storage) 421 { 422 // The contained object is in *__storage._M_ptr 423 return static_cast<_Tp*>(__storage._M_ptr); 424 } 425 }; 426 }; 427 428 /// Exchange the states of two @c any objects. 429 inline void swap(any& __x, any& __y) noexcept { __x.swap(__y); } 430 431 /// Create an `any` holding a `_Tp` constructed from `__args...`. 432 template <typename _Tp, typename... _Args> 433 inline 434 enable_if_t<is_constructible_v<any, in_place_type_t<_Tp>, _Args...>, any> 435 make_any(_Args&&... __args) 436 { 437 return any(in_place_type<_Tp>, std::forward<_Args>(__args)...); 438 } 439 440 /// Create an `any` holding a `_Tp` constructed from `__il` and `__args...`. 441 template <typename _Tp, typename _Up, typename... _Args> 442 inline 443 enable_if_t<is_constructible_v<any, in_place_type_t<_Tp>, 444 initializer_list<_Up>&, _Args...>, any> 445 make_any(initializer_list<_Up> __il, _Args&&... __args) 446 { 447 return any(in_place_type<_Tp>, __il, std::forward<_Args>(__args)...); 448 } 449 450 /** 451 * @brief Access the contained object. 452 * 453 * @tparam _ValueType A const-reference or CopyConstructible type. 454 * @param __any The object to access. 455 * @return The contained object. 456 * @throw bad_any_cast If <code> 457 * __any.type() != typeid(remove_reference_t<_ValueType>) 458 * </code> 459 */ 460 template<typename _ValueType> 461 inline _ValueType any_cast(const any& __any) 462 { 463 using _Up = __remove_cvref_t<_ValueType>; 464 static_assert(any::__is_valid_cast<_ValueType>(), 465 "Template argument must be a reference or CopyConstructible type"); 466 static_assert(is_constructible_v<_ValueType, const _Up&>, 467 "Template argument must be constructible from a const value."); 468 auto __p = any_cast<_Up>(&__any); 469 if (__p) 470 return static_cast<_ValueType>(*__p); 471 __throw_bad_any_cast(); 472 } 473 474 /** 475 * @brief Access the contained object. 476 * 477 * @tparam _ValueType A reference or CopyConstructible type. 478 * @param __any The object to access. 479 * @return The contained object. 480 * @throw bad_any_cast If <code> 481 * __any.type() != typeid(remove_reference_t<_ValueType>) 482 * </code> 483 * 484 * @{ 485 */ 486 template<typename _ValueType> 487 inline _ValueType any_cast(any& __any) 488 { 489 using _Up = __remove_cvref_t<_ValueType>; 490 static_assert(any::__is_valid_cast<_ValueType>(), 491 "Template argument must be a reference or CopyConstructible type"); 492 static_assert(is_constructible_v<_ValueType, _Up&>, 493 "Template argument must be constructible from an lvalue."); 494 auto __p = any_cast<_Up>(&__any); 495 if (__p) 496 return static_cast<_ValueType>(*__p); 497 __throw_bad_any_cast(); 498 } 499 500 template<typename _ValueType> 501 inline _ValueType any_cast(any&& __any) 502 { 503 using _Up = __remove_cvref_t<_ValueType>; 504 static_assert(any::__is_valid_cast<_ValueType>(), 505 "Template argument must be a reference or CopyConstructible type"); 506 static_assert(is_constructible_v<_ValueType, _Up>, 507 "Template argument must be constructible from an rvalue."); 508 auto __p = any_cast<_Up>(&__any); 509 if (__p) 510 return static_cast<_ValueType>(std::move(*__p)); 511 __throw_bad_any_cast(); 512 } 513 /// @} 514 515 /// @cond undocumented 516 template<typename _Tp> 517 void* __any_caster(const any* __any) 518 { 519 // any_cast<T> returns non-null if __any->type() == typeid(T) and 520 // typeid(T) ignores cv-qualifiers so remove them: 521 using _Up = remove_cv_t<_Tp>; 522 // The contained value has a decayed type, so if decay_t<U> is not U, 523 // then it's not possible to have a contained value of type U: 524 if constexpr (!is_same_v<decay_t<_Up>, _Up>) 525 return nullptr; 526 // Only copy constructible types can be used for contained values: 527 else if constexpr (!is_copy_constructible_v<_Up>) 528 return nullptr; 529 // First try comparing function addresses, which works without RTTI 530 else if (__any->_M_manager == &any::_Manager<_Up>::_S_manage 531 #if __cpp_rtti 532 || __any->type() == typeid(_Tp) 533 #endif 534 ) 535 { 536 return any::_Manager<_Up>::_S_access(__any->_M_storage); 537 } 538 return nullptr; 539 } 540 /// @endcond 541 542 /** 543 * @brief Access the contained object. 544 * 545 * @tparam _ValueType The type of the contained object. 546 * @param __any A pointer to the object to access. 547 * @return The address of the contained object if <code> 548 * __any != nullptr && __any.type() == typeid(_ValueType) 549 * </code>, otherwise a null pointer. 550 * 551 * @{ 552 */ 553 template<typename _ValueType> 554 inline const _ValueType* any_cast(const any* __any) noexcept 555 { 556 if constexpr (is_object_v<_ValueType>) 557 if (__any) 558 return static_cast<_ValueType*>(__any_caster<_ValueType>(__any)); 559 return nullptr; 560 } 561 562 template<typename _ValueType> 563 inline _ValueType* any_cast(any* __any) noexcept 564 { 565 if constexpr (is_object_v<_ValueType>) 566 if (__any) 567 return static_cast<_ValueType*>(__any_caster<_ValueType>(__any)); 568 return nullptr; 569 } 570 /// @} 571 572 template<typename _Tp> 573 void 574 any::_Manager_internal<_Tp>:: 575 _S_manage(_Op __which, const any* __any, _Arg* __arg) 576 { 577 // The contained object is in _M_storage._M_buffer 578 auto __ptr = reinterpret_cast<const _Tp*>(&__any->_M_storage._M_buffer); 579 switch (__which) 580 { 581 case _Op_access: 582 __arg->_M_obj = const_cast<_Tp*>(__ptr); 583 break; 584 case _Op_get_type_info: 585 #if __cpp_rtti 586 __arg->_M_typeinfo = &typeid(_Tp); 587 #endif 588 break; 589 case _Op_clone: 590 ::new(&__arg->_M_any->_M_storage._M_buffer) _Tp(*__ptr); 591 __arg->_M_any->_M_manager = __any->_M_manager; 592 break; 593 case _Op_destroy: 594 __ptr->~_Tp(); 595 break; 596 case _Op_xfer: 597 ::new(&__arg->_M_any->_M_storage._M_buffer) _Tp 598 (std::move(*const_cast<_Tp*>(__ptr))); 599 __ptr->~_Tp(); 600 __arg->_M_any->_M_manager = __any->_M_manager; 601 const_cast<any*>(__any)->_M_manager = nullptr; 602 break; 603 } 604 } 605 606 template<typename _Tp> 607 void 608 any::_Manager_external<_Tp>:: 609 _S_manage(_Op __which, const any* __any, _Arg* __arg) 610 { 611 // The contained object is *_M_storage._M_ptr 612 auto __ptr = static_cast<const _Tp*>(__any->_M_storage._M_ptr); 613 switch (__which) 614 { 615 case _Op_access: 616 __arg->_M_obj = const_cast<_Tp*>(__ptr); 617 break; 618 case _Op_get_type_info: 619 #if __cpp_rtti 620 __arg->_M_typeinfo = &typeid(_Tp); 621 #endif 622 break; 623 case _Op_clone: 624 __arg->_M_any->_M_storage._M_ptr = new _Tp(*__ptr); 625 __arg->_M_any->_M_manager = __any->_M_manager; 626 break; 627 case _Op_destroy: 628 delete __ptr; 629 break; 630 case _Op_xfer: 631 __arg->_M_any->_M_storage._M_ptr = __any->_M_storage._M_ptr; 632 __arg->_M_any->_M_manager = __any->_M_manager; 633 const_cast<any*>(__any)->_M_manager = nullptr; 634 break; 635 } 636 } 637 638 /// @} 639 640 namespace __detail::__variant 641 { 642 template<typename> struct _Never_valueless_alt; // see <variant> 643 644 // Provide the strong exception-safety guarantee when emplacing an 645 // any into a variant. 646 template<> 647 struct _Never_valueless_alt<std::any> 648 : std::true_type 649 { }; 650 } // namespace __detail::__variant 651 652 _GLIBCXX_END_NAMESPACE_VERSION 653 } // namespace std 654 655 #endif // C++17 656 #endif // _GLIBCXX_ANY
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