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The C and C++ Include Header Files
cat -n /usr/include/c++/15/any
1 // <any> -*- C++ -*- 2 3 // Copyright (C) 2014-2025 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 #ifdef _GLIBCXX_SYSHDR 33 #pragma GCC system_header 34 #endif 35 36 #define __glibcxx_want_any 37 #include <bits/version.h> 38 39 #ifdef __cpp_lib_any // C++ >= 17 40 41 #include <initializer_list> 42 #include <typeinfo> 43 #include <new> 44 #include <type_traits> 45 #include <bits/utility.h> // in_place_type_t 46 47 #pragma GCC diagnostic push 48 #pragma GCC diagnostic ignored "-Wdeprecated-declarations" // aligned_storage 49 50 namespace std _GLIBCXX_VISIBILITY(default) 51 { 52 _GLIBCXX_BEGIN_NAMESPACE_VERSION 53 54 /** 55 * @addtogroup utilities 56 * @{ 57 */ 58 59 /** 60 * @brief Exception class thrown by a failed @c any_cast 61 * @ingroup exceptions 62 */ 63 class bad_any_cast : public bad_cast 64 { 65 public: 66 virtual const char* what() const noexcept { return "bad any_cast"; } 67 }; 68 69 [[gnu::noreturn]] inline void __throw_bad_any_cast() 70 { 71 #if __cpp_exceptions 72 throw bad_any_cast{}; 73 #else 74 __builtin_abort(); 75 #endif 76 } 77 78 /** 79 * @brief A type-safe container of any type. 80 * 81 * An `any` object's state is either empty or it stores a contained object 82 * of CopyConstructible type. 83 * 84 * @since C++17 85 */ 86 class any 87 { 88 // Holds either pointer to a heap object or the contained object itself. 89 union _Storage 90 { 91 constexpr _Storage() : _M_ptr{nullptr} {} 92 93 // Prevent trivial copies of this type, buffer might hold a non-POD. 94 _Storage(const _Storage&) = delete; 95 _Storage& operator=(const _Storage&) = delete; 96 97 void* _M_ptr; 98 unsigned char _M_buffer[sizeof(_M_ptr)]; 99 }; 100 101 template<typename _Tp, typename _Safe = is_nothrow_move_constructible<_Tp>, 102 bool _Fits = (sizeof(_Tp) <= sizeof(_Storage)) 103 && (alignof(_Tp) <= alignof(_Storage))> 104 using _Internal = std::integral_constant<bool, _Safe::value && _Fits>; 105 106 template<typename _Tp> 107 struct _Manager_internal; // uses small-object optimization 108 109 template<typename _Tp> 110 struct _Manager_external; // creates contained object on the heap 111 112 template<typename _Tp> 113 using _Manager = __conditional_t<_Internal<_Tp>::value, 114 _Manager_internal<_Tp>, 115 _Manager_external<_Tp>>; 116 117 template<typename _Tp, typename _VTp = decay_t<_Tp>> 118 using _Decay_if_not_any = enable_if_t<!is_same_v<_VTp, any>, _VTp>; 119 120 /// Emplace with an object created from @p __args as the contained object. 121 template <typename _Tp, typename... _Args, 122 typename _Mgr = _Manager<_Tp>> 123 void __do_emplace(_Args&&... __args) 124 { 125 reset(); 126 _Mgr::_S_create(_M_storage, std::forward<_Args>(__args)...); 127 _M_manager = &_Mgr::_S_manage; 128 } 129 130 /// Emplace with an object created from @p __il and @p __args as 131 /// the contained object. 132 template <typename _Tp, typename _Up, typename... _Args, 133 typename _Mgr = _Manager<_Tp>> 134 void __do_emplace(initializer_list<_Up> __il, _Args&&... __args) 135 { 136 reset(); 137 _Mgr::_S_create(_M_storage, __il, std::forward<_Args>(__args)...); 138 _M_manager = &_Mgr::_S_manage; 139 } 140 141 template <typename _Res, typename _Tp, typename... _Args> 142 using __any_constructible 143 = enable_if<__and_<is_copy_constructible<_Tp>, 144 is_constructible<_Tp, _Args...>>::value, 145 _Res>; 146 147 template <typename _Tp, typename... _Args> 148 using __any_constructible_t 149 = typename __any_constructible<bool, _Tp, _Args...>::type; 150 151 template<typename _VTp, typename... _Args> 152 using __emplace_t 153 = typename __any_constructible<_VTp&, _VTp, _Args...>::type; 154 155 public: 156 // construct/destruct 157 158 /// Default constructor, creates an empty object. 159 constexpr any() noexcept : _M_manager(nullptr) { } 160 161 /// Copy constructor, copies the state of @p __other 162 any(const any& __other) 163 { 164 if (!__other.has_value()) 165 _M_manager = nullptr; 166 else 167 { 168 _Arg __arg; 169 __arg._M_any = this; 170 __other._M_manager(_Op_clone, &__other, &__arg); 171 } 172 } 173 174 /** 175 * @brief Move constructor, transfer the state from @p __other 176 * 177 * @post @c !__other.has_value() (this postcondition is a GNU extension) 178 */ 179 any(any&& __other) noexcept 180 { 181 if (!__other.has_value()) 182 _M_manager = nullptr; 183 else 184 { 185 _Arg __arg; 186 __arg._M_any = this; 187 __other._M_manager(_Op_xfer, &__other, &__arg); 188 } 189 } 190 191 /// Construct with a copy of @p __value as the contained object. 192 template <typename _Tp, typename _VTp = _Decay_if_not_any<_Tp>, 193 typename _Mgr = _Manager<_VTp>, 194 enable_if_t<is_copy_constructible_v<_VTp> 195 && !__is_in_place_type_v<_VTp>, bool> = true> 196 any(_Tp&& __value) 197 : _M_manager(&_Mgr::_S_manage) 198 { 199 _Mgr::_S_create(_M_storage, std::forward<_Tp>(__value)); 200 } 201 202 /// Construct with an object created from @p __args as the contained object. 203 template <typename _Tp, typename... _Args, typename _VTp = decay_t<_Tp>, 204 typename _Mgr = _Manager<_VTp>, 205 __any_constructible_t<_VTp, _Args&&...> = false> 206 explicit 207 any(in_place_type_t<_Tp>, _Args&&... __args) 208 : _M_manager(&_Mgr::_S_manage) 209 { 210 _Mgr::_S_create(_M_storage, std::forward<_Args>(__args)...); 211 } 212 213 /// Construct with an object created from @p __il and @p __args as 214 /// the contained object. 215 template <typename _Tp, typename _Up, typename... _Args, 216 typename _VTp = decay_t<_Tp>, typename _Mgr = _Manager<_VTp>, 217 __any_constructible_t<_VTp, initializer_list<_Up>&, 218 _Args&&...> = false> 219 explicit 220 any(in_place_type_t<_Tp>, initializer_list<_Up> __il, _Args&&... __args) 221 : _M_manager(&_Mgr::_S_manage) 222 { 223 _Mgr::_S_create(_M_storage, __il, std::forward<_Args>(__args)...); 224 } 225 226 /// Destructor, calls @c reset() 227 ~any() { reset(); } 228 229 // assignments 230 231 /// Copy the state of another object. 232 any& 233 operator=(const any& __rhs) 234 { 235 *this = any(__rhs); 236 return *this; 237 } 238 239 /** 240 * @brief Move assignment operator 241 * 242 * @post @c !__rhs.has_value() (not guaranteed for other implementations) 243 */ 244 any& 245 operator=(any&& __rhs) noexcept 246 { 247 if (!__rhs.has_value()) 248 reset(); 249 else if (this != &__rhs) 250 { 251 reset(); 252 _Arg __arg; 253 __arg._M_any = this; 254 __rhs._M_manager(_Op_xfer, &__rhs, &__arg); 255 } 256 return *this; 257 } 258 259 /// Store a copy of @p __rhs as the contained object. 260 template<typename _Tp> 261 enable_if_t<is_copy_constructible<_Decay_if_not_any<_Tp>>::value, any&> 262 operator=(_Tp&& __rhs) 263 { 264 *this = any(std::forward<_Tp>(__rhs)); 265 return *this; 266 } 267 268 /// Emplace with an object created from @p __args as the contained object. 269 template <typename _Tp, typename... _Args> 270 __emplace_t<decay_t<_Tp>, _Args...> 271 emplace(_Args&&... __args) 272 { 273 using _VTp = decay_t<_Tp>; 274 __do_emplace<_VTp>(std::forward<_Args>(__args)...); 275 return *any::_Manager<_VTp>::_S_access(_M_storage); 276 } 277 278 /// Emplace with an object created from @p __il and @p __args as 279 /// the contained object. 280 template <typename _Tp, typename _Up, typename... _Args> 281 __emplace_t<decay_t<_Tp>, initializer_list<_Up>&, _Args&&...> 282 emplace(initializer_list<_Up> __il, _Args&&... __args) 283 { 284 using _VTp = decay_t<_Tp>; 285 __do_emplace<_VTp, _Up>(__il, std::forward<_Args>(__args)...); 286 return *any::_Manager<_VTp>::_S_access(_M_storage); 287 } 288 289 // modifiers 290 291 /// If not empty, destroy the contained object. 292 void reset() noexcept 293 { 294 if (has_value()) 295 { 296 _M_manager(_Op_destroy, this, nullptr); 297 _M_manager = nullptr; 298 } 299 } 300 301 /// Exchange state with another object. 302 void swap(any& __rhs) noexcept 303 { 304 if (!has_value() && !__rhs.has_value()) 305 return; 306 307 if (has_value() && __rhs.has_value()) 308 { 309 if (this == &__rhs) 310 return; 311 312 any __tmp; 313 _Arg __arg; 314 __arg._M_any = &__tmp; 315 __rhs._M_manager(_Op_xfer, &__rhs, &__arg); 316 __arg._M_any = &__rhs; 317 _M_manager(_Op_xfer, this, &__arg); 318 __arg._M_any = this; 319 __tmp._M_manager(_Op_xfer, &__tmp, &__arg); 320 } 321 else 322 { 323 any* __empty = !has_value() ? this : &__rhs; 324 any* __full = !has_value() ? &__rhs : this; 325 _Arg __arg; 326 __arg._M_any = __empty; 327 __full->_M_manager(_Op_xfer, __full, &__arg); 328 } 329 } 330 331 // observers 332 333 /// Reports whether there is a contained object or not. 334 bool has_value() const noexcept { return _M_manager != nullptr; } 335 336 #if __cpp_rtti 337 /// The @c typeid of the contained object, or @c typeid(void) if empty. 338 const type_info& type() const noexcept 339 { 340 if (!has_value()) 341 return typeid(void); 342 _Arg __arg; 343 _M_manager(_Op_get_type_info, this, &__arg); 344 return *__arg._M_typeinfo; 345 } 346 #endif 347 348 /// @cond undocumented 349 template<typename _Tp> 350 static constexpr bool __is_valid_cast() 351 { return __or_<is_reference<_Tp>, is_copy_constructible<_Tp>>::value; } 352 /// @endcond 353 354 private: 355 enum _Op { 356 _Op_access, _Op_get_type_info, _Op_clone, _Op_destroy, _Op_xfer 357 }; 358 359 union _Arg 360 { 361 void* _M_obj; 362 const std::type_info* _M_typeinfo; 363 any* _M_any; 364 }; 365 366 void (*_M_manager)(_Op, const any*, _Arg*); 367 _Storage _M_storage; 368 369 /// @cond undocumented 370 template<typename _Tp> 371 friend void* __any_caster(const any* __any); 372 /// @endcond 373 374 // Manage in-place contained object. 375 template<typename _Tp> 376 struct _Manager_internal 377 { 378 static void 379 _S_manage(_Op __which, const any* __anyp, _Arg* __arg); 380 381 template<typename _Up> 382 static void 383 _S_create(_Storage& __storage, _Up&& __value) 384 { 385 void* __addr = &__storage._M_buffer; 386 ::new (__addr) _Tp(std::forward<_Up>(__value)); 387 } 388 389 template<typename... _Args> 390 static void 391 _S_create(_Storage& __storage, _Args&&... __args) 392 { 393 void* __addr = &__storage._M_buffer; 394 ::new (__addr) _Tp(std::forward<_Args>(__args)...); 395 } 396 397 static _Tp* 398 _S_access(const _Storage& __storage) 399 { 400 // The contained object is in __storage._M_buffer 401 const void* __addr = &__storage._M_buffer; 402 return static_cast<_Tp*>(const_cast<void*>(__addr)); 403 } 404 }; 405 406 // Manage external contained object. 407 template<typename _Tp> 408 struct _Manager_external 409 { 410 static void 411 _S_manage(_Op __which, const any* __anyp, _Arg* __arg); 412 413 template<typename _Up> 414 static void 415 _S_create(_Storage& __storage, _Up&& __value) 416 { 417 __storage._M_ptr = new _Tp(std::forward<_Up>(__value)); 418 } 419 template<typename... _Args> 420 static void 421 _S_create(_Storage& __storage, _Args&&... __args) 422 { 423 __storage._M_ptr = new _Tp(std::forward<_Args>(__args)...); 424 } 425 static _Tp* 426 _S_access(const _Storage& __storage) 427 { 428 // The contained object is in *__storage._M_ptr 429 return static_cast<_Tp*>(__storage._M_ptr); 430 } 431 }; 432 }; 433 434 /// Exchange the states of two @c any objects. 435 inline void swap(any& __x, any& __y) noexcept { __x.swap(__y); } 436 437 /// Create an `any` holding a `_Tp` constructed from `__args...`. 438 template <typename _Tp, typename... _Args> 439 inline 440 enable_if_t<is_constructible_v<any, in_place_type_t<_Tp>, _Args...>, any> 441 make_any(_Args&&... __args) 442 { 443 return any(in_place_type<_Tp>, std::forward<_Args>(__args)...); 444 } 445 446 /// Create an `any` holding a `_Tp` constructed from `__il` and `__args...`. 447 template <typename _Tp, typename _Up, typename... _Args> 448 inline 449 enable_if_t<is_constructible_v<any, in_place_type_t<_Tp>, 450 initializer_list<_Up>&, _Args...>, any> 451 make_any(initializer_list<_Up> __il, _Args&&... __args) 452 { 453 return any(in_place_type<_Tp>, __il, std::forward<_Args>(__args)...); 454 } 455 456 /** 457 * @brief Access the contained object. 458 * 459 * @tparam _ValueType A const-reference or CopyConstructible type. 460 * @param __any The object to access. 461 * @return The contained object. 462 * @throw bad_any_cast If <code> 463 * __any.type() != typeid(remove_reference_t<_ValueType>) 464 * </code> 465 */ 466 template<typename _ValueType> 467 inline _ValueType any_cast(const any& __any) 468 { 469 using _Up = __remove_cvref_t<_ValueType>; 470 static_assert(any::__is_valid_cast<_ValueType>(), 471 "Template argument must be a reference or CopyConstructible type"); 472 static_assert(is_constructible_v<_ValueType, const _Up&>, 473 "Template argument must be constructible from a const value."); 474 auto __p = any_cast<_Up>(&__any); 475 if (__p) 476 return static_cast<_ValueType>(*__p); 477 __throw_bad_any_cast(); 478 } 479 480 /** 481 * @brief Access the contained object. 482 * 483 * @tparam _ValueType A reference or CopyConstructible type. 484 * @param __any The object to access. 485 * @return The contained object. 486 * @throw bad_any_cast If <code> 487 * __any.type() != typeid(remove_reference_t<_ValueType>) 488 * </code> 489 * 490 * @{ 491 */ 492 template<typename _ValueType> 493 inline _ValueType any_cast(any& __any) 494 { 495 using _Up = __remove_cvref_t<_ValueType>; 496 static_assert(any::__is_valid_cast<_ValueType>(), 497 "Template argument must be a reference or CopyConstructible type"); 498 static_assert(is_constructible_v<_ValueType, _Up&>, 499 "Template argument must be constructible from an lvalue."); 500 auto __p = any_cast<_Up>(&__any); 501 if (__p) 502 return static_cast<_ValueType>(*__p); 503 __throw_bad_any_cast(); 504 } 505 506 template<typename _ValueType> 507 inline _ValueType any_cast(any&& __any) 508 { 509 using _Up = __remove_cvref_t<_ValueType>; 510 static_assert(any::__is_valid_cast<_ValueType>(), 511 "Template argument must be a reference or CopyConstructible type"); 512 static_assert(is_constructible_v<_ValueType, _Up>, 513 "Template argument must be constructible from an rvalue."); 514 auto __p = any_cast<_Up>(&__any); 515 if (__p) 516 return static_cast<_ValueType>(std::move(*__p)); 517 __throw_bad_any_cast(); 518 } 519 /// @} 520 521 /// @cond undocumented 522 template<typename _Tp> 523 void* __any_caster(const any* __any) 524 { 525 // any_cast<T> returns non-null if __any->type() == typeid(T) and 526 // typeid(T) ignores cv-qualifiers so remove them: 527 using _Up = remove_cv_t<_Tp>; 528 // The contained value has a decayed type, so if decay_t<U> is not U, 529 // then it's not possible to have a contained value of type U: 530 if constexpr (!is_same_v<decay_t<_Up>, _Up>) 531 return nullptr; 532 // Only copy constructible types can be used for contained values: 533 else if constexpr (!is_copy_constructible_v<_Up>) 534 return nullptr; 535 // First try comparing function addresses, which works without RTTI 536 else if (__any->_M_manager == &any::_Manager<_Up>::_S_manage 537 #if __cpp_rtti 538 || __any->type() == typeid(_Tp) 539 #endif 540 ) 541 { 542 return any::_Manager<_Up>::_S_access(__any->_M_storage); 543 } 544 return nullptr; 545 } 546 /// @endcond 547 548 /** 549 * @brief Access the contained object. 550 * 551 * @tparam _ValueType The type of the contained object. 552 * @param __any A pointer to the object to access. 553 * @return The address of the contained object if <code> 554 * __any != nullptr && __any.type() == typeid(_ValueType) 555 * </code>, otherwise a null pointer. 556 * 557 * @{ 558 */ 559 template<typename _ValueType> 560 inline const _ValueType* any_cast(const any* __any) noexcept 561 { 562 // _GLIBCXX_RESOLVE_LIB_DEFECTS 563 // 3305. any_cast<void> 564 static_assert(!is_void_v<_ValueType>); 565 566 // As an optimization, don't bother instantiating __any_caster for 567 // function types, since std::any can only hold objects. 568 if constexpr (is_object_v<_ValueType>) 569 if (__any) 570 return static_cast<_ValueType*>(__any_caster<_ValueType>(__any)); 571 return nullptr; 572 } 573 574 template<typename _ValueType> 575 inline _ValueType* any_cast(any* __any) noexcept 576 { 577 static_assert(!is_void_v<_ValueType>); 578 579 if constexpr (is_object_v<_ValueType>) 580 if (__any) 581 return static_cast<_ValueType*>(__any_caster<_ValueType>(__any)); 582 return nullptr; 583 } 584 /// @} 585 586 template<typename _Tp> 587 void 588 any::_Manager_internal<_Tp>:: 589 _S_manage(_Op __which, const any* __any, _Arg* __arg) 590 { 591 // The contained object is in _M_storage._M_buffer 592 auto __ptr = reinterpret_cast<const _Tp*>(&__any->_M_storage._M_buffer); 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 ::new(&__arg->_M_any->_M_storage._M_buffer) _Tp(*__ptr); 605 __arg->_M_any->_M_manager = __any->_M_manager; 606 break; 607 case _Op_destroy: 608 __ptr->~_Tp(); 609 break; 610 case _Op_xfer: 611 ::new(&__arg->_M_any->_M_storage._M_buffer) _Tp 612 (std::move(*const_cast<_Tp*>(__ptr))); 613 __ptr->~_Tp(); 614 __arg->_M_any->_M_manager = __any->_M_manager; 615 const_cast<any*>(__any)->_M_manager = nullptr; 616 break; 617 } 618 } 619 620 template<typename _Tp> 621 void 622 any::_Manager_external<_Tp>:: 623 _S_manage(_Op __which, const any* __any, _Arg* __arg) 624 { 625 // The contained object is *_M_storage._M_ptr 626 auto __ptr = static_cast<const _Tp*>(__any->_M_storage._M_ptr); 627 switch (__which) 628 { 629 case _Op_access: 630 __arg->_M_obj = const_cast<_Tp*>(__ptr); 631 break; 632 case _Op_get_type_info: 633 #if __cpp_rtti 634 __arg->_M_typeinfo = &typeid(_Tp); 635 #endif 636 break; 637 case _Op_clone: 638 __arg->_M_any->_M_storage._M_ptr = new _Tp(*__ptr); 639 __arg->_M_any->_M_manager = __any->_M_manager; 640 break; 641 case _Op_destroy: 642 delete __ptr; 643 break; 644 case _Op_xfer: 645 __arg->_M_any->_M_storage._M_ptr = __any->_M_storage._M_ptr; 646 __arg->_M_any->_M_manager = __any->_M_manager; 647 const_cast<any*>(__any)->_M_manager = nullptr; 648 break; 649 } 650 } 651 652 /// @} 653 654 namespace __detail::__variant 655 { 656 template<typename> struct _Never_valueless_alt; // see <variant> 657 658 // Provide the strong exception-safety guarantee when emplacing an 659 // any into a variant. 660 template<> 661 struct _Never_valueless_alt<std::any> 662 : std::true_type 663 { }; 664 } // namespace __detail::__variant 665 666 _GLIBCXX_END_NAMESPACE_VERSION 667 } // namespace std 668 669 #pragma GCC diagnostic pop 670 671 #endif // __cpp_lib_any 672 #endif // _GLIBCXX_ANY
