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The C and C++ Include Header Files
cat -n /usr/include/c++/15/experimental/any
1 // <experimental/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 experimental/any 26 * This is a TS C++ Library header. 27 * @ingroup libfund-ts 28 */ 29 30 #ifndef _GLIBCXX_EXPERIMENTAL_ANY 31 #define _GLIBCXX_EXPERIMENTAL_ANY 1 32 33 #ifdef _GLIBCXX_SYSHDR 34 #pragma GCC system_header 35 #endif 36 37 #include <bits/requires_hosted.h> // experimental is currently omitted 38 39 #if __cplusplus >= 201402L 40 41 #include <typeinfo> 42 #include <new> 43 #include <type_traits> 44 #include <bits/move.h> 45 #include <experimental/bits/lfts_config.h> 46 47 namespace std _GLIBCXX_VISIBILITY(default) 48 { 49 _GLIBCXX_BEGIN_NAMESPACE_VERSION 50 51 namespace experimental 52 { 53 inline namespace fundamentals_v1 54 { 55 /** 56 * @defgroup any Type-safe container of any type 57 * @ingroup libfund-ts 58 * 59 * A type-safe container for single values of value types, as 60 * described in n3804 "Any Library Proposal (Revision 3)". 61 * 62 * @{ 63 */ 64 65 #define __cpp_lib_experimental_any 201411 66 67 /** 68 * @brief Exception class thrown by a failed @c any_cast 69 * @ingroup exceptions 70 */ 71 class bad_any_cast : public bad_cast 72 { 73 public: 74 virtual const char* what() const noexcept { return "bad any_cast"; } 75 }; 76 77 /// @cond undocumented 78 [[gnu::noreturn]] inline void __throw_bad_any_cast() 79 { 80 #if __cpp_exceptions 81 throw bad_any_cast{}; 82 #else 83 __builtin_abort(); 84 #endif 85 } 86 /// @endcond 87 88 /** 89 * @brief A type-safe container of any type. 90 * 91 * An @c any object's state is either empty or it stores a contained object 92 * of CopyConstructible type. 93 */ 94 class any 95 { 96 // Holds either pointer to a heap object or the contained object itself. 97 union _Storage 98 { 99 // This constructor intentionally doesn't initialize anything. 100 _Storage() = default; 101 102 // Prevent trivial copies of this type, buffer might hold a non-POD. 103 _Storage(const _Storage&) = delete; 104 _Storage& operator=(const _Storage&) = delete; 105 106 void* _M_ptr; 107 unsigned char _M_buffer[sizeof(_M_ptr)]; 108 }; 109 110 template<typename _Tp, typename _Safe = is_nothrow_move_constructible<_Tp>, 111 bool _Fits = (sizeof(_Tp) <= sizeof(_Storage)) 112 && (alignof(_Tp) <= alignof(_Storage))> 113 using _Internal = std::integral_constant<bool, _Safe::value && _Fits>; 114 115 template<typename _Tp> 116 struct _Manager_internal; // uses small-object optimization 117 118 template<typename _Tp> 119 struct _Manager_external; // creates contained object on the heap 120 121 template<typename _Tp> 122 using _Manager = __conditional_t<_Internal<_Tp>::value, 123 _Manager_internal<_Tp>, 124 _Manager_external<_Tp>>; 125 126 template<typename _Tp, typename _Decayed = decay_t<_Tp>> 127 using _Decay = enable_if_t<!is_same<_Decayed, any>::value, _Decayed>; 128 129 public: 130 // construct/destruct 131 132 /// Default constructor, creates an empty object. 133 any() noexcept : _M_manager(nullptr) { } 134 135 /// Copy constructor, copies the state of @p __other 136 any(const any& __other) 137 { 138 if (__other.empty()) 139 _M_manager = nullptr; 140 else 141 { 142 _Arg __arg; 143 __arg._M_any = this; 144 __other._M_manager(_Op_clone, &__other, &__arg); 145 } 146 } 147 148 /** 149 * @brief Move constructor, transfer the state from @p __other 150 * 151 * @post @c __other.empty() (this postcondition is a GNU extension) 152 */ 153 any(any&& __other) noexcept 154 { 155 if (__other.empty()) 156 _M_manager = nullptr; 157 else 158 { 159 _Arg __arg; 160 __arg._M_any = this; 161 __other._M_manager(_Op_xfer, &__other, &__arg); 162 } 163 } 164 165 /// Construct with a copy of @p __value as the contained object. 166 template <typename _ValueType, typename _Tp = _Decay<_ValueType>, 167 typename _Mgr = _Manager<_Tp>, 168 typename enable_if<is_constructible<_Tp, _ValueType&&>::value, 169 bool>::type = true> 170 any(_ValueType&& __value) 171 : _M_manager(&_Mgr::_S_manage) 172 { 173 _Mgr::_S_create(_M_storage, std::forward<_ValueType>(__value)); 174 static_assert(is_copy_constructible<_Tp>::value, 175 "The contained object must be CopyConstructible"); 176 } 177 178 /// Construct with a copy of @p __value as the contained object. 179 template <typename _ValueType, typename _Tp = _Decay<_ValueType>, 180 typename _Mgr = _Manager<_Tp>, 181 typename enable_if<!is_constructible<_Tp, _ValueType&&>::value, 182 bool>::type = false> 183 any(_ValueType&& __value) 184 : _M_manager(&_Mgr::_S_manage) 185 { 186 _Mgr::_S_create(_M_storage, __value); 187 static_assert(is_copy_constructible<_Tp>::value, 188 "The contained object must be CopyConstructible"); 189 } 190 191 /// Destructor, calls @c clear() 192 ~any() { clear(); } 193 194 // assignments 195 196 /// Copy the state of another object. 197 any& operator=(const any& __rhs) 198 { 199 *this = any(__rhs); 200 return *this; 201 } 202 203 /** 204 * @brief Move assignment operator 205 * 206 * @post @c __rhs.empty() (not guaranteed for other implementations) 207 */ 208 any& operator=(any&& __rhs) noexcept 209 { 210 if (__rhs.empty()) 211 clear(); 212 else if (this != &__rhs) 213 { 214 clear(); 215 _Arg __arg; 216 __arg._M_any = this; 217 __rhs._M_manager(_Op_xfer, &__rhs, &__arg); 218 } 219 return *this; 220 } 221 222 /// Store a copy of @p __rhs as the contained object. 223 template<typename _ValueType> 224 enable_if_t<!is_same<any, decay_t<_ValueType>>::value, any&> 225 operator=(_ValueType&& __rhs) 226 { 227 *this = any(std::forward<_ValueType>(__rhs)); 228 return *this; 229 } 230 231 // modifiers 232 233 /// If not empty, destroy the contained object. 234 void clear() noexcept 235 { 236 if (!empty()) 237 { 238 _M_manager(_Op_destroy, this, nullptr); 239 _M_manager = nullptr; 240 } 241 } 242 243 /// Exchange state with another object. 244 void swap(any& __rhs) noexcept 245 { 246 if (empty() && __rhs.empty()) 247 return; 248 249 if (!empty() && !__rhs.empty()) 250 { 251 if (this == &__rhs) 252 return; 253 254 any __tmp; 255 _Arg __arg; 256 __arg._M_any = &__tmp; 257 __rhs._M_manager(_Op_xfer, &__rhs, &__arg); 258 __arg._M_any = &__rhs; 259 _M_manager(_Op_xfer, this, &__arg); 260 __arg._M_any = this; 261 __tmp._M_manager(_Op_xfer, &__tmp, &__arg); 262 } 263 else 264 { 265 any* __empty = empty() ? this : &__rhs; 266 any* __full = empty() ? &__rhs : this; 267 _Arg __arg; 268 __arg._M_any = __empty; 269 __full->_M_manager(_Op_xfer, __full, &__arg); 270 } 271 } 272 273 // observers 274 275 /// Reports whether there is a contained object or not. 276 _GLIBCXX_NODISCARD bool empty() const noexcept { return _M_manager == nullptr; } 277 278 #if __cpp_rtti 279 /// The @c typeid of the contained object, or @c typeid(void) if empty. 280 const type_info& type() const noexcept 281 { 282 if (empty()) 283 return typeid(void); 284 _Arg __arg; 285 _M_manager(_Op_get_type_info, this, &__arg); 286 return *__arg._M_typeinfo; 287 } 288 #endif 289 290 template<typename _Tp> 291 static constexpr bool __is_valid_cast() 292 { return __or_<is_reference<_Tp>, is_copy_constructible<_Tp>>::value; } 293 294 private: 295 enum _Op { 296 _Op_access, _Op_get_type_info, _Op_clone, _Op_destroy, _Op_xfer 297 }; 298 299 union _Arg 300 { 301 void* _M_obj; 302 const std::type_info* _M_typeinfo; 303 any* _M_any; 304 }; 305 306 void (*_M_manager)(_Op, const any*, _Arg*); 307 _Storage _M_storage; 308 309 template<typename _Tp> 310 friend enable_if_t<is_object<_Tp>::value, void*> 311 __any_caster(const any* __any); 312 313 // Manage in-place contained object. 314 template<typename _Tp> 315 struct _Manager_internal 316 { 317 static void 318 _S_manage(_Op __which, const any* __anyp, _Arg* __arg); 319 320 template<typename _Up> 321 static void 322 _S_create(_Storage& __storage, _Up&& __value) 323 { 324 void* __addr = &__storage._M_buffer; 325 ::new (__addr) _Tp(std::forward<_Up>(__value)); 326 } 327 }; 328 329 // Manage external contained object. 330 template<typename _Tp> 331 struct _Manager_external 332 { 333 static void 334 _S_manage(_Op __which, const any* __anyp, _Arg* __arg); 335 336 template<typename _Up> 337 static void 338 _S_create(_Storage& __storage, _Up&& __value) 339 { 340 __storage._M_ptr = new _Tp(std::forward<_Up>(__value)); 341 } 342 }; 343 }; 344 345 /// Exchange the states of two @c any objects. 346 inline void swap(any& __x, any& __y) noexcept { __x.swap(__y); } 347 348 /** 349 * @brief Access the contained object. 350 * 351 * @tparam _ValueType A const-reference or CopyConstructible type. 352 * @param __any The object to access. 353 * @return The contained object. 354 * @throw bad_any_cast If <code> 355 * __any.type() != typeid(remove_reference_t<_ValueType>) 356 * </code> 357 */ 358 template<typename _ValueType> 359 inline _ValueType any_cast(const any& __any) 360 { 361 static_assert(any::__is_valid_cast<_ValueType>(), 362 "Template argument must be a reference or CopyConstructible type"); 363 auto __p = any_cast<add_const_t<remove_reference_t<_ValueType>>>(&__any); 364 if (__p) 365 return *__p; 366 __throw_bad_any_cast(); 367 } 368 369 /** 370 * @brief Access the contained object. 371 * 372 * @tparam _ValueType A reference or CopyConstructible type. 373 * @param __any The object to access. 374 * @return The contained object. 375 * @throw bad_any_cast If <code> 376 * __any.type() != typeid(remove_reference_t<_ValueType>) 377 * </code> 378 * 379 * @{ 380 */ 381 template<typename _ValueType> 382 inline _ValueType any_cast(any& __any) 383 { 384 static_assert(any::__is_valid_cast<_ValueType>(), 385 "Template argument must be a reference or CopyConstructible type"); 386 auto __p = any_cast<remove_reference_t<_ValueType>>(&__any); 387 if (__p) 388 return *__p; 389 __throw_bad_any_cast(); 390 } 391 392 template<typename _ValueType, 393 typename enable_if<!is_move_constructible<_ValueType>::value 394 || is_lvalue_reference<_ValueType>::value, 395 bool>::type = true> 396 inline _ValueType any_cast(any&& __any) 397 { 398 static_assert(any::__is_valid_cast<_ValueType>(), 399 "Template argument must be a reference or CopyConstructible type"); 400 auto __p = any_cast<remove_reference_t<_ValueType>>(&__any); 401 if (__p) 402 return *__p; 403 __throw_bad_any_cast(); 404 } 405 406 template<typename _ValueType, 407 typename enable_if<is_move_constructible<_ValueType>::value 408 && !is_lvalue_reference<_ValueType>::value, 409 bool>::type = false> 410 inline _ValueType any_cast(any&& __any) 411 { 412 static_assert(any::__is_valid_cast<_ValueType>(), 413 "Template argument must be a reference or CopyConstructible type"); 414 auto __p = any_cast<remove_reference_t<_ValueType>>(&__any); 415 if (__p) 416 return std::move(*__p); 417 __throw_bad_any_cast(); 418 } 419 /// @} 420 421 /// @cond undocumented 422 template<typename _Tp> 423 enable_if_t<is_object<_Tp>::value, void*> 424 __any_caster(const any* __any) 425 { 426 // any_cast<T> returns non-null if __any->type() == typeid(T) and 427 // typeid(T) ignores cv-qualifiers so remove them: 428 using _Up = remove_cv_t<_Tp>; 429 // The contained value has a decayed type, so if decay_t<U> is not U, 430 // then it's not possible to have a contained value of type U. 431 using __does_not_decay = is_same<decay_t<_Up>, _Up>; 432 // Only copy constructible types can be used for contained values. 433 using __is_copyable = is_copy_constructible<_Up>; 434 // If the type _Tp could never be stored in an any we don't want to 435 // instantiate _Manager<_Tp>, so use _Manager<any::_Op> instead, which 436 // is explicitly specialized and has a no-op _S_manage function. 437 using _Vp = __conditional_t<__and_<__does_not_decay, __is_copyable>{}, 438 _Up, any::_Op>; 439 // First try comparing function addresses, which works without RTTI 440 if (__any->_M_manager == &any::_Manager<_Vp>::_S_manage 441 #if __cpp_rtti 442 || __any->type() == typeid(_Tp) 443 #endif 444 ) 445 { 446 any::_Arg __arg; 447 __any->_M_manager(any::_Op_access, __any, &__arg); 448 return __arg._M_obj; 449 } 450 return nullptr; 451 } 452 453 // This overload exists so that std::any_cast<void(*)()>(a) is well-formed. 454 template<typename _Tp> 455 enable_if_t<!is_object<_Tp>::value, _Tp*> 456 __any_caster(const any*) noexcept 457 { return nullptr; } 458 /// @endcond 459 460 /** 461 * @brief Access the contained object. 462 * 463 * @tparam _ValueType The type of the contained object. 464 * @param __any A pointer to the object to access. 465 * @return The address of the contained object if <code> 466 * __any != nullptr && __any.type() == typeid(_ValueType) 467 * </code>, otherwise a null pointer. 468 * 469 * @{ 470 */ 471 template<typename _ValueType> 472 inline const _ValueType* any_cast(const any* __any) noexcept 473 { 474 if (__any) 475 return static_cast<_ValueType*>(__any_caster<_ValueType>(__any)); 476 return nullptr; 477 } 478 479 template<typename _ValueType> 480 inline _ValueType* any_cast(any* __any) noexcept 481 { 482 if (__any) 483 return static_cast<_ValueType*>(__any_caster<_ValueType>(__any)); 484 return nullptr; 485 } 486 /// @} 487 488 template<typename _Tp> 489 void 490 any::_Manager_internal<_Tp>:: 491 _S_manage(_Op __which, const any* __any, _Arg* __arg) 492 { 493 // The contained object is in _M_storage._M_buffer 494 auto __ptr = reinterpret_cast<const _Tp*>(&__any->_M_storage._M_buffer); 495 switch (__which) 496 { 497 case _Op_access: 498 __arg->_M_obj = const_cast<_Tp*>(__ptr); 499 break; 500 case _Op_get_type_info: 501 #if __cpp_rtti 502 __arg->_M_typeinfo = &typeid(_Tp); 503 #endif 504 break; 505 case _Op_clone: 506 ::new(&__arg->_M_any->_M_storage._M_buffer) _Tp(*__ptr); 507 __arg->_M_any->_M_manager = __any->_M_manager; 508 break; 509 case _Op_destroy: 510 __ptr->~_Tp(); 511 break; 512 case _Op_xfer: 513 ::new(&__arg->_M_any->_M_storage._M_buffer) _Tp 514 (std::move(*const_cast<_Tp*>(__ptr))); 515 __ptr->~_Tp(); 516 __arg->_M_any->_M_manager = __any->_M_manager; 517 const_cast<any*>(__any)->_M_manager = nullptr; 518 break; 519 } 520 } 521 522 template<typename _Tp> 523 void 524 any::_Manager_external<_Tp>:: 525 _S_manage(_Op __which, const any* __any, _Arg* __arg) 526 { 527 // The contained object is *_M_storage._M_ptr 528 auto __ptr = static_cast<const _Tp*>(__any->_M_storage._M_ptr); 529 switch (__which) 530 { 531 case _Op_access: 532 __arg->_M_obj = const_cast<_Tp*>(__ptr); 533 break; 534 case _Op_get_type_info: 535 #if __cpp_rtti 536 __arg->_M_typeinfo = &typeid(_Tp); 537 #endif 538 break; 539 case _Op_clone: 540 __arg->_M_any->_M_storage._M_ptr = new _Tp(*__ptr); 541 __arg->_M_any->_M_manager = __any->_M_manager; 542 break; 543 case _Op_destroy: 544 delete __ptr; 545 break; 546 case _Op_xfer: 547 __arg->_M_any->_M_storage._M_ptr = __any->_M_storage._M_ptr; 548 __arg->_M_any->_M_manager = __any->_M_manager; 549 const_cast<any*>(__any)->_M_manager = nullptr; 550 break; 551 } 552 } 553 554 // Dummy specialization used by __any_caster. 555 template<> 556 struct any::_Manager_internal<any::_Op> 557 { 558 static void 559 _S_manage(_Op, const any*, _Arg*) { } 560 }; 561 562 /// @} group any 563 } // namespace fundamentals_v1 564 } // namespace experimental 565 566 _GLIBCXX_END_NAMESPACE_VERSION 567 } // namespace std 568 569 #endif // C++14 570 571 #endif // _GLIBCXX_EXPERIMENTAL_ANY
