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