source: Daodan/MSYS2/mingw32/include/c++/11.2.0/bits/std_function.h@ 1194

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1// Implementation of std::function -*- C++ -*-
2
3// Copyright (C) 2004-2021 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/bits/std_function.h
26 * This is an internal header file, included by other library headers.
27 * Do not attempt to use it directly. @headername{functional}
28 */
29
30#ifndef _GLIBCXX_STD_FUNCTION_H
31#define _GLIBCXX_STD_FUNCTION_H 1
32
33#pragma GCC system_header
34
35#if __cplusplus < 201103L
36# include <bits/c++0x_warning.h>
37#else
38
39#include <typeinfo>
40#include <bits/stl_function.h>
41#include <bits/invoke.h>
42#include <bits/refwrap.h>
43#include <bits/functexcept.h>
44
45namespace std _GLIBCXX_VISIBILITY(default)
46{
47_GLIBCXX_BEGIN_NAMESPACE_VERSION
48
49 /**
50 * @brief Exception class thrown when class template function's
51 * operator() is called with an empty target.
52 * @ingroup exceptions
53 */
54 class bad_function_call : public std::exception
55 {
56 public:
57 virtual ~bad_function_call() noexcept;
58
59 const char* what() const noexcept;
60 };
61
62 /**
63 * Trait identifying "location-invariant" types, meaning that the
64 * address of the object (or any of its members) will not escape.
65 * Trivially copyable types are location-invariant and users can
66 * specialize this trait for other types.
67 */
68 template<typename _Tp>
69 struct __is_location_invariant
70 : is_trivially_copyable<_Tp>::type
71 { };
72
73 class _Undefined_class;
74
75 union _Nocopy_types
76 {
77 void* _M_object;
78 const void* _M_const_object;
79 void (*_M_function_pointer)();
80 void (_Undefined_class::*_M_member_pointer)();
81 };
82
83 union [[gnu::may_alias]] _Any_data
84 {
85 void* _M_access() { return &_M_pod_data[0]; }
86 const void* _M_access() const { return &_M_pod_data[0]; }
87
88 template<typename _Tp>
89 _Tp&
90 _M_access()
91 { return *static_cast<_Tp*>(_M_access()); }
92
93 template<typename _Tp>
94 const _Tp&
95 _M_access() const
96 { return *static_cast<const _Tp*>(_M_access()); }
97
98 _Nocopy_types _M_unused;
99 char _M_pod_data[sizeof(_Nocopy_types)];
100 };
101
102 enum _Manager_operation
103 {
104 __get_type_info,
105 __get_functor_ptr,
106 __clone_functor,
107 __destroy_functor
108 };
109
110 template<typename _Signature>
111 class function;
112
113 /// Base class of all polymorphic function object wrappers.
114 class _Function_base
115 {
116 public:
117 static const size_t _M_max_size = sizeof(_Nocopy_types);
118 static const size_t _M_max_align = __alignof__(_Nocopy_types);
119
120 template<typename _Functor>
121 class _Base_manager
122 {
123 protected:
124 static const bool __stored_locally =
125 (__is_location_invariant<_Functor>::value
126 && sizeof(_Functor) <= _M_max_size
127 && __alignof__(_Functor) <= _M_max_align
128 && (_M_max_align % __alignof__(_Functor) == 0));
129
130 typedef integral_constant<bool, __stored_locally> _Local_storage;
131
132 // Retrieve a pointer to the function object
133 static _Functor*
134 _M_get_pointer(const _Any_data& __source)
135 {
136 if _GLIBCXX17_CONSTEXPR (__stored_locally)
137 {
138 const _Functor& __f = __source._M_access<_Functor>();
139 return const_cast<_Functor*>(std::__addressof(__f));
140 }
141 else // have stored a pointer
142 return __source._M_access<_Functor*>();
143 }
144
145 // Clone a location-invariant function object that fits within
146 // an _Any_data structure.
147 static void
148 _M_clone(_Any_data& __dest, const _Any_data& __source, true_type)
149 {
150 ::new (__dest._M_access()) _Functor(__source._M_access<_Functor>());
151 }
152
153 // Clone a function object that is not location-invariant or
154 // that cannot fit into an _Any_data structure.
155 static void
156 _M_clone(_Any_data& __dest, const _Any_data& __source, false_type)
157 {
158 __dest._M_access<_Functor*>() =
159 new _Functor(*__source._M_access<const _Functor*>());
160 }
161
162 // Destroying a location-invariant object may still require
163 // destruction.
164 static void
165 _M_destroy(_Any_data& __victim, true_type)
166 {
167 __victim._M_access<_Functor>().~_Functor();
168 }
169
170 // Destroying an object located on the heap.
171 static void
172 _M_destroy(_Any_data& __victim, false_type)
173 {
174 delete __victim._M_access<_Functor*>();
175 }
176
177 public:
178 static bool
179 _M_manager(_Any_data& __dest, const _Any_data& __source,
180 _Manager_operation __op)
181 {
182 switch (__op)
183 {
184 case __get_type_info:
185#if __cpp_rtti
186 __dest._M_access<const type_info*>() = &typeid(_Functor);
187#else
188 __dest._M_access<const type_info*>() = nullptr;
189#endif
190 break;
191 case __get_functor_ptr:
192 __dest._M_access<_Functor*>() = _M_get_pointer(__source);
193 break;
194
195 case __clone_functor:
196 _M_clone(__dest, __source, _Local_storage());
197 break;
198
199 case __destroy_functor:
200 _M_destroy(__dest, _Local_storage());
201 break;
202 }
203 return false;
204 }
205
206 static void
207 _M_init_functor(_Any_data& __functor, _Functor&& __f)
208 { _M_init_functor(__functor, std::move(__f), _Local_storage()); }
209
210 template<typename _Signature>
211 static bool
212 _M_not_empty_function(const function<_Signature>& __f)
213 { return static_cast<bool>(__f); }
214
215 template<typename _Tp>
216 static bool
217 _M_not_empty_function(_Tp* __fp)
218 { return __fp != nullptr; }
219
220 template<typename _Class, typename _Tp>
221 static bool
222 _M_not_empty_function(_Tp _Class::* __mp)
223 { return __mp != nullptr; }
224
225 template<typename _Tp>
226 static bool
227 _M_not_empty_function(const _Tp&)
228 { return true; }
229
230 private:
231 static void
232 _M_init_functor(_Any_data& __functor, _Functor&& __f, true_type)
233 { ::new (__functor._M_access()) _Functor(std::move(__f)); }
234
235 static void
236 _M_init_functor(_Any_data& __functor, _Functor&& __f, false_type)
237 { __functor._M_access<_Functor*>() = new _Functor(std::move(__f)); }
238 };
239
240 _Function_base() : _M_manager(nullptr) { }
241
242 ~_Function_base()
243 {
244 if (_M_manager)
245 _M_manager(_M_functor, _M_functor, __destroy_functor);
246 }
247
248 bool _M_empty() const { return !_M_manager; }
249
250 typedef bool (*_Manager_type)(_Any_data&, const _Any_data&,
251 _Manager_operation);
252
253 _Any_data _M_functor;
254 _Manager_type _M_manager;
255 };
256
257 template<typename _Signature, typename _Functor>
258 class _Function_handler;
259
260 template<typename _Res, typename _Functor, typename... _ArgTypes>
261 class _Function_handler<_Res(_ArgTypes...), _Functor>
262 : public _Function_base::_Base_manager<_Functor>
263 {
264 typedef _Function_base::_Base_manager<_Functor> _Base;
265
266 public:
267 static bool
268 _M_manager(_Any_data& __dest, const _Any_data& __source,
269 _Manager_operation __op)
270 {
271 switch (__op)
272 {
273#if __cpp_rtti
274 case __get_type_info:
275 __dest._M_access<const type_info*>() = &typeid(_Functor);
276 break;
277#endif
278 case __get_functor_ptr:
279 __dest._M_access<_Functor*>() = _Base::_M_get_pointer(__source);
280 break;
281
282 default:
283 _Base::_M_manager(__dest, __source, __op);
284 }
285 return false;
286 }
287
288 static _Res
289 _M_invoke(const _Any_data& __functor, _ArgTypes&&... __args)
290 {
291 return std::__invoke_r<_Res>(*_Base::_M_get_pointer(__functor),
292 std::forward<_ArgTypes>(__args)...);
293 }
294 };
295
296 // Specialization for invalid types
297 template<>
298 class _Function_handler<void, void>
299 {
300 public:
301 static bool
302 _M_manager(_Any_data&, const _Any_data&, _Manager_operation)
303 { return false; }
304 };
305
306 // Avoids instantiating ill-formed specializations of _Function_handler
307 // in std::function<_Signature>::target<_Functor>().
308 // e.g. _Function_handler<Sig, void()> and _Function_handler<Sig, void>
309 // would be ill-formed.
310 template<typename _Signature, typename _Functor,
311 bool __valid = is_object<_Functor>::value>
312 struct _Target_handler
313 : _Function_handler<_Signature, typename remove_cv<_Functor>::type>
314 { };
315
316 template<typename _Signature, typename _Functor>
317 struct _Target_handler<_Signature, _Functor, false>
318 : _Function_handler<void, void>
319 { };
320
321 /**
322 * @brief Primary class template for std::function.
323 * @ingroup functors
324 *
325 * Polymorphic function wrapper.
326 */
327 template<typename _Res, typename... _ArgTypes>
328 class function<_Res(_ArgTypes...)>
329 : public _Maybe_unary_or_binary_function<_Res, _ArgTypes...>,
330 private _Function_base
331 {
332 template<typename _Func,
333 typename _Res2 = __invoke_result<_Func&, _ArgTypes...>>
334 struct _Callable
335 : __is_invocable_impl<_Res2, _Res>::type
336 { };
337
338 // Used so the return type convertibility checks aren't done when
339 // performing overload resolution for copy construction/assignment.
340 template<typename _Tp>
341 struct _Callable<function, _Tp> : false_type { };
342
343 template<typename _Cond, typename _Tp>
344 using _Requires = typename enable_if<_Cond::value, _Tp>::type;
345
346 public:
347 typedef _Res result_type;
348
349 // [3.7.2.1] construct/copy/destroy
350
351 /**
352 * @brief Default construct creates an empty function call wrapper.
353 * @post @c !(bool)*this
354 */
355 function() noexcept
356 : _Function_base() { }
357
358 /**
359 * @brief Creates an empty function call wrapper.
360 * @post @c !(bool)*this
361 */
362 function(nullptr_t) noexcept
363 : _Function_base() { }
364
365 /**
366 * @brief %Function copy constructor.
367 * @param __x A %function object with identical call signature.
368 * @post @c bool(*this) == bool(__x)
369 *
370 * The newly-created %function contains a copy of the target of @a
371 * __x (if it has one).
372 */
373 function(const function& __x)
374 : _Function_base()
375 {
376 if (static_cast<bool>(__x))
377 {
378 __x._M_manager(_M_functor, __x._M_functor, __clone_functor);
379 _M_invoker = __x._M_invoker;
380 _M_manager = __x._M_manager;
381 }
382 }
383
384 /**
385 * @brief %Function move constructor.
386 * @param __x A %function object rvalue with identical call signature.
387 *
388 * The newly-created %function contains the target of @a __x
389 * (if it has one).
390 */
391 function(function&& __x) noexcept
392 : _Function_base()
393 { __x.swap(*this); }
394
395 /**
396 * @brief Builds a %function that targets a copy of the incoming
397 * function object.
398 * @param __f A %function object that is callable with parameters of
399 * type @c T1, @c T2, ..., @c TN and returns a value convertible
400 * to @c Res.
401 *
402 * The newly-created %function object will target a copy of
403 * @a __f. If @a __f is @c reference_wrapper<F>, then this function
404 * object will contain a reference to the function object @c
405 * __f.get(). If @a __f is a NULL function pointer or NULL
406 * pointer-to-member, the newly-created object will be empty.
407 *
408 * If @a __f is a non-NULL function pointer or an object of type @c
409 * reference_wrapper<F>, this function will not throw.
410 */
411 template<typename _Functor,
412 typename = _Requires<__not_<is_same<_Functor, function>>, void>,
413 typename = _Requires<_Callable<_Functor>, void>>
414 function(_Functor __f)
415 : _Function_base()
416 {
417 typedef _Function_handler<_Res(_ArgTypes...), _Functor> _My_handler;
418
419 if (_My_handler::_M_not_empty_function(__f))
420 {
421 _My_handler::_M_init_functor(_M_functor, std::move(__f));
422 _M_invoker = &_My_handler::_M_invoke;
423 _M_manager = &_My_handler::_M_manager;
424 }
425 }
426
427 /**
428 * @brief %Function assignment operator.
429 * @param __x A %function with identical call signature.
430 * @post @c (bool)*this == (bool)x
431 * @returns @c *this
432 *
433 * The target of @a __x is copied to @c *this. If @a __x has no
434 * target, then @c *this will be empty.
435 *
436 * If @a __x targets a function pointer or a reference to a function
437 * object, then this operation will not throw an %exception.
438 */
439 function&
440 operator=(const function& __x)
441 {
442 function(__x).swap(*this);
443 return *this;
444 }
445
446 /**
447 * @brief %Function move-assignment operator.
448 * @param __x A %function rvalue with identical call signature.
449 * @returns @c *this
450 *
451 * The target of @a __x is moved to @c *this. If @a __x has no
452 * target, then @c *this will be empty.
453 *
454 * If @a __x targets a function pointer or a reference to a function
455 * object, then this operation will not throw an %exception.
456 */
457 function&
458 operator=(function&& __x) noexcept
459 {
460 function(std::move(__x)).swap(*this);
461 return *this;
462 }
463
464 /**
465 * @brief %Function assignment to zero.
466 * @post @c !(bool)*this
467 * @returns @c *this
468 *
469 * The target of @c *this is deallocated, leaving it empty.
470 */
471 function&
472 operator=(nullptr_t) noexcept
473 {
474 if (_M_manager)
475 {
476 _M_manager(_M_functor, _M_functor, __destroy_functor);
477 _M_manager = nullptr;
478 _M_invoker = nullptr;
479 }
480 return *this;
481 }
482
483 /**
484 * @brief %Function assignment to a new target.
485 * @param __f A %function object that is callable with parameters of
486 * type @c T1, @c T2, ..., @c TN and returns a value convertible
487 * to @c Res.
488 * @return @c *this
489 *
490 * This %function object wrapper will target a copy of @a
491 * __f. If @a __f is @c reference_wrapper<F>, then this function
492 * object will contain a reference to the function object @c
493 * __f.get(). If @a __f is a NULL function pointer or NULL
494 * pointer-to-member, @c this object will be empty.
495 *
496 * If @a __f is a non-NULL function pointer or an object of type @c
497 * reference_wrapper<F>, this function will not throw.
498 */
499 template<typename _Functor>
500 _Requires<_Callable<typename decay<_Functor>::type>, function&>
501 operator=(_Functor&& __f)
502 {
503 function(std::forward<_Functor>(__f)).swap(*this);
504 return *this;
505 }
506
507 /// @overload
508 template<typename _Functor>
509 function&
510 operator=(reference_wrapper<_Functor> __f) noexcept
511 {
512 function(__f).swap(*this);
513 return *this;
514 }
515
516 // [3.7.2.2] function modifiers
517
518 /**
519 * @brief Swap the targets of two %function objects.
520 * @param __x A %function with identical call signature.
521 *
522 * Swap the targets of @c this function object and @a __f. This
523 * function will not throw an %exception.
524 */
525 void swap(function& __x) noexcept
526 {
527 std::swap(_M_functor, __x._M_functor);
528 std::swap(_M_manager, __x._M_manager);
529 std::swap(_M_invoker, __x._M_invoker);
530 }
531
532 // [3.7.2.3] function capacity
533
534 /**
535 * @brief Determine if the %function wrapper has a target.
536 *
537 * @return @c true when this %function object contains a target,
538 * or @c false when it is empty.
539 *
540 * This function will not throw an %exception.
541 */
542 explicit operator bool() const noexcept
543 { return !_M_empty(); }
544
545 // [3.7.2.4] function invocation
546
547 /**
548 * @brief Invokes the function targeted by @c *this.
549 * @returns the result of the target.
550 * @throws bad_function_call when @c !(bool)*this
551 *
552 * The function call operator invokes the target function object
553 * stored by @c this.
554 */
555 _Res
556 operator()(_ArgTypes... __args) const
557 {
558 if (_M_empty())
559 __throw_bad_function_call();
560 return _M_invoker(_M_functor, std::forward<_ArgTypes>(__args)...);
561 }
562
563#if __cpp_rtti
564 // [3.7.2.5] function target access
565 /**
566 * @brief Determine the type of the target of this function object
567 * wrapper.
568 *
569 * @returns the type identifier of the target function object, or
570 * @c typeid(void) if @c !(bool)*this.
571 *
572 * This function will not throw an %exception.
573 */
574 const type_info&
575 target_type() const noexcept
576 {
577 if (_M_manager)
578 {
579 _Any_data __typeinfo_result;
580 _M_manager(__typeinfo_result, _M_functor, __get_type_info);
581 if (auto __ti = __typeinfo_result._M_access<const type_info*>())
582 return *__ti;
583 }
584 return typeid(void);
585 }
586#endif
587
588 /**
589 * @brief Access the stored target function object.
590 *
591 * @return Returns a pointer to the stored target function object,
592 * if @c typeid(_Functor).equals(target_type()); otherwise, a null
593 * pointer.
594 *
595 * This function does not throw exceptions.
596 *
597 * @{
598 */
599 template<typename _Functor>
600 _Functor*
601 target() noexcept
602 {
603 const function* __const_this = this;
604 const _Functor* __func = __const_this->template target<_Functor>();
605 // If is_function_v<_Functor> is true then const_cast<_Functor*>
606 // would be ill-formed, so use *const_cast<_Functor**> instead.
607 return *const_cast<_Functor**>(&__func);
608 }
609
610 template<typename _Functor>
611 const _Functor*
612 target() const noexcept
613 {
614 if _GLIBCXX17_CONSTEXPR (is_object<_Functor>::value)
615 {
616 // For C++11 and C++14 if-constexpr is not used above, so
617 // _Target_handler avoids ill-formed _Function_handler types.
618 using _Handler = _Target_handler<_Res(_ArgTypes...), _Functor>;
619
620 if (_M_manager == &_Handler::_M_manager
621#if __cpp_rtti
622 || (_M_manager && typeid(_Functor) == target_type())
623#endif
624 )
625 {
626 _Any_data __ptr;
627 _M_manager(__ptr, _M_functor, __get_functor_ptr);
628 return __ptr._M_access<const _Functor*>();
629 }
630 }
631 return nullptr;
632 }
633 /// @}
634
635 private:
636 using _Invoker_type = _Res (*)(const _Any_data&, _ArgTypes&&...);
637 _Invoker_type _M_invoker;
638 };
639
640#if __cpp_deduction_guides >= 201606
641 template<typename>
642 struct __function_guide_helper
643 { };
644
645 template<typename _Res, typename _Tp, bool _Nx, typename... _Args>
646 struct __function_guide_helper<
647 _Res (_Tp::*) (_Args...) noexcept(_Nx)
648 >
649 { using type = _Res(_Args...); };
650
651 template<typename _Res, typename _Tp, bool _Nx, typename... _Args>
652 struct __function_guide_helper<
653 _Res (_Tp::*) (_Args...) & noexcept(_Nx)
654 >
655 { using type = _Res(_Args...); };
656
657 template<typename _Res, typename _Tp, bool _Nx, typename... _Args>
658 struct __function_guide_helper<
659 _Res (_Tp::*) (_Args...) const noexcept(_Nx)
660 >
661 { using type = _Res(_Args...); };
662
663 template<typename _Res, typename _Tp, bool _Nx, typename... _Args>
664 struct __function_guide_helper<
665 _Res (_Tp::*) (_Args...) const & noexcept(_Nx)
666 >
667 { using type = _Res(_Args...); };
668
669 template<typename _Res, typename... _ArgTypes>
670 function(_Res(*)(_ArgTypes...)) -> function<_Res(_ArgTypes...)>;
671
672 template<typename _Functor, typename _Signature = typename
673 __function_guide_helper<decltype(&_Functor::operator())>::type>
674 function(_Functor) -> function<_Signature>;
675#endif
676
677 // [20.7.15.2.6] null pointer comparisons
678
679 /**
680 * @brief Compares a polymorphic function object wrapper against 0
681 * (the NULL pointer).
682 * @returns @c true if the wrapper has no target, @c false otherwise
683 *
684 * This function will not throw an %exception.
685 */
686 template<typename _Res, typename... _Args>
687 inline bool
688 operator==(const function<_Res(_Args...)>& __f, nullptr_t) noexcept
689 { return !static_cast<bool>(__f); }
690
691#if __cpp_impl_three_way_comparison < 201907L
692 /// @overload
693 template<typename _Res, typename... _Args>
694 inline bool
695 operator==(nullptr_t, const function<_Res(_Args...)>& __f) noexcept
696 { return !static_cast<bool>(__f); }
697
698 /**
699 * @brief Compares a polymorphic function object wrapper against 0
700 * (the NULL pointer).
701 * @returns @c false if the wrapper has no target, @c true otherwise
702 *
703 * This function will not throw an %exception.
704 */
705 template<typename _Res, typename... _Args>
706 inline bool
707 operator!=(const function<_Res(_Args...)>& __f, nullptr_t) noexcept
708 { return static_cast<bool>(__f); }
709
710 /// @overload
711 template<typename _Res, typename... _Args>
712 inline bool
713 operator!=(nullptr_t, const function<_Res(_Args...)>& __f) noexcept
714 { return static_cast<bool>(__f); }
715#endif
716
717 // [20.7.15.2.7] specialized algorithms
718
719 /**
720 * @brief Swap the targets of two polymorphic function object wrappers.
721 *
722 * This function will not throw an %exception.
723 */
724 // _GLIBCXX_RESOLVE_LIB_DEFECTS
725 // 2062. Effect contradictions w/o no-throw guarantee of std::function swaps
726 template<typename _Res, typename... _Args>
727 inline void
728 swap(function<_Res(_Args...)>& __x, function<_Res(_Args...)>& __y) noexcept
729 { __x.swap(__y); }
730
731#if __cplusplus >= 201703L
732 namespace __detail::__variant
733 {
734 template<typename> struct _Never_valueless_alt; // see <variant>
735
736 // Provide the strong exception-safety guarantee when emplacing a
737 // function into a variant.
738 template<typename _Signature>
739 struct _Never_valueless_alt<std::function<_Signature>>
740 : std::true_type
741 { };
742 } // namespace __detail::__variant
743#endif // C++17
744
745_GLIBCXX_END_NAMESPACE_VERSION
746} // namespace std
747
748#endif // C++11
749#endif // _GLIBCXX_STD_FUNCTION_H
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