xref: /netbsd-src/external/gpl3/gcc/dist/libstdc++-v3/include/bits/stl_vector.h (revision 4b169a6ba595ae283ca507b26b15fdff40495b1c)
1 // Vector implementation -*- C++ -*-
2 
3 // Copyright (C) 2001-2022 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 /*
26  *
27  * Copyright (c) 1994
28  * Hewlett-Packard Company
29  *
30  * Permission to use, copy, modify, distribute and sell this software
31  * and its documentation for any purpose is hereby granted without fee,
32  * provided that the above copyright notice appear in all copies and
33  * that both that copyright notice and this permission notice appear
34  * in supporting documentation.  Hewlett-Packard Company makes no
35  * representations about the suitability of this software for any
36  * purpose.  It is provided "as is" without express or implied warranty.
37  *
38  *
39  * Copyright (c) 1996
40  * Silicon Graphics Computer Systems, Inc.
41  *
42  * Permission to use, copy, modify, distribute and sell this software
43  * and its documentation for any purpose is hereby granted without fee,
44  * provided that the above copyright notice appear in all copies and
45  * that both that copyright notice and this permission notice appear
46  * in supporting documentation.  Silicon Graphics makes no
47  * representations about the suitability of this  software for any
48  * purpose.  It is provided "as is" without express or implied warranty.
49  */
50 
51 /** @file bits/stl_vector.h
52  *  This is an internal header file, included by other library headers.
53  *  Do not attempt to use it directly. @headername{vector}
54  */
55 
56 #ifndef _STL_VECTOR_H
57 #define _STL_VECTOR_H 1
58 
59 #include <bits/stl_iterator_base_funcs.h>
60 #include <bits/functexcept.h>
61 #include <bits/concept_check.h>
62 #if __cplusplus >= 201103L
63 #include <initializer_list>
64 #endif
65 #if __cplusplus >= 202002L
66 # include <compare>
67 #define __cpp_lib_constexpr_vector 201907L
68 #endif
69 
70 #include <debug/assertions.h>
71 
72 #if _GLIBCXX_SANITIZE_STD_ALLOCATOR && _GLIBCXX_SANITIZE_VECTOR
73 extern "C" void
74 __sanitizer_annotate_contiguous_container(const void*, const void*,
75 					  const void*, const void*);
76 #endif
77 
78 namespace std _GLIBCXX_VISIBILITY(default)
79 {
80 _GLIBCXX_BEGIN_NAMESPACE_VERSION
81 _GLIBCXX_BEGIN_NAMESPACE_CONTAINER
82 
83   /// See bits/stl_deque.h's _Deque_base for an explanation.
84   template<typename _Tp, typename _Alloc>
85     struct _Vector_base
86     {
87       typedef typename __gnu_cxx::__alloc_traits<_Alloc>::template
88 	rebind<_Tp>::other _Tp_alloc_type;
89       typedef typename __gnu_cxx::__alloc_traits<_Tp_alloc_type>::pointer
90        	pointer;
91 
92       struct _Vector_impl_data
93       {
94 	pointer _M_start;
95 	pointer _M_finish;
96 	pointer _M_end_of_storage;
97 
98 	_GLIBCXX20_CONSTEXPR
99 	_Vector_impl_data() _GLIBCXX_NOEXCEPT
100 	: _M_start(), _M_finish(), _M_end_of_storage()
101 	{ }
102 
103 #if __cplusplus >= 201103L
104 	_GLIBCXX20_CONSTEXPR
105 	_Vector_impl_data(_Vector_impl_data&& __x) noexcept
106 	: _M_start(__x._M_start), _M_finish(__x._M_finish),
107 	  _M_end_of_storage(__x._M_end_of_storage)
108 	{ __x._M_start = __x._M_finish = __x._M_end_of_storage = pointer(); }
109 #endif
110 
111 	_GLIBCXX20_CONSTEXPR
112 	void
113 	_M_copy_data(_Vector_impl_data const& __x) _GLIBCXX_NOEXCEPT
114 	{
115 	  _M_start = __x._M_start;
116 	  _M_finish = __x._M_finish;
117 	  _M_end_of_storage = __x._M_end_of_storage;
118 	}
119 
120 	_GLIBCXX20_CONSTEXPR
121 	void
122 	_M_swap_data(_Vector_impl_data& __x) _GLIBCXX_NOEXCEPT
123 	{
124 	  // Do not use std::swap(_M_start, __x._M_start), etc as it loses
125 	  // information used by TBAA.
126 	  _Vector_impl_data __tmp;
127 	  __tmp._M_copy_data(*this);
128 	  _M_copy_data(__x);
129 	  __x._M_copy_data(__tmp);
130 	}
131       };
132 
133       struct _Vector_impl
134 	: public _Tp_alloc_type, public _Vector_impl_data
135       {
136 	_GLIBCXX20_CONSTEXPR
137 	_Vector_impl() _GLIBCXX_NOEXCEPT_IF(
138 	    is_nothrow_default_constructible<_Tp_alloc_type>::value)
139 	: _Tp_alloc_type()
140 	{ }
141 
142 	_GLIBCXX20_CONSTEXPR
143 	_Vector_impl(_Tp_alloc_type const& __a) _GLIBCXX_NOEXCEPT
144 	: _Tp_alloc_type(__a)
145 	{ }
146 
147 #if __cplusplus >= 201103L
148 	// Not defaulted, to enforce noexcept(true) even when
149 	// !is_nothrow_move_constructible<_Tp_alloc_type>.
150 	_GLIBCXX20_CONSTEXPR
151 	_Vector_impl(_Vector_impl&& __x) noexcept
152 	: _Tp_alloc_type(std::move(__x)), _Vector_impl_data(std::move(__x))
153 	{ }
154 
155 	_GLIBCXX20_CONSTEXPR
156 	_Vector_impl(_Tp_alloc_type&& __a) noexcept
157 	: _Tp_alloc_type(std::move(__a))
158 	{ }
159 
160 	_GLIBCXX20_CONSTEXPR
161 	_Vector_impl(_Tp_alloc_type&& __a, _Vector_impl&& __rv) noexcept
162 	: _Tp_alloc_type(std::move(__a)), _Vector_impl_data(std::move(__rv))
163 	{ }
164 #endif
165 
166 #if _GLIBCXX_SANITIZE_STD_ALLOCATOR && _GLIBCXX_SANITIZE_VECTOR
167 	template<typename = _Tp_alloc_type>
168 	  struct _Asan
169 	  {
170 	    typedef typename __gnu_cxx::__alloc_traits<_Tp_alloc_type>
171 	      ::size_type size_type;
172 
173 	    static _GLIBCXX20_CONSTEXPR void
174 	    _S_shrink(_Vector_impl&, size_type) { }
175 	    static _GLIBCXX20_CONSTEXPR void
176 	    _S_on_dealloc(_Vector_impl&) { }
177 
178 	    typedef _Vector_impl& _Reinit;
179 
180 	    struct _Grow
181 	    {
182 	      _GLIBCXX20_CONSTEXPR _Grow(_Vector_impl&, size_type) { }
183 	      _GLIBCXX20_CONSTEXPR void _M_grew(size_type) { }
184 	    };
185 	  };
186 
187 	// Enable ASan annotations for memory obtained from std::allocator.
188 	template<typename _Up>
189 	  struct _Asan<allocator<_Up> >
190 	  {
191 	    typedef typename __gnu_cxx::__alloc_traits<_Tp_alloc_type>
192 	      ::size_type size_type;
193 
194 	    // Adjust ASan annotation for [_M_start, _M_end_of_storage) to
195 	    // mark end of valid region as __curr instead of __prev.
196 	    static _GLIBCXX20_CONSTEXPR void
197 	    _S_adjust(_Vector_impl& __impl, pointer __prev, pointer __curr)
198 	    {
199 #if __cpp_lib_is_constant_evaluated
200 	      if (std::is_constant_evaluated())
201 		return;
202 #endif
203 	      __sanitizer_annotate_contiguous_container(__impl._M_start,
204 		  __impl._M_end_of_storage, __prev, __curr);
205 	    }
206 
207 	    static _GLIBCXX20_CONSTEXPR void
208 	    _S_grow(_Vector_impl& __impl, size_type __n)
209 	    { _S_adjust(__impl, __impl._M_finish, __impl._M_finish + __n); }
210 
211 	    static _GLIBCXX20_CONSTEXPR void
212 	    _S_shrink(_Vector_impl& __impl, size_type __n)
213 	    { _S_adjust(__impl, __impl._M_finish + __n, __impl._M_finish); }
214 
215 	    static _GLIBCXX20_CONSTEXPR void
216 	    _S_on_dealloc(_Vector_impl& __impl)
217 	    {
218 	      if (__impl._M_start)
219 		_S_adjust(__impl, __impl._M_finish, __impl._M_end_of_storage);
220 	    }
221 
222 	    // Used on reallocation to tell ASan unused capacity is invalid.
223 	    struct _Reinit
224 	    {
225 	      explicit _GLIBCXX20_CONSTEXPR
226 	      _Reinit(_Vector_impl& __impl) : _M_impl(__impl)
227 	      {
228 		// Mark unused capacity as valid again before deallocating it.
229 		_S_on_dealloc(_M_impl);
230 	      }
231 
232 	      _GLIBCXX20_CONSTEXPR
233 	      ~_Reinit()
234 	      {
235 		// Mark unused capacity as invalid after reallocation.
236 		if (_M_impl._M_start)
237 		  _S_adjust(_M_impl, _M_impl._M_end_of_storage,
238 			    _M_impl._M_finish);
239 	      }
240 
241 	      _Vector_impl& _M_impl;
242 
243 #if __cplusplus >= 201103L
244 	      _Reinit(const _Reinit&) = delete;
245 	      _Reinit& operator=(const _Reinit&) = delete;
246 #endif
247 	    };
248 
249 	    // Tell ASan when unused capacity is initialized to be valid.
250 	    struct _Grow
251 	    {
252 	      _GLIBCXX20_CONSTEXPR
253 	      _Grow(_Vector_impl& __impl, size_type __n)
254 	      : _M_impl(__impl), _M_n(__n)
255 	      { _S_grow(_M_impl, __n); }
256 
257 	      _GLIBCXX20_CONSTEXPR
258 	      ~_Grow() { if (_M_n) _S_shrink(_M_impl, _M_n); }
259 
260 	      _GLIBCXX20_CONSTEXPR
261 	      void _M_grew(size_type __n) { _M_n -= __n; }
262 
263 #if __cplusplus >= 201103L
264 	      _Grow(const _Grow&) = delete;
265 	      _Grow& operator=(const _Grow&) = delete;
266 #endif
267 	    private:
268 	      _Vector_impl& _M_impl;
269 	      size_type _M_n;
270 	    };
271 	  };
272 
273 #define _GLIBCXX_ASAN_ANNOTATE_REINIT \
274   typename _Base::_Vector_impl::template _Asan<>::_Reinit const \
275 	__attribute__((__unused__)) __reinit_guard(this->_M_impl)
276 #define _GLIBCXX_ASAN_ANNOTATE_GROW(n) \
277   typename _Base::_Vector_impl::template _Asan<>::_Grow \
278 	__attribute__((__unused__)) __grow_guard(this->_M_impl, (n))
279 #define _GLIBCXX_ASAN_ANNOTATE_GREW(n) __grow_guard._M_grew(n)
280 #define _GLIBCXX_ASAN_ANNOTATE_SHRINK(n) \
281   _Base::_Vector_impl::template _Asan<>::_S_shrink(this->_M_impl, n)
282 #define _GLIBCXX_ASAN_ANNOTATE_BEFORE_DEALLOC \
283   _Base::_Vector_impl::template _Asan<>::_S_on_dealloc(this->_M_impl)
284 #else // ! (_GLIBCXX_SANITIZE_STD_ALLOCATOR && _GLIBCXX_SANITIZE_VECTOR)
285 #define _GLIBCXX_ASAN_ANNOTATE_REINIT
286 #define _GLIBCXX_ASAN_ANNOTATE_GROW(n)
287 #define _GLIBCXX_ASAN_ANNOTATE_GREW(n)
288 #define _GLIBCXX_ASAN_ANNOTATE_SHRINK(n)
289 #define _GLIBCXX_ASAN_ANNOTATE_BEFORE_DEALLOC
290 #endif // _GLIBCXX_SANITIZE_STD_ALLOCATOR && _GLIBCXX_SANITIZE_VECTOR
291       };
292 
293     public:
294       typedef _Alloc allocator_type;
295 
296       _GLIBCXX20_CONSTEXPR
297       _Tp_alloc_type&
298       _M_get_Tp_allocator() _GLIBCXX_NOEXCEPT
299       { return this->_M_impl; }
300 
301       _GLIBCXX20_CONSTEXPR
302       const _Tp_alloc_type&
303       _M_get_Tp_allocator() const _GLIBCXX_NOEXCEPT
304       { return this->_M_impl; }
305 
306       _GLIBCXX20_CONSTEXPR
307       allocator_type
308       get_allocator() const _GLIBCXX_NOEXCEPT
309       { return allocator_type(_M_get_Tp_allocator()); }
310 
311 #if __cplusplus >= 201103L
312       _Vector_base() = default;
313 #else
314       _Vector_base() { }
315 #endif
316 
317       _GLIBCXX20_CONSTEXPR
318       _Vector_base(const allocator_type& __a) _GLIBCXX_NOEXCEPT
319       : _M_impl(__a) { }
320 
321       // Kept for ABI compatibility.
322 #if !_GLIBCXX_INLINE_VERSION
323       _GLIBCXX20_CONSTEXPR
324       _Vector_base(size_t __n)
325       : _M_impl()
326       { _M_create_storage(__n); }
327 #endif
328 
329       _GLIBCXX20_CONSTEXPR
330       _Vector_base(size_t __n, const allocator_type& __a)
331       : _M_impl(__a)
332       { _M_create_storage(__n); }
333 
334 #if __cplusplus >= 201103L
335       _Vector_base(_Vector_base&&) = default;
336 
337       // Kept for ABI compatibility.
338 # if !_GLIBCXX_INLINE_VERSION
339       _GLIBCXX20_CONSTEXPR
340       _Vector_base(_Tp_alloc_type&& __a) noexcept
341       : _M_impl(std::move(__a)) { }
342 
343       _GLIBCXX20_CONSTEXPR
344       _Vector_base(_Vector_base&& __x, const allocator_type& __a)
345       : _M_impl(__a)
346       {
347 	if (__x.get_allocator() == __a)
348 	  this->_M_impl._M_swap_data(__x._M_impl);
349 	else
350 	  {
351 	    size_t __n = __x._M_impl._M_finish - __x._M_impl._M_start;
352 	    _M_create_storage(__n);
353 	  }
354       }
355 # endif
356 
357       _GLIBCXX20_CONSTEXPR
358       _Vector_base(const allocator_type& __a, _Vector_base&& __x)
359       : _M_impl(_Tp_alloc_type(__a), std::move(__x._M_impl))
360       { }
361 #endif
362 
363       _GLIBCXX20_CONSTEXPR
364       ~_Vector_base() _GLIBCXX_NOEXCEPT
365       {
366 	_M_deallocate(_M_impl._M_start,
367 		      _M_impl._M_end_of_storage - _M_impl._M_start);
368       }
369 
370     public:
371       _Vector_impl _M_impl;
372 
373       _GLIBCXX20_CONSTEXPR
374       pointer
375       _M_allocate(size_t __n)
376       {
377 	typedef __gnu_cxx::__alloc_traits<_Tp_alloc_type> _Tr;
378 	return __n != 0 ? _Tr::allocate(_M_impl, __n) : pointer();
379       }
380 
381       _GLIBCXX20_CONSTEXPR
382       void
383       _M_deallocate(pointer __p, size_t __n)
384       {
385 	typedef __gnu_cxx::__alloc_traits<_Tp_alloc_type> _Tr;
386 	if (__p)
387 	  _Tr::deallocate(_M_impl, __p, __n);
388       }
389 
390     protected:
391       _GLIBCXX20_CONSTEXPR
392       void
393       _M_create_storage(size_t __n)
394       {
395 	this->_M_impl._M_start = this->_M_allocate(__n);
396 	this->_M_impl._M_finish = this->_M_impl._M_start;
397 	this->_M_impl._M_end_of_storage = this->_M_impl._M_start + __n;
398       }
399     };
400 
401   /**
402    *  @brief A standard container which offers fixed time access to
403    *  individual elements in any order.
404    *
405    *  @ingroup sequences
406    *
407    *  @tparam _Tp  Type of element.
408    *  @tparam _Alloc  Allocator type, defaults to allocator<_Tp>.
409    *
410    *  Meets the requirements of a <a href="tables.html#65">container</a>, a
411    *  <a href="tables.html#66">reversible container</a>, and a
412    *  <a href="tables.html#67">sequence</a>, including the
413    *  <a href="tables.html#68">optional sequence requirements</a> with the
414    *  %exception of @c push_front and @c pop_front.
415    *
416    *  In some terminology a %vector can be described as a dynamic
417    *  C-style array, it offers fast and efficient access to individual
418    *  elements in any order and saves the user from worrying about
419    *  memory and size allocation.  Subscripting ( @c [] ) access is
420    *  also provided as with C-style arrays.
421   */
422   template<typename _Tp, typename _Alloc = std::allocator<_Tp> >
423     class vector : protected _Vector_base<_Tp, _Alloc>
424     {
425 #ifdef _GLIBCXX_CONCEPT_CHECKS
426       // Concept requirements.
427       typedef typename _Alloc::value_type		_Alloc_value_type;
428 # if __cplusplus < 201103L
429       __glibcxx_class_requires(_Tp, _SGIAssignableConcept)
430 # endif
431       __glibcxx_class_requires2(_Tp, _Alloc_value_type, _SameTypeConcept)
432 #endif
433 
434 #if __cplusplus >= 201103L
435       static_assert(is_same<typename remove_cv<_Tp>::type, _Tp>::value,
436 	  "std::vector must have a non-const, non-volatile value_type");
437 # if __cplusplus > 201703L || defined __STRICT_ANSI__
438       static_assert(is_same<typename _Alloc::value_type, _Tp>::value,
439 	  "std::vector must have the same value_type as its allocator");
440 # endif
441 #endif
442 
443       typedef _Vector_base<_Tp, _Alloc>			_Base;
444       typedef typename _Base::_Tp_alloc_type		_Tp_alloc_type;
445       typedef __gnu_cxx::__alloc_traits<_Tp_alloc_type>	_Alloc_traits;
446 
447     public:
448       typedef _Tp					value_type;
449       typedef typename _Base::pointer			pointer;
450       typedef typename _Alloc_traits::const_pointer	const_pointer;
451       typedef typename _Alloc_traits::reference		reference;
452       typedef typename _Alloc_traits::const_reference	const_reference;
453       typedef __gnu_cxx::__normal_iterator<pointer, vector> iterator;
454       typedef __gnu_cxx::__normal_iterator<const_pointer, vector>
455       const_iterator;
456       typedef std::reverse_iterator<const_iterator>	const_reverse_iterator;
457       typedef std::reverse_iterator<iterator>		reverse_iterator;
458       typedef size_t					size_type;
459       typedef ptrdiff_t					difference_type;
460       typedef _Alloc					allocator_type;
461 
462     private:
463 #if __cplusplus >= 201103L
464       static constexpr bool
465       _S_nothrow_relocate(true_type)
466       {
467 	return noexcept(std::__relocate_a(std::declval<pointer>(),
468 					  std::declval<pointer>(),
469 					  std::declval<pointer>(),
470 					  std::declval<_Tp_alloc_type&>()));
471       }
472 
473       static constexpr bool
474       _S_nothrow_relocate(false_type)
475       { return false; }
476 
477       static constexpr bool
478       _S_use_relocate()
479       {
480 	// Instantiating std::__relocate_a might cause an error outside the
481 	// immediate context (in __relocate_object_a's noexcept-specifier),
482 	// so only do it if we know the type can be move-inserted into *this.
483 	return _S_nothrow_relocate(__is_move_insertable<_Tp_alloc_type>{});
484       }
485 
486       static pointer
487       _S_do_relocate(pointer __first, pointer __last, pointer __result,
488 		     _Tp_alloc_type& __alloc, true_type) noexcept
489       {
490 	return std::__relocate_a(__first, __last, __result, __alloc);
491       }
492 
493       static pointer
494       _S_do_relocate(pointer, pointer, pointer __result,
495 		     _Tp_alloc_type&, false_type) noexcept
496       { return __result; }
497 
498       static _GLIBCXX20_CONSTEXPR pointer
499       _S_relocate(pointer __first, pointer __last, pointer __result,
500 		  _Tp_alloc_type& __alloc) noexcept
501       {
502 #if __cpp_if_constexpr
503 	// All callers have already checked _S_use_relocate() so just do it.
504 	return std::__relocate_a(__first, __last, __result, __alloc);
505 #else
506 	using __do_it = __bool_constant<_S_use_relocate()>;
507 	return _S_do_relocate(__first, __last, __result, __alloc, __do_it{});
508 #endif
509       }
510 #endif // C++11
511 
512     protected:
513       using _Base::_M_allocate;
514       using _Base::_M_deallocate;
515       using _Base::_M_impl;
516       using _Base::_M_get_Tp_allocator;
517 
518     public:
519       // [23.2.4.1] construct/copy/destroy
520       // (assign() and get_allocator() are also listed in this section)
521 
522       /**
523        *  @brief  Creates a %vector with no elements.
524        */
525 #if __cplusplus >= 201103L
526       vector() = default;
527 #else
528       vector() { }
529 #endif
530 
531       /**
532        *  @brief  Creates a %vector with no elements.
533        *  @param  __a  An allocator object.
534        */
535       explicit
536       _GLIBCXX20_CONSTEXPR
537       vector(const allocator_type& __a) _GLIBCXX_NOEXCEPT
538       : _Base(__a) { }
539 
540 #if __cplusplus >= 201103L
541       /**
542        *  @brief  Creates a %vector with default constructed elements.
543        *  @param  __n  The number of elements to initially create.
544        *  @param  __a  An allocator.
545        *
546        *  This constructor fills the %vector with @a __n default
547        *  constructed elements.
548        */
549       explicit
550       _GLIBCXX20_CONSTEXPR
551       vector(size_type __n, const allocator_type& __a = allocator_type())
552       : _Base(_S_check_init_len(__n, __a), __a)
553       { _M_default_initialize(__n); }
554 
555       /**
556        *  @brief  Creates a %vector with copies of an exemplar element.
557        *  @param  __n  The number of elements to initially create.
558        *  @param  __value  An element to copy.
559        *  @param  __a  An allocator.
560        *
561        *  This constructor fills the %vector with @a __n copies of @a __value.
562        */
563       _GLIBCXX20_CONSTEXPR
564       vector(size_type __n, const value_type& __value,
565 	     const allocator_type& __a = allocator_type())
566       : _Base(_S_check_init_len(__n, __a), __a)
567       { _M_fill_initialize(__n, __value); }
568 #else
569       /**
570        *  @brief  Creates a %vector with copies of an exemplar element.
571        *  @param  __n  The number of elements to initially create.
572        *  @param  __value  An element to copy.
573        *  @param  __a  An allocator.
574        *
575        *  This constructor fills the %vector with @a __n copies of @a __value.
576        */
577       explicit
578       vector(size_type __n, const value_type& __value = value_type(),
579 	     const allocator_type& __a = allocator_type())
580       : _Base(_S_check_init_len(__n, __a), __a)
581       { _M_fill_initialize(__n, __value); }
582 #endif
583 
584       /**
585        *  @brief  %Vector copy constructor.
586        *  @param  __x  A %vector of identical element and allocator types.
587        *
588        *  All the elements of @a __x are copied, but any unused capacity in
589        *  @a __x  will not be copied
590        *  (i.e. capacity() == size() in the new %vector).
591        *
592        *  The newly-created %vector uses a copy of the allocator object used
593        *  by @a __x (unless the allocator traits dictate a different object).
594        */
595       _GLIBCXX20_CONSTEXPR
596       vector(const vector& __x)
597       : _Base(__x.size(),
598 	_Alloc_traits::_S_select_on_copy(__x._M_get_Tp_allocator()))
599       {
600 	this->_M_impl._M_finish =
601 	  std::__uninitialized_copy_a(__x.begin(), __x.end(),
602 				      this->_M_impl._M_start,
603 				      _M_get_Tp_allocator());
604       }
605 
606 #if __cplusplus >= 201103L
607       /**
608        *  @brief  %Vector move constructor.
609        *
610        *  The newly-created %vector contains the exact contents of the
611        *  moved instance.
612        *  The contents of the moved instance are a valid, but unspecified
613        *  %vector.
614        */
615       vector(vector&&) noexcept = default;
616 
617       /// Copy constructor with alternative allocator
618       _GLIBCXX20_CONSTEXPR
619       vector(const vector& __x, const __type_identity_t<allocator_type>& __a)
620       : _Base(__x.size(), __a)
621       {
622 	this->_M_impl._M_finish =
623 	  std::__uninitialized_copy_a(__x.begin(), __x.end(),
624 				      this->_M_impl._M_start,
625 				      _M_get_Tp_allocator());
626       }
627 
628     private:
629       _GLIBCXX20_CONSTEXPR
630       vector(vector&& __rv, const allocator_type& __m, true_type) noexcept
631       : _Base(__m, std::move(__rv))
632       { }
633 
634       _GLIBCXX20_CONSTEXPR
635       vector(vector&& __rv, const allocator_type& __m, false_type)
636       : _Base(__m)
637       {
638 	if (__rv.get_allocator() == __m)
639 	  this->_M_impl._M_swap_data(__rv._M_impl);
640 	else if (!__rv.empty())
641 	  {
642 	    this->_M_create_storage(__rv.size());
643 	    this->_M_impl._M_finish =
644 	      std::__uninitialized_move_a(__rv.begin(), __rv.end(),
645 					  this->_M_impl._M_start,
646 					  _M_get_Tp_allocator());
647 	    __rv.clear();
648 	  }
649       }
650 
651     public:
652       /// Move constructor with alternative allocator
653       _GLIBCXX20_CONSTEXPR
654       vector(vector&& __rv, const __type_identity_t<allocator_type>& __m)
655       noexcept( noexcept(
656 	vector(std::declval<vector&&>(), std::declval<const allocator_type&>(),
657 	       std::declval<typename _Alloc_traits::is_always_equal>())) )
658       : vector(std::move(__rv), __m, typename _Alloc_traits::is_always_equal{})
659       { }
660 
661       /**
662        *  @brief  Builds a %vector from an initializer list.
663        *  @param  __l  An initializer_list.
664        *  @param  __a  An allocator.
665        *
666        *  Create a %vector consisting of copies of the elements in the
667        *  initializer_list @a __l.
668        *
669        *  This will call the element type's copy constructor N times
670        *  (where N is @a __l.size()) and do no memory reallocation.
671        */
672       _GLIBCXX20_CONSTEXPR
673       vector(initializer_list<value_type> __l,
674 	     const allocator_type& __a = allocator_type())
675       : _Base(__a)
676       {
677 	_M_range_initialize(__l.begin(), __l.end(),
678 			    random_access_iterator_tag());
679       }
680 #endif
681 
682       /**
683        *  @brief  Builds a %vector from a range.
684        *  @param  __first  An input iterator.
685        *  @param  __last  An input iterator.
686        *  @param  __a  An allocator.
687        *
688        *  Create a %vector consisting of copies of the elements from
689        *  [first,last).
690        *
691        *  If the iterators are forward, bidirectional, or
692        *  random-access, then this will call the elements' copy
693        *  constructor N times (where N is distance(first,last)) and do
694        *  no memory reallocation.  But if only input iterators are
695        *  used, then this will do at most 2N calls to the copy
696        *  constructor, and logN memory reallocations.
697        */
698 #if __cplusplus >= 201103L
699       template<typename _InputIterator,
700 	       typename = std::_RequireInputIter<_InputIterator>>
701 	_GLIBCXX20_CONSTEXPR
702 	vector(_InputIterator __first, _InputIterator __last,
703 	       const allocator_type& __a = allocator_type())
704 	: _Base(__a)
705 	{
706 	  _M_range_initialize(__first, __last,
707 			      std::__iterator_category(__first));
708 	}
709 #else
710       template<typename _InputIterator>
711 	vector(_InputIterator __first, _InputIterator __last,
712 	       const allocator_type& __a = allocator_type())
713 	: _Base(__a)
714 	{
715 	  // Check whether it's an integral type.  If so, it's not an iterator.
716 	  typedef typename std::__is_integer<_InputIterator>::__type _Integral;
717 	  _M_initialize_dispatch(__first, __last, _Integral());
718 	}
719 #endif
720 
721       /**
722        *  The dtor only erases the elements, and note that if the
723        *  elements themselves are pointers, the pointed-to memory is
724        *  not touched in any way.  Managing the pointer is the user's
725        *  responsibility.
726        */
727       _GLIBCXX20_CONSTEXPR
728       ~vector() _GLIBCXX_NOEXCEPT
729       {
730 	std::_Destroy(this->_M_impl._M_start, this->_M_impl._M_finish,
731 		      _M_get_Tp_allocator());
732 	_GLIBCXX_ASAN_ANNOTATE_BEFORE_DEALLOC;
733       }
734 
735       /**
736        *  @brief  %Vector assignment operator.
737        *  @param  __x  A %vector of identical element and allocator types.
738        *
739        *  All the elements of @a __x are copied, but any unused capacity in
740        *  @a __x will not be copied.
741        *
742        *  Whether the allocator is copied depends on the allocator traits.
743        */
744       _GLIBCXX20_CONSTEXPR
745       vector&
746       operator=(const vector& __x);
747 
748 #if __cplusplus >= 201103L
749       /**
750        *  @brief  %Vector move assignment operator.
751        *  @param  __x  A %vector of identical element and allocator types.
752        *
753        *  The contents of @a __x are moved into this %vector (without copying,
754        *  if the allocators permit it).
755        *  Afterwards @a __x is a valid, but unspecified %vector.
756        *
757        *  Whether the allocator is moved depends on the allocator traits.
758        */
759       _GLIBCXX20_CONSTEXPR
760       vector&
761       operator=(vector&& __x) noexcept(_Alloc_traits::_S_nothrow_move())
762       {
763 	constexpr bool __move_storage =
764 	  _Alloc_traits::_S_propagate_on_move_assign()
765 	  || _Alloc_traits::_S_always_equal();
766 	_M_move_assign(std::move(__x), __bool_constant<__move_storage>());
767 	return *this;
768       }
769 
770       /**
771        *  @brief  %Vector list assignment operator.
772        *  @param  __l  An initializer_list.
773        *
774        *  This function fills a %vector with copies of the elements in the
775        *  initializer list @a __l.
776        *
777        *  Note that the assignment completely changes the %vector and
778        *  that the resulting %vector's size is the same as the number
779        *  of elements assigned.
780        */
781       _GLIBCXX20_CONSTEXPR
782       vector&
783       operator=(initializer_list<value_type> __l)
784       {
785 	this->_M_assign_aux(__l.begin(), __l.end(),
786 			    random_access_iterator_tag());
787 	return *this;
788       }
789 #endif
790 
791       /**
792        *  @brief  Assigns a given value to a %vector.
793        *  @param  __n  Number of elements to be assigned.
794        *  @param  __val  Value to be assigned.
795        *
796        *  This function fills a %vector with @a __n copies of the given
797        *  value.  Note that the assignment completely changes the
798        *  %vector and that the resulting %vector's size is the same as
799        *  the number of elements assigned.
800        */
801       _GLIBCXX20_CONSTEXPR
802       void
803       assign(size_type __n, const value_type& __val)
804       { _M_fill_assign(__n, __val); }
805 
806       /**
807        *  @brief  Assigns a range to a %vector.
808        *  @param  __first  An input iterator.
809        *  @param  __last   An input iterator.
810        *
811        *  This function fills a %vector with copies of the elements in the
812        *  range [__first,__last).
813        *
814        *  Note that the assignment completely changes the %vector and
815        *  that the resulting %vector's size is the same as the number
816        *  of elements assigned.
817        */
818 #if __cplusplus >= 201103L
819       template<typename _InputIterator,
820 	       typename = std::_RequireInputIter<_InputIterator>>
821 	_GLIBCXX20_CONSTEXPR
822 	void
823 	assign(_InputIterator __first, _InputIterator __last)
824 	{ _M_assign_dispatch(__first, __last, __false_type()); }
825 #else
826       template<typename _InputIterator>
827 	void
828 	assign(_InputIterator __first, _InputIterator __last)
829 	{
830 	  // Check whether it's an integral type.  If so, it's not an iterator.
831 	  typedef typename std::__is_integer<_InputIterator>::__type _Integral;
832 	  _M_assign_dispatch(__first, __last, _Integral());
833 	}
834 #endif
835 
836 #if __cplusplus >= 201103L
837       /**
838        *  @brief  Assigns an initializer list to a %vector.
839        *  @param  __l  An initializer_list.
840        *
841        *  This function fills a %vector with copies of the elements in the
842        *  initializer list @a __l.
843        *
844        *  Note that the assignment completely changes the %vector and
845        *  that the resulting %vector's size is the same as the number
846        *  of elements assigned.
847        */
848       _GLIBCXX20_CONSTEXPR
849       void
850       assign(initializer_list<value_type> __l)
851       {
852 	this->_M_assign_aux(__l.begin(), __l.end(),
853 			    random_access_iterator_tag());
854       }
855 #endif
856 
857       /// Get a copy of the memory allocation object.
858       using _Base::get_allocator;
859 
860       // iterators
861       /**
862        *  Returns a read/write iterator that points to the first
863        *  element in the %vector.  Iteration is done in ordinary
864        *  element order.
865        */
866       _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
867       iterator
868       begin() _GLIBCXX_NOEXCEPT
869       { return iterator(this->_M_impl._M_start); }
870 
871       /**
872        *  Returns a read-only (constant) iterator that points to the
873        *  first element in the %vector.  Iteration is done in ordinary
874        *  element order.
875        */
876       _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
877       const_iterator
878       begin() const _GLIBCXX_NOEXCEPT
879       { return const_iterator(this->_M_impl._M_start); }
880 
881       /**
882        *  Returns a read/write iterator that points one past the last
883        *  element in the %vector.  Iteration is done in ordinary
884        *  element order.
885        */
886       _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
887       iterator
888       end() _GLIBCXX_NOEXCEPT
889       { return iterator(this->_M_impl._M_finish); }
890 
891       /**
892        *  Returns a read-only (constant) iterator that points one past
893        *  the last element in the %vector.  Iteration is done in
894        *  ordinary element order.
895        */
896       _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
897       const_iterator
898       end() const _GLIBCXX_NOEXCEPT
899       { return const_iterator(this->_M_impl._M_finish); }
900 
901       /**
902        *  Returns a read/write reverse iterator that points to the
903        *  last element in the %vector.  Iteration is done in reverse
904        *  element order.
905        */
906       _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
907       reverse_iterator
908       rbegin() _GLIBCXX_NOEXCEPT
909       { return reverse_iterator(end()); }
910 
911       /**
912        *  Returns a read-only (constant) reverse iterator that points
913        *  to the last element in the %vector.  Iteration is done in
914        *  reverse element order.
915        */
916       _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
917       const_reverse_iterator
918       rbegin() const _GLIBCXX_NOEXCEPT
919       { return const_reverse_iterator(end()); }
920 
921       /**
922        *  Returns a read/write reverse iterator that points to one
923        *  before the first element in the %vector.  Iteration is done
924        *  in reverse element order.
925        */
926       _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
927       reverse_iterator
928       rend() _GLIBCXX_NOEXCEPT
929       { return reverse_iterator(begin()); }
930 
931       /**
932        *  Returns a read-only (constant) reverse iterator that points
933        *  to one before the first element in the %vector.  Iteration
934        *  is done in reverse element order.
935        */
936       _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
937       const_reverse_iterator
938       rend() const _GLIBCXX_NOEXCEPT
939       { return const_reverse_iterator(begin()); }
940 
941 #if __cplusplus >= 201103L
942       /**
943        *  Returns a read-only (constant) iterator that points to the
944        *  first element in the %vector.  Iteration is done in ordinary
945        *  element order.
946        */
947       [[__nodiscard__]] _GLIBCXX20_CONSTEXPR
948       const_iterator
949       cbegin() const noexcept
950       { return const_iterator(this->_M_impl._M_start); }
951 
952       /**
953        *  Returns a read-only (constant) iterator that points one past
954        *  the last element in the %vector.  Iteration is done in
955        *  ordinary element order.
956        */
957       [[__nodiscard__]] _GLIBCXX20_CONSTEXPR
958       const_iterator
959       cend() const noexcept
960       { return const_iterator(this->_M_impl._M_finish); }
961 
962       /**
963        *  Returns a read-only (constant) reverse iterator that points
964        *  to the last element in the %vector.  Iteration is done in
965        *  reverse element order.
966        */
967       [[__nodiscard__]] _GLIBCXX20_CONSTEXPR
968       const_reverse_iterator
969       crbegin() const noexcept
970       { return const_reverse_iterator(end()); }
971 
972       /**
973        *  Returns a read-only (constant) reverse iterator that points
974        *  to one before the first element in the %vector.  Iteration
975        *  is done in reverse element order.
976        */
977       [[__nodiscard__]] _GLIBCXX20_CONSTEXPR
978       const_reverse_iterator
979       crend() const noexcept
980       { return const_reverse_iterator(begin()); }
981 #endif
982 
983       // [23.2.4.2] capacity
984       /**  Returns the number of elements in the %vector.  */
985       _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
986       size_type
987       size() const _GLIBCXX_NOEXCEPT
988       { return size_type(this->_M_impl._M_finish - this->_M_impl._M_start); }
989 
990       /**  Returns the size() of the largest possible %vector.  */
991       _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
992       size_type
993       max_size() const _GLIBCXX_NOEXCEPT
994       { return _S_max_size(_M_get_Tp_allocator()); }
995 
996 #if __cplusplus >= 201103L
997       /**
998        *  @brief  Resizes the %vector to the specified number of elements.
999        *  @param  __new_size  Number of elements the %vector should contain.
1000        *
1001        *  This function will %resize the %vector to the specified
1002        *  number of elements.  If the number is smaller than the
1003        *  %vector's current size the %vector is truncated, otherwise
1004        *  default constructed elements are appended.
1005        */
1006       _GLIBCXX20_CONSTEXPR
1007       void
1008       resize(size_type __new_size)
1009       {
1010 	if (__new_size > size())
1011 	  _M_default_append(__new_size - size());
1012 	else if (__new_size < size())
1013 	  _M_erase_at_end(this->_M_impl._M_start + __new_size);
1014       }
1015 
1016       /**
1017        *  @brief  Resizes the %vector to the specified number of elements.
1018        *  @param  __new_size  Number of elements the %vector should contain.
1019        *  @param  __x  Data with which new elements should be populated.
1020        *
1021        *  This function will %resize the %vector to the specified
1022        *  number of elements.  If the number is smaller than the
1023        *  %vector's current size the %vector is truncated, otherwise
1024        *  the %vector is extended and new elements are populated with
1025        *  given data.
1026        */
1027       _GLIBCXX20_CONSTEXPR
1028       void
1029       resize(size_type __new_size, const value_type& __x)
1030       {
1031 	if (__new_size > size())
1032 	  _M_fill_insert(end(), __new_size - size(), __x);
1033 	else if (__new_size < size())
1034 	  _M_erase_at_end(this->_M_impl._M_start + __new_size);
1035       }
1036 #else
1037       /**
1038        *  @brief  Resizes the %vector to the specified number of elements.
1039        *  @param  __new_size  Number of elements the %vector should contain.
1040        *  @param  __x  Data with which new elements should be populated.
1041        *
1042        *  This function will %resize the %vector to the specified
1043        *  number of elements.  If the number is smaller than the
1044        *  %vector's current size the %vector is truncated, otherwise
1045        *  the %vector is extended and new elements are populated with
1046        *  given data.
1047        */
1048       _GLIBCXX20_CONSTEXPR
1049       void
1050       resize(size_type __new_size, value_type __x = value_type())
1051       {
1052 	if (__new_size > size())
1053 	  _M_fill_insert(end(), __new_size - size(), __x);
1054 	else if (__new_size < size())
1055 	  _M_erase_at_end(this->_M_impl._M_start + __new_size);
1056       }
1057 #endif
1058 
1059 #if __cplusplus >= 201103L
1060       /**  A non-binding request to reduce capacity() to size().  */
1061       _GLIBCXX20_CONSTEXPR
1062       void
1063       shrink_to_fit()
1064       { _M_shrink_to_fit(); }
1065 #endif
1066 
1067       /**
1068        *  Returns the total number of elements that the %vector can
1069        *  hold before needing to allocate more memory.
1070        */
1071       _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
1072       size_type
1073       capacity() const _GLIBCXX_NOEXCEPT
1074       { return size_type(this->_M_impl._M_end_of_storage
1075 			 - this->_M_impl._M_start); }
1076 
1077       /**
1078        *  Returns true if the %vector is empty.  (Thus begin() would
1079        *  equal end().)
1080        */
1081       _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
1082       bool
1083       empty() const _GLIBCXX_NOEXCEPT
1084       { return begin() == end(); }
1085 
1086       /**
1087        *  @brief  Attempt to preallocate enough memory for specified number of
1088        *          elements.
1089        *  @param  __n  Number of elements required.
1090        *  @throw  std::length_error  If @a n exceeds @c max_size().
1091        *
1092        *  This function attempts to reserve enough memory for the
1093        *  %vector to hold the specified number of elements.  If the
1094        *  number requested is more than max_size(), length_error is
1095        *  thrown.
1096        *
1097        *  The advantage of this function is that if optimal code is a
1098        *  necessity and the user can determine the number of elements
1099        *  that will be required, the user can reserve the memory in
1100        *  %advance, and thus prevent a possible reallocation of memory
1101        *  and copying of %vector data.
1102        */
1103       _GLIBCXX20_CONSTEXPR
1104       void
1105       reserve(size_type __n);
1106 
1107       // element access
1108       /**
1109        *  @brief  Subscript access to the data contained in the %vector.
1110        *  @param __n The index of the element for which data should be
1111        *  accessed.
1112        *  @return  Read/write reference to data.
1113        *
1114        *  This operator allows for easy, array-style, data access.
1115        *  Note that data access with this operator is unchecked and
1116        *  out_of_range lookups are not defined. (For checked lookups
1117        *  see at().)
1118        */
1119       _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
1120       reference
1121       operator[](size_type __n) _GLIBCXX_NOEXCEPT
1122       {
1123 	__glibcxx_requires_subscript(__n);
1124 	return *(this->_M_impl._M_start + __n);
1125       }
1126 
1127       /**
1128        *  @brief  Subscript access to the data contained in the %vector.
1129        *  @param __n The index of the element for which data should be
1130        *  accessed.
1131        *  @return  Read-only (constant) reference to data.
1132        *
1133        *  This operator allows for easy, array-style, data access.
1134        *  Note that data access with this operator is unchecked and
1135        *  out_of_range lookups are not defined. (For checked lookups
1136        *  see at().)
1137        */
1138       _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
1139       const_reference
1140       operator[](size_type __n) const _GLIBCXX_NOEXCEPT
1141       {
1142 	__glibcxx_requires_subscript(__n);
1143 	return *(this->_M_impl._M_start + __n);
1144       }
1145 
1146     protected:
1147       /// Safety check used only from at().
1148       _GLIBCXX20_CONSTEXPR
1149       void
1150       _M_range_check(size_type __n) const
1151       {
1152 	if (__n >= this->size())
1153 	  __throw_out_of_range_fmt(__N("vector::_M_range_check: __n "
1154 				       "(which is %zu) >= this->size() "
1155 				       "(which is %zu)"),
1156 				   __n, this->size());
1157       }
1158 
1159     public:
1160       /**
1161        *  @brief  Provides access to the data contained in the %vector.
1162        *  @param __n The index of the element for which data should be
1163        *  accessed.
1164        *  @return  Read/write reference to data.
1165        *  @throw  std::out_of_range  If @a __n is an invalid index.
1166        *
1167        *  This function provides for safer data access.  The parameter
1168        *  is first checked that it is in the range of the vector.  The
1169        *  function throws out_of_range if the check fails.
1170        */
1171       _GLIBCXX20_CONSTEXPR
1172       reference
1173       at(size_type __n)
1174       {
1175 	_M_range_check(__n);
1176 	return (*this)[__n];
1177       }
1178 
1179       /**
1180        *  @brief  Provides access to the data contained in the %vector.
1181        *  @param __n The index of the element for which data should be
1182        *  accessed.
1183        *  @return  Read-only (constant) reference to data.
1184        *  @throw  std::out_of_range  If @a __n is an invalid index.
1185        *
1186        *  This function provides for safer data access.  The parameter
1187        *  is first checked that it is in the range of the vector.  The
1188        *  function throws out_of_range if the check fails.
1189        */
1190       _GLIBCXX20_CONSTEXPR
1191       const_reference
1192       at(size_type __n) const
1193       {
1194 	_M_range_check(__n);
1195 	return (*this)[__n];
1196       }
1197 
1198       /**
1199        *  Returns a read/write reference to the data at the first
1200        *  element of the %vector.
1201        */
1202       _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
1203       reference
1204       front() _GLIBCXX_NOEXCEPT
1205       {
1206 	__glibcxx_requires_nonempty();
1207 	return *begin();
1208       }
1209 
1210       /**
1211        *  Returns a read-only (constant) reference to the data at the first
1212        *  element of the %vector.
1213        */
1214       _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
1215       const_reference
1216       front() const _GLIBCXX_NOEXCEPT
1217       {
1218 	__glibcxx_requires_nonempty();
1219 	return *begin();
1220       }
1221 
1222       /**
1223        *  Returns a read/write reference to the data at the last
1224        *  element of the %vector.
1225        */
1226       _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
1227       reference
1228       back() _GLIBCXX_NOEXCEPT
1229       {
1230 	__glibcxx_requires_nonempty();
1231 	return *(end() - 1);
1232       }
1233 
1234       /**
1235        *  Returns a read-only (constant) reference to the data at the
1236        *  last element of the %vector.
1237        */
1238       _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
1239       const_reference
1240       back() const _GLIBCXX_NOEXCEPT
1241       {
1242 	__glibcxx_requires_nonempty();
1243 	return *(end() - 1);
1244       }
1245 
1246       // _GLIBCXX_RESOLVE_LIB_DEFECTS
1247       // DR 464. Suggestion for new member functions in standard containers.
1248       // data access
1249       /**
1250        *   Returns a pointer such that [data(), data() + size()) is a valid
1251        *   range.  For a non-empty %vector, data() == &front().
1252        */
1253       _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
1254       _Tp*
1255       data() _GLIBCXX_NOEXCEPT
1256       { return _M_data_ptr(this->_M_impl._M_start); }
1257 
1258       _GLIBCXX_NODISCARD _GLIBCXX20_CONSTEXPR
1259       const _Tp*
1260       data() const _GLIBCXX_NOEXCEPT
1261       { return _M_data_ptr(this->_M_impl._M_start); }
1262 
1263       // [23.2.4.3] modifiers
1264       /**
1265        *  @brief  Add data to the end of the %vector.
1266        *  @param  __x  Data to be added.
1267        *
1268        *  This is a typical stack operation.  The function creates an
1269        *  element at the end of the %vector and assigns the given data
1270        *  to it.  Due to the nature of a %vector this operation can be
1271        *  done in constant time if the %vector has preallocated space
1272        *  available.
1273        */
1274       _GLIBCXX20_CONSTEXPR
1275       void
1276       push_back(const value_type& __x)
1277       {
1278 	if (this->_M_impl._M_finish != this->_M_impl._M_end_of_storage)
1279 	  {
1280 	    _GLIBCXX_ASAN_ANNOTATE_GROW(1);
1281 	    _Alloc_traits::construct(this->_M_impl, this->_M_impl._M_finish,
1282 				     __x);
1283 	    ++this->_M_impl._M_finish;
1284 	    _GLIBCXX_ASAN_ANNOTATE_GREW(1);
1285 	  }
1286 	else
1287 	  _M_realloc_insert(end(), __x);
1288       }
1289 
1290 #if __cplusplus >= 201103L
1291       _GLIBCXX20_CONSTEXPR
1292       void
1293       push_back(value_type&& __x)
1294       { emplace_back(std::move(__x)); }
1295 
1296       template<typename... _Args>
1297 #if __cplusplus > 201402L
1298 	_GLIBCXX20_CONSTEXPR
1299 	reference
1300 #else
1301 	void
1302 #endif
1303 	emplace_back(_Args&&... __args);
1304 #endif
1305 
1306       /**
1307        *  @brief  Removes last element.
1308        *
1309        *  This is a typical stack operation. It shrinks the %vector by one.
1310        *
1311        *  Note that no data is returned, and if the last element's
1312        *  data is needed, it should be retrieved before pop_back() is
1313        *  called.
1314        */
1315       _GLIBCXX20_CONSTEXPR
1316       void
1317       pop_back() _GLIBCXX_NOEXCEPT
1318       {
1319 	__glibcxx_requires_nonempty();
1320 	--this->_M_impl._M_finish;
1321 	_Alloc_traits::destroy(this->_M_impl, this->_M_impl._M_finish);
1322 	_GLIBCXX_ASAN_ANNOTATE_SHRINK(1);
1323       }
1324 
1325 #if __cplusplus >= 201103L
1326       /**
1327        *  @brief  Inserts an object in %vector before specified iterator.
1328        *  @param  __position  A const_iterator into the %vector.
1329        *  @param  __args  Arguments.
1330        *  @return  An iterator that points to the inserted data.
1331        *
1332        *  This function will insert an object of type T constructed
1333        *  with T(std::forward<Args>(args)...) before the specified location.
1334        *  Note that this kind of operation could be expensive for a %vector
1335        *  and if it is frequently used the user should consider using
1336        *  std::list.
1337        */
1338       template<typename... _Args>
1339 	_GLIBCXX20_CONSTEXPR
1340 	iterator
1341 	emplace(const_iterator __position, _Args&&... __args)
1342 	{ return _M_emplace_aux(__position, std::forward<_Args>(__args)...); }
1343 
1344       /**
1345        *  @brief  Inserts given value into %vector before specified iterator.
1346        *  @param  __position  A const_iterator into the %vector.
1347        *  @param  __x  Data to be inserted.
1348        *  @return  An iterator that points to the inserted data.
1349        *
1350        *  This function will insert a copy of the given value before
1351        *  the specified location.  Note that this kind of operation
1352        *  could be expensive for a %vector and if it is frequently
1353        *  used the user should consider using std::list.
1354        */
1355       _GLIBCXX20_CONSTEXPR
1356       iterator
1357       insert(const_iterator __position, const value_type& __x);
1358 #else
1359       /**
1360        *  @brief  Inserts given value into %vector before specified iterator.
1361        *  @param  __position  An iterator into the %vector.
1362        *  @param  __x  Data to be inserted.
1363        *  @return  An iterator that points to the inserted data.
1364        *
1365        *  This function will insert a copy of the given value before
1366        *  the specified location.  Note that this kind of operation
1367        *  could be expensive for a %vector and if it is frequently
1368        *  used the user should consider using std::list.
1369        */
1370       iterator
1371       insert(iterator __position, const value_type& __x);
1372 #endif
1373 
1374 #if __cplusplus >= 201103L
1375       /**
1376        *  @brief  Inserts given rvalue into %vector before specified iterator.
1377        *  @param  __position  A const_iterator into the %vector.
1378        *  @param  __x  Data to be inserted.
1379        *  @return  An iterator that points to the inserted data.
1380        *
1381        *  This function will insert a copy of the given rvalue before
1382        *  the specified location.  Note that this kind of operation
1383        *  could be expensive for a %vector and if it is frequently
1384        *  used the user should consider using std::list.
1385        */
1386       _GLIBCXX20_CONSTEXPR
1387       iterator
1388       insert(const_iterator __position, value_type&& __x)
1389       { return _M_insert_rval(__position, std::move(__x)); }
1390 
1391       /**
1392        *  @brief  Inserts an initializer_list into the %vector.
1393        *  @param  __position  An iterator into the %vector.
1394        *  @param  __l  An initializer_list.
1395        *
1396        *  This function will insert copies of the data in the
1397        *  initializer_list @a l into the %vector before the location
1398        *  specified by @a position.
1399        *
1400        *  Note that this kind of operation could be expensive for a
1401        *  %vector and if it is frequently used the user should
1402        *  consider using std::list.
1403        */
1404       _GLIBCXX20_CONSTEXPR
1405       iterator
1406       insert(const_iterator __position, initializer_list<value_type> __l)
1407       {
1408 	auto __offset = __position - cbegin();
1409 	_M_range_insert(begin() + __offset, __l.begin(), __l.end(),
1410 			std::random_access_iterator_tag());
1411 	return begin() + __offset;
1412       }
1413 #endif
1414 
1415 #if __cplusplus >= 201103L
1416       /**
1417        *  @brief  Inserts a number of copies of given data into the %vector.
1418        *  @param  __position  A const_iterator into the %vector.
1419        *  @param  __n  Number of elements to be inserted.
1420        *  @param  __x  Data to be inserted.
1421        *  @return  An iterator that points to the inserted data.
1422        *
1423        *  This function will insert a specified number of copies of
1424        *  the given data before the location specified by @a position.
1425        *
1426        *  Note that this kind of operation could be expensive for a
1427        *  %vector and if it is frequently used the user should
1428        *  consider using std::list.
1429        */
1430       _GLIBCXX20_CONSTEXPR
1431       iterator
1432       insert(const_iterator __position, size_type __n, const value_type& __x)
1433       {
1434 	difference_type __offset = __position - cbegin();
1435 	_M_fill_insert(begin() + __offset, __n, __x);
1436 	return begin() + __offset;
1437       }
1438 #else
1439       /**
1440        *  @brief  Inserts a number of copies of given data into the %vector.
1441        *  @param  __position  An iterator into the %vector.
1442        *  @param  __n  Number of elements to be inserted.
1443        *  @param  __x  Data to be inserted.
1444        *
1445        *  This function will insert a specified number of copies of
1446        *  the given data before the location specified by @a position.
1447        *
1448        *  Note that this kind of operation could be expensive for a
1449        *  %vector and if it is frequently used the user should
1450        *  consider using std::list.
1451        */
1452       void
1453       insert(iterator __position, size_type __n, const value_type& __x)
1454       { _M_fill_insert(__position, __n, __x); }
1455 #endif
1456 
1457 #if __cplusplus >= 201103L
1458       /**
1459        *  @brief  Inserts a range into the %vector.
1460        *  @param  __position  A const_iterator into the %vector.
1461        *  @param  __first  An input iterator.
1462        *  @param  __last   An input iterator.
1463        *  @return  An iterator that points to the inserted data.
1464        *
1465        *  This function will insert copies of the data in the range
1466        *  [__first,__last) into the %vector before the location specified
1467        *  by @a pos.
1468        *
1469        *  Note that this kind of operation could be expensive for a
1470        *  %vector and if it is frequently used the user should
1471        *  consider using std::list.
1472        */
1473       template<typename _InputIterator,
1474 	       typename = std::_RequireInputIter<_InputIterator>>
1475 	_GLIBCXX20_CONSTEXPR
1476 	iterator
1477 	insert(const_iterator __position, _InputIterator __first,
1478 	       _InputIterator __last)
1479 	{
1480 	  difference_type __offset = __position - cbegin();
1481 	  _M_insert_dispatch(begin() + __offset,
1482 			     __first, __last, __false_type());
1483 	  return begin() + __offset;
1484 	}
1485 #else
1486       /**
1487        *  @brief  Inserts a range into the %vector.
1488        *  @param  __position  An iterator into the %vector.
1489        *  @param  __first  An input iterator.
1490        *  @param  __last   An input iterator.
1491        *
1492        *  This function will insert copies of the data in the range
1493        *  [__first,__last) into the %vector before the location specified
1494        *  by @a pos.
1495        *
1496        *  Note that this kind of operation could be expensive for a
1497        *  %vector and if it is frequently used the user should
1498        *  consider using std::list.
1499        */
1500       template<typename _InputIterator>
1501 	void
1502 	insert(iterator __position, _InputIterator __first,
1503 	       _InputIterator __last)
1504 	{
1505 	  // Check whether it's an integral type.  If so, it's not an iterator.
1506 	  typedef typename std::__is_integer<_InputIterator>::__type _Integral;
1507 	  _M_insert_dispatch(__position, __first, __last, _Integral());
1508 	}
1509 #endif
1510 
1511       /**
1512        *  @brief  Remove element at given position.
1513        *  @param  __position  Iterator pointing to element to be erased.
1514        *  @return  An iterator pointing to the next element (or end()).
1515        *
1516        *  This function will erase the element at the given position and thus
1517        *  shorten the %vector by one.
1518        *
1519        *  Note This operation could be expensive and if it is
1520        *  frequently used the user should consider using std::list.
1521        *  The user is also cautioned that this function only erases
1522        *  the element, and that if the element is itself a pointer,
1523        *  the pointed-to memory is not touched in any way.  Managing
1524        *  the pointer is the user's responsibility.
1525        */
1526       _GLIBCXX20_CONSTEXPR
1527       iterator
1528 #if __cplusplus >= 201103L
1529       erase(const_iterator __position)
1530       { return _M_erase(begin() + (__position - cbegin())); }
1531 #else
1532       erase(iterator __position)
1533       { return _M_erase(__position); }
1534 #endif
1535 
1536       /**
1537        *  @brief  Remove a range of elements.
1538        *  @param  __first  Iterator pointing to the first element to be erased.
1539        *  @param  __last  Iterator pointing to one past the last element to be
1540        *                  erased.
1541        *  @return  An iterator pointing to the element pointed to by @a __last
1542        *           prior to erasing (or end()).
1543        *
1544        *  This function will erase the elements in the range
1545        *  [__first,__last) and shorten the %vector accordingly.
1546        *
1547        *  Note This operation could be expensive and if it is
1548        *  frequently used the user should consider using std::list.
1549        *  The user is also cautioned that this function only erases
1550        *  the elements, and that if the elements themselves are
1551        *  pointers, the pointed-to memory is not touched in any way.
1552        *  Managing the pointer is the user's responsibility.
1553        */
1554       _GLIBCXX20_CONSTEXPR
1555       iterator
1556 #if __cplusplus >= 201103L
1557       erase(const_iterator __first, const_iterator __last)
1558       {
1559 	const auto __beg = begin();
1560 	const auto __cbeg = cbegin();
1561 	return _M_erase(__beg + (__first - __cbeg), __beg + (__last - __cbeg));
1562       }
1563 #else
1564       erase(iterator __first, iterator __last)
1565       { return _M_erase(__first, __last); }
1566 #endif
1567 
1568       /**
1569        *  @brief  Swaps data with another %vector.
1570        *  @param  __x  A %vector of the same element and allocator types.
1571        *
1572        *  This exchanges the elements between two vectors in constant time.
1573        *  (Three pointers, so it should be quite fast.)
1574        *  Note that the global std::swap() function is specialized such that
1575        *  std::swap(v1,v2) will feed to this function.
1576        *
1577        *  Whether the allocators are swapped depends on the allocator traits.
1578        */
1579       _GLIBCXX20_CONSTEXPR
1580       void
1581       swap(vector& __x) _GLIBCXX_NOEXCEPT
1582       {
1583 #if __cplusplus >= 201103L
1584 	__glibcxx_assert(_Alloc_traits::propagate_on_container_swap::value
1585 			 || _M_get_Tp_allocator() == __x._M_get_Tp_allocator());
1586 #endif
1587 	this->_M_impl._M_swap_data(__x._M_impl);
1588 	_Alloc_traits::_S_on_swap(_M_get_Tp_allocator(),
1589 				  __x._M_get_Tp_allocator());
1590       }
1591 
1592       /**
1593        *  Erases all the elements.  Note that this function only erases the
1594        *  elements, and that if the elements themselves are pointers, the
1595        *  pointed-to memory is not touched in any way.  Managing the pointer is
1596        *  the user's responsibility.
1597        */
1598       _GLIBCXX20_CONSTEXPR
1599       void
1600       clear() _GLIBCXX_NOEXCEPT
1601       { _M_erase_at_end(this->_M_impl._M_start); }
1602 
1603     protected:
1604       /**
1605        *  Memory expansion handler.  Uses the member allocation function to
1606        *  obtain @a n bytes of memory, and then copies [first,last) into it.
1607        */
1608       template<typename _ForwardIterator>
1609 	_GLIBCXX20_CONSTEXPR
1610 	pointer
1611 	_M_allocate_and_copy(size_type __n,
1612 			     _ForwardIterator __first, _ForwardIterator __last)
1613 	{
1614 	  pointer __result = this->_M_allocate(__n);
1615 	  __try
1616 	    {
1617 	      std::__uninitialized_copy_a(__first, __last, __result,
1618 					  _M_get_Tp_allocator());
1619 	      return __result;
1620 	    }
1621 	  __catch(...)
1622 	    {
1623 	      _M_deallocate(__result, __n);
1624 	      __throw_exception_again;
1625 	    }
1626 	}
1627 
1628 
1629       // Internal constructor functions follow.
1630 
1631       // Called by the range constructor to implement [23.1.1]/9
1632 
1633 #if __cplusplus < 201103L
1634       // _GLIBCXX_RESOLVE_LIB_DEFECTS
1635       // 438. Ambiguity in the "do the right thing" clause
1636       template<typename _Integer>
1637 	void
1638 	_M_initialize_dispatch(_Integer __n, _Integer __value, __true_type)
1639 	{
1640 	  this->_M_impl._M_start = _M_allocate(_S_check_init_len(
1641 		static_cast<size_type>(__n), _M_get_Tp_allocator()));
1642 	  this->_M_impl._M_end_of_storage =
1643 	    this->_M_impl._M_start + static_cast<size_type>(__n);
1644 	  _M_fill_initialize(static_cast<size_type>(__n), __value);
1645 	}
1646 
1647       // Called by the range constructor to implement [23.1.1]/9
1648       template<typename _InputIterator>
1649 	void
1650 	_M_initialize_dispatch(_InputIterator __first, _InputIterator __last,
1651 			       __false_type)
1652 	{
1653 	  _M_range_initialize(__first, __last,
1654 			      std::__iterator_category(__first));
1655 	}
1656 #endif
1657 
1658       // Called by the second initialize_dispatch above
1659       template<typename _InputIterator>
1660 	_GLIBCXX20_CONSTEXPR
1661 	void
1662 	_M_range_initialize(_InputIterator __first, _InputIterator __last,
1663 			    std::input_iterator_tag)
1664 	{
1665 	  __try {
1666 	    for (; __first != __last; ++__first)
1667 #if __cplusplus >= 201103L
1668 	      emplace_back(*__first);
1669 #else
1670 	      push_back(*__first);
1671 #endif
1672 	  } __catch(...) {
1673 	    clear();
1674 	    __throw_exception_again;
1675 	  }
1676 	}
1677 
1678       // Called by the second initialize_dispatch above
1679       template<typename _ForwardIterator>
1680 	_GLIBCXX20_CONSTEXPR
1681 	void
1682 	_M_range_initialize(_ForwardIterator __first, _ForwardIterator __last,
1683 			    std::forward_iterator_tag)
1684 	{
1685 	  const size_type __n = std::distance(__first, __last);
1686 	  this->_M_impl._M_start
1687 	    = this->_M_allocate(_S_check_init_len(__n, _M_get_Tp_allocator()));
1688 	  this->_M_impl._M_end_of_storage = this->_M_impl._M_start + __n;
1689 	  this->_M_impl._M_finish =
1690 	    std::__uninitialized_copy_a(__first, __last,
1691 					this->_M_impl._M_start,
1692 					_M_get_Tp_allocator());
1693 	}
1694 
1695       // Called by the first initialize_dispatch above and by the
1696       // vector(n,value,a) constructor.
1697       _GLIBCXX20_CONSTEXPR
1698       void
1699       _M_fill_initialize(size_type __n, const value_type& __value)
1700       {
1701 	this->_M_impl._M_finish =
1702 	  std::__uninitialized_fill_n_a(this->_M_impl._M_start, __n, __value,
1703 					_M_get_Tp_allocator());
1704       }
1705 
1706 #if __cplusplus >= 201103L
1707       // Called by the vector(n) constructor.
1708       _GLIBCXX20_CONSTEXPR
1709       void
1710       _M_default_initialize(size_type __n)
1711       {
1712 	this->_M_impl._M_finish =
1713 	  std::__uninitialized_default_n_a(this->_M_impl._M_start, __n,
1714 					   _M_get_Tp_allocator());
1715       }
1716 #endif
1717 
1718       // Internal assign functions follow.  The *_aux functions do the actual
1719       // assignment work for the range versions.
1720 
1721       // Called by the range assign to implement [23.1.1]/9
1722 
1723       // _GLIBCXX_RESOLVE_LIB_DEFECTS
1724       // 438. Ambiguity in the "do the right thing" clause
1725       template<typename _Integer>
1726 	_GLIBCXX20_CONSTEXPR
1727 	void
1728 	_M_assign_dispatch(_Integer __n, _Integer __val, __true_type)
1729 	{ _M_fill_assign(__n, __val); }
1730 
1731       // Called by the range assign to implement [23.1.1]/9
1732       template<typename _InputIterator>
1733 	_GLIBCXX20_CONSTEXPR
1734 	void
1735 	_M_assign_dispatch(_InputIterator __first, _InputIterator __last,
1736 			   __false_type)
1737 	{ _M_assign_aux(__first, __last, std::__iterator_category(__first)); }
1738 
1739       // Called by the second assign_dispatch above
1740       template<typename _InputIterator>
1741 	_GLIBCXX20_CONSTEXPR
1742 	void
1743 	_M_assign_aux(_InputIterator __first, _InputIterator __last,
1744 		      std::input_iterator_tag);
1745 
1746       // Called by the second assign_dispatch above
1747       template<typename _ForwardIterator>
1748 	_GLIBCXX20_CONSTEXPR
1749 	void
1750 	_M_assign_aux(_ForwardIterator __first, _ForwardIterator __last,
1751 		      std::forward_iterator_tag);
1752 
1753       // Called by assign(n,t), and the range assign when it turns out
1754       // to be the same thing.
1755       _GLIBCXX20_CONSTEXPR
1756       void
1757       _M_fill_assign(size_type __n, const value_type& __val);
1758 
1759       // Internal insert functions follow.
1760 
1761       // Called by the range insert to implement [23.1.1]/9
1762 
1763       // _GLIBCXX_RESOLVE_LIB_DEFECTS
1764       // 438. Ambiguity in the "do the right thing" clause
1765       template<typename _Integer>
1766 	_GLIBCXX20_CONSTEXPR
1767 	void
1768 	_M_insert_dispatch(iterator __pos, _Integer __n, _Integer __val,
1769 			   __true_type)
1770 	{ _M_fill_insert(__pos, __n, __val); }
1771 
1772       // Called by the range insert to implement [23.1.1]/9
1773       template<typename _InputIterator>
1774 	_GLIBCXX20_CONSTEXPR
1775 	void
1776 	_M_insert_dispatch(iterator __pos, _InputIterator __first,
1777 			   _InputIterator __last, __false_type)
1778 	{
1779 	  _M_range_insert(__pos, __first, __last,
1780 			  std::__iterator_category(__first));
1781 	}
1782 
1783       // Called by the second insert_dispatch above
1784       template<typename _InputIterator>
1785 	_GLIBCXX20_CONSTEXPR
1786 	void
1787 	_M_range_insert(iterator __pos, _InputIterator __first,
1788 			_InputIterator __last, std::input_iterator_tag);
1789 
1790       // Called by the second insert_dispatch above
1791       template<typename _ForwardIterator>
1792 	_GLIBCXX20_CONSTEXPR
1793 	void
1794 	_M_range_insert(iterator __pos, _ForwardIterator __first,
1795 			_ForwardIterator __last, std::forward_iterator_tag);
1796 
1797       // Called by insert(p,n,x), and the range insert when it turns out to be
1798       // the same thing.
1799       _GLIBCXX20_CONSTEXPR
1800       void
1801       _M_fill_insert(iterator __pos, size_type __n, const value_type& __x);
1802 
1803 #if __cplusplus >= 201103L
1804       // Called by resize(n).
1805       _GLIBCXX20_CONSTEXPR
1806       void
1807       _M_default_append(size_type __n);
1808 
1809       _GLIBCXX20_CONSTEXPR
1810       bool
1811       _M_shrink_to_fit();
1812 #endif
1813 
1814 #if __cplusplus < 201103L
1815       // Called by insert(p,x)
1816       void
1817       _M_insert_aux(iterator __position, const value_type& __x);
1818 
1819       void
1820       _M_realloc_insert(iterator __position, const value_type& __x);
1821 #else
1822       // A value_type object constructed with _Alloc_traits::construct()
1823       // and destroyed with _Alloc_traits::destroy().
1824       struct _Temporary_value
1825       {
1826 	template<typename... _Args>
1827 	  _GLIBCXX20_CONSTEXPR explicit
1828 	  _Temporary_value(vector* __vec, _Args&&... __args) : _M_this(__vec)
1829 	  {
1830 	    _Alloc_traits::construct(_M_this->_M_impl, _M_ptr(),
1831 				     std::forward<_Args>(__args)...);
1832 	  }
1833 
1834 	_GLIBCXX20_CONSTEXPR
1835 	~_Temporary_value()
1836 	{ _Alloc_traits::destroy(_M_this->_M_impl, _M_ptr()); }
1837 
1838 	_GLIBCXX20_CONSTEXPR value_type&
1839 	_M_val() noexcept { return _M_storage._M_val; }
1840 
1841       private:
1842 	_GLIBCXX20_CONSTEXPR _Tp*
1843 	_M_ptr() noexcept { return std::__addressof(_M_storage._M_val); }
1844 
1845 	union _Storage
1846 	{
1847 	  constexpr _Storage() : _M_byte() { }
1848 	  _GLIBCXX20_CONSTEXPR ~_Storage() { }
1849 	  _Storage& operator=(const _Storage&) = delete;
1850 	  unsigned char _M_byte;
1851 	  _Tp _M_val;
1852 	};
1853 
1854 	vector*  _M_this;
1855 	_Storage _M_storage;
1856       };
1857 
1858       // Called by insert(p,x) and other functions when insertion needs to
1859       // reallocate or move existing elements. _Arg is either _Tp& or _Tp.
1860       template<typename _Arg>
1861 	_GLIBCXX20_CONSTEXPR
1862 	void
1863 	_M_insert_aux(iterator __position, _Arg&& __arg);
1864 
1865       template<typename... _Args>
1866 	_GLIBCXX20_CONSTEXPR
1867 	void
1868 	_M_realloc_insert(iterator __position, _Args&&... __args);
1869 
1870       // Either move-construct at the end, or forward to _M_insert_aux.
1871       _GLIBCXX20_CONSTEXPR
1872       iterator
1873       _M_insert_rval(const_iterator __position, value_type&& __v);
1874 
1875       // Try to emplace at the end, otherwise forward to _M_insert_aux.
1876       template<typename... _Args>
1877 	_GLIBCXX20_CONSTEXPR
1878 	iterator
1879 	_M_emplace_aux(const_iterator __position, _Args&&... __args);
1880 
1881       // Emplacing an rvalue of the correct type can use _M_insert_rval.
1882       _GLIBCXX20_CONSTEXPR
1883       iterator
1884       _M_emplace_aux(const_iterator __position, value_type&& __v)
1885       { return _M_insert_rval(__position, std::move(__v)); }
1886 #endif
1887 
1888       // Called by _M_fill_insert, _M_insert_aux etc.
1889       _GLIBCXX20_CONSTEXPR
1890       size_type
1891       _M_check_len(size_type __n, const char* __s) const
1892       {
1893 	if (max_size() - size() < __n)
1894 	  __throw_length_error(__N(__s));
1895 
1896 	const size_type __len = size() + (std::max)(size(), __n);
1897 	return (__len < size() || __len > max_size()) ? max_size() : __len;
1898       }
1899 
1900       // Called by constructors to check initial size.
1901       static _GLIBCXX20_CONSTEXPR size_type
1902       _S_check_init_len(size_type __n, const allocator_type& __a)
1903       {
1904 	if (__n > _S_max_size(_Tp_alloc_type(__a)))
1905 	  __throw_length_error(
1906 	      __N("cannot create std::vector larger than max_size()"));
1907 	return __n;
1908       }
1909 
1910       static _GLIBCXX20_CONSTEXPR size_type
1911       _S_max_size(const _Tp_alloc_type& __a) _GLIBCXX_NOEXCEPT
1912       {
1913 	// std::distance(begin(), end()) cannot be greater than PTRDIFF_MAX,
1914 	// and realistically we can't store more than PTRDIFF_MAX/sizeof(T)
1915 	// (even if std::allocator_traits::max_size says we can).
1916 	const size_t __diffmax
1917 	  = __gnu_cxx::__numeric_traits<ptrdiff_t>::__max / sizeof(_Tp);
1918 	const size_t __allocmax = _Alloc_traits::max_size(__a);
1919 	return (std::min)(__diffmax, __allocmax);
1920       }
1921 
1922       // Internal erase functions follow.
1923 
1924       // Called by erase(q1,q2), clear(), resize(), _M_fill_assign,
1925       // _M_assign_aux.
1926       _GLIBCXX20_CONSTEXPR
1927       void
1928       _M_erase_at_end(pointer __pos) _GLIBCXX_NOEXCEPT
1929       {
1930 	if (size_type __n = this->_M_impl._M_finish - __pos)
1931 	  {
1932 	    std::_Destroy(__pos, this->_M_impl._M_finish,
1933 			  _M_get_Tp_allocator());
1934 	    this->_M_impl._M_finish = __pos;
1935 	    _GLIBCXX_ASAN_ANNOTATE_SHRINK(__n);
1936 	  }
1937       }
1938 
1939       _GLIBCXX20_CONSTEXPR
1940       iterator
1941       _M_erase(iterator __position);
1942 
1943       _GLIBCXX20_CONSTEXPR
1944       iterator
1945       _M_erase(iterator __first, iterator __last);
1946 
1947 #if __cplusplus >= 201103L
1948     private:
1949       // Constant-time move assignment when source object's memory can be
1950       // moved, either because the source's allocator will move too
1951       // or because the allocators are equal.
1952       _GLIBCXX20_CONSTEXPR
1953       void
1954       _M_move_assign(vector&& __x, true_type) noexcept
1955       {
1956 	vector __tmp(get_allocator());
1957 	this->_M_impl._M_swap_data(__x._M_impl);
1958 	__tmp._M_impl._M_swap_data(__x._M_impl);
1959 	std::__alloc_on_move(_M_get_Tp_allocator(), __x._M_get_Tp_allocator());
1960       }
1961 
1962       // Do move assignment when it might not be possible to move source
1963       // object's memory, resulting in a linear-time operation.
1964       _GLIBCXX20_CONSTEXPR
1965       void
1966       _M_move_assign(vector&& __x, false_type)
1967       {
1968 	if (__x._M_get_Tp_allocator() == this->_M_get_Tp_allocator())
1969 	  _M_move_assign(std::move(__x), true_type());
1970 	else
1971 	  {
1972 	    // The rvalue's allocator cannot be moved and is not equal,
1973 	    // so we need to individually move each element.
1974 	    this->_M_assign_aux(std::make_move_iterator(__x.begin()),
1975 			        std::make_move_iterator(__x.end()),
1976 				std::random_access_iterator_tag());
1977 	    __x.clear();
1978 	  }
1979       }
1980 #endif
1981 
1982       template<typename _Up>
1983 	_GLIBCXX20_CONSTEXPR
1984 	_Up*
1985 	_M_data_ptr(_Up* __ptr) const _GLIBCXX_NOEXCEPT
1986 	{ return __ptr; }
1987 
1988 #if __cplusplus >= 201103L
1989       template<typename _Ptr>
1990 	_GLIBCXX20_CONSTEXPR
1991 	typename std::pointer_traits<_Ptr>::element_type*
1992 	_M_data_ptr(_Ptr __ptr) const
1993 	{ return empty() ? nullptr : std::__to_address(__ptr); }
1994 #else
1995       template<typename _Up>
1996 	_Up*
1997 	_M_data_ptr(_Up* __ptr) _GLIBCXX_NOEXCEPT
1998 	{ return __ptr; }
1999 
2000       template<typename _Ptr>
2001 	value_type*
2002 	_M_data_ptr(_Ptr __ptr)
2003 	{ return empty() ? (value_type*)0 : __ptr.operator->(); }
2004 
2005       template<typename _Ptr>
2006 	const value_type*
2007 	_M_data_ptr(_Ptr __ptr) const
2008 	{ return empty() ? (const value_type*)0 : __ptr.operator->(); }
2009 #endif
2010     };
2011 
2012 #if __cpp_deduction_guides >= 201606
2013   template<typename _InputIterator, typename _ValT
2014 	     = typename iterator_traits<_InputIterator>::value_type,
2015 	   typename _Allocator = allocator<_ValT>,
2016 	   typename = _RequireInputIter<_InputIterator>,
2017 	   typename = _RequireAllocator<_Allocator>>
2018     vector(_InputIterator, _InputIterator, _Allocator = _Allocator())
2019       -> vector<_ValT, _Allocator>;
2020 #endif
2021 
2022   /**
2023    *  @brief  Vector equality comparison.
2024    *  @param  __x  A %vector.
2025    *  @param  __y  A %vector of the same type as @a __x.
2026    *  @return  True iff the size and elements of the vectors are equal.
2027    *
2028    *  This is an equivalence relation.  It is linear in the size of the
2029    *  vectors.  Vectors are considered equivalent if their sizes are equal,
2030    *  and if corresponding elements compare equal.
2031   */
2032   template<typename _Tp, typename _Alloc>
2033     _GLIBCXX20_CONSTEXPR
2034     inline bool
2035     operator==(const vector<_Tp, _Alloc>& __x, const vector<_Tp, _Alloc>& __y)
2036     { return (__x.size() == __y.size()
2037 	      && std::equal(__x.begin(), __x.end(), __y.begin())); }
2038 
2039 #if __cpp_lib_three_way_comparison
2040   /**
2041    *  @brief  Vector ordering relation.
2042    *  @param  __x  A `vector`.
2043    *  @param  __y  A `vector` of the same type as `__x`.
2044    *  @return  A value indicating whether `__x` is less than, equal to,
2045    *           greater than, or incomparable with `__y`.
2046    *
2047    *  See `std::lexicographical_compare_three_way()` for how the determination
2048    *  is made. This operator is used to synthesize relational operators like
2049    *  `<` and `>=` etc.
2050   */
2051   template<typename _Tp, typename _Alloc>
2052     _GLIBCXX20_CONSTEXPR
2053     inline __detail::__synth3way_t<_Tp>
2054     operator<=>(const vector<_Tp, _Alloc>& __x, const vector<_Tp, _Alloc>& __y)
2055     {
2056       return std::lexicographical_compare_three_way(__x.begin(), __x.end(),
2057 						    __y.begin(), __y.end(),
2058 						    __detail::__synth3way);
2059     }
2060 #else
2061   /**
2062    *  @brief  Vector ordering relation.
2063    *  @param  __x  A %vector.
2064    *  @param  __y  A %vector of the same type as @a __x.
2065    *  @return  True iff @a __x is lexicographically less than @a __y.
2066    *
2067    *  This is a total ordering relation.  It is linear in the size of the
2068    *  vectors.  The elements must be comparable with @c <.
2069    *
2070    *  See std::lexicographical_compare() for how the determination is made.
2071   */
2072   template<typename _Tp, typename _Alloc>
2073     inline bool
2074     operator<(const vector<_Tp, _Alloc>& __x, const vector<_Tp, _Alloc>& __y)
2075     { return std::lexicographical_compare(__x.begin(), __x.end(),
2076 					  __y.begin(), __y.end()); }
2077 
2078   /// Based on operator==
2079   template<typename _Tp, typename _Alloc>
2080     inline bool
2081     operator!=(const vector<_Tp, _Alloc>& __x, const vector<_Tp, _Alloc>& __y)
2082     { return !(__x == __y); }
2083 
2084   /// Based on operator<
2085   template<typename _Tp, typename _Alloc>
2086     inline bool
2087     operator>(const vector<_Tp, _Alloc>& __x, const vector<_Tp, _Alloc>& __y)
2088     { return __y < __x; }
2089 
2090   /// Based on operator<
2091   template<typename _Tp, typename _Alloc>
2092     inline bool
2093     operator<=(const vector<_Tp, _Alloc>& __x, const vector<_Tp, _Alloc>& __y)
2094     { return !(__y < __x); }
2095 
2096   /// Based on operator<
2097   template<typename _Tp, typename _Alloc>
2098     inline bool
2099     operator>=(const vector<_Tp, _Alloc>& __x, const vector<_Tp, _Alloc>& __y)
2100     { return !(__x < __y); }
2101 #endif // three-way comparison
2102 
2103   /// See std::vector::swap().
2104   template<typename _Tp, typename _Alloc>
2105     _GLIBCXX20_CONSTEXPR
2106     inline void
2107     swap(vector<_Tp, _Alloc>& __x, vector<_Tp, _Alloc>& __y)
2108     _GLIBCXX_NOEXCEPT_IF(noexcept(__x.swap(__y)))
2109     { __x.swap(__y); }
2110 
2111 _GLIBCXX_END_NAMESPACE_CONTAINER
2112 
2113 #if __cplusplus >= 201703L
2114   namespace __detail::__variant
2115   {
2116     template<typename> struct _Never_valueless_alt; // see <variant>
2117 
2118     // Provide the strong exception-safety guarantee when emplacing a
2119     // vector into a variant, but only if move assignment cannot throw.
2120     template<typename _Tp, typename _Alloc>
2121       struct _Never_valueless_alt<_GLIBCXX_STD_C::vector<_Tp, _Alloc>>
2122       : std::is_nothrow_move_assignable<_GLIBCXX_STD_C::vector<_Tp, _Alloc>>
2123       { };
2124   }  // namespace __detail::__variant
2125 #endif // C++17
2126 
2127 _GLIBCXX_END_NAMESPACE_VERSION
2128 } // namespace std
2129 
2130 #endif /* _STL_VECTOR_H */
2131