libstdc++
helper_functions.h
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1 // Debugging support implementation -*- C++ -*-
2 
3 // Copyright (C) 2003-2021 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 
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22 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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24 
25 /** @file debug/helper_functions.h
26  * This file is a GNU debug extension to the Standard C++ Library.
27  */
28 
29 #ifndef _GLIBCXX_DEBUG_HELPER_FUNCTIONS_H
30 #define _GLIBCXX_DEBUG_HELPER_FUNCTIONS_H 1
31 
32 #include <bits/move.h> // for __addressof
33 #include <bits/stl_iterator_base_types.h> // for iterator_traits,
34  // categories and _Iter_base
35 #include <bits/cpp_type_traits.h> // for __is_integer
36 
37 #include <bits/stl_pair.h> // for pair
38 
39 namespace __gnu_debug
40 {
41  template<typename _Iterator, typename _Sequence, typename _Category>
42  class _Safe_iterator;
43 
44 #if __cplusplus >= 201103L
45  template<typename _Iterator, typename _Sequence>
46  class _Safe_local_iterator;
47 #endif
48 
49  /** The precision to which we can calculate the distance between
50  * two iterators.
51  */
53  {
54  __dp_none, // Not even an iterator type
55  __dp_equality, //< Can compare iterator equality, only
56  __dp_sign, //< Can determine equality and ordering
57  __dp_sign_max_size, //< __dp_sign and gives max range size
58  __dp_exact //< Can determine distance precisely
59  };
60 
61  template<typename _Iterator,
62  typename = typename std::__is_integer<_Iterator>::__type>
63  struct _Distance_traits
64  {
65  private:
66  typedef
68 
69  template<typename _DiffType,
70  typename = typename std::__is_void<_DiffType>::__type>
71  struct _DiffTraits
72  { typedef _DiffType __type; };
73 
74  template<typename _DiffType>
75  struct _DiffTraits<_DiffType, std::__true_type>
76  { typedef std::ptrdiff_t __type; };
77 
78  typedef typename _DiffTraits<_ItDiffType>::__type _DiffType;
79 
80  public:
82  };
83 
84  template<typename _Integral>
85  struct _Distance_traits<_Integral, std::__true_type>
87 
88  /** Determine the distance between two iterators with some known
89  * precision.
90  */
91  template<typename _Iterator>
92  _GLIBCXX_CONSTEXPR
93  inline typename _Distance_traits<_Iterator>::__type
94  __get_distance(_Iterator __lhs, _Iterator __rhs,
96  { return std::make_pair(__rhs - __lhs, __dp_exact); }
97 
98  template<typename _Iterator>
99  _GLIBCXX14_CONSTEXPR
100  inline typename _Distance_traits<_Iterator>::__type
101  __get_distance(_Iterator __lhs, _Iterator __rhs,
103  {
104  if (__lhs == __rhs)
105  return std::make_pair(0, __dp_exact);
106 
107  return std::make_pair(1, __dp_equality);
108  }
109 
110  template<typename _Iterator>
111  _GLIBCXX_CONSTEXPR
112  inline typename _Distance_traits<_Iterator>::__type
113  __get_distance(_Iterator __lhs, _Iterator __rhs)
114  { return __get_distance(__lhs, __rhs, std::__iterator_category(__lhs)); }
115 
116  // An arbitrary iterator pointer is not singular.
117  inline bool
118  __check_singular_aux(const void*) { return false; }
119 
120  // We may have an iterator that derives from _Safe_iterator_base but isn't
121  // a _Safe_iterator.
122  template<typename _Iterator>
123  _GLIBCXX_CONSTEXPR
124  inline bool
125  __check_singular(_Iterator const& __x)
126  {
127  return
128 #ifdef _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED
129  __builtin_is_constant_evaluated() ? false :
130 #endif
131  __check_singular_aux(std::__addressof(__x));
132  }
133 
134  /** Non-NULL pointers are nonsingular. */
135  template<typename _Tp>
136  _GLIBCXX_CONSTEXPR
137  inline bool
138  __check_singular(_Tp* const& __ptr)
139  {
140  return
141 #ifdef _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED
142  __builtin_is_constant_evaluated() ? false :
143 #endif
144  __ptr == 0;
145  }
146 
147  /** We say that integral types for a valid range, and defer to other
148  * routines to realize what to do with integral types instead of
149  * iterators.
150  */
151  template<typename _Integral>
152  _GLIBCXX_CONSTEXPR
153  inline bool
154  __valid_range_aux(_Integral, _Integral, std::__true_type)
155  { return true; }
156 
157  template<typename _Integral>
158  _GLIBCXX20_CONSTEXPR
159  inline bool
160  __valid_range_aux(_Integral, _Integral,
161  typename _Distance_traits<_Integral>::__type& __dist,
162  std::__true_type)
163  {
164  __dist = std::make_pair(0, __dp_none);
165  return true;
166  }
167 
168  template<typename _InputIterator>
169  _GLIBCXX_CONSTEXPR
170  inline bool
171  __valid_range_aux(_InputIterator __first, _InputIterator __last,
173  {
174  return __first == __last
175  || (!__check_singular(__first) && !__check_singular(__last));
176  }
177 
178  template<typename _InputIterator>
179  _GLIBCXX_CONSTEXPR
180  inline bool
181  __valid_range_aux(_InputIterator __first, _InputIterator __last,
183  {
184  return
185  __valid_range_aux(__first, __last, std::input_iterator_tag())
186  && __first <= __last;
187  }
188 
189  /** We have iterators, so figure out what kind of iterators they are
190  * to see if we can check the range ahead of time.
191  */
192  template<typename _InputIterator>
193  _GLIBCXX_CONSTEXPR
194  inline bool
195  __valid_range_aux(_InputIterator __first, _InputIterator __last,
196  std::__false_type)
197  {
198  return __valid_range_aux(__first, __last,
199  std::__iterator_category(__first));
200  }
201 
202  template<typename _InputIterator>
203  _GLIBCXX20_CONSTEXPR
204  inline bool
205  __valid_range_aux(_InputIterator __first, _InputIterator __last,
206  typename _Distance_traits<_InputIterator>::__type& __dist,
207  std::__false_type)
208  {
209  if (!__valid_range_aux(__first, __last, std::input_iterator_tag()))
210  return false;
211 
212  __dist = __get_distance(__first, __last);
213  switch (__dist.second)
214  {
215  case __dp_none:
216  break;
217  case __dp_equality:
218  if (__dist.first == 0)
219  return true;
220  break;
221  case __dp_sign:
222  case __dp_sign_max_size:
223  case __dp_exact:
224  return __dist.first >= 0;
225  }
226 
227  // Can't tell so assume it is fine.
228  return true;
229  }
230 
231  /** Don't know what these iterators are, or if they are even
232  * iterators (we may get an integral type for InputIterator), so
233  * see if they are integral and pass them on to the next phase
234  * otherwise.
235  */
236  template<typename _InputIterator>
237  _GLIBCXX20_CONSTEXPR
238  inline bool
239  __valid_range(_InputIterator __first, _InputIterator __last,
241  {
242  typedef typename std::__is_integer<_InputIterator>::__type _Integral;
243  return __valid_range_aux(__first, __last, __dist, _Integral());
244  }
245 
246  template<typename _Iterator, typename _Sequence, typename _Category>
247  bool
248  __valid_range(const _Safe_iterator<_Iterator, _Sequence, _Category>&,
249  const _Safe_iterator<_Iterator, _Sequence, _Category>&,
250  typename _Distance_traits<_Iterator>::__type&);
251 
252 #if __cplusplus >= 201103L
253  template<typename _Iterator,typename _Sequence>
254  bool
255  __valid_range(const _Safe_local_iterator<_Iterator, _Sequence>&,
256  const _Safe_local_iterator<_Iterator, _Sequence>&,
257  typename _Distance_traits<_Iterator>::__type&);
258 #endif
259 
260  template<typename _InputIterator>
261  _GLIBCXX14_CONSTEXPR
262  inline bool
263  __valid_range(_InputIterator __first, _InputIterator __last)
264  {
265  typedef typename std::__is_integer<_InputIterator>::__type _Integral;
266  return __valid_range_aux(__first, __last, _Integral());
267  }
268 
269  template<typename _Iterator, typename _Sequence, typename _Category>
270  bool
271  __valid_range(const _Safe_iterator<_Iterator, _Sequence, _Category>&,
272  const _Safe_iterator<_Iterator, _Sequence, _Category>&);
273 
274 #if __cplusplus >= 201103L
275  template<typename _Iterator, typename _Sequence>
276  bool
277  __valid_range(const _Safe_local_iterator<_Iterator, _Sequence>&,
278  const _Safe_local_iterator<_Iterator, _Sequence>&);
279 #endif
280 
281  // Fallback method, always ok.
282  template<typename _InputIterator, typename _Size>
283  _GLIBCXX_CONSTEXPR
284  inline bool
285  __can_advance(_InputIterator, _Size)
286  { return true; }
287 
288  template<typename _Iterator, typename _Sequence, typename _Category,
289  typename _Size>
290  bool
291  __can_advance(const _Safe_iterator<_Iterator, _Sequence, _Category>&,
292  _Size);
293 
294  template<typename _InputIterator, typename _Diff>
295  _GLIBCXX_CONSTEXPR
296  inline bool
297  __can_advance(_InputIterator, const std::pair<_Diff, _Distance_precision>&, int)
298  { return true; }
299 
300  template<typename _Iterator, typename _Sequence, typename _Category,
301  typename _Diff>
302  bool
303  __can_advance(const _Safe_iterator<_Iterator, _Sequence, _Category>&,
305 
306  /** Helper function to extract base iterator of random access safe iterator
307  * in order to reduce performance impact of debug mode. Limited to random
308  * access iterator because it is the only category for which it is possible
309  * to check for correct iterators order in the __valid_range function
310  * thanks to the < operator.
311  */
312  template<typename _Iterator>
313  _GLIBCXX_CONSTEXPR
314  inline _Iterator
315  __base(_Iterator __it)
316  { return __it; }
317 
318 #if __cplusplus < 201103L
319  template<typename _Iterator>
320  struct _Unsafe_type
321  { typedef _Iterator _Type; };
322 #endif
323 
324  /* Remove debug mode safe iterator layer, if any. */
325  template<typename _Iterator>
326  inline _Iterator
327  __unsafe(_Iterator __it)
328  { return __it; }
329 }
330 
331 #endif
constexpr _Distance_traits< _Iterator >::__type __get_distance(_Iterator __lhs, _Iterator __rhs, std::random_access_iterator_tag)
Traits class for iterators.
constexpr bool __valid_range_aux(_Integral, _Integral, std::__true_type)
Marking input iterators.
constexpr bool __valid_range(_InputIterator __first, _InputIterator __last, typename _Distance_traits< _InputIterator >::__type &__dist)
constexpr iterator_traits< _Iter >::iterator_category __iterator_category(const _Iter &)
Struct holding two objects of arbitrary type.
Definition: stl_pair.h:211
GNU debug classes for public use.
constexpr _Iterator __base(_Iterator __it)
constexpr _Tp * __addressof(_Tp &__r) noexcept
Same as C++11 std::addressof.
Definition: move.h:49
ISO C++ entities toplevel namespace is std.
Random-access iterators support a superset of bidirectional iterator operations.