libstdc++
exception_ptr.h
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1 // Exception Handling support header (exception_ptr class) for -*- C++ -*-
2 
3 // Copyright (C) 2008-2023 Free Software Foundation, Inc.
4 //
5 // This file is part of GCC.
6 //
7 // GCC is free software; you can redistribute it and/or modify
8 // it under the terms of the GNU General Public License as published by
9 // the Free Software Foundation; either version 3, or (at your option)
10 // any later version.
11 //
12 // GCC is distributed in the hope that it will be useful,
13 // but WITHOUT ANY WARRANTY; without even the implied warranty of
14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 // GNU General Public License for more details.
16 //
17 // Under Section 7 of GPL version 3, you are granted additional
18 // permissions described in the GCC Runtime Library Exception, version
19 // 3.1, as published by the Free Software Foundation.
20 
21 // You should have received a copy of the GNU General Public License and
22 // a copy of the GCC Runtime Library Exception along with this program;
23 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
24 // <http://www.gnu.org/licenses/>.
25 
26 /** @file bits/exception_ptr.h
27  * This is an internal header file, included by other library headers.
28  * Do not attempt to use it directly. @headername{exception}
29  */
30 
31 #ifndef _EXCEPTION_PTR_H
32 #define _EXCEPTION_PTR_H
33 
34 #include <bits/c++config.h>
35 #include <bits/exception_defines.h>
37 #include <typeinfo>
38 #include <new>
39 
40 #if __cplusplus >= 201103L
41 # include <bits/move.h>
42 #endif
43 
44 #ifdef _GLIBCXX_EH_PTR_RELOPS_COMPAT
45 # define _GLIBCXX_EH_PTR_USED __attribute__((__used__))
46 #else
47 # define _GLIBCXX_EH_PTR_USED
48 #endif
49 
50 extern "C++" {
51 
52 namespace std _GLIBCXX_VISIBILITY(default)
53 {
54  class type_info;
55 
56  /**
57  * @addtogroup exceptions
58  * @{
59  */
60 
61  namespace __exception_ptr
62  {
63  class exception_ptr;
64  }
65 
66  using __exception_ptr::exception_ptr;
67 
68  /** Obtain an exception_ptr to the currently handled exception.
69  *
70  * If there is none, or the currently handled exception is foreign,
71  * return the null value.
72  *
73  * @since C++11
74  */
75  exception_ptr current_exception() _GLIBCXX_USE_NOEXCEPT;
76 
77  template<typename _Ex>
78  exception_ptr make_exception_ptr(_Ex) _GLIBCXX_USE_NOEXCEPT;
79 
80  /// Throw the object pointed to by the exception_ptr.
81  void rethrow_exception(exception_ptr) __attribute__ ((__noreturn__));
82 
83  namespace __exception_ptr
84  {
85  using std::rethrow_exception; // So that ADL finds it.
86 
87  /**
88  * @brief An opaque pointer to an arbitrary exception.
89  *
90  * The actual name of this type is unspecified, so the alias
91  * `std::exception_ptr` should be used to refer to it.
92  *
93  * @headerfile exception
94  * @since C++11 (but usable in C++98 as a GCC extension)
95  * @ingroup exceptions
96  */
98  {
99  void* _M_exception_object;
100 
101  explicit exception_ptr(void* __e) _GLIBCXX_USE_NOEXCEPT;
102 
103  void _M_addref() _GLIBCXX_USE_NOEXCEPT;
104  void _M_release() _GLIBCXX_USE_NOEXCEPT;
105 
106  void *_M_get() const _GLIBCXX_NOEXCEPT __attribute__ ((__pure__));
107 
108  friend exception_ptr std::current_exception() _GLIBCXX_USE_NOEXCEPT;
110  template<typename _Ex>
111  friend exception_ptr std::make_exception_ptr(_Ex) _GLIBCXX_USE_NOEXCEPT;
112 
113  public:
114  exception_ptr() _GLIBCXX_USE_NOEXCEPT;
115 
116  exception_ptr(const exception_ptr&) _GLIBCXX_USE_NOEXCEPT;
117 
118 #if __cplusplus >= 201103L
119  exception_ptr(nullptr_t) noexcept
120  : _M_exception_object(nullptr)
121  { }
122 
123  exception_ptr(exception_ptr&& __o) noexcept
124  : _M_exception_object(__o._M_exception_object)
125  { __o._M_exception_object = nullptr; }
126 #endif
127 
128 #if (__cplusplus < 201103L) || defined (_GLIBCXX_EH_PTR_COMPAT)
129  typedef void (exception_ptr::*__safe_bool)();
130 
131  // For construction from nullptr or 0.
132  exception_ptr(__safe_bool) _GLIBCXX_USE_NOEXCEPT;
133 #endif
134 
135  exception_ptr&
136  operator=(const exception_ptr&) _GLIBCXX_USE_NOEXCEPT;
137 
138 #if __cplusplus >= 201103L
139  exception_ptr&
140  operator=(exception_ptr&& __o) noexcept
141  {
142  exception_ptr(static_cast<exception_ptr&&>(__o)).swap(*this);
143  return *this;
144  }
145 #endif
146 
147  ~exception_ptr() _GLIBCXX_USE_NOEXCEPT;
148 
149  void
150  swap(exception_ptr&) _GLIBCXX_USE_NOEXCEPT;
151 
152 #ifdef _GLIBCXX_EH_PTR_COMPAT
153  // Retained for compatibility with CXXABI_1.3.
154  void _M_safe_bool_dummy() _GLIBCXX_USE_NOEXCEPT
155  __attribute__ ((__const__));
156  bool operator!() const _GLIBCXX_USE_NOEXCEPT
157  __attribute__ ((__pure__));
158  operator __safe_bool() const _GLIBCXX_USE_NOEXCEPT;
159 #endif
160 
161 #if __cplusplus >= 201103L
162  explicit operator bool() const noexcept
163  { return _M_exception_object; }
164 #endif
165 
166 #if __cpp_impl_three_way_comparison >= 201907L \
167  && ! defined _GLIBCXX_EH_PTR_RELOPS_COMPAT
168  friend bool
169  operator==(const exception_ptr&, const exception_ptr&) noexcept = default;
170 #else
171  friend _GLIBCXX_EH_PTR_USED bool
172  operator==(const exception_ptr& __x, const exception_ptr& __y)
173  _GLIBCXX_USE_NOEXCEPT
174  { return __x._M_exception_object == __y._M_exception_object; }
175 
176  friend _GLIBCXX_EH_PTR_USED bool
177  operator!=(const exception_ptr& __x, const exception_ptr& __y)
178  _GLIBCXX_USE_NOEXCEPT
179  { return __x._M_exception_object != __y._M_exception_object; }
180 #endif
181 
182  const class std::type_info*
183  __cxa_exception_type() const _GLIBCXX_USE_NOEXCEPT
184  __attribute__ ((__pure__));
185  };
186 
187  _GLIBCXX_EH_PTR_USED
188  inline
189  exception_ptr::exception_ptr() _GLIBCXX_USE_NOEXCEPT
190  : _M_exception_object(0)
191  { }
192 
193  _GLIBCXX_EH_PTR_USED
194  inline
195  exception_ptr::exception_ptr(const exception_ptr& __other)
196  _GLIBCXX_USE_NOEXCEPT
197  : _M_exception_object(__other._M_exception_object)
198  {
199  if (_M_exception_object)
200  _M_addref();
201  }
202 
203  _GLIBCXX_EH_PTR_USED
204  inline
205  exception_ptr::~exception_ptr() _GLIBCXX_USE_NOEXCEPT
206  {
207  if (_M_exception_object)
208  _M_release();
209  }
210 
211  _GLIBCXX_EH_PTR_USED
212  inline exception_ptr&
213  exception_ptr::operator=(const exception_ptr& __other) _GLIBCXX_USE_NOEXCEPT
214  {
215  exception_ptr(__other).swap(*this);
216  return *this;
217  }
218 
219  _GLIBCXX_EH_PTR_USED
220  inline void
221  exception_ptr::swap(exception_ptr &__other) _GLIBCXX_USE_NOEXCEPT
222  {
223  void *__tmp = _M_exception_object;
224  _M_exception_object = __other._M_exception_object;
225  __other._M_exception_object = __tmp;
226  }
227 
228  /// @relates exception_ptr
229  inline void
231  { __lhs.swap(__rhs); }
232 
233  /// @cond undocumented
234  template<typename _Ex>
235  _GLIBCXX_CDTOR_CALLABI
236  inline void
237  __dest_thunk(void* __x)
238  { static_cast<_Ex*>(__x)->~_Ex(); }
239  /// @endcond
240 
241  } // namespace __exception_ptr
242 
243  using __exception_ptr::swap; // So that std::swap(exp1, exp2) finds it.
244 
245  /// Obtain an exception_ptr pointing to a copy of the supplied object.
246 #if (__cplusplus >= 201103L && __cpp_rtti) || __cpp_exceptions
247  template<typename _Ex>
248  exception_ptr
249  make_exception_ptr(_Ex __ex) _GLIBCXX_USE_NOEXCEPT
250  {
251 #if __cplusplus >= 201103L && __cpp_rtti
252  using _Ex2 = typename decay<_Ex>::type;
253  void* __e = __cxxabiv1::__cxa_allocate_exception(sizeof(_Ex));
254  (void) __cxxabiv1::__cxa_init_primary_exception(
255  __e, const_cast<std::type_info*>(&typeid(_Ex)),
256  __exception_ptr::__dest_thunk<_Ex2>);
257  __try
258  {
259  ::new (__e) _Ex2(__ex);
260  return exception_ptr(__e);
261  }
262  __catch(...)
263  {
264  __cxxabiv1::__cxa_free_exception(__e);
265  return current_exception();
266  }
267 #else
268  try
269  {
270  throw __ex;
271  }
272  catch(...)
273  {
274  return current_exception();
275  }
276 #endif
277  }
278 #else // no RTTI and no exceptions
279  // This is always_inline so the linker will never use this useless definition
280  // instead of a working one compiled with RTTI and/or exceptions enabled.
281  template<typename _Ex>
282  __attribute__ ((__always_inline__))
283  inline exception_ptr
284  make_exception_ptr(_Ex) _GLIBCXX_USE_NOEXCEPT
285  { return exception_ptr(); }
286 #endif
287 
288 #undef _GLIBCXX_EH_PTR_USED
289 
290  /// @} group exceptions
291 } // namespace std
292 
293 } // extern "C++"
294 
295 #endif
exception_ptr current_exception() noexcept
void rethrow_exception(exception_ptr)
Throw the object pointed to by the exception_ptr.
ISO C++ entities toplevel namespace is std.
exception_ptr make_exception_ptr(_Ex) noexcept
Obtain an exception_ptr pointing to a copy of the supplied object.
void swap(exception_ptr &__lhs, exception_ptr &__rhs)
An opaque pointer to an arbitrary exception.
Definition: exception_ptr.h:97
Part of RTTI.
Definition: typeinfo:92