libstdc++
nested_exception.h
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1 // Nested Exception support header (nested_exception class) for -*- C++ -*-
2 
3 // Copyright (C) 2009-2021 Free Software Foundation, Inc.
4 //
5 // This file is part of the GNU ISO C++ Library. This library is free
6 // software; you can redistribute it and/or modify it under the
7 // terms of the GNU General Public License as published by the
8 // Free Software Foundation; either version 3, or (at your option)
9 // any later version.
10 
11 // This library is distributed in the hope that it will be useful,
12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 // GNU General Public License for more details.
15 
16 // Under Section 7 of GPL version 3, you are granted additional
17 // permissions described in the GCC Runtime Library Exception, version
18 // 3.1, as published by the Free Software Foundation.
19 
20 // You should have received a copy of the GNU General Public License and
21 // a copy of the GCC Runtime Library Exception along with this program;
22 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
23 // <http://www.gnu.org/licenses/>.
24 
25 /** @file bits/nested_exception.h
26  * This is an internal header file, included by other library headers.
27  * Do not attempt to use it directly. @headername{exception}
28  */
29 
30 #ifndef _GLIBCXX_NESTED_EXCEPTION_H
31 #define _GLIBCXX_NESTED_EXCEPTION_H 1
32 
33 #pragma GCC visibility push(default)
34 
35 #if __cplusplus < 201103L
36 # include <bits/c++0x_warning.h>
37 #else
38 
39 #include <bits/c++config.h>
40 #include <bits/move.h>
41 
42 extern "C++" {
43 
44 namespace std
45 {
46  /**
47  * @addtogroup exceptions
48  * @{
49  */
50 
51  /// Exception class with exception_ptr data member.
53  {
54  exception_ptr _M_ptr;
55 
56  public:
57  nested_exception() noexcept : _M_ptr(current_exception()) { }
58 
59  nested_exception(const nested_exception&) noexcept = default;
60 
61  nested_exception& operator=(const nested_exception&) noexcept = default;
62 
63  virtual ~nested_exception() noexcept;
64 
65  [[noreturn]]
66  void
67  rethrow_nested() const
68  {
69  if (_M_ptr)
70  rethrow_exception(_M_ptr);
72  }
73 
75  nested_ptr() const noexcept
76  { return _M_ptr; }
77  };
78 
79  /// @cond undocumented
80 
81  template<typename _Except>
82  struct _Nested_exception : public _Except, public nested_exception
83  {
84  explicit _Nested_exception(const _Except& __ex)
85  : _Except(__ex)
86  { }
87 
88  explicit _Nested_exception(_Except&& __ex)
89  : _Except(static_cast<_Except&&>(__ex))
90  { }
91  };
92 
93  // [except.nested]/8
94  // Throw an exception of unspecified type that is publicly derived from
95  // both remove_reference_t<_Tp> and nested_exception.
96  template<typename _Tp>
97  [[noreturn]]
98  inline void
99  __throw_with_nested_impl(_Tp&& __t, true_type)
100  {
101  using _Up = typename remove_reference<_Tp>::type;
102  throw _Nested_exception<_Up>{std::forward<_Tp>(__t)};
103  }
104 
105  template<typename _Tp>
106  [[noreturn]]
107  inline void
108  __throw_with_nested_impl(_Tp&& __t, false_type)
109  { throw std::forward<_Tp>(__t); }
110 
111  /// @endcond
112 
113  /// If @p __t is derived from nested_exception, throws @p __t.
114  /// Else, throws an implementation-defined object derived from both.
115  template<typename _Tp>
116  [[noreturn]]
117  inline void
118  throw_with_nested(_Tp&& __t)
119  {
120  using _Up = typename decay<_Tp>::type;
121  using _CopyConstructible
122  = __and_<is_copy_constructible<_Up>, is_move_constructible<_Up>>;
123  static_assert(_CopyConstructible::value,
124  "throw_with_nested argument must be CopyConstructible");
125  using __nest = __and_<is_class<_Up>, __bool_constant<!__is_final(_Up)>,
126  __not_<is_base_of<nested_exception, _Up>>>;
127  std::__throw_with_nested_impl(std::forward<_Tp>(__t), __nest{});
128  }
129 
130  /// @cond undocumented
131 
132  // Determine if dynamic_cast<const nested_exception&> would be well-formed.
133  template<typename _Tp>
134  using __rethrow_if_nested_cond = typename enable_if<
135  __and_<is_polymorphic<_Tp>,
136  __or_<__not_<is_base_of<nested_exception, _Tp>>,
137  is_convertible<_Tp*, nested_exception*>>>::value
138  >::type;
139 
140  // Attempt dynamic_cast to nested_exception and call rethrow_nested().
141  template<typename _Ex>
142  inline __rethrow_if_nested_cond<_Ex>
143  __rethrow_if_nested_impl(const _Ex* __ptr)
144  {
145  if (auto __ne_ptr = dynamic_cast<const nested_exception*>(__ptr))
146  __ne_ptr->rethrow_nested();
147  }
148 
149  // Otherwise, no effects.
150  inline void
151  __rethrow_if_nested_impl(const void*)
152  { }
153 
154  /// @endcond
155 
156  /// If @p __ex is derived from nested_exception, @p __ex.rethrow_nested().
157  template<typename _Ex>
158  inline void
159  rethrow_if_nested(const _Ex& __ex)
160  { std::__rethrow_if_nested_impl(std::__addressof(__ex)); }
161 
162  /// @} group exceptions
163 } // namespace std
164 
165 } // extern "C++"
166 
167 #endif // C++11
168 
169 #pragma GCC visibility pop
170 
171 #endif // _GLIBCXX_NESTED_EXCEPTION_H
integral_constant< bool, true > true_type
The type used as a compile-time boolean with true value.
Definition: type_traits:83
integral_constant< bool, false > false_type
The type used as a compile-time boolean with false value.
Definition: type_traits:86
constexpr _Tp * __addressof(_Tp &__r) noexcept
Same as C++11 std::addressof.
Definition: move.h:49
exception_ptr current_exception() noexcept
void rethrow_exception(exception_ptr)
Throw the object pointed to by the exception_ptr.
void terminate() noexcept
void rethrow_if_nested(const _Ex &__ex)
If __ex is derived from nested_exception, __ex.rethrow_nested().
void throw_with_nested(_Tp &&__t)
If __t is derived from nested_exception, throws __t. Else, throws an implementation-defined object de...
ISO C++ entities toplevel namespace is std.
is_move_constructible
Definition: type_traits:1009
An opaque pointer to an arbitrary exception.
Definition: exception_ptr.h:87
Exception class with exception_ptr data member.