nested_exception.h revision 1.11 
1// Nested Exception support header (nested_exception class) for -*- C++ -*-
2
3// Copyright (C) 2009-2020 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
42extern "C++" {
43
44namespace std
45{
46  /**
47   * @addtogroup exceptions
48   * @{
49   */
50
51  /// Exception class with exception_ptr data member.
52  class nested_exception
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);
71      std::terminate();
72    }
73
74    exception_ptr
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
172