1// Nested Exception support header (nested_exception class) for -*- C++ -*-
2
3// Copyright (C) 2009-2017 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 template<typename _Except>
80 struct _Nested_exception : public _Except, public nested_exception
81 {
82 explicit _Nested_exception(const _Except& __ex)
83 : _Except(__ex)
84 { }
85
86 explicit _Nested_exception(_Except&& __ex)
87 : _Except(static_cast<_Except&&>(__ex))
88 { }
89 };
90
91 // [except.nested]/8
92 // Throw an exception of unspecified type that is publicly derived from
93 // both remove_reference_t<_Tp> and nested_exception.
94 template<typename _Tp>
95 inline void
96 __throw_with_nested_impl(_Tp&& __t, true_type)
97 {
98 using _Up = typename remove_reference<_Tp>::type;
99 throw _Nested_exception<_Up>{std::forward<_Tp>(__t)};
100 }
101
102 template<typename _Tp>
103 inline void
104 __throw_with_nested_impl(_Tp&& __t, false_type)
105 { throw std::forward<_Tp>(__t); }
106
107 /// If @p __t is derived from nested_exception, throws @p __t.
108 /// Else, throws an implementation-defined object derived from both.
109 template<typename _Tp>
110 [[noreturn]]
111 inline void
112 throw_with_nested(_Tp&& __t)
113 {
114 using _Up = typename decay<_Tp>::type;
115 using _CopyConstructible
116 = __and_<is_copy_constructible<_Up>, is_move_constructible<_Up>>;
117 static_assert(_CopyConstructible::value,
118 "throw_with_nested argument must be CopyConstructible");
119 using __nest = __and_<is_class<_Up>, __bool_constant<!__is_final(_Up)>,
120 __not_<is_base_of<nested_exception, _Up>>>;
121 std::__throw_with_nested_impl(std::forward<_Tp>(__t), __nest{});
122 }
123
124 // Determine if dynamic_cast<const nested_exception&> would be well-formed.
125 template<typename _Tp>
126 using __rethrow_if_nested_cond = typename enable_if<
127 __and_<is_polymorphic<_Tp>,
128 __or_<__not_<is_base_of<nested_exception, _Tp>>,
129 is_convertible<_Tp*, nested_exception*>>>::value
130 >::type;
131
132 // Attempt dynamic_cast to nested_exception and call rethrow_nested().
133 template<typename _Ex>
134 inline __rethrow_if_nested_cond<_Ex>
135 __rethrow_if_nested_impl(const _Ex* __ptr)
136 {
137 if (auto __ne_ptr = dynamic_cast<const nested_exception*>(__ptr))
138 __ne_ptr->rethrow_nested();
139 }
140
141 // Otherwise, no effects.
142 inline void
143 __rethrow_if_nested_impl(const void*)
144 { }
145
146 /// If @p __ex is derived from nested_exception, @p __ex.rethrow_nested().
147 template<typename _Ex>
148 inline void
149 rethrow_if_nested(const _Ex& __ex)
150 { std::__rethrow_if_nested_impl(std::__addressof(__ex)); }
151
152 // @} group exceptions
153} // namespace std
154
155} // extern "C++"
156
157#endif // C++11
158
159#pragma GCC visibility pop
160
161#endif // _GLIBCXX_NESTED_EXCEPTION_H
162