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 [[noreturn]]
96 inline void
97 __throw_with_nested_impl(_Tp&& __t, true_type)
98 {
99 using _Up = typename remove_reference<_Tp>::type;
100 throw _Nested_exception<_Up>{std::forward<_Tp>(__t)};
101 }
102
103 template<typename _Tp>
104 [[noreturn]]
105 inline void
106 __throw_with_nested_impl(_Tp&& __t, false_type)
107 { throw std::forward<_Tp>(__t); }
108
109 /// If @p __t is derived from nested_exception, throws @p __t.
110 /// Else, throws an implementation-defined object derived from both.
111 template<typename _Tp>
112 [[noreturn]]
113 inline void
114 throw_with_nested(_Tp&& __t)
115 {
116 using _Up = typename decay<_Tp>::type;
117 using _CopyConstructible
118 = __and_<is_copy_constructible<_Up>, is_move_constructible<_Up>>;
119 static_assert(_CopyConstructible::value,
120 "throw_with_nested argument must be CopyConstructible");
121 using __nest = __and_<is_class<_Up>, __bool_constant<!__is_final(_Up)>,
122 __not_<is_base_of<nested_exception, _Up>>>;
123 std::__throw_with_nested_impl(std::forward<_Tp>(__t), __nest{});
124 }
125
126 // Determine if dynamic_cast<const nested_exception&> would be well-formed.
127 template<typename _Tp>
128 using __rethrow_if_nested_cond = typename enable_if<
129 __and_<is_polymorphic<_Tp>,
130 __or_<__not_<is_base_of<nested_exception, _Tp>>,
131 is_convertible<_Tp*, nested_exception*>>>::value
132 >::type;
133
134 // Attempt dynamic_cast to nested_exception and call rethrow_nested().
135 template<typename _Ex>
136 inline __rethrow_if_nested_cond<_Ex>
137 __rethrow_if_nested_impl(const _Ex* __ptr)
138 {
139 if (auto __ne_ptr = dynamic_cast<const nested_exception*>(__ptr))
140 __ne_ptr->rethrow_nested();
141 }
142
143 // Otherwise, no effects.
144 inline void
145 __rethrow_if_nested_impl(const void*)
146 { }
147
148 /// If @p __ex is derived from nested_exception, @p __ex.rethrow_nested().
149 template<typename _Ex>
150 inline void
151 rethrow_if_nested(const _Ex& __ex)
152 { std::__rethrow_if_nested_impl(std::__addressof(__ex)); }
153
154 // @} group exceptions
155} // namespace std
156
157} // extern "C++"
158
159#endif // C++11
160
161#pragma GCC visibility pop
162
163#endif // _GLIBCXX_NESTED_EXCEPTION_H
164