1// Nested Exception support header (nested_exception class) for -*- C++ -*- 
2 
3// Copyright (C) 2009-2019 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