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1 // Nested Exception support header (nested_exception class) for -*- C++ -*-
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2
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3 // Copyright (C) 2009-2020 Free Software Foundation, Inc.
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111
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4 //
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5 // This file is part of the GNU ISO C++ Library. This library is free
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6 // software; you can redistribute it and/or modify it under the
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7 // terms of the GNU General Public License as published by the
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8 // Free Software Foundation; either version 3, or (at your option)
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9 // any later version.
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10
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11 // This library is distributed in the hope that it will be useful,
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12 // but WITHOUT ANY WARRANTY; without even the implied warranty of
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13 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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14 // GNU General Public License for more details.
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15
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16 // Under Section 7 of GPL version 3, you are granted additional
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17 // permissions described in the GCC Runtime Library Exception, version
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18 // 3.1, as published by the Free Software Foundation.
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19
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20 // You should have received a copy of the GNU General Public License and
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21 // a copy of the GCC Runtime Library Exception along with this program;
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22 // see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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23 // <http://www.gnu.org/licenses/>.
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24
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25 /** @file bits/nested_exception.h
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26 * This is an internal header file, included by other library headers.
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27 * Do not attempt to use it directly. @headername{exception}
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28 */
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29
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30 #ifndef _GLIBCXX_NESTED_EXCEPTION_H
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31 #define _GLIBCXX_NESTED_EXCEPTION_H 1
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32
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33 #pragma GCC visibility push(default)
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34
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35 #if __cplusplus < 201103L
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36 # include <bits/c++0x_warning.h>
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37 #else
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38
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39 #include <bits/c++config.h>
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40 #include <bits/move.h>
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41
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42 extern "C++" {
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43
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44 namespace std
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45 {
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46 /**
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47 * @addtogroup exceptions
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48 * @{
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49 */
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50
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51 /// Exception class with exception_ptr data member.
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52 class nested_exception
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53 {
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54 exception_ptr _M_ptr;
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55
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56 public:
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57 nested_exception() noexcept : _M_ptr(current_exception()) { }
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58
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59 nested_exception(const nested_exception&) noexcept = default;
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60
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61 nested_exception& operator=(const nested_exception&) noexcept = default;
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62
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63 virtual ~nested_exception() noexcept;
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64
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65 [[noreturn]]
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66 void
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67 rethrow_nested() const
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68 {
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69 if (_M_ptr)
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70 rethrow_exception(_M_ptr);
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71 std::terminate();
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72 }
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73
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74 exception_ptr
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75 nested_ptr() const noexcept
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76 { return _M_ptr; }
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77 };
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78
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79 /// @cond undocumented
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80
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81 template<typename _Except>
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82 struct _Nested_exception : public _Except, public nested_exception
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83 {
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84 explicit _Nested_exception(const _Except& __ex)
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85 : _Except(__ex)
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86 { }
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87
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88 explicit _Nested_exception(_Except&& __ex)
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89 : _Except(static_cast<_Except&&>(__ex))
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90 { }
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91 };
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92
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93 // [except.nested]/8
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94 // Throw an exception of unspecified type that is publicly derived from
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95 // both remove_reference_t<_Tp> and nested_exception.
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96 template<typename _Tp>
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97 [[noreturn]]
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98 inline void
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99 __throw_with_nested_impl(_Tp&& __t, true_type)
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100 {
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101 using _Up = typename remove_reference<_Tp>::type;
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102 throw _Nested_exception<_Up>{std::forward<_Tp>(__t)};
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103 }
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104
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105 template<typename _Tp>
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106 [[noreturn]]
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107 inline void
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108 __throw_with_nested_impl(_Tp&& __t, false_type)
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109 { throw std::forward<_Tp>(__t); }
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110
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111 /// @endcond
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112
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113 /// If @p __t is derived from nested_exception, throws @p __t.
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114 /// Else, throws an implementation-defined object derived from both.
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115 template<typename _Tp>
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116 [[noreturn]]
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117 inline void
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118 throw_with_nested(_Tp&& __t)
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119 {
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120 using _Up = typename decay<_Tp>::type;
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121 using _CopyConstructible
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122 = __and_<is_copy_constructible<_Up>, is_move_constructible<_Up>>;
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123 static_assert(_CopyConstructible::value,
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124 "throw_with_nested argument must be CopyConstructible");
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125 using __nest = __and_<is_class<_Up>, __bool_constant<!__is_final(_Up)>,
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126 __not_<is_base_of<nested_exception, _Up>>>;
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127 std::__throw_with_nested_impl(std::forward<_Tp>(__t), __nest{});
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128 }
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129
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130 /// @cond undocumented
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131
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132 // Determine if dynamic_cast<const nested_exception&> would be well-formed.
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133 template<typename _Tp>
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134 using __rethrow_if_nested_cond = typename enable_if<
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135 __and_<is_polymorphic<_Tp>,
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136 __or_<__not_<is_base_of<nested_exception, _Tp>>,
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137 is_convertible<_Tp*, nested_exception*>>>::value
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138 >::type;
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139
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140 // Attempt dynamic_cast to nested_exception and call rethrow_nested().
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141 template<typename _Ex>
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142 inline __rethrow_if_nested_cond<_Ex>
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143 __rethrow_if_nested_impl(const _Ex* __ptr)
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144 {
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145 if (auto __ne_ptr = dynamic_cast<const nested_exception*>(__ptr))
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146 __ne_ptr->rethrow_nested();
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147 }
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148
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149 // Otherwise, no effects.
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150 inline void
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151 __rethrow_if_nested_impl(const void*)
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152 { }
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153
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154 /// @endcond
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155
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156 /// If @p __ex is derived from nested_exception, @p __ex.rethrow_nested().
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157 template<typename _Ex>
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158 inline void
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159 rethrow_if_nested(const _Ex& __ex)
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160 { std::__rethrow_if_nested_impl(std::__addressof(__ex)); }
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161
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162 // @} group exceptions
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163 } // namespace std
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164
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165 } // extern "C++"
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166
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167 #endif // C++11
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168
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169 #pragma GCC visibility pop
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170
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171 #endif // _GLIBCXX_NESTED_EXCEPTION_H
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