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The C and C++ Include Header Files
/usr/include/c++/13/bits/nested_exception.h
$ cat -n /usr/include/c++/13/bits/nested_exception.h 1 // Nested Exception support header (nested_exception class) for -*- C++ -*- 2 3 // Copyright (C) 2009-2023 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 #if __cplusplus < 201103L 34 # include <bits/c++0x_warning.h> 35 #else 36 37 #include <bits/move.h> 38 #include <bits/exception_ptr.h> 39 40 extern "C++" { 41 42 namespace std _GLIBCXX_VISIBILITY(default) 43 { 44 /** 45 * @addtogroup exceptions 46 * @{ 47 */ 48 49 /** Mixin class that stores the current exception. 50 * 51 * This type can be used via `std::throw_with_nested` to store 52 * the current exception nested within another exception. 53 * 54 * @headerfile exception 55 * @since C++11 56 * @see std::throw_with_nested 57 * @ingroup exceptions 58 */ 59 class nested_exception 60 { 61 exception_ptr _M_ptr; 62 63 public: 64 /// The default constructor stores the current exception (if any). 65 nested_exception() noexcept : _M_ptr(current_exception()) { } 66 67 nested_exception(const nested_exception&) noexcept = default; 68 69 nested_exception& operator=(const nested_exception&) noexcept = default; 70 71 virtual ~nested_exception() noexcept; 72 73 /// Rethrow the stored exception, or terminate if none was stored. 74 [[noreturn]] 75 void 76 rethrow_nested() const 77 { 78 if (_M_ptr) 79 rethrow_exception(_M_ptr); 80 std::terminate(); 81 } 82 83 /// Access the stored exception. 84 exception_ptr 85 nested_ptr() const noexcept 86 { return _M_ptr; } 87 }; 88 89 /// @cond undocumented 90 91 template<typename _Except> 92 struct _Nested_exception : public _Except, public nested_exception 93 { 94 explicit _Nested_exception(const _Except& __ex) 95 : _Except(__ex) 96 { } 97 98 explicit _Nested_exception(_Except&& __ex) 99 : _Except(static_cast<_Except&&>(__ex)) 100 { } 101 }; 102 103 #if __cplusplus < 201703L || ! defined __cpp_if_constexpr 104 // [except.nested]/8 105 // Throw an exception of unspecified type that is publicly derived from 106 // both remove_reference_t<_Tp> and nested_exception. 107 template<typename _Tp> 108 [[noreturn]] 109 inline void 110 __throw_with_nested_impl(_Tp&& __t, true_type) 111 { 112 throw _Nested_exception<__remove_cvref_t<_Tp>>{std::forward<_Tp>(__t)}; 113 } 114 115 template<typename _Tp> 116 [[noreturn]] 117 inline void 118 __throw_with_nested_impl(_Tp&& __t, false_type) 119 { throw std::forward<_Tp>(__t); } 120 #endif 121 122 /// @endcond 123 124 /** Throw an exception that also stores the currently active exception. 125 * 126 * If `_Tp` is derived from `std::nested_exception` or is not usable 127 * as a base-class, throws a copy of `__t`. 128 * Otherwise, throws an object of an implementation-defined type derived 129 * from both `_Tp` and `std::nested_exception`, containing a copy of `__t` 130 * and the result of `std::current_exception()`. 131 * 132 * In other words, throws the argument as a new exception that contains 133 * the currently active exception nested within it. This is intended for 134 * use in a catch handler to replace the caught exception with a different 135 * type, while still preserving the original exception. When the new 136 * exception is caught, the nested exception can be rethrown by using 137 * `std::rethrow_if_nested`. 138 * 139 * This can be used at API boundaries, for example to catch a library's 140 * internal exception type and rethrow it nested with a `std::runtime_error`, 141 * or vice versa. 142 * 143 * @since C++11 144 */ 145 template<typename _Tp> 146 [[noreturn]] 147 inline void 148 throw_with_nested(_Tp&& __t) 149 { 150 using _Up = typename decay<_Tp>::type; 151 using _CopyConstructible 152 = __and_<is_copy_constructible<_Up>, is_move_constructible<_Up>>; 153 static_assert(_CopyConstructible::value, 154 "throw_with_nested argument must be CopyConstructible"); 155 156 #if __cplusplus >= 201703L && __cpp_if_constexpr 157 if constexpr (is_class_v<_Up>) 158 if constexpr (!is_final_v<_Up>) 159 if constexpr (!is_base_of_v<nested_exception, _Up>) 160 throw _Nested_exception<_Up>{std::forward<_Tp>(__t)}; 161 throw std::forward<_Tp>(__t); 162 #else 163 using __nest = __and_<is_class<_Up>, __bool_constant<!__is_final(_Up)>, 164 __not_<is_base_of<nested_exception, _Up>>>; 165 std::__throw_with_nested_impl(std::forward<_Tp>(__t), __nest{}); 166 #endif 167 } 168 169 #if __cplusplus < 201703L || ! defined __cpp_if_constexpr 170 /// @cond undocumented 171 172 // Attempt dynamic_cast to nested_exception and call rethrow_nested(). 173 template<typename _Ex> 174 inline void 175 __rethrow_if_nested_impl(const _Ex* __ptr, true_type) 176 { 177 if (auto __ne_ptr = dynamic_cast<const nested_exception*>(__ptr)) 178 __ne_ptr->rethrow_nested(); 179 } 180 181 // Otherwise, no effects. 182 inline void 183 __rethrow_if_nested_impl(const void*, false_type) 184 { } 185 186 /// @endcond 187 #endif 188 189 /** Rethrow a nested exception 190 * 191 * If `__ex` contains a `std::nested_exception` object, call its 192 * `rethrow_nested()` member to rethrow the stored exception. 193 * 194 * After catching an exception thrown by a call to `std::throw_with_nested` 195 * this function can be used to rethrow the exception that was active when 196 * `std::throw_with_nested` was called. 197 * 198 * @since C++11 199 */ 200 // _GLIBCXX_RESOLVE_LIB_DEFECTS 201 // 2484. rethrow_if_nested() is doubly unimplementable 202 // 2784. Resolution to LWG 2484 is missing "otherwise, no effects" and [...] 203 template<typename _Ex> 204 # if ! __cpp_rtti 205 [[__gnu__::__always_inline__]] 206 #endif 207 inline void 208 rethrow_if_nested(const _Ex& __ex) 209 { 210 const _Ex* __ptr = __builtin_addressof(__ex); 211 #if __cplusplus < 201703L || ! defined __cpp_if_constexpr 212 # if __cpp_rtti 213 using __cast = __and_<is_polymorphic<_Ex>, 214 __or_<__not_<is_base_of<nested_exception, _Ex>>, 215 is_convertible<_Ex*, nested_exception*>>>; 216 # else 217 using __cast = __and_<is_polymorphic<_Ex>, 218 is_base_of<nested_exception, _Ex>, 219 is_convertible<_Ex*, nested_exception*>>; 220 # endif 221 std::__rethrow_if_nested_impl(__ptr, __cast{}); 222 #else 223 if constexpr (!is_polymorphic_v<_Ex>) 224 return; 225 else if constexpr (is_base_of_v<nested_exception, _Ex> 226 && !is_convertible_v<_Ex*, nested_exception*>) 227 return; // nested_exception base class is inaccessible or ambiguous. 228 # if ! __cpp_rtti 229 else if constexpr (!is_base_of_v<nested_exception, _Ex>) 230 return; // Cannot do polymorphic casts without RTTI. 231 # endif 232 else if (auto __ne_ptr = dynamic_cast<const nested_exception*>(__ptr)) 233 __ne_ptr->rethrow_nested(); 234 #endif 235 } 236 237 /// @} group exceptions 238 } // namespace std 239 240 } // extern "C++" 241 242 #endif // C++11 243 #endif // _GLIBCXX_NESTED_EXCEPTION_H
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