1 // Nested Exception support header (nested_exception class) for -*- C++ -*- 2 3 // Copyright (C) 2009-2016 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 42 #if ATOMIC_INT_LOCK_FREE < 2 43 # error This platform does not support exception propagation. 44 #endif 45 46 extern "C++" { 47 48 namespace std 49 { 50 /** 51 * @addtogroup exceptions 52 * @{ 53 */ 54 55 /// Exception class with exception_ptr data member. 56 class nested_exception 57 { 58 exception_ptr _M_ptr; 59 60 public: 61 nested_exception() noexcept : _M_ptr(current_exception()) { } 62 63 nested_exception(const nested_exception&) noexcept = default; 64 65 nested_exception& operator=(const nested_exception&) noexcept = default; 66 67 virtual ~nested_exception() noexcept; 68 69 [[noreturn]] 70 void 71 rethrow_nested() const 72 { 73 if (_M_ptr) 74 rethrow_exception(_M_ptr); 75 std::terminate(); 76 } 77 78 exception_ptr 79 nested_ptr() const noexcept 80 { return _M_ptr; } 81 }; 82 83 template<typename _Except> 84 struct _Nested_exception : public _Except, public nested_exception 85 { 86 explicit _Nested_exception(const _Except& __ex) 87 : _Except(__ex) 88 { } 89 90 explicit _Nested_exception(_Except&& __ex) 91 : _Except(static_cast<_Except&&>(__ex)) 92 { } 93 }; 94 95 // [except.nested]/8 96 // Throw an exception of unspecified type that is publicly derived from 97 // both remove_reference_t<_Tp> and nested_exception. 98 template<typename _Tp> 99 inline void 100 __throw_with_nested_impl(_Tp&& __t, true_type) 101 { 102 using _Up = typename remove_reference<_Tp>::type; 103 throw _Nested_exception<_Up>{std::forward<_Tp>(__t)}; 104 } 105 106 template<typename _Tp> 107 inline void 108 __throw_with_nested_impl(_Tp&& __t, false_type) 109 { throw std::forward<_Tp>(__t); } 110 111 /// If @p __t is derived from nested_exception, throws @p __t. 112 /// Else, throws an implementation-defined object derived from both. 113 template<typename _Tp> 114 [[noreturn]] 115 inline void 116 throw_with_nested(_Tp&& __t) 117 { 118 using _Up = typename decay<_Tp>::type; 119 using _CopyConstructible 120 = __and_<is_copy_constructible<_Up>, is_move_constructible<_Up>>; 121 static_assert(_CopyConstructible::value, 122 "throw_with_nested argument must be CopyConstructible"); 123 using __nest = __and_<is_class<_Up>, __bool_constant<!__is_final(_Up)>, 124 __not_<is_base_of<nested_exception, _Up>>>; 125 std::__throw_with_nested_impl(std::forward<_Tp>(__t), __nest{}); 126 } 127 128 // Determine if dynamic_cast<const nested_exception&> would be well-formed. 129 template<typename _Tp> 130 using __rethrow_if_nested_cond = typename enable_if< 131 __and_<is_polymorphic<_Tp>, 132 __or_<__not_<is_base_of<nested_exception, _Tp>>, 133 is_convertible<_Tp*, nested_exception*>>>::value 134 >::type; 135 136 // Attempt dynamic_cast to nested_exception and call rethrow_nested(). 137 template<typename _Ex> 138 inline __rethrow_if_nested_cond<_Ex> 139 __rethrow_if_nested_impl(const _Ex* __ptr) 140 { 141 if (auto __ne_ptr = dynamic_cast<const nested_exception*>(__ptr)) 142 __ne_ptr->rethrow_nested(); 143 } 144 145 // Otherwise, no effects. 146 inline void 147 __rethrow_if_nested_impl(const void*) 148 { } 149 150 /// If @p __ex is derived from nested_exception, @p __ex.rethrow_nested(). 151 template<typename _Ex> 152 inline void 153 rethrow_if_nested(const _Ex& __ex) 154 { std::__rethrow_if_nested_impl(std::__addressof(__ex)); } 155 156 // @} group exceptions 157 } // namespace std 158 159 } // extern "C++" 160 161 #endif // C++11 162 163 #pragma GCC visibility pop 164 165 #endif // _GLIBCXX_NESTED_EXCEPTION_H 166