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 42 extern "C++" { 43 44 namespace 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 inline void 96 __throw_with_nested_impl(_Tp&& __t, true_type) 97 { 98 using _Up = typename remove_reference<_Tp>::type; 99 throw _Nested_exception<_Up>{std::forward<_Tp>(__t)}; 100 } 101 102 template<typename _Tp> 103 inline void 104 __throw_with_nested_impl(_Tp&& __t, false_type) 105 { throw std::forward<_Tp>(__t); } 106 107 /// If @p __t is derived from nested_exception, throws @p __t. 108 /// Else, throws an implementation-defined object derived from both. 109 template<typename _Tp> 110 [[noreturn]] 111 inline void 112 throw_with_nested(_Tp&& __t) 113 { 114 using _Up = typename decay<_Tp>::type; 115 using _CopyConstructible 116 = __and_<is_copy_constructible<_Up>, is_move_constructible<_Up>>; 117 static_assert(_CopyConstructible::value, 118 "throw_with_nested argument must be CopyConstructible"); 119 using __nest = __and_<is_class<_Up>, __bool_constant<!__is_final(_Up)>, 120 __not_<is_base_of<nested_exception, _Up>>>; 121 std::__throw_with_nested_impl(std::forward<_Tp>(__t), __nest{}); 122 } 123 124 // Determine if dynamic_cast<const nested_exception&> would be well-formed. 125 template<typename _Tp> 126 using __rethrow_if_nested_cond = typename enable_if< 127 __and_<is_polymorphic<_Tp>, 128 __or_<__not_<is_base_of<nested_exception, _Tp>>, 129 is_convertible<_Tp*, nested_exception*>>>::value 130 >::type; 131 132 // Attempt dynamic_cast to nested_exception and call rethrow_nested(). 133 template<typename _Ex> 134 inline __rethrow_if_nested_cond<_Ex> 135 __rethrow_if_nested_impl(const _Ex* __ptr) 136 { 137 if (auto __ne_ptr = dynamic_cast<const nested_exception*>(__ptr)) 138 __ne_ptr->rethrow_nested(); 139 } 140 141 // Otherwise, no effects. 142 inline void 143 __rethrow_if_nested_impl(const void*) 144 { } 145 146 /// If @p __ex is derived from nested_exception, @p __ex.rethrow_nested(). 147 template<typename _Ex> 148 inline void 149 rethrow_if_nested(const _Ex& __ex) 150 { std::__rethrow_if_nested_impl(std::__addressof(__ex)); } 151 152 // @} group exceptions 153 } // namespace std 154 155 } // extern "C++" 156 157 #endif // C++11 158 159 #pragma GCC visibility pop 160 161 #endif // _GLIBCXX_NESTED_EXCEPTION_H 162