libstdc++-v3/libsupc++/nested_exception.h

   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   template<typename _Tp,
  96            bool __with_nested = !__is_base_of(nested_exception, _Tp)>
  97     struct _Throw_with_nested_impl
  98     {
  99       template<typename _Up>
 100         static void _S_throw(_Up&& __t)
 101         { throw _Nested_exception<_Tp>{static_cast<_Up&&>(__t)}; }
 102     };
 103
 104   template<typename _Tp>
 105     struct _Throw_with_nested_impl<_Tp, false>
 106     {
 107       template<typename _Up>
 108         static void _S_throw(_Up&& __t)
 109         { throw static_cast<_Up&&>(__t); }
 110     };
 111
 112   template<typename _Tp, bool = __is_class(_Tp) && !__is_final(_Tp)>
 113     struct _Throw_with_nested_helper : _Throw_with_nested_impl<_Tp>
 114     { };
 115
 116   template<typename _Tp>
 117     struct _Throw_with_nested_helper<_Tp, false>
 118     : _Throw_with_nested_impl<_Tp, false>
 119     { };
 120
 121   template<typename _Tp>
 122     struct _Throw_with_nested_helper<_Tp&, false>
 123     : _Throw_with_nested_helper<_Tp>
 124     { };
 125
 126   template<typename _Tp>
 127     struct _Throw_with_nested_helper<_Tp&&, false>
 128     : _Throw_with_nested_helper<_Tp>
 129     { };
 130
 131   /// If @p __t is derived from nested_exception, throws @p __t.
 132   /// Else, throws an implementation-defined object derived from both.
 133   template<typename _Tp>
 134     [[noreturn]]
 135     inline void
 136     throw_with_nested(_Tp&& __t)
 137     {
 138       _Throw_with_nested_helper<_Tp>::_S_throw(static_cast<_Tp&&>(__t));
 139     }
 140
 141   template<typename _Tp, bool = __is_polymorphic(_Tp)>
 142     struct _Rethrow_if_nested_impl
 143     {
 144       static void _S_rethrow(const _Tp& __t)
 145       {
 146         if (auto __tp =
 147             dynamic_cast<const nested_exception*>(std::__addressof(__t)))
 148           __tp->rethrow_nested();
 149       }
 150     };
 151
 152   template<typename _Tp>
 153     struct _Rethrow_if_nested_impl<_Tp, false>
 154     {
 155       static void _S_rethrow(const _Tp&) { }
 156     };
 157
 158   /// If @p __ex is derived from nested_exception, @p __ex.rethrow_nested().
 159   template<typename _Ex>
 160     inline void
 161     rethrow_if_nested(const _Ex& __ex)
 162     {
 163       _Rethrow_if_nested_impl<_Ex>::_S_rethrow(__ex);
 164     }
 165
 166   // @} group exceptions
 167 } // namespace std
 168
 169 } // extern "C++"
 170
 171 #endif // C++11
 172
 173 #pragma GCC visibility pop
 174
 175 #endif // _GLIBCXX_NESTED_EXCEPTION_H