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   // [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 remove_reference<_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