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

   1 // Nested Exception support header (nested_exception class) for -*- C++ -*-
   2
   3 // Copyright (C) 2009-2021 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   /// @cond undocumented
  80
  81   template<typename _Except>
  82     struct _Nested_exception : public _Except, public nested_exception
  83     {
  84       explicit _Nested_exception(const _Except& __ex)
  85       : _Except(__ex)
  86       { }
  87
  88       explicit _Nested_exception(_Except&& __ex)
  89       : _Except(static_cast<_Except&&>(__ex))
  90       { }
  91     };
  92
  93   // [except.nested]/8
  94   // Throw an exception of unspecified type that is publicly derived from
  95   // both remove_reference_t<_Tp> and nested_exception.
  96   template<typename _Tp>
  97     [[noreturn]]
  98     inline void
  99     __throw_with_nested_impl(_Tp&& __t, true_type)
 100     {
 101       using _Up = typename remove_reference<_Tp>::type;
 102       throw _Nested_exception<_Up>{std::forward<_Tp>(__t)};
 103     }
 104
 105   template<typename _Tp>
 106     [[noreturn]]
 107     inline void
 108     __throw_with_nested_impl(_Tp&& __t, false_type)
 109     { throw std::forward<_Tp>(__t); }
 110
 111   /// @endcond
 112
 113   /// If @p __t is derived from nested_exception, throws @p __t.
 114   /// Else, throws an implementation-defined object derived from both.
 115   template<typename _Tp>
 116     [[noreturn]]
 117     inline void
 118     throw_with_nested(_Tp&& __t)
 119     {
 120       using _Up = typename decay<_Tp>::type;
 121       using _CopyConstructible
 122         = __and_<is_copy_constructible<_Up>, is_move_constructible<_Up>>;
 123       static_assert(_CopyConstructible::value,
 124           "throw_with_nested argument must be CopyConstructible");
 125       using __nest = __and_<is_class<_Up>, __bool_constant<!__is_final(_Up)>,
 126                             __not_<is_base_of<nested_exception, _Up>>>;
 127       std::__throw_with_nested_impl(std::forward<_Tp>(__t), __nest{});
 128     }
 129
 130   /// @cond undocumented
 131
 132   // Determine if dynamic_cast<const nested_exception&> would be well-formed.
 133   template<typename _Tp>
 134     using __rethrow_if_nested_cond = typename enable_if<
 135       __and_<is_polymorphic<_Tp>,
 136              __or_<__not_<is_base_of<nested_exception, _Tp>>,
 137                    is_convertible<_Tp*, nested_exception*>>>::value
 138     >::type;
 139
 140   // Attempt dynamic_cast to nested_exception and call rethrow_nested().
 141   template<typename _Ex>
 142     inline __rethrow_if_nested_cond<_Ex>
 143     __rethrow_if_nested_impl(const _Ex* __ptr)
 144     {
 145       if (auto __ne_ptr = dynamic_cast<const nested_exception*>(__ptr))
 146         __ne_ptr->rethrow_nested();
 147     }
 148
 149   // Otherwise, no effects.
 150   inline void
 151   __rethrow_if_nested_impl(const void*)
 152   { }
 153
 154   /// @endcond
 155
 156   /// If @p __ex is derived from nested_exception, @p __ex.rethrow_nested().
 157   template<typename _Ex>
 158     inline void
 159     rethrow_if_nested(const _Ex& __ex)
 160     { std::__rethrow_if_nested_impl(std::__addressof(__ex)); }
 161
 162   // @} group exceptions
 163 } // namespace std
 164
 165 } // extern "C++"
 166
 167 #endif // C++11
 168
 169 #pragma GCC visibility pop
 170
 171 #endif // _GLIBCXX_NESTED_EXCEPTION_H