libstdc++
nested_exception.h
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00001 // Nested Exception support header (nested_exception class) for -*- C++ -*-
00002 
00003 // Copyright (C) 2009-2016 Free Software Foundation, Inc.
00004 //
00005 // This file is part of the GNU ISO C++ Library.  This library is free
00006 // software; you can redistribute it and/or modify it under the
00007 // terms of the GNU General Public License as published by the
00008 // Free Software Foundation; either version 3, or (at your option)
00009 // any later version.
00010 
00011 // This library is distributed in the hope that it will be useful,
00012 // but WITHOUT ANY WARRANTY; without even the implied warranty of
00013 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00014 // GNU General Public License for more details.
00015 
00016 // Under Section 7 of GPL version 3, you are granted additional
00017 // permissions described in the GCC Runtime Library Exception, version
00018 // 3.1, as published by the Free Software Foundation.
00019 
00020 // You should have received a copy of the GNU General Public License and
00021 // a copy of the GCC Runtime Library Exception along with this program;
00022 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
00023 // <http://www.gnu.org/licenses/>.
00024 
00025 /** @file bits/nested_exception.h
00026  *  This is an internal header file, included by other library headers.
00027  *  Do not attempt to use it directly. @headername{exception}
00028  */
00029 
00030 #ifndef _GLIBCXX_NESTED_EXCEPTION_H
00031 #define _GLIBCXX_NESTED_EXCEPTION_H 1
00032 
00033 #pragma GCC visibility push(default)
00034 
00035 #if __cplusplus < 201103L
00036 # include <bits/c++0x_warning.h>
00037 #else
00038 
00039 #include <bits/c++config.h>
00040 #include <bits/move.h>
00041 
00042 #if ATOMIC_INT_LOCK_FREE < 2
00043 #  error This platform does not support exception propagation.
00044 #endif
00045 
00046 extern "C++" {
00047 
00048 namespace std
00049 {
00050   /**
00051    * @addtogroup exceptions
00052    * @{
00053    */
00054 
00055   /// Exception class with exception_ptr data member.
00056   class nested_exception
00057   {
00058     exception_ptr _M_ptr;
00059 
00060   public:
00061     nested_exception() noexcept : _M_ptr(current_exception()) { }
00062 
00063     nested_exception(const nested_exception&) noexcept = default;
00064 
00065     nested_exception& operator=(const nested_exception&) noexcept = default;
00066 
00067     virtual ~nested_exception() noexcept;
00068 
00069     [[noreturn]]
00070     void
00071     rethrow_nested() const
00072     {
00073       if (_M_ptr)
00074         rethrow_exception(_M_ptr);
00075       std::terminate();
00076     }
00077 
00078     exception_ptr
00079     nested_ptr() const noexcept
00080     { return _M_ptr; }
00081   };
00082 
00083   template<typename _Except>
00084     struct _Nested_exception : public _Except, public nested_exception
00085     {
00086       explicit _Nested_exception(const _Except& __ex)
00087       : _Except(__ex)
00088       { }
00089 
00090       explicit _Nested_exception(_Except&& __ex)
00091       : _Except(static_cast<_Except&&>(__ex))
00092       { }
00093     };
00094 
00095   template<typename _Tp,
00096            bool __with_nested = !__is_base_of(nested_exception, _Tp)>
00097     struct _Throw_with_nested_impl
00098     {
00099       template<typename _Up>
00100         static void _S_throw(_Up&& __t)
00101         { throw _Nested_exception<_Tp>{static_cast<_Up&&>(__t)}; }
00102     };
00103 
00104   template<typename _Tp>
00105     struct _Throw_with_nested_impl<_Tp, false>
00106     {
00107       template<typename _Up>
00108         static void _S_throw(_Up&& __t)
00109         { throw static_cast<_Up&&>(__t); }
00110     };
00111 
00112   template<typename _Tp, bool = __is_class(_Tp) && !__is_final(_Tp)>
00113     struct _Throw_with_nested_helper : _Throw_with_nested_impl<_Tp>
00114     { };
00115 
00116   template<typename _Tp>
00117     struct _Throw_with_nested_helper<_Tp, false>
00118     : _Throw_with_nested_impl<_Tp, false>
00119     { };
00120 
00121   template<typename _Tp>
00122     struct _Throw_with_nested_helper<_Tp&, false>
00123     : _Throw_with_nested_helper<_Tp>
00124     { };
00125 
00126   template<typename _Tp>
00127     struct _Throw_with_nested_helper<_Tp&&, false>
00128     : _Throw_with_nested_helper<_Tp>
00129     { };
00130 
00131   /// If @p __t is derived from nested_exception, throws @p __t.
00132   /// Else, throws an implementation-defined object derived from both.
00133   template<typename _Tp>
00134     [[noreturn]]
00135     inline void
00136     throw_with_nested(_Tp&& __t)
00137     {
00138       _Throw_with_nested_helper<_Tp>::_S_throw(static_cast<_Tp&&>(__t));
00139     }
00140 
00141   template<typename _Tp, bool = __is_polymorphic(_Tp)>
00142     struct _Rethrow_if_nested_impl
00143     {
00144       static void _S_rethrow(const _Tp& __t)
00145       {
00146         if (auto __tp =
00147             dynamic_cast<const nested_exception*>(std::__addressof(__t)))
00148           __tp->rethrow_nested();
00149       }
00150     };
00151 
00152   template<typename _Tp>
00153     struct _Rethrow_if_nested_impl<_Tp, false>
00154     {
00155       static void _S_rethrow(const _Tp&) { }
00156     };
00157 
00158   /// If @p __ex is derived from nested_exception, @p __ex.rethrow_nested().
00159   template<typename _Ex>
00160     inline void
00161     rethrow_if_nested(const _Ex& __ex)
00162     {
00163       _Rethrow_if_nested_impl<_Ex>::_S_rethrow(__ex);
00164     }
00165 
00166   // @} group exceptions
00167 } // namespace std
00168 
00169 } // extern "C++"
00170 
00171 #endif // C++11
00172 
00173 #pragma GCC visibility pop
00174 
00175 #endif // _GLIBCXX_NESTED_EXCEPTION_H