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

   1 // Nested Exception support header (nested_exception class) for -*- C++ -*-
   2
   3 // Copyright (C) 2009, 2010, 2011 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 #ifndef __GXX_EXPERIMENTAL_CXX0X__
  36 # include <bits/c++0x_warning.h>
  37 #else
  38
  39 #include <bits/c++config.h>
  40
  41 #if ATOMIC_INT_LOCK_FREE < 2
  42 #  error This platform does not support exception propagation.
  43 #endif
  44
  45 extern "C++" {
  46
  47 namespace std
  48 {
  49   /**
  50    * @addtogroup exceptions
  51    * @{
  52    */
  53
  54   /// Exception class with exception_ptr data member.
  55   class nested_exception
  56   {
  57     exception_ptr _M_ptr;
  58
  59   public:
  60     nested_exception() noexcept : _M_ptr(current_exception()) { }
  61
  62     nested_exception(const nested_exception&) = default;
  63
  64     nested_exception& operator=(const nested_exception&) = default;
  65
  66     virtual ~nested_exception() noexcept;
  67
  68     void
  69     rethrow_nested() const __attribute__ ((__noreturn__))
  70     { rethrow_exception(_M_ptr); }
  71
  72     exception_ptr
  73     nested_ptr() const
  74     { return _M_ptr; }
  75   };
  76
  77   template<typename _Except>
  78     struct _Nested_exception : public _Except, public nested_exception
  79     {
  80       explicit _Nested_exception(_Except&& __ex)
  81       : _Except(static_cast<_Except&&>(__ex))
  82       { }
  83     };
  84
  85   template<typename _Ex>
  86     struct __get_nested_helper
  87     {
  88       static const nested_exception*
  89       _S_get(const _Ex& __ex)
  90       { return dynamic_cast<const nested_exception*>(&__ex); }
  91     };
  92
  93   template<typename _Ex>
  94     struct __get_nested_helper<_Ex*>
  95     {
  96       static const nested_exception*
  97       _S_get(const _Ex* __ex)
  98       { return dynamic_cast<const nested_exception*>(__ex); }
  99     };
 100
 101   template<typename _Ex>
 102     inline const nested_exception*
 103     __get_nested_exception(const _Ex& __ex)
 104     { return __get_nested_helper<_Ex>::_S_get(__ex); }
 105
 106   template<typename _Ex>
 107     void
 108     __throw_with_nested(_Ex&&, const nested_exception* = 0)
 109     __attribute__ ((__noreturn__));
 110
 111   template<typename _Ex>
 112     void
 113     __throw_with_nested(_Ex&&, ...) __attribute__ ((__noreturn__));
 114
 115   // This function should never be called, but is needed to avoid a warning
 116   // about ambiguous base classes when instantiating throw_with_nested<_Ex>()
 117   // with a type that has an accessible nested_exception base.
 118   template<typename _Ex>
 119     inline void
 120     __throw_with_nested(_Ex&& __ex, const nested_exception*)
 121     { throw __ex; }
 122
 123   template<typename _Ex>
 124     inline void
 125     __throw_with_nested(_Ex&& __ex, ...)
 126     { throw _Nested_exception<_Ex>(static_cast<_Ex&&>(__ex)); }
 127
 128   template<typename _Ex>
 129     void
 130     throw_with_nested(_Ex __ex) __attribute__ ((__noreturn__));
 131
 132   /// If @p __ex is derived from nested_exception, @p __ex.
 133   /// Else, an implementation-defined object derived from both.
 134   template<typename _Ex>
 135     inline void
 136     throw_with_nested(_Ex __ex)
 137     {
 138       if (__get_nested_exception(__ex))
 139         throw __ex;
 140       __throw_with_nested(static_cast<_Ex&&>(__ex), &__ex);
 141     }
 142
 143   /// If @p __ex is derived from nested_exception, @p __ex.rethrow_nested().
 144   template<typename _Ex>
 145     inline void
 146     rethrow_if_nested(const _Ex& __ex)
 147     {
 148       if (const nested_exception* __nested = __get_nested_exception(__ex))
 149         __nested->rethrow_nested();
 150     }
 151
 152   /// Overload, See N2619
 153   inline void
 154   rethrow_if_nested(const nested_exception& __ex)
 155   { __ex.rethrow_nested(); }
 156
 157   // @} group exceptions
 158 } // namespace std
 159
 160 } // extern "C++"
 161
 162 #endif // __GXX_EXPERIMENTAL_CXX0X__
 163
 164 #pragma GCC visibility pop
 165
 166 #endif // _GLIBCXX_NESTED_EXCEPTION_H