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

   1 // Exception Handling support header (exception_ptr class) for -*- C++ -*-
   2
   3 // Copyright (C) 2008-2021 Free Software Foundation, Inc.
   4 //
   5 // This file is part of GCC.
   6 //
   7 // GCC is free software; you can redistribute it and/or modify
   8 // it under the terms of the GNU General Public License as published by
   9 // the Free Software Foundation; either version 3, or (at your option)
  10 // any later version.
  11 //
  12 // GCC is distributed in the hope that it will be useful,
  13 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  14 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15 // GNU General Public License for more details.
  16 //
  17 // Under Section 7 of GPL version 3, you are granted additional
  18 // permissions described in the GCC Runtime Library Exception, version
  19 // 3.1, as published by the Free Software Foundation.
  20
  21 // You should have received a copy of the GNU General Public License and
  22 // a copy of the GCC Runtime Library Exception along with this program;
  23 // see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  24 // <http://www.gnu.org/licenses/>.
  25
  26 /** @file bits/exception_ptr.h
  27  *  This is an internal header file, included by other library headers.
  28  *  Do not attempt to use it directly. @headername{exception}
  29  */
  30
  31 #ifndef _EXCEPTION_PTR_H
  32 #define _EXCEPTION_PTR_H
  33
  34 #pragma GCC visibility push(default)
  35
  36 #include <bits/c++config.h>
  37 #include <bits/exception_defines.h>
  38 #include <bits/cxxabi_init_exception.h>
  39 #include <typeinfo>
  40 #include <new>
  41
  42 #ifdef _GLIBCXX_EH_PTR_RELOPS_COMPAT
  43 # define _GLIBCXX_EH_PTR_USED __attribute__((__used__))
  44 #else
  45 # define _GLIBCXX_EH_PTR_USED
  46 #endif
  47
  48 extern "C++" {
  49
  50 namespace std
  51 {
  52   class type_info;
  53
  54   /**
  55    * @addtogroup exceptions
  56    * @{
  57    */
  58
  59   namespace __exception_ptr
  60   {
  61     class exception_ptr;
  62   }
  63
  64   using __exception_ptr::exception_ptr;
  65
  66   /** Obtain an exception_ptr to the currently handled exception. If there
  67    *  is none, or the currently handled exception is foreign, return the null
  68    *  value.
  69    */
  70   exception_ptr current_exception() _GLIBCXX_USE_NOEXCEPT;
  71
  72   template<typename _Ex>
  73   exception_ptr make_exception_ptr(_Ex) _GLIBCXX_USE_NOEXCEPT;
  74
  75   /// Throw the object pointed to by the exception_ptr.
  76   void rethrow_exception(exception_ptr) __attribute__ ((__noreturn__));
  77
  78   namespace __exception_ptr
  79   {
  80     using std::rethrow_exception;
  81
  82     /**
  83      *  @brief An opaque pointer to an arbitrary exception.
  84      *  @ingroup exceptions
  85      */
  86     class exception_ptr
  87     {
  88       void* _M_exception_object;
  89
  90       explicit exception_ptr(void* __e) _GLIBCXX_USE_NOEXCEPT;
  91
  92       void _M_addref() _GLIBCXX_USE_NOEXCEPT;
  93       void _M_release() _GLIBCXX_USE_NOEXCEPT;
  94
  95       void *_M_get() const _GLIBCXX_NOEXCEPT __attribute__ ((__pure__));
  96
  97       friend exception_ptr std::current_exception() _GLIBCXX_USE_NOEXCEPT;
  98       friend void std::rethrow_exception(exception_ptr);
  99       template<typename _Ex>
 100       friend exception_ptr std::make_exception_ptr(_Ex) _GLIBCXX_USE_NOEXCEPT;
 101
 102     public:
 103       exception_ptr() _GLIBCXX_USE_NOEXCEPT;
 104
 105       exception_ptr(const exception_ptr&) _GLIBCXX_USE_NOEXCEPT;
 106
 107 #if __cplusplus >= 201103L
 108       exception_ptr(nullptr_t) noexcept
 109       : _M_exception_object(nullptr)
 110       { }
 111
 112       exception_ptr(exception_ptr&& __o) noexcept
 113       : _M_exception_object(__o._M_exception_object)
 114       { __o._M_exception_object = nullptr; }
 115 #endif
 116
 117 #if (__cplusplus < 201103L) || defined (_GLIBCXX_EH_PTR_COMPAT)
 118       typedef void (exception_ptr::*__safe_bool)();
 119
 120       // For construction from nullptr or 0.
 121       exception_ptr(__safe_bool) _GLIBCXX_USE_NOEXCEPT;
 122 #endif
 123
 124       exception_ptr&
 125       operator=(const exception_ptr&) _GLIBCXX_USE_NOEXCEPT;
 126
 127 #if __cplusplus >= 201103L
 128       exception_ptr&
 129       operator=(exception_ptr&& __o) noexcept
 130       {
 131         exception_ptr(static_cast<exception_ptr&&>(__o)).swap(*this);
 132         return *this;
 133       }
 134 #endif
 135
 136       ~exception_ptr() _GLIBCXX_USE_NOEXCEPT;
 137
 138       void
 139       swap(exception_ptr&) _GLIBCXX_USE_NOEXCEPT;
 140
 141 #ifdef _GLIBCXX_EH_PTR_COMPAT
 142       // Retained for compatibility with CXXABI_1.3.
 143       void _M_safe_bool_dummy() _GLIBCXX_USE_NOEXCEPT
 144         __attribute__ ((__const__));
 145       bool operator!() const _GLIBCXX_USE_NOEXCEPT
 146         __attribute__ ((__pure__));
 147       operator __safe_bool() const _GLIBCXX_USE_NOEXCEPT;
 148 #endif
 149
 150 #if __cplusplus >= 201103L
 151       explicit operator bool() const noexcept
 152       { return _M_exception_object; }
 153 #endif
 154
 155 #if __cpp_impl_three_way_comparison >= 201907L \
 156       && ! defined _GLIBCXX_EH_PTR_RELOPS_COMPAT
 157       friend bool
 158       operator==(const exception_ptr&, const exception_ptr&) noexcept = default;
 159 #else
 160       friend _GLIBCXX_EH_PTR_USED bool
 161       operator==(const exception_ptr& __x, const exception_ptr& __y)
 162       _GLIBCXX_USE_NOEXCEPT
 163       { return __x._M_exception_object == __y._M_exception_object; }
 164
 165       friend _GLIBCXX_EH_PTR_USED bool
 166       operator!=(const exception_ptr& __x, const exception_ptr& __y)
 167       _GLIBCXX_USE_NOEXCEPT
 168       { return __x._M_exception_object != __y._M_exception_object; }
 169 #endif
 170
 171       const class std::type_info*
 172       __cxa_exception_type() const _GLIBCXX_USE_NOEXCEPT
 173         __attribute__ ((__pure__));
 174     };
 175
 176     _GLIBCXX_EH_PTR_USED
 177     inline
 178     exception_ptr::exception_ptr() _GLIBCXX_NOEXCEPT
 179     : _M_exception_object(0)
 180     { }
 181
 182     _GLIBCXX_EH_PTR_USED
 183     inline
 184     exception_ptr::exception_ptr(const exception_ptr& __other) _GLIBCXX_NOEXCEPT
 185     : _M_exception_object(__other._M_exception_object)
 186     {
 187       if (_M_exception_object)
 188         _M_addref();
 189     }
 190
 191     _GLIBCXX_EH_PTR_USED
 192     inline
 193     exception_ptr::~exception_ptr() _GLIBCXX_USE_NOEXCEPT
 194     {
 195       if (_M_exception_object)
 196         _M_release();
 197     }
 198
 199     _GLIBCXX_EH_PTR_USED
 200     inline exception_ptr&
 201     exception_ptr::operator=(const exception_ptr& __other) _GLIBCXX_USE_NOEXCEPT
 202     {
 203       exception_ptr(__other).swap(*this);
 204       return *this;
 205     }
 206
 207     _GLIBCXX_EH_PTR_USED
 208     inline void
 209     exception_ptr::swap(exception_ptr &__other) _GLIBCXX_USE_NOEXCEPT
 210     {
 211       void *__tmp = _M_exception_object;
 212       _M_exception_object = __other._M_exception_object;
 213       __other._M_exception_object = __tmp;
 214     }
 215
 216     /// @relates exception_ptr
 217     inline void
 218     swap(exception_ptr& __lhs, exception_ptr& __rhs)
 219     { __lhs.swap(__rhs); }
 220
 221     /// @cond undocumented
 222     template<typename _Ex>
 223       inline void
 224       __dest_thunk(void* __x)
 225       { static_cast<_Ex*>(__x)->~_Ex(); }
 226     /// @endcond
 227
 228   } // namespace __exception_ptr
 229
 230   /// Obtain an exception_ptr pointing to a copy of the supplied object.
 231   template<typename _Ex>
 232     exception_ptr
 233     make_exception_ptr(_Ex __ex) _GLIBCXX_USE_NOEXCEPT
 234     {
 235 #if __cpp_exceptions && __cpp_rtti && !_GLIBCXX_HAVE_CDTOR_CALLABI
 236       void* __e = __cxxabiv1::__cxa_allocate_exception(sizeof(_Ex));
 237       (void) __cxxabiv1::__cxa_init_primary_exception(
 238           __e, const_cast<std::type_info*>(&typeid(__ex)),
 239           __exception_ptr::__dest_thunk<_Ex>);
 240       try
 241         {
 242           ::new (__e) _Ex(__ex);
 243           return exception_ptr(__e);
 244         }
 245       catch(...)
 246         {
 247           __cxxabiv1::__cxa_free_exception(__e);
 248           return current_exception();
 249         }
 250 #elif __cpp_exceptions
 251       try
 252         {
 253           throw __ex;
 254         }
 255       catch(...)
 256         {
 257           return current_exception();
 258         }
 259 #else // no RTTI and no exceptions
 260       return exception_ptr();
 261 #endif
 262     }
 263
 264 #undef _GLIBCXX_EH_PTR_USED
 265
 266   /// @} group exceptions
 267 } // namespace std
 268
 269 } // extern "C++"
 270
 271 #pragma GCC visibility pop
 272
 273 #endif