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 #if __cplusplus >= 201103L
  43 # include <bits/move.h>
  44 #endif
  45
  46 #ifdef _GLIBCXX_EH_PTR_RELOPS_COMPAT
  47 # define _GLIBCXX_EH_PTR_USED __attribute__((__used__))
  48 #else
  49 # define _GLIBCXX_EH_PTR_USED
  50 #endif
  51
  52 extern "C++" {
  53
  54 namespace std
  55 {
  56   class type_info;
  57
  58   /**
  59    * @addtogroup exceptions
  60    * @{
  61    */
  62
  63   namespace __exception_ptr
  64   {
  65     class exception_ptr;
  66   }
  67
  68   using __exception_ptr::exception_ptr;
  69
  70   /** Obtain an exception_ptr to the currently handled exception. If there
  71    *  is none, or the currently handled exception is foreign, return the null
  72    *  value.
  73    */
  74   exception_ptr current_exception() _GLIBCXX_USE_NOEXCEPT;
  75
  76   template<typename _Ex>
  77   exception_ptr make_exception_ptr(_Ex) _GLIBCXX_USE_NOEXCEPT;
  78
  79   /// Throw the object pointed to by the exception_ptr.
  80   void rethrow_exception(exception_ptr) __attribute__ ((__noreturn__));
  81
  82   namespace __exception_ptr
  83   {
  84     using std::rethrow_exception;
  85
  86     /**
  87      *  @brief An opaque pointer to an arbitrary exception.
  88      *  @ingroup exceptions
  89      */
  90     class exception_ptr
  91     {
  92       void* _M_exception_object;
  93
  94       explicit exception_ptr(void* __e) _GLIBCXX_USE_NOEXCEPT;
  95
  96       void _M_addref() _GLIBCXX_USE_NOEXCEPT;
  97       void _M_release() _GLIBCXX_USE_NOEXCEPT;
  98
  99       void *_M_get() const _GLIBCXX_NOEXCEPT __attribute__ ((__pure__));
 100
 101       friend exception_ptr std::current_exception() _GLIBCXX_USE_NOEXCEPT;
 102       friend void std::rethrow_exception(exception_ptr);
 103       template<typename _Ex>
 104       friend exception_ptr std::make_exception_ptr(_Ex) _GLIBCXX_USE_NOEXCEPT;
 105
 106     public:
 107       exception_ptr() _GLIBCXX_USE_NOEXCEPT;
 108
 109       exception_ptr(const exception_ptr&) _GLIBCXX_USE_NOEXCEPT;
 110
 111 #if __cplusplus >= 201103L
 112       exception_ptr(nullptr_t) noexcept
 113       : _M_exception_object(nullptr)
 114       { }
 115
 116       exception_ptr(exception_ptr&& __o) noexcept
 117       : _M_exception_object(__o._M_exception_object)
 118       { __o._M_exception_object = nullptr; }
 119 #endif
 120
 121 #if (__cplusplus < 201103L) || defined (_GLIBCXX_EH_PTR_COMPAT)
 122       typedef void (exception_ptr::*__safe_bool)();
 123
 124       // For construction from nullptr or 0.
 125       exception_ptr(__safe_bool) _GLIBCXX_USE_NOEXCEPT;
 126 #endif
 127
 128       exception_ptr&
 129       operator=(const exception_ptr&) _GLIBCXX_USE_NOEXCEPT;
 130
 131 #if __cplusplus >= 201103L
 132       exception_ptr&
 133       operator=(exception_ptr&& __o) noexcept
 134       {
 135         exception_ptr(static_cast<exception_ptr&&>(__o)).swap(*this);
 136         return *this;
 137       }
 138 #endif
 139
 140       ~exception_ptr() _GLIBCXX_USE_NOEXCEPT;
 141
 142       void
 143       swap(exception_ptr&) _GLIBCXX_USE_NOEXCEPT;
 144
 145 #ifdef _GLIBCXX_EH_PTR_COMPAT
 146       // Retained for compatibility with CXXABI_1.3.
 147       void _M_safe_bool_dummy() _GLIBCXX_USE_NOEXCEPT
 148         __attribute__ ((__const__));
 149       bool operator!() const _GLIBCXX_USE_NOEXCEPT
 150         __attribute__ ((__pure__));
 151       operator __safe_bool() const _GLIBCXX_USE_NOEXCEPT;
 152 #endif
 153
 154 #if __cplusplus >= 201103L
 155       explicit operator bool() const noexcept
 156       { return _M_exception_object; }
 157 #endif
 158
 159 #if __cpp_impl_three_way_comparison >= 201907L \
 160       && ! defined _GLIBCXX_EH_PTR_RELOPS_COMPAT
 161       friend bool
 162       operator==(const exception_ptr&, const exception_ptr&) noexcept = default;
 163 #else
 164       friend _GLIBCXX_EH_PTR_USED bool
 165       operator==(const exception_ptr& __x, const exception_ptr& __y)
 166       _GLIBCXX_USE_NOEXCEPT
 167       { return __x._M_exception_object == __y._M_exception_object; }
 168
 169       friend _GLIBCXX_EH_PTR_USED bool
 170       operator!=(const exception_ptr& __x, const exception_ptr& __y)
 171       _GLIBCXX_USE_NOEXCEPT
 172       { return __x._M_exception_object != __y._M_exception_object; }
 173 #endif
 174
 175       const class std::type_info*
 176       __cxa_exception_type() const _GLIBCXX_USE_NOEXCEPT
 177         __attribute__ ((__pure__));
 178     };
 179
 180     _GLIBCXX_EH_PTR_USED
 181     inline
 182     exception_ptr::exception_ptr() _GLIBCXX_USE_NOEXCEPT
 183     : _M_exception_object(0)
 184     { }
 185
 186     _GLIBCXX_EH_PTR_USED
 187     inline
 188     exception_ptr::exception_ptr(const exception_ptr& __other)
 189     _GLIBCXX_USE_NOEXCEPT
 190     : _M_exception_object(__other._M_exception_object)
 191     {
 192       if (_M_exception_object)
 193         _M_addref();
 194     }
 195
 196     _GLIBCXX_EH_PTR_USED
 197     inline
 198     exception_ptr::~exception_ptr() _GLIBCXX_USE_NOEXCEPT
 199     {
 200       if (_M_exception_object)
 201         _M_release();
 202     }
 203
 204     _GLIBCXX_EH_PTR_USED
 205     inline exception_ptr&
 206     exception_ptr::operator=(const exception_ptr& __other) _GLIBCXX_USE_NOEXCEPT
 207     {
 208       exception_ptr(__other).swap(*this);
 209       return *this;
 210     }
 211
 212     _GLIBCXX_EH_PTR_USED
 213     inline void
 214     exception_ptr::swap(exception_ptr &__other) _GLIBCXX_USE_NOEXCEPT
 215     {
 216       void *__tmp = _M_exception_object;
 217       _M_exception_object = __other._M_exception_object;
 218       __other._M_exception_object = __tmp;
 219     }
 220
 221     /// @relates exception_ptr
 222     inline void
 223     swap(exception_ptr& __lhs, exception_ptr& __rhs)
 224     { __lhs.swap(__rhs); }
 225
 226     /// @cond undocumented
 227     template<typename _Ex>
 228       _GLIBCXX_CDTOR_CALLABI
 229       inline void
 230       __dest_thunk(void* __x)
 231       { static_cast<_Ex*>(__x)->~_Ex(); }
 232     /// @endcond
 233
 234   } // namespace __exception_ptr
 235
 236   /// Obtain an exception_ptr pointing to a copy of the supplied object.
 237 #if (__cplusplus >= 201103L && __cpp_rtti) || __cpp_exceptions
 238   template<typename _Ex>
 239     exception_ptr
 240     make_exception_ptr(_Ex __ex) _GLIBCXX_USE_NOEXCEPT
 241     {
 242 #if __cplusplus >= 201103L && __cpp_rtti
 243       using _Ex2 = typename decay<_Ex>::type;
 244       void* __e = __cxxabiv1::__cxa_allocate_exception(sizeof(_Ex));
 245       (void) __cxxabiv1::__cxa_init_primary_exception(
 246           __e, const_cast<std::type_info*>(&typeid(_Ex)),
 247           __exception_ptr::__dest_thunk<_Ex2>);
 248       __try
 249         {
 250           ::new (__e) _Ex2(__ex);
 251           return exception_ptr(__e);
 252         }
 253       __catch(...)
 254         {
 255           __cxxabiv1::__cxa_free_exception(__e);
 256           return current_exception();
 257         }
 258 #else
 259       try
 260         {
 261           throw __ex;
 262         }
 263       catch(...)
 264         {
 265           return current_exception();
 266         }
 267 #endif
 268     }
 269 #else // no RTTI and no exceptions
 270   // This is always_inline so the linker will never use this useless definition
 271   // instead of a working one compiled with RTTI and/or exceptions enabled.
 272   template<typename _Ex>
 273     __attribute__ ((__always_inline__))
 274     exception_ptr
 275     make_exception_ptr(_Ex) _GLIBCXX_USE_NOEXCEPT
 276     { return exception_ptr(); }
 277 #endif
 278
 279 #undef _GLIBCXX_EH_PTR_USED
 280
 281   /// @} group exceptions
 282 } // namespace std
 283
 284 } // extern "C++"
 285
 286 #pragma GCC visibility pop
 287
 288 #endif