libstdc++-v3/libsupc++/eh_ptr.cc

   1 // -*- C++ -*- Implement the members of exception_ptr.
   2 // Copyright (C) 2008-2021 Free Software Foundation, Inc.
   3 //
   4 // This file is part of GCC.
   5 //
   6 // GCC is free software; you can redistribute it and/or modify
   7 // it under the terms of the GNU General Public License as published by
   8 // the Free Software Foundation; either version 3, or (at your option)
   9 // any later version.
  10 //
  11 // GCC 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 #include <bits/c++config.h>
  26 #include "eh_atomics.h"
  27
  28 #if ! _GLIBCXX_INLINE_VERSION
  29 // This macro causes exception_ptr to declare an older API (with corresponding
  30 // definitions in this file) and to mark some inline functions as "used" so
  31 // that definitions will be emitted in this translation unit.
  32 #define _GLIBCXX_EH_PTR_COMPAT
  33 #endif
  34
  35 #include <exception>
  36 #include <bits/exception_ptr.h>
  37 #include "unwind-cxx.h"
  38
  39 using namespace __cxxabiv1;
  40
  41 // Verify assumptions about member layout in exception types
  42 namespace
  43 {
  44 template<typename Ex>
  45   constexpr std::size_t unwindhdr()
  46   { return offsetof(Ex, unwindHeader); }
  47
  48 template<typename Ex>
  49   constexpr std::size_t termHandler()
  50   { return unwindhdr<Ex>() - offsetof(Ex, terminateHandler); }
  51
  52 static_assert( termHandler<__cxa_exception>()
  53                == termHandler<__cxa_dependent_exception>(),
  54                "__cxa_dependent_exception::termHandler layout must be"
  55                " consistent with __cxa_exception::termHandler" );
  56
  57 #ifndef __ARM_EABI_UNWINDER__
  58 template<typename Ex>
  59   constexpr std::ptrdiff_t adjptr()
  60   { return unwindhdr<Ex>() - offsetof(Ex, adjustedPtr); }
  61
  62 static_assert( adjptr<__cxa_exception>()
  63                == adjptr<__cxa_dependent_exception>(),
  64                "__cxa_dependent_exception::adjustedPtr layout must be"
  65                " consistent with __cxa_exception::adjustedPtr" );
  66 #endif
  67 }
  68
  69 // Define non-inline functions.
  70
  71 std::__exception_ptr::exception_ptr::exception_ptr(void* obj) noexcept
  72 : _M_exception_object(obj)  { _M_addref(); }
  73
  74
  75 std::__exception_ptr::exception_ptr::exception_ptr(__safe_bool) noexcept
  76 : _M_exception_object(nullptr) { }
  77
  78
  79 void
  80 std::__exception_ptr::exception_ptr::_M_addref() noexcept
  81 {
  82   if (__builtin_expect(_M_exception_object != nullptr, true))
  83     {
  84       __cxa_refcounted_exception *eh =
  85         __get_refcounted_exception_header_from_obj (_M_exception_object);
  86       __gnu_cxx::__eh_atomic_inc (&eh->referenceCount);
  87     }
  88 }
  89
  90
  91 void
  92 std::__exception_ptr::exception_ptr::_M_release() noexcept
  93 {
  94   if (__builtin_expect(_M_exception_object != nullptr, true))
  95     {
  96       __cxa_refcounted_exception *eh =
  97         __get_refcounted_exception_header_from_obj (_M_exception_object);
  98       if (__gnu_cxx::__eh_atomic_dec (&eh->referenceCount))
  99         {
 100           if (eh->exc.exceptionDestructor)
 101             eh->exc.exceptionDestructor (_M_exception_object);
 102
 103           __cxa_free_exception (_M_exception_object);
 104           _M_exception_object = nullptr;
 105         }
 106     }
 107 }
 108
 109
 110 void*
 111 std::__exception_ptr::exception_ptr::_M_get() const noexcept
 112 { return _M_exception_object; }
 113
 114
 115
 116 // Retained for compatibility with CXXABI_1.3.
 117 void
 118 std::__exception_ptr::exception_ptr::_M_safe_bool_dummy() noexcept { }
 119
 120
 121 // Retained for compatibility with CXXABI_1.3.
 122 bool
 123 std::__exception_ptr::exception_ptr::operator!() const noexcept
 124 { return _M_exception_object == nullptr; }
 125
 126
 127 // Retained for compatibility with CXXABI_1.3.
 128 std::__exception_ptr::exception_ptr::operator __safe_bool() const noexcept
 129 {
 130   return _M_exception_object ? &exception_ptr::_M_safe_bool_dummy : nullptr;
 131 }
 132
 133 const std::type_info*
 134 std::__exception_ptr::exception_ptr::__cxa_exception_type() const noexcept
 135 {
 136   __cxa_exception *eh = __get_exception_header_from_obj (_M_exception_object);
 137   return eh->exceptionType;
 138 }
 139
 140 std::exception_ptr
 141 std::current_exception() noexcept
 142 {
 143   __cxa_eh_globals *globals = __cxa_get_globals ();
 144   __cxa_exception *header = globals->caughtExceptions;
 145
 146   if (!header)
 147     return std::exception_ptr();
 148
 149   // Since foreign exceptions can't be counted, we can't return them.
 150   if (!__is_gxx_exception_class (header->unwindHeader.exception_class))
 151     return std::exception_ptr();
 152
 153   return std::exception_ptr(
 154     __get_object_from_ambiguous_exception (header));
 155 }
 156
 157
 158 static void
 159 __gxx_dependent_exception_cleanup(_Unwind_Reason_Code code,
 160                                   _Unwind_Exception *exc)
 161 {
 162   // This cleanup is set only for dependents.
 163   __cxa_dependent_exception *dep = __get_dependent_exception_from_ue (exc);
 164   __cxa_refcounted_exception *header =
 165     __get_refcounted_exception_header_from_obj (dep->primaryException);
 166
 167   // We only want to be called through _Unwind_DeleteException.
 168   // _Unwind_DeleteException in the HP-UX IA64 libunwind library
 169   // returns _URC_NO_REASON and not _URC_FOREIGN_EXCEPTION_CAUGHT
 170   // like the GCC _Unwind_DeleteException function does.
 171   if (code != _URC_FOREIGN_EXCEPTION_CAUGHT && code != _URC_NO_REASON)
 172     __terminate (header->exc.terminateHandler);
 173
 174   __cxa_free_dependent_exception (dep);
 175
 176   if (__gnu_cxx::__eh_atomic_dec (&header->referenceCount))
 177     {
 178       if (header->exc.exceptionDestructor)
 179         header->exc.exceptionDestructor (header + 1);
 180
 181       __cxa_free_exception (header + 1);
 182     }
 183 }
 184
 185
 186 void
 187 std::rethrow_exception(std::exception_ptr ep)
 188 {
 189   void *obj = ep._M_get();
 190   __cxa_refcounted_exception *eh
 191     = __get_refcounted_exception_header_from_obj (obj);
 192
 193   __cxa_dependent_exception *dep = __cxa_allocate_dependent_exception ();
 194   dep->primaryException = obj;
 195   __gnu_cxx::__eh_atomic_inc (&eh->referenceCount);
 196
 197   dep->unexpectedHandler = get_unexpected ();
 198   dep->terminateHandler = get_terminate ();
 199   __GXX_INIT_DEPENDENT_EXCEPTION_CLASS(dep->unwindHeader.exception_class);
 200   dep->unwindHeader.exception_cleanup = __gxx_dependent_exception_cleanup;
 201
 202   __cxa_eh_globals *globals = __cxa_get_globals ();
 203   globals->uncaughtExceptions += 1;
 204
 205 #ifdef __USING_SJLJ_EXCEPTIONS__
 206   _Unwind_SjLj_RaiseException (&dep->unwindHeader);
 207 #else
 208   _Unwind_RaiseException (&dep->unwindHeader);
 209 #endif
 210
 211   // Some sort of unwinding error.  Note that terminate is a handler.
 212   __cxa_begin_catch (&dep->unwindHeader);
 213   std::terminate();
 214 }
 215
 216 #undef _GLIBCXX_EH_PTR_COMPAT