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

   1 // -*- C++ -*- Exception handling routines for catching.
   2 // Copyright (C) 2001-2022 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 <cstdlib>
  26 #include "unwind-cxx.h"
  27
  28 using namespace __cxxabiv1;
  29
  30 extern "C" void *
  31 __cxxabiv1::__cxa_get_exception_ptr(void *exc_obj_in) _GLIBCXX_NOTHROW
  32 {
  33   _Unwind_Exception *exceptionObject
  34     = reinterpret_cast <_Unwind_Exception *>(exc_obj_in);
  35
  36   return __gxx_caught_object(exceptionObject);
  37 }
  38
  39 extern "C" void *
  40 __cxxabiv1::__cxa_begin_catch (void *exc_obj_in) _GLIBCXX_NOTHROW
  41 {
  42   _Unwind_Exception *exceptionObject
  43     = reinterpret_cast <_Unwind_Exception *>(exc_obj_in);
  44   __cxa_eh_globals *globals = __cxa_get_globals ();
  45   __cxa_exception *prev = globals->caughtExceptions;
  46   __cxa_exception *header = __get_exception_header_from_ue (exceptionObject);
  47   void* objectp;
  48
  49   // Foreign exceptions can't be stacked here.  If the exception stack is
  50   // empty, then fine.  Otherwise we really have no choice but to terminate.
  51   // Note that this use of "header" is a lie.  It's fine so long as we only
  52   // examine header->unwindHeader though.
  53   if (!__is_gxx_exception_class(header->unwindHeader.exception_class))
  54     {
  55       if (prev != 0)
  56         std::terminate ();
  57
  58       // Remember for end_catch and rethrow.
  59       globals->caughtExceptions = header;
  60
  61       // ??? No sensible value to return; we don't know what the
  62       // object is, much less where it is in relation to the header.
  63       return 0;
  64     }
  65
  66   int count = header->handlerCount;
  67   // Count is less than zero if this exception was rethrown from an
  68   // immediately enclosing region.
  69   if (count < 0)
  70     count = -count + 1;
  71   else
  72     count += 1;
  73   header->handlerCount = count;
  74   globals->uncaughtExceptions -= 1;
  75
  76   if (header != prev)
  77     {
  78       header->nextException = prev;
  79       globals->caughtExceptions = header;
  80     }
  81
  82   objectp = __gxx_caught_object(exceptionObject);
  83
  84   PROBE2 (catch, objectp, header->exceptionType);
  85
  86 #ifdef __ARM_EABI_UNWINDER__
  87   _Unwind_Complete(exceptionObject);
  88 #endif
  89   return objectp;
  90 }
  91
  92
  93 extern "C" void
  94 __cxxabiv1::__cxa_end_catch ()
  95 {
  96   __cxa_eh_globals *globals = __cxa_get_globals_fast ();
  97   __cxa_exception *header = globals->caughtExceptions;
  98
  99   // A rethrow of a foreign exception will be removed from the
 100   // the exception stack immediately by __cxa_rethrow.
 101   if (!header)
 102     return;
 103
 104   // A foreign exception couldn't have been stacked (see above),
 105   // so by definition processing must be complete.
 106   if (!__is_gxx_exception_class(header->unwindHeader.exception_class))
 107     {
 108       globals->caughtExceptions = 0;
 109       _Unwind_DeleteException (&header->unwindHeader);
 110       return;
 111     }
 112
 113   int count = header->handlerCount;
 114   if (count < 0)
 115     {
 116       // This exception was rethrown.  Decrement the (inverted) catch
 117       // count and remove it from the chain when it reaches zero.
 118       if (++count == 0)
 119         globals->caughtExceptions = header->nextException;
 120     }
 121   else if (--count == 0)
 122     {
 123       // Handling for this exception is complete.  Destroy the object.
 124       globals->caughtExceptions = header->nextException;
 125       _Unwind_DeleteException (&header->unwindHeader);
 126       return;
 127     }
 128   else if (count < 0)
 129     // A bug in the exception handling library or compiler.
 130     std::terminate ();
 131
 132   header->handlerCount = count;
 133 }
 134
 135
 136 bool
 137 std::uncaught_exception() throw()
 138 {
 139 #if __cpp_exceptions
 140   __cxa_eh_globals *globals = __cxa_get_globals ();
 141   return globals->uncaughtExceptions != 0;
 142 #else
 143   return false;
 144 #endif
 145 }
 146
 147 int
 148 std::uncaught_exceptions() throw()
 149 {
 150 #if __cpp_exceptions
 151   __cxa_eh_globals *globals = __cxa_get_globals ();
 152   return globals->uncaughtExceptions;
 153 #else
 154   return 0;
 155 #endif
 156 }