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

   1 // -*- C++ -*- Exception handling routines for catching.
   2 // Copyright (C) 2001, 2003, 2004 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 2, 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 // You should have received a copy of the GNU General Public License
  17 // along with GCC; see the file COPYING.  If not, write to
  18 // the Free Software Foundation, 59 Temple Place - Suite 330,
  19 // Boston, MA 02111-1307, USA.
  20
  21 // As a special exception, you may use this file as part of a free software
  22 // library without restriction.  Specifically, if other files instantiate
  23 // templates or use macros or inline functions from this file, or you compile
  24 // this file and link it with other files to produce an executable, this
  25 // file does not by itself cause the resulting executable to be covered by
  26 // the GNU General Public License.  This exception does not however
  27 // invalidate any other reasons why the executable file might be covered by
  28 // the GNU General Public License.
  29
  30
  31 #include <cstdlib>
  32 #include "unwind-cxx.h"
  33
  34 using namespace __cxxabiv1;
  35
  36 extern "C" void *
  37 __cxxabiv1::__cxa_get_exception_ptr(void *exc_obj_in) throw()
  38 {
  39   _Unwind_Exception *exceptionObject
  40     = reinterpret_cast <_Unwind_Exception *>(exc_obj_in);
  41   __cxa_exception *header = __get_exception_header_from_ue (exceptionObject);
  42
  43   return header->adjustedPtr;
  44 }
  45
  46 extern "C" void *
  47 __cxxabiv1::__cxa_begin_catch (void *exc_obj_in) throw()
  48 {
  49   _Unwind_Exception *exceptionObject
  50     = reinterpret_cast <_Unwind_Exception *>(exc_obj_in);
  51   __cxa_eh_globals *globals = __cxa_get_globals ();
  52   __cxa_exception *prev = globals->caughtExceptions;
  53   __cxa_exception *header = __get_exception_header_from_ue (exceptionObject);
  54
  55   // Foreign exceptions can't be stacked here.  If the exception stack is
  56   // empty, then fine.  Otherwise we really have no choice but to terminate.
  57   // Note that this use of "header" is a lie.  It's fine so long as we only
  58   // examine header->unwindHeader though.
  59   if (header->unwindHeader.exception_class != __gxx_exception_class)
  60     {
  61       if (prev != 0)
  62         std::terminate ();
  63
  64       // Remember for end_catch and rethrow.
  65       globals->caughtExceptions = header;
  66
  67       // ??? No sensible value to return; we don't know what the
  68       // object is, much less where it is in relation to the header.
  69       return 0;
  70     }
  71
  72   int count = header->handlerCount;
  73   // Count is less than zero if this exception was rethrown from an
  74   // immediately enclosing region.
  75   if (count < 0)
  76     count = -count + 1;
  77   else
  78     count += 1;
  79   header->handlerCount = count;
  80   globals->uncaughtExceptions -= 1;
  81
  82   if (header != prev)
  83     {
  84       header->nextException = prev;
  85       globals->caughtExceptions = header;
  86     }
  87
  88   return header->adjustedPtr;
  89 }
  90
  91
  92 extern "C" void
  93 __cxxabiv1::__cxa_end_catch ()
  94 {
  95   __cxa_eh_globals *globals = __cxa_get_globals_fast ();
  96   __cxa_exception *header = globals->caughtExceptions;
  97
  98   // A rethrow of a foreign exception will be removed from the
  99   // the exception stack immediately by __cxa_rethrow.
 100   if (!header)
 101     return;
 102
 103   // A foreign exception couldn't have been stacked (see above),
 104   // so by definition processing must be complete.
 105   if (header->unwindHeader.exception_class != __gxx_exception_class)
 106     {
 107       globals->caughtExceptions = 0;
 108       _Unwind_DeleteException (&header->unwindHeader);
 109       return;
 110     }
 111
 112   int count = header->handlerCount;
 113   if (count < 0)
 114     {
 115       // This exception was rethrown.  Decrement the (inverted) catch
 116       // count and remove it from the chain when it reaches zero.
 117       if (++count == 0)
 118         globals->caughtExceptions = header->nextException;
 119     }
 120   else if (--count == 0)
 121     {
 122       // Handling for this exception is complete.  Destroy the object.
 123       globals->caughtExceptions = header->nextException;
 124       _Unwind_DeleteException (&header->unwindHeader);
 125       return;
 126     }
 127   else if (count < 0)
 128     // A bug in the exception handling library or compiler.
 129     std::terminate ();
 130
 131   header->handlerCount = count;
 132 }
 133
 134
 135 bool
 136 std::uncaught_exception() throw()
 137 {
 138   __cxa_eh_globals *globals = __cxa_get_globals ();
 139   return globals->uncaughtExceptions != 0;
 140 }