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

   1 // -*- C++ -*- Exception handling routines for catching.
   2 // Copyright (C) 2001, 2003 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
  37 extern "C" void *
  38 __cxa_begin_catch (void *exc_obj_in)
  39 {
  40   _Unwind_Exception *exceptionObject
  41     = reinterpret_cast <_Unwind_Exception *>(exc_obj_in);
  42   __cxa_eh_globals *globals = __cxa_get_globals ();
  43   __cxa_exception *prev = globals->caughtExceptions;
  44   __cxa_exception *header = __get_exception_header_from_ue (exceptionObject);
  45
  46   // Foreign exceptions can't be stacked here.  If the exception stack is
  47   // empty, then fine.  Otherwise we really have no choice but to terminate.
  48   // Note that this use of "header" is a lie.  It's fine so long as we only
  49   // examine header->unwindHeader though.
  50   if (header->unwindHeader.exception_class != __gxx_exception_class)
  51     {
  52       if (prev != 0)
  53         std::terminate ();
  54
  55       // Remember for end_catch and rethrow.
  56       globals->caughtExceptions = header;
  57
  58       // ??? No sensible value to return; we don't know what the
  59       // object is, much less where it is in relation to the header.
  60       return 0;
  61     }
  62
  63   int count = header->handlerCount;
  64   if (count < 0)
  65     // This exception was rethrown from an immediately enclosing region.
  66     count = -count + 1;
  67   else
  68     count += 1;
  69   header->handlerCount = count;
  70
  71   globals->uncaughtExceptions -= 1;
  72   if (header != prev)
  73     {
  74       header->nextException = prev;
  75       globals->caughtExceptions = header;
  76     }
  77
  78   return header->adjustedPtr;
  79 }
  80
  81
  82 extern "C" void
  83 __cxa_end_catch ()
  84 {
  85   __cxa_eh_globals *globals = __cxa_get_globals_fast ();
  86   __cxa_exception *header = globals->caughtExceptions;
  87
  88   // A rethrow of a foreign exception will be removed from the
  89   // the exception stack immediately by __cxa_rethrow.
  90   if (!header)
  91     return;
  92
  93   // A foreign exception couldn't have been stacked (see above),
  94   // so by definition processing must be complete.
  95   if (header->unwindHeader.exception_class != __gxx_exception_class)
  96     {
  97       globals->caughtExceptions = 0;
  98       _Unwind_DeleteException (&header->unwindHeader);
  99       return;
 100     }
 101
 102   int count = header->handlerCount;
 103   if (count < 0)
 104     {
 105       // This exception was rethrown.  Decrement the (inverted) catch
 106       // count and remove it from the chain when it reaches zero.
 107       if (++count == 0)
 108         {
 109           globals->uncaughtExceptions += 1;
 110           globals->caughtExceptions = header->nextException;
 111         }
 112     }
 113   else if (--count == 0)
 114     {
 115       // Handling for this exception is complete.  Destroy the object.
 116       globals->caughtExceptions = header->nextException;
 117       _Unwind_DeleteException (&header->unwindHeader);
 118       return;
 119     }
 120   else if (count < 0)
 121     // A bug in the exception handling library or compiler.
 122     std::terminate ();
 123
 124   header->handlerCount = count;
 125 }
 126
 127
 128 bool
 129 std::uncaught_exception() throw()
 130 {
 131   __cxa_eh_globals *globals = __cxa_get_globals ();
 132   return globals->uncaughtExceptions != 0;
 133 }