1 // -*- C++ -*- Exception handling routines for catching.
2 // Copyright (C) 2001, 2003 Free Software Foundation, Inc.
3 //
4 // This file is part of GNU CC.
5 //
6 // GNU CC 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 // GNU CC 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 GNU CC; 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 }
134