1/* Emergency actions in case of a fatal signal.
2   Copyright (C) 2003-2004, 2009-2012 Free Software Foundation, Inc.
3   Written by Bruno Haible <bruno@clisp.org>, 2003.
4
5   This program is free software: you can redistribute it and/or modify
6   it under the terms of the GNU General Public License as published by
7   the Free Software Foundation; either version 3 of the License, or
8   (at your option) any later version.
9
10   This program is distributed in the hope that it will be useful,
11   but WITHOUT ANY WARRANTY; without even the implied warranty of
12   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
13   GNU General Public License for more details.
14
15   You should have received a copy of the GNU General Public License
16   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
17
18
19#ifdef __cplusplus
20extern "C" {
21#endif
22
23
24/* It is often useful to do some cleanup action when a usually fatal signal
25   terminates the process, like removing a temporary file or killing a
26   subprocess that may be stuck waiting for a device, pipe or network input.
27   Such signals are SIGHUP, SIGINT, SIGPIPE, SIGTERM, and possibly others.
28   The limitation of this facility is that it cannot work for SIGKILL.
29
30   Signals with a SIG_IGN handler are considered to be non-fatal.  The
31   functions in this file assume that when a SIG_IGN handler is installed
32   for a signal, it was installed before any functions in this file were
33   called and it stays so for the whole lifetime of the process.  */
34
35/* Register a cleanup function to be executed when a catchable fatal signal
36   occurs.
37
38   Restrictions for the cleanup function:
39     - The cleanup function can do all kinds of system calls.
40     - It can also access application dependent memory locations and data
41       structures provided they are in a consistent state. One way to ensure
42       this is through block_fatal_signals()/unblock_fatal_signals(), see
43       below.  Another - more tricky - way to ensure this is the careful use
44       of 'volatile'.
45   However,
46     - malloc() and similarly complex facilities are not safe to be called
47       because they are not guaranteed to be in a consistent state.
48     - Also, the cleanup function must not block the catchable fatal signals
49       and leave them blocked upon return.
50
51   The cleanup function is executed asynchronously.  It is unspecified
52   whether during its execution the catchable fatal signals are blocked
53   or not.  */
54extern void at_fatal_signal (void (*function) (void));
55
56
57/* Sometimes it is necessary to block the usually fatal signals while the
58   data structures being accessed by the cleanup action are being built or
59   reorganized.  This is the case, for example, when a temporary file or
60   directory is created through mkstemp() or mkdtemp(), because these
61   functions create the temporary file or directory _before_ returning its
62   name to the application.  */
63
64/* Temporarily delay the catchable fatal signals.
65   The signals will be blocked (= delayed) until the next call to
66   unblock_fatal_signals().  If the signals are already blocked, a further
67   call to block_fatal_signals() has no effect.  */
68extern void block_fatal_signals (void);
69
70/* Stop delaying the catchable fatal signals.  */
71extern void unblock_fatal_signals (void);
72
73
74#ifdef __cplusplus
75}
76#endif
77