| 1 | /* Emergency actions in case of a fatal signal.
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| 2 | Copyright (C) 2003-2004 Free Software Foundation, Inc.
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| 3 | Written by Bruno Haible <bruno@clisp.org>, 2003.
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| 4 |
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| 5 | This program is free software; you can redistribute it and/or modify
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| 6 | it under the terms of the GNU General Public License as published by
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| 7 | the Free Software Foundation; either version 2, or (at your option)
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| 8 | any later version.
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| 9 |
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| 10 | This program is distributed in the hope that it will be useful,
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| 11 | but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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| 13 | GNU General Public License for more details.
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| 14 |
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| 15 | You should have received a copy of the GNU General Public License
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| 16 | along with this program; if not, write to the Free Software Foundation,
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| 17 | Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
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| 18 |
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| 19 |
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| 20 | #ifdef __cplusplus
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| 21 | extern "C" {
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| 22 | #endif
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| 23 |
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| 24 |
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| 25 | /* It is often useful to do some cleanup action when a usually fatal signal
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| 26 | terminates the process, like removing a temporary file or killing a
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| 27 | subprocess that may be stuck waiting for a device, pipe or network input.
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| 28 | Such signals are SIGHUP, SIGINT, SIGPIPE, SIGTERM, and possibly others.
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| 29 | The limitation of this facility is that it cannot work for SIGKILL.
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| 30 |
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| 31 | Signals with a SIG_IGN handler are considered to be non-fatal. The
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| 32 | functions in this file assume that when a SIG_IGN handler is installed
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| 33 | for a signal, it was installed before any functions in this file were
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| 34 | called and it stays so for the whole lifetime of the process. */
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| 35 |
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| 36 | /* Register a cleanup function to be executed when a catchable fatal signal
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| 37 | occurs.
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| 38 |
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| 39 | Restrictions for the cleanup function:
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| 40 | - The cleanup function can do all kinds of system calls.
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| 41 | - It can also access application dependent memory locations and data
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| 42 | structures provided they are in a consistent state. One way to ensure
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| 43 | this is through block_fatal_signals()/unblock_fatal_signals(), see
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| 44 | below. Another - more tricky - way to ensure this is the careful use
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| 45 | of 'volatile'.
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| 46 | However,
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| 47 | - malloc() and similarly complex facilities are not safe to be called
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| 48 | because they are not guaranteed to be in a consistent state.
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| 49 | - Also, the cleanup function must not block the catchable fatal signals
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| 50 | and leave them blocked upon return.
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| 51 |
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| 52 | The cleanup function is executed asynchronously. It is unspecified
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| 53 | whether during its execution the catchable fatal signals are blocked
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| 54 | or not. */
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| 55 | extern void at_fatal_signal (void (*function) (void));
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| 56 |
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| 57 |
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| 58 | /* Sometimes it is necessary to block the usually fatal signals while the
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| 59 | data structures being accessed by the cleanup action are being built or
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| 60 | reorganized. This is the case, for example, when a temporary file or
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| 61 | directory is created through mkstemp() or mkdtemp(), because these
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| 62 | functions create the temporary file or directory _before_ returning its
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| 63 | name to the application. */
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| 64 |
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| 65 | /* Temporarily delay the catchable fatal signals.
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| 66 | The signals will be blocked (= delayed) until the next call to
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| 67 | unblock_fatal_signals(). If the signals are already blocked, a further
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| 68 | call to block_fatal_signals() has no effect. */
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| 69 | extern void block_fatal_signals (void);
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| 70 |
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| 71 | /* Stop delaying the catchable fatal signals. */
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| 72 | extern void unblock_fatal_signals (void);
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| 73 |
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| 74 |
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| 75 | #ifdef __cplusplus
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| 76 | }
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| 77 | #endif
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