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 20 extern "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. */ 54 extern 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. */ 68 extern void block_fatal_signals (void); 69 70 /* Stop delaying the catchable fatal signals. */ 71 extern void unblock_fatal_signals (void); 72 73 74 #ifdef __cplusplus 75 } 76 #endif 77