1 /* Emergency actions in case of a fatal signal. 2 Copyright (C) 2003-2004 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 2, or (at your option) 8 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, write to the Free Software Foundation, 17 Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */ 18 19 20 #ifdef __cplusplus 21 extern "C" { 22 #endif 23 24 25 /* It is often useful to do some cleanup action when a usually fatal signal 26 terminates the process, like removing a temporary file or killing a 27 subprocess that may be stuck waiting for a device, pipe or network input. 28 Such signals are SIGHUP, SIGINT, SIGPIPE, SIGTERM, and possibly others. 29 The limitation of this facility is that it cannot work for SIGKILL. 30 31 Signals with a SIG_IGN handler are considered to be non-fatal. The 32 functions in this file assume that when a SIG_IGN handler is installed 33 for a signal, it was installed before any functions in this file were 34 called and it stays so for the whole lifetime of the process. */ 35 36 /* Register a cleanup function to be executed when a catchable fatal signal 37 occurs. 38 39 Restrictions for the cleanup function: 40 - The cleanup function can do all kinds of system calls. 41 - It can also access application dependent memory locations and data 42 structures provided they are in a consistent state. One way to ensure 43 this is through block_fatal_signals()/unblock_fatal_signals(), see 44 below. Another - more tricky - way to ensure this is the careful use 45 of 'volatile'. 46 However, 47 - malloc() and similarly complex facilities are not safe to be called 48 because they are not guaranteed to be in a consistent state. 49 - Also, the cleanup function must not block the catchable fatal signals 50 and leave them blocked upon return. 51 52 The cleanup function is executed asynchronously. It is unspecified 53 whether during its execution the catchable fatal signals are blocked 54 or not. */ 55 extern void at_fatal_signal (void (*function) (void)); 56 57 58 /* Sometimes it is necessary to block the usually fatal signals while the 59 data structures being accessed by the cleanup action are being built or 60 reorganized. This is the case, for example, when a temporary file or 61 directory is created through mkstemp() or mkdtemp(), because these 62 functions create the temporary file or directory _before_ returning its 63 name to the application. */ 64 65 /* Temporarily delay the catchable fatal signals. 66 The signals will be blocked (= delayed) until the next call to 67 unblock_fatal_signals(). If the signals are already blocked, a further 68 call to block_fatal_signals() has no effect. */ 69 extern void block_fatal_signals (void); 70 71 /* Stop delaying the catchable fatal signals. */ 72 extern void unblock_fatal_signals (void); 73 74 75 #ifdef __cplusplus 76 } 77 #endif 78