1 /* Emergency actions in case of a fatal signal. 2 Copyright (C) 2003-2004, 2009-2021 Free Software Foundation, Inc. 3 Written by Bruno Haible <bruno@clisp.org>, 2003. 4 5 This file is free software: you can redistribute it and/or modify 6 it under the terms of the GNU Lesser General Public License as 7 published by the Free Software Foundation; either version 2.1 of the 8 License, or (at your option) any later version. 9 10 This file 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 Lesser General Public License for more details. 14 15 You should have received a copy of the GNU Lesser General Public License 16 along with this program. If not, see <https://www.gnu.org/licenses/>. */ 17 18 19 #ifndef _FATAL_SIGNAL_H 20 #define _FATAL_SIGNAL_H 21 22 #include <signal.h> 23 24 #ifdef __cplusplus 25 extern "C" { 26 #endif 27 28 29 /* It is often useful to do some cleanup action when a usually fatal signal 30 terminates the process, like removing a temporary file or killing a 31 subprocess that may be stuck waiting for a device, pipe or network input. 32 Such signals are SIGHUP, SIGINT, SIGPIPE, SIGTERM, and possibly others. 33 The limitation of this facility is that it cannot work for SIGKILL. 34 35 Signals with a SIG_IGN handler are considered to be non-fatal. The 36 functions in this file assume that when a SIG_IGN handler is installed 37 for a signal, it was installed before any functions in this file were 38 called and it stays so for the whole lifetime of the process. */ 39 40 /* Register a cleanup function to be executed when a catchable fatal signal 41 occurs. 42 43 Restrictions for the cleanup function: 44 - The cleanup function can do all kinds of system calls. It may also 45 modify (clobber) errno. 46 - It can also access application dependent memory locations and data 47 structures provided they are in a consistent state. One way to ensure 48 this is through block_fatal_signals()/unblock_fatal_signals(), see 49 below. Another - more tricky - way to ensure this is the careful use 50 of 'volatile'. 51 However, 52 - malloc() and similarly complex facilities are not safe to be called 53 because they are not guaranteed to be in a consistent state. 54 - Also, the cleanup function must not block the catchable fatal signals 55 and leave them blocked upon return. 56 57 The cleanup function is executed asynchronously. It is unspecified 58 whether during its execution the catchable fatal signals are blocked 59 or not. 60 61 Return 0 upon success, or -1 if there was a memory allocation problem. */ 62 extern int at_fatal_signal (_GL_ASYNC_SAFE void (*function) (int sig)); 63 64 65 /* Sometimes it is necessary to block the usually fatal signals while the 66 data structures being accessed by the cleanup action are being built or 67 reorganized. This is the case, for example, when a temporary file or 68 directory is created through mkstemp() or mkdtemp(), because these 69 functions create the temporary file or directory _before_ returning its 70 name to the application. */ 71 72 /* Temporarily delay the catchable fatal signals. 73 The signals will be blocked (= delayed) until the next call to 74 unblock_fatal_signals(). If the signals are already blocked, a further 75 call to block_fatal_signals() has no effect. */ 76 extern void block_fatal_signals (void); 77 78 /* Stop delaying the catchable fatal signals. */ 79 extern void unblock_fatal_signals (void); 80 81 82 /* Return the list of signals that block_fatal_signals/unblock_fatal_signals 83 would block or unblock. 84 Fills signals[0..count-1] and returns count. */ 85 extern unsigned int get_fatal_signals (int signals[64]); 86 87 /* Return the list of signals that block_fatal_signals/unblock_fatal_signals 88 would block or unblock. */ 89 extern const sigset_t * get_fatal_signal_set (void); 90 91 92 #ifdef __cplusplus 93 } 94 #endif 95 96 #endif /* _FATAL_SIGNAL_H */