105436638acc7c010349a69c3395f1a57c642dc62Ying Wang/* Emergency actions in case of a fatal signal. 205436638acc7c010349a69c3395f1a57c642dc62Ying Wang Copyright (C) 2003-2004, 2009-2012 Free Software Foundation, Inc. 305436638acc7c010349a69c3395f1a57c642dc62Ying Wang Written by Bruno Haible <bruno@clisp.org>, 2003. 405436638acc7c010349a69c3395f1a57c642dc62Ying Wang 505436638acc7c010349a69c3395f1a57c642dc62Ying Wang This program is free software: you can redistribute it and/or modify 605436638acc7c010349a69c3395f1a57c642dc62Ying Wang it under the terms of the GNU General Public License as published by 705436638acc7c010349a69c3395f1a57c642dc62Ying Wang the Free Software Foundation; either version 3 of the License, or 805436638acc7c010349a69c3395f1a57c642dc62Ying Wang (at your option) any later version. 905436638acc7c010349a69c3395f1a57c642dc62Ying Wang 1005436638acc7c010349a69c3395f1a57c642dc62Ying Wang This program is distributed in the hope that it will be useful, 1105436638acc7c010349a69c3395f1a57c642dc62Ying Wang but WITHOUT ANY WARRANTY; without even the implied warranty of 1205436638acc7c010349a69c3395f1a57c642dc62Ying Wang MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 1305436638acc7c010349a69c3395f1a57c642dc62Ying Wang GNU General Public License for more details. 1405436638acc7c010349a69c3395f1a57c642dc62Ying Wang 1505436638acc7c010349a69c3395f1a57c642dc62Ying Wang You should have received a copy of the GNU General Public License 1605436638acc7c010349a69c3395f1a57c642dc62Ying Wang along with this program. If not, see <http://www.gnu.org/licenses/>. */ 1705436638acc7c010349a69c3395f1a57c642dc62Ying Wang 1805436638acc7c010349a69c3395f1a57c642dc62Ying Wang 1905436638acc7c010349a69c3395f1a57c642dc62Ying Wang#ifdef __cplusplus 2005436638acc7c010349a69c3395f1a57c642dc62Ying Wangextern "C" { 2105436638acc7c010349a69c3395f1a57c642dc62Ying Wang#endif 2205436638acc7c010349a69c3395f1a57c642dc62Ying Wang 2305436638acc7c010349a69c3395f1a57c642dc62Ying Wang 2405436638acc7c010349a69c3395f1a57c642dc62Ying Wang/* It is often useful to do some cleanup action when a usually fatal signal 2505436638acc7c010349a69c3395f1a57c642dc62Ying Wang terminates the process, like removing a temporary file or killing a 2605436638acc7c010349a69c3395f1a57c642dc62Ying Wang subprocess that may be stuck waiting for a device, pipe or network input. 2705436638acc7c010349a69c3395f1a57c642dc62Ying Wang Such signals are SIGHUP, SIGINT, SIGPIPE, SIGTERM, and possibly others. 2805436638acc7c010349a69c3395f1a57c642dc62Ying Wang The limitation of this facility is that it cannot work for SIGKILL. 2905436638acc7c010349a69c3395f1a57c642dc62Ying Wang 3005436638acc7c010349a69c3395f1a57c642dc62Ying Wang Signals with a SIG_IGN handler are considered to be non-fatal. The 3105436638acc7c010349a69c3395f1a57c642dc62Ying Wang functions in this file assume that when a SIG_IGN handler is installed 3205436638acc7c010349a69c3395f1a57c642dc62Ying Wang for a signal, it was installed before any functions in this file were 3305436638acc7c010349a69c3395f1a57c642dc62Ying Wang called and it stays so for the whole lifetime of the process. */ 3405436638acc7c010349a69c3395f1a57c642dc62Ying Wang 3505436638acc7c010349a69c3395f1a57c642dc62Ying Wang/* Register a cleanup function to be executed when a catchable fatal signal 3605436638acc7c010349a69c3395f1a57c642dc62Ying Wang occurs. 3705436638acc7c010349a69c3395f1a57c642dc62Ying Wang 3805436638acc7c010349a69c3395f1a57c642dc62Ying Wang Restrictions for the cleanup function: 3905436638acc7c010349a69c3395f1a57c642dc62Ying Wang - The cleanup function can do all kinds of system calls. 4005436638acc7c010349a69c3395f1a57c642dc62Ying Wang - It can also access application dependent memory locations and data 4105436638acc7c010349a69c3395f1a57c642dc62Ying Wang structures provided they are in a consistent state. One way to ensure 4205436638acc7c010349a69c3395f1a57c642dc62Ying Wang this is through block_fatal_signals()/unblock_fatal_signals(), see 4305436638acc7c010349a69c3395f1a57c642dc62Ying Wang below. Another - more tricky - way to ensure this is the careful use 4405436638acc7c010349a69c3395f1a57c642dc62Ying Wang of 'volatile'. 4505436638acc7c010349a69c3395f1a57c642dc62Ying Wang However, 4605436638acc7c010349a69c3395f1a57c642dc62Ying Wang - malloc() and similarly complex facilities are not safe to be called 4705436638acc7c010349a69c3395f1a57c642dc62Ying Wang because they are not guaranteed to be in a consistent state. 4805436638acc7c010349a69c3395f1a57c642dc62Ying Wang - Also, the cleanup function must not block the catchable fatal signals 4905436638acc7c010349a69c3395f1a57c642dc62Ying Wang and leave them blocked upon return. 5005436638acc7c010349a69c3395f1a57c642dc62Ying Wang 5105436638acc7c010349a69c3395f1a57c642dc62Ying Wang The cleanup function is executed asynchronously. It is unspecified 5205436638acc7c010349a69c3395f1a57c642dc62Ying Wang whether during its execution the catchable fatal signals are blocked 5305436638acc7c010349a69c3395f1a57c642dc62Ying Wang or not. */ 5405436638acc7c010349a69c3395f1a57c642dc62Ying Wangextern void at_fatal_signal (void (*function) (void)); 5505436638acc7c010349a69c3395f1a57c642dc62Ying Wang 5605436638acc7c010349a69c3395f1a57c642dc62Ying Wang 5705436638acc7c010349a69c3395f1a57c642dc62Ying Wang/* Sometimes it is necessary to block the usually fatal signals while the 5805436638acc7c010349a69c3395f1a57c642dc62Ying Wang data structures being accessed by the cleanup action are being built or 5905436638acc7c010349a69c3395f1a57c642dc62Ying Wang reorganized. This is the case, for example, when a temporary file or 6005436638acc7c010349a69c3395f1a57c642dc62Ying Wang directory is created through mkstemp() or mkdtemp(), because these 6105436638acc7c010349a69c3395f1a57c642dc62Ying Wang functions create the temporary file or directory _before_ returning its 6205436638acc7c010349a69c3395f1a57c642dc62Ying Wang name to the application. */ 6305436638acc7c010349a69c3395f1a57c642dc62Ying Wang 6405436638acc7c010349a69c3395f1a57c642dc62Ying Wang/* Temporarily delay the catchable fatal signals. 6505436638acc7c010349a69c3395f1a57c642dc62Ying Wang The signals will be blocked (= delayed) until the next call to 6605436638acc7c010349a69c3395f1a57c642dc62Ying Wang unblock_fatal_signals(). If the signals are already blocked, a further 6705436638acc7c010349a69c3395f1a57c642dc62Ying Wang call to block_fatal_signals() has no effect. */ 6805436638acc7c010349a69c3395f1a57c642dc62Ying Wangextern void block_fatal_signals (void); 6905436638acc7c010349a69c3395f1a57c642dc62Ying Wang 7005436638acc7c010349a69c3395f1a57c642dc62Ying Wang/* Stop delaying the catchable fatal signals. */ 7105436638acc7c010349a69c3395f1a57c642dc62Ying Wangextern void unblock_fatal_signals (void); 7205436638acc7c010349a69c3395f1a57c642dc62Ying Wang 7305436638acc7c010349a69c3395f1a57c642dc62Ying Wang 7405436638acc7c010349a69c3395f1a57c642dc62Ying Wang#ifdef __cplusplus 7505436638acc7c010349a69c3395f1a57c642dc62Ying Wang} 7605436638acc7c010349a69c3395f1a57c642dc62Ying Wang#endif 77