1 /* Emergency actions in case of a fatal signal.
2 Copyright (C) 2003 Free Software Foundation, Inc.
3 Written by Bruno Haible <bruno@clisp.org>, 2003.
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)
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.
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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
25 #include "fatal-signal.h"
37 #define SIZEOF(a) (sizeof(a) / sizeof(a[0]))
40 /* ========================================================================= */
43 /* The list of fatal signals.
44 These are those signals whose default action is to terminate the process
45 without a core dump, except
46 SIGKILL - because it cannot be caught,
47 SIGALRM SIGUSR1 SIGUSR2 SIGPOLL SIGIO SIGLOST - because applications
48 often use them for their own purpose,
49 SIGPROF SIGVTALRM - because they are used for profiling,
50 SIGSTKFLT - because it is more similar to SIGFPE, SIGSEGV, SIGBUS,
51 SIGSYS - because it is more similar to SIGABRT, SIGSEGV,
52 SIGPWR - because it of too special use,
53 SIGRTMIN...SIGRTMAX - because they are reserved for application use.
55 SIGXCPU, SIGXFSZ - because they are quite similar to SIGTERM. */
57 static const int fatal_signals[] =
59 /* ISO C 99 signals. */
66 /* POSIX:2001 signals. */
83 #define num_fatal_signals (SIZEOF (fatal_signals) - 1)
86 /* ========================================================================= */
89 typedef void (*action_t) (void);
91 /* Type of an entry in the actions array.
92 The 'action' field is accessed from within the fatal_signal_handler(),
93 therefore we mark it as 'volatile'. */
96 volatile action_t action;
100 /* The registered cleanup actions. */
101 static actions_entry_t static_actions[32];
102 static actions_entry_t * volatile actions = static_actions;
103 static sig_atomic_t volatile actions_count = 0;
104 static size_t actions_allocated = SIZEOF (static_actions);
107 /* Uninstall the handlers. */
109 uninstall_handlers ()
113 for (i = 0; i < num_fatal_signals; i++)
114 signal (fatal_signals[i], SIG_DFL);
118 /* The signal handler. It gets called asynchronously. */
120 fatal_signal_handler (int sig)
124 /* Get the last registered cleanup action, in a reentrant way. */
126 size_t n = actions_count;
131 action = actions[n].action;
132 /* Execute the action. */
136 /* Now execute the signal's default action.
137 If signal() blocks the signal being delivered for the duration of the
138 signal handler's execution, the re-raised signal is delivered when this
139 handler returns; otherwise it is delivered already during raise(). */
140 uninstall_handlers ();
144 kill (getpid (), sig);
149 /* Install the handlers. */
155 for (i = 0; i < num_fatal_signals; i++)
156 signal (fatal_signals[i], &fatal_signal_handler);
160 /* Register a cleanup function to be executed when a catchable fatal signal
163 at_fatal_signal (action_t action)
165 static bool cleanup_initialized = false;
166 if (!cleanup_initialized)
169 cleanup_initialized = true;
172 if (actions_count == actions_allocated)
174 /* Extend the actions array. Note that we cannot use xrealloc(),
175 because then the cleanup() function could access an already
176 deallocated array. */
177 actions_entry_t *old_actions = actions;
178 size_t new_actions_allocated = 2 * actions_allocated;
179 actions_entry_t *new_actions =
180 xmalloc (new_actions_allocated * sizeof (actions_entry_t));
182 memcpy (new_actions, old_actions,
183 actions_allocated * sizeof (actions_entry_t));
184 actions = new_actions;
185 actions_allocated = new_actions_allocated;
186 /* Now we can free the old actions array. */
187 if (old_actions != static_actions)
190 /* The two uses of 'volatile' in the types above (and ISO C 99 section
191 5.1.2.3.(5)) ensure that we increment the actions_count only after
192 the new action has been written to the memory location
193 actions[actions_count]. */
194 actions[actions_count].action = action;
199 /* ========================================================================= */
202 #if HAVE_POSIX_SIGNALBLOCKING
204 static sigset_t fatal_signal_set;
207 init_fatal_signal_set ()
209 static bool fatal_signal_set_initialized = false;
210 if (!fatal_signal_set_initialized)
214 sigemptyset (&fatal_signal_set);
215 for (i = 0; i < num_fatal_signals; i++)
216 sigaddset (&fatal_signal_set, fatal_signals[i]);
218 fatal_signal_set_initialized = true;
222 /* Temporarily delay the catchable fatal signals. */
224 block_fatal_signals ()
226 init_fatal_signal_set ();
227 sigprocmask (SIG_BLOCK, &fatal_signal_set, NULL);
230 /* Stop delaying the catchable fatal signals. */
232 unblock_fatal_signals ()
234 init_fatal_signal_set ();
235 sigprocmask (SIG_UNBLOCK, &fatal_signal_set, NULL);
240 /* Don't bother caring about the old systems which don't have POSIX signal
244 block_fatal_signals ()
249 unblock_fatal_signals ()