Mercurial > hg > octave-nkf > gnulib-hg
annotate lib/fatal-signal.c @ 5536:f64f1da7e350
Signals whose handler is set to SIG_IGN are not fatal.
| author | Bruno Haible <bruno@clisp.org> |
|---|---|
| date | Sat, 18 Dec 2004 18:20:45 +0000 (2004-12-18) |
| parents | 83d8d561903a |
| children | 0fc3beabfb42 |
| rev | line source |
|---|---|
| 4770 | 1 /* Emergency actions in case of a fatal signal. |
|
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Signals whose handler is set to SIG_IGN are not fatal.
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2 Copyright (C) 2003-2004 Free Software Foundation, Inc. |
| 4770 | 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., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ | |
| 18 | |
| 19 | |
| 20 #ifdef HAVE_CONFIG_H | |
| 21 # include "config.h" | |
| 22 #endif | |
| 23 | |
| 24 /* Specification. */ | |
| 25 #include "fatal-signal.h" | |
| 26 | |
| 27 #include <stdbool.h> | |
| 28 #include <stdlib.h> | |
| 29 #include <signal.h> | |
| 30 #include <string.h> | |
| 31 #if HAVE_UNISTD_H | |
| 32 # include <unistd.h> | |
| 33 #endif | |
| 34 | |
| 35 #include "xalloc.h" | |
| 36 | |
| 37 #define SIZEOF(a) (sizeof(a) / sizeof(a[0])) | |
| 38 | |
| 39 | |
| 40 /* ========================================================================= */ | |
| 41 | |
| 42 | |
| 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, | |
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53 SIGRTMIN...SIGRTMAX - because they are reserved for application use. |
| 4770 | 54 plus |
| 55 SIGXCPU, SIGXFSZ - because they are quite similar to SIGTERM. */ | |
| 56 | |
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57 static int fatal_signals[] = |
| 4770 | 58 { |
| 59 /* ISO C 99 signals. */ | |
| 60 #ifdef SIGINT | |
| 61 SIGINT, | |
| 62 #endif | |
| 63 #ifdef SIGTERM | |
| 64 SIGTERM, | |
| 65 #endif | |
| 66 /* POSIX:2001 signals. */ | |
| 67 #ifdef SIGHUP | |
| 68 SIGHUP, | |
| 69 #endif | |
| 70 #ifdef SIGPIPE | |
| 71 SIGPIPE, | |
| 72 #endif | |
| 73 /* BSD signals. */ | |
| 74 #ifdef SIGXCPU | |
| 75 SIGXCPU, | |
| 76 #endif | |
| 77 #ifdef SIGXFSZ | |
| 78 SIGXFSZ, | |
| 79 #endif | |
| 80 0 | |
| 81 }; | |
| 82 | |
| 83 #define num_fatal_signals (SIZEOF (fatal_signals) - 1) | |
| 84 | |
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85 /* Eliminate signals whose signal handler is SIG_IGN. */ |
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86 |
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87 static void |
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88 init_fatal_signals (void) |
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89 { |
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90 static bool fatal_signals_initialized = false; |
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91 if (!fatal_signals_initialized) |
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92 { |
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93 size_t i; |
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94 |
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95 for (i = 0; i < num_fatal_signals; i++) |
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96 { |
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97 struct sigaction action; |
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98 |
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99 if (sigaction (fatal_signals[i], NULL, &action) >= 0 |
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100 && action.sa_handler == SIG_IGN) |
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101 fatal_signals[i] = -1; |
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102 } |
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103 |
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104 fatal_signals_initialized = true; |
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105 } |
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106 } |
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107 |
| 4770 | 108 |
| 109 /* ========================================================================= */ | |
| 110 | |
| 111 | |
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112 typedef void (*action_t) (void); |
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113 |
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114 /* Type of an entry in the actions array. |
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115 The 'action' field is accessed from within the fatal_signal_handler(), |
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116 therefore we mark it as 'volatile'. */ |
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117 typedef struct |
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118 { |
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119 volatile action_t action; |
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120 } |
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121 actions_entry_t; |
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122 |
| 4770 | 123 /* The registered cleanup actions. */ |
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124 static actions_entry_t static_actions[32]; |
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125 static actions_entry_t * volatile actions = static_actions; |
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126 static sig_atomic_t volatile actions_count = 0; |
| 4770 | 127 static size_t actions_allocated = SIZEOF (static_actions); |
| 128 | |
| 129 | |
| 130 /* Uninstall the handlers. */ | |
| 131 static inline void | |
| 132 uninstall_handlers () | |
| 133 { | |
| 134 size_t i; | |
| 135 | |
| 136 for (i = 0; i < num_fatal_signals; i++) | |
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137 if (fatal_signals[i] >= 0) |
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138 signal (fatal_signals[i], SIG_DFL); |
| 4770 | 139 } |
| 140 | |
| 141 | |
| 142 /* The signal handler. It gets called asynchronously. */ | |
| 143 static void | |
| 144 fatal_signal_handler (int sig) | |
| 145 { | |
| 146 for (;;) | |
| 147 { | |
| 148 /* Get the last registered cleanup action, in a reentrant way. */ | |
| 149 action_t action; | |
| 150 size_t n = actions_count; | |
| 151 if (n == 0) | |
| 152 break; | |
| 153 n--; | |
| 154 actions_count = n; | |
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155 action = actions[n].action; |
| 4770 | 156 /* Execute the action. */ |
| 157 action (); | |
| 158 } | |
| 159 | |
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160 /* Now execute the signal's default action. |
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161 If signal() blocks the signal being delivered for the duration of the |
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162 signal handler's execution, the re-raised signal is delivered when this |
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163 handler returns; otherwise it is delivered already during raise(). */ |
| 4770 | 164 uninstall_handlers (); |
| 165 #if HAVE_RAISE | |
| 166 raise (sig); | |
| 167 #else | |
| 168 kill (getpid (), sig); | |
| 169 #endif | |
| 170 } | |
| 171 | |
| 172 | |
| 173 /* Install the handlers. */ | |
| 174 static inline void | |
| 175 install_handlers () | |
| 176 { | |
| 177 size_t i; | |
| 178 | |
| 179 for (i = 0; i < num_fatal_signals; i++) | |
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180 if (fatal_signals[i] >= 0) |
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181 signal (fatal_signals[i], &fatal_signal_handler); |
| 4770 | 182 } |
| 183 | |
| 184 | |
| 185 /* Register a cleanup function to be executed when a catchable fatal signal | |
| 186 occurs. */ | |
| 187 void | |
| 188 at_fatal_signal (action_t action) | |
| 189 { | |
| 190 static bool cleanup_initialized = false; | |
| 191 if (!cleanup_initialized) | |
| 192 { | |
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193 init_fatal_signals (); |
| 4770 | 194 install_handlers (); |
| 195 cleanup_initialized = true; | |
| 196 } | |
| 197 | |
| 198 if (actions_count == actions_allocated) | |
| 199 { | |
| 200 /* Extend the actions array. Note that we cannot use xrealloc(), | |
| 201 because then the cleanup() function could access an already | |
| 202 deallocated array. */ | |
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203 actions_entry_t *old_actions = actions; |
| 4770 | 204 size_t new_actions_allocated = 2 * actions_allocated; |
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205 actions_entry_t *new_actions = |
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206 xmalloc (new_actions_allocated * sizeof (actions_entry_t)); |
| 4770 | 207 |
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208 memcpy (new_actions, old_actions, |
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209 actions_allocated * sizeof (actions_entry_t)); |
| 4770 | 210 actions = new_actions; |
| 211 actions_allocated = new_actions_allocated; | |
| 212 /* Now we can free the old actions array. */ | |
| 213 if (old_actions != static_actions) | |
| 214 free (old_actions); | |
| 215 } | |
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216 /* The two uses of 'volatile' in the types above (and ISO C 99 section |
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217 5.1.2.3.(5)) ensure that we increment the actions_count only after |
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218 the new action has been written to the memory location |
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219 actions[actions_count]. */ |
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220 actions[actions_count].action = action; |
| 4770 | 221 actions_count++; |
| 222 } | |
| 223 | |
| 224 | |
| 225 /* ========================================================================= */ | |
| 226 | |
| 227 | |
| 228 #if HAVE_POSIX_SIGNALBLOCKING | |
| 229 | |
| 230 static sigset_t fatal_signal_set; | |
| 231 | |
| 232 static void | |
| 233 init_fatal_signal_set () | |
| 234 { | |
| 235 static bool fatal_signal_set_initialized = false; | |
| 236 if (!fatal_signal_set_initialized) | |
| 237 { | |
| 238 size_t i; | |
| 239 | |
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240 init_fatal_signals (); |
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241 |
| 4770 | 242 sigemptyset (&fatal_signal_set); |
| 243 for (i = 0; i < num_fatal_signals; i++) | |
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244 if (fatal_signals[i] >= 0) |
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245 sigaddset (&fatal_signal_set, fatal_signals[i]); |
| 4770 | 246 |
| 247 fatal_signal_set_initialized = true; | |
| 248 } | |
| 249 } | |
| 250 | |
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251 /* Temporarily delay the catchable fatal signals. */ |
| 4770 | 252 void |
| 253 block_fatal_signals () | |
| 254 { | |
| 255 init_fatal_signal_set (); | |
| 256 sigprocmask (SIG_BLOCK, &fatal_signal_set, NULL); | |
| 257 } | |
| 258 | |
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259 /* Stop delaying the catchable fatal signals. */ |
| 4770 | 260 void |
| 261 unblock_fatal_signals () | |
| 262 { | |
| 263 init_fatal_signal_set (); | |
| 264 sigprocmask (SIG_UNBLOCK, &fatal_signal_set, NULL); | |
| 265 } | |
| 266 | |
| 267 #else | |
| 268 | |
| 269 /* Don't bother caring about the old systems which don't have POSIX signal | |
| 270 blocking. */ | |
| 271 | |
| 272 void | |
| 273 block_fatal_signals () | |
| 274 { | |
| 275 } | |
| 276 | |
| 277 void | |
| 278 unblock_fatal_signals () | |
| 279 { | |
| 280 } | |
| 281 | |
| 282 #endif |