Mercurial > hg > octave-nkf > gnulib-hg
annotate lib/fatal-signal.c @ 7014:43bb3848f1c7
Merge from gettext 0.15: Be more careful to use 'volatile'.
| author | Bruno Haible <bruno@clisp.org> |
|---|---|
| date | Sat, 22 Jul 2006 14:44:27 +0000 (2006-07-22) |
| parents | 1b0092424a44 |
| children | 1c4ed7637c24 |
| rev | line source |
|---|---|
| 4770 | 1 /* Emergency actions in case of a fatal signal. |
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Include <unistd.h> unconditionally.
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2 Copyright (C) 2003-2004, 2006 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, | |
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17 Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */ |
| 4770 | 18 |
| 19 | |
| 20 #ifdef HAVE_CONFIG_H | |
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21 # include <config.h> |
| 4770 | 22 #endif |
| 23 | |
| 24 /* Specification. */ | |
| 25 #include "fatal-signal.h" | |
| 26 | |
| 27 #include <stdbool.h> | |
| 28 #include <stdlib.h> | |
| 29 #include <signal.h> | |
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30 #include <unistd.h> |
| 4770 | 31 |
| 32 #include "xalloc.h" | |
| 33 | |
| 34 #define SIZEOF(a) (sizeof(a) / sizeof(a[0])) | |
| 35 | |
| 36 | |
| 37 /* ========================================================================= */ | |
| 38 | |
| 39 | |
| 40 /* The list of fatal signals. | |
| 41 These are those signals whose default action is to terminate the process | |
| 42 without a core dump, except | |
| 43 SIGKILL - because it cannot be caught, | |
| 44 SIGALRM SIGUSR1 SIGUSR2 SIGPOLL SIGIO SIGLOST - because applications | |
| 45 often use them for their own purpose, | |
| 46 SIGPROF SIGVTALRM - because they are used for profiling, | |
| 47 SIGSTKFLT - because it is more similar to SIGFPE, SIGSEGV, SIGBUS, | |
| 48 SIGSYS - because it is more similar to SIGABRT, SIGSEGV, | |
| 49 SIGPWR - because it of too special use, | |
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50 SIGRTMIN...SIGRTMAX - because they are reserved for application use. |
| 4770 | 51 plus |
| 52 SIGXCPU, SIGXFSZ - because they are quite similar to SIGTERM. */ | |
| 53 | |
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54 static int fatal_signals[] = |
| 4770 | 55 { |
| 56 /* ISO C 99 signals. */ | |
| 57 #ifdef SIGINT | |
| 58 SIGINT, | |
| 59 #endif | |
| 60 #ifdef SIGTERM | |
| 61 SIGTERM, | |
| 62 #endif | |
| 63 /* POSIX:2001 signals. */ | |
| 64 #ifdef SIGHUP | |
| 65 SIGHUP, | |
| 66 #endif | |
| 67 #ifdef SIGPIPE | |
| 68 SIGPIPE, | |
| 69 #endif | |
| 70 /* BSD signals. */ | |
| 71 #ifdef SIGXCPU | |
| 72 SIGXCPU, | |
| 73 #endif | |
| 74 #ifdef SIGXFSZ | |
| 75 SIGXFSZ, | |
| 76 #endif | |
| 77 0 | |
| 78 }; | |
| 79 | |
| 80 #define num_fatal_signals (SIZEOF (fatal_signals) - 1) | |
| 81 | |
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82 /* Eliminate signals whose signal handler is SIG_IGN. */ |
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83 |
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84 static void |
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85 init_fatal_signals (void) |
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86 { |
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87 static bool fatal_signals_initialized = false; |
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88 if (!fatal_signals_initialized) |
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89 { |
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90 #if HAVE_SIGACTION |
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91 size_t i; |
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92 |
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93 for (i = 0; i < num_fatal_signals; i++) |
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94 { |
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95 struct sigaction action; |
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96 |
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97 if (sigaction (fatal_signals[i], NULL, &action) >= 0 |
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98 && action.sa_handler == SIG_IGN) |
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99 fatal_signals[i] = -1; |
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100 } |
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101 #endif |
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102 |
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103 fatal_signals_initialized = true; |
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104 } |
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105 } |
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106 |
| 4770 | 107 |
| 108 /* ========================================================================= */ | |
| 109 | |
| 110 | |
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111 typedef void (*action_t) (void); |
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112 |
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113 /* Type of an entry in the actions array. |
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114 The 'action' field is accessed from within the fatal_signal_handler(), |
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115 therefore we mark it as 'volatile'. */ |
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116 typedef struct |
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117 { |
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118 volatile action_t action; |
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119 } |
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120 actions_entry_t; |
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121 |
| 4770 | 122 /* The registered cleanup actions. */ |
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123 static actions_entry_t static_actions[32]; |
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124 static actions_entry_t * volatile actions = static_actions; |
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125 static sig_atomic_t volatile actions_count = 0; |
| 4770 | 126 static size_t actions_allocated = SIZEOF (static_actions); |
| 127 | |
| 128 | |
| 129 /* Uninstall the handlers. */ | |
| 130 static inline void | |
| 131 uninstall_handlers () | |
| 132 { | |
| 133 size_t i; | |
| 134 | |
| 135 for (i = 0; i < num_fatal_signals; i++) | |
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136 if (fatal_signals[i] >= 0) |
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137 signal (fatal_signals[i], SIG_DFL); |
| 4770 | 138 } |
| 139 | |
| 140 | |
| 141 /* The signal handler. It gets called asynchronously. */ | |
| 142 static void | |
| 143 fatal_signal_handler (int sig) | |
| 144 { | |
| 145 for (;;) | |
| 146 { | |
| 147 /* Get the last registered cleanup action, in a reentrant way. */ | |
| 148 action_t action; | |
| 149 size_t n = actions_count; | |
| 150 if (n == 0) | |
| 151 break; | |
| 152 n--; | |
| 153 actions_count = n; | |
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154 action = actions[n].action; |
| 4770 | 155 /* Execute the action. */ |
| 156 action (); | |
| 157 } | |
| 158 | |
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159 /* Now execute the signal's default action. |
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160 If signal() blocks the signal being delivered for the duration of the |
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161 signal handler's execution, the re-raised signal is delivered when this |
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162 handler returns; otherwise it is delivered already during raise(). */ |
| 4770 | 163 uninstall_handlers (); |
| 164 #if HAVE_RAISE | |
| 165 raise (sig); | |
| 166 #else | |
| 167 kill (getpid (), sig); | |
| 168 #endif | |
| 169 } | |
| 170 | |
| 171 | |
| 172 /* Install the handlers. */ | |
| 173 static inline void | |
| 174 install_handlers () | |
| 175 { | |
| 176 size_t i; | |
| 177 | |
| 178 for (i = 0; i < num_fatal_signals; i++) | |
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179 if (fatal_signals[i] >= 0) |
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180 signal (fatal_signals[i], &fatal_signal_handler); |
| 4770 | 181 } |
| 182 | |
| 183 | |
| 184 /* Register a cleanup function to be executed when a catchable fatal signal | |
| 185 occurs. */ | |
| 186 void | |
| 187 at_fatal_signal (action_t action) | |
| 188 { | |
| 189 static bool cleanup_initialized = false; | |
| 190 if (!cleanup_initialized) | |
| 191 { | |
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192 init_fatal_signals (); |
| 4770 | 193 install_handlers (); |
| 194 cleanup_initialized = true; | |
| 195 } | |
| 196 | |
| 197 if (actions_count == actions_allocated) | |
| 198 { | |
| 199 /* Extend the actions array. Note that we cannot use xrealloc(), | |
| 200 because then the cleanup() function could access an already | |
| 201 deallocated array. */ | |
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202 actions_entry_t *old_actions = actions; |
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203 size_t old_actions_allocated = actions_allocated; |
| 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)); |
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207 size_t k; |
| 4770 | 208 |
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209 /* Don't use memcpy() here, because memcpy takes non-volatile arguments |
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210 and is therefore not guaranteed to complete all memory stores before |
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211 the next statement. */ |
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212 for (k = 0; k < old_actions_allocated; k++) |
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213 new_actions[k] = old_actions[k]; |
| 4770 | 214 actions = new_actions; |
| 215 actions_allocated = new_actions_allocated; | |
| 216 /* Now we can free the old actions array. */ | |
| 217 if (old_actions != static_actions) | |
| 218 free (old_actions); | |
| 219 } | |
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220 /* The two uses of 'volatile' in the types above (and ISO C 99 section |
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221 5.1.2.3.(5)) ensure that we increment the actions_count only after |
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222 the new action has been written to the memory location |
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223 actions[actions_count]. */ |
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224 actions[actions_count].action = action; |
| 4770 | 225 actions_count++; |
| 226 } | |
| 227 | |
| 228 | |
| 229 /* ========================================================================= */ | |
| 230 | |
| 231 | |
| 232 #if HAVE_POSIX_SIGNALBLOCKING | |
| 233 | |
| 234 static sigset_t fatal_signal_set; | |
| 235 | |
| 236 static void | |
| 237 init_fatal_signal_set () | |
| 238 { | |
| 239 static bool fatal_signal_set_initialized = false; | |
| 240 if (!fatal_signal_set_initialized) | |
| 241 { | |
| 242 size_t i; | |
| 243 | |
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244 init_fatal_signals (); |
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245 |
| 4770 | 246 sigemptyset (&fatal_signal_set); |
| 247 for (i = 0; i < num_fatal_signals; i++) | |
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248 if (fatal_signals[i] >= 0) |
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249 sigaddset (&fatal_signal_set, fatal_signals[i]); |
| 4770 | 250 |
| 251 fatal_signal_set_initialized = true; | |
| 252 } | |
| 253 } | |
| 254 | |
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255 /* Temporarily delay the catchable fatal signals. */ |
| 4770 | 256 void |
| 257 block_fatal_signals () | |
| 258 { | |
| 259 init_fatal_signal_set (); | |
| 260 sigprocmask (SIG_BLOCK, &fatal_signal_set, NULL); | |
| 261 } | |
| 262 | |
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263 /* Stop delaying the catchable fatal signals. */ |
| 4770 | 264 void |
| 265 unblock_fatal_signals () | |
| 266 { | |
| 267 init_fatal_signal_set (); | |
| 268 sigprocmask (SIG_UNBLOCK, &fatal_signal_set, NULL); | |
| 269 } | |
| 270 | |
| 271 #else | |
| 272 | |
| 273 /* Don't bother caring about the old systems which don't have POSIX signal | |
| 274 blocking. */ | |
| 275 | |
| 276 void | |
| 277 block_fatal_signals () | |
| 278 { | |
| 279 } | |
| 280 | |
| 281 void | |
| 282 unblock_fatal_signals () | |
| 283 { | |
| 284 } | |
| 285 | |
| 286 #endif |