libguile/scmsigs.c

   1 /* Copyright (C) 1995,1996,1997,1998,1999,2000,2001 Free Software Foundation, Inc.
   2  *
   3  * This program is free software; you can redistribute it and/or modify
   4  * it under the terms of the GNU General Public License as published by
   5  * the Free Software Foundation; either version 2, or (at your option)
   6  * any later version.
   7  *
   8  * This program is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11  * GNU General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU General Public License
  14  * along with this software; see the file COPYING.  If not, write to
  15  * the Free Software Foundation, Inc., 59 Temple Place, Suite 330,
  16  * Boston, MA 02111-1307 USA
  17  *
  18  * As a special exception, the Free Software Foundation gives permission
  19  * for additional uses of the text contained in its release of GUILE.
  20  *
  21  * The exception is that, if you link the GUILE library with other files
  22  * to produce an executable, this does not by itself cause the
  23  * resulting executable to be covered by the GNU General Public License.
  24  * Your use of that executable is in no way restricted on account of
  25  * linking the GUILE library code into it.
  26  *
  27  * This exception does not however invalidate any other reasons why
  28  * the executable file might be covered by the GNU General Public License.
  29  *
  30  * This exception applies only to the code released by the
  31  * Free Software Foundation under the name GUILE.  If you copy
  32  * code from other Free Software Foundation releases into a copy of
  33  * GUILE, as the General Public License permits, the exception does
  34  * not apply to the code that you add in this way.  To avoid misleading
  35  * anyone as to the status of such modified files, you must delete
  36  * this exception notice from them.
  37  *
  38  * If you write modifications of your own for GUILE, it is your choice
  39  * whether to permit this exception to apply to your modifications.
  40  * If you do not wish that, delete this exception notice.  */
  41
  42
  43 \f
  44
  45 #include <signal.h>
  46 #include <errno.h>
  47
  48 #include "libguile/_scm.h"
  49
  50 #include "libguile/async.h"
  51 #include "libguile/eval.h"
  52 #include "libguile/root.h"
  53 #include "libguile/vectors.h"
  54
  55 #include "libguile/validate.h"
  56 #include "libguile/scmsigs.h"
  57
  58 #ifdef HAVE_UNISTD_H
  59 #include <unistd.h>
  60 #endif
  61
  62 /* The thread system has its own sleep and usleep functions.  */
  63 #ifndef USE_THREADS
  64
  65 #if defined(MISSING_SLEEP_DECL)
  66 int sleep ();
  67 #endif
  68
  69 #if defined(HAVE_USLEEP) && defined(MISSING_USLEEP_DECL)
  70 int usleep ();
  71 #endif
  72
  73 #endif
  74
  75 #ifdef __MINGW32__
  76 #include <windows.h>
  77 #define alarm(sec) (0)
  78 /* This weird comma expression is because Sleep is void under Windows. */
  79 #define sleep(sec) (Sleep ((sec) * 1000), 0)
  80 #define kill(pid, sig) raise (sig)
  81 #endif
  82
  83 \f
  84
  85 /* SIGRETTYPE is the type that signal handlers return.  See <signal.h> */
  86
  87 #ifdef RETSIGTYPE
  88 # define SIGRETTYPE RETSIGTYPE
  89 #else
  90 # ifdef STDC_HEADERS
  91 #  define SIGRETTYPE void
  92 # else
  93 #  define SIGRETTYPE int
  94 # endif
  95 #endif
  96
  97 \f
  98
  99 /* take_signal is installed as the C signal handler whenever a Scheme
 100    handler is set.  when a signal arrives, take_signal marks the corresponding
 101    element of got_signal and marks signal_async.  the thunk in signal_async
 102    (sys_deliver_signals) will be run at the next opportunity, outside a
 103    critical section. sys_deliver_signals runs each Scheme handler for
 104    which got_signal is set.  */
 105
 106 static SCM signal_async;
 107
 108 static char got_signal[NSIG];
 109
 110 /* a Scheme vector of handler procedures.  */
 111 static SCM *signal_handlers;
 112
 113 /* saves the original C handlers, when a new handler is installed.
 114    set to SIG_ERR if the original handler is installed.  */
 115 #ifdef HAVE_SIGACTION
 116 static struct sigaction orig_handlers[NSIG];
 117 #else
 118 static SIGRETTYPE (*orig_handlers[NSIG])(int);
 119 #endif
 120
 121 static SIGRETTYPE
 122 take_signal (int signum)
 123 {
 124   int saved_errno = errno;
 125   SCM ignored;
 126
 127   if (!scm_ints_disabled)
 128     {
 129       /* For reasons of speed, the SCM_NEWCELL macro doesn't defer
 130          interrupts.  Instead, it first sets its argument to point to
 131          the first cell in the list, and then advances the freelist
 132          pointer to the next cell.  Now, if this procedure is
 133          interrupted, the only anomalous state possible is to have
 134          both SCM_NEWCELL's argument and scm_freelist pointing to the
 135          same cell.  To deal with this case, we always throw away the
 136          first cell in scm_freelist here.
 137
 138          At least, that's the theory.  I'm not convinced that that's
 139          the only anomalous path we need to worry about.  */
 140       SCM_NEWCELL (ignored);
 141     }
 142   got_signal[signum] = 1;
 143 #if HAVE_SIGACTION
 144   /* unblock the signal before the scheme handler gets to run, since
 145      it may use longjmp to escape (i.e., throw an exception).  */
 146   {
 147     sigset_t set;
 148     sigemptyset (&set);
 149     sigaddset (&set, signum);
 150     sigprocmask (SIG_UNBLOCK, &set, NULL);
 151   }
 152 #endif
 153   scm_system_async_mark (signal_async);
 154   errno = saved_errno;
 155 }
 156
 157 static SCM
 158 sys_deliver_signals (void)
 159 {
 160   int i;
 161
 162   for (i = 0; i < NSIG; i++)
 163     {
 164       if (got_signal[i])
 165         {
 166           /* The flag is reset before calling the handler in case the
 167              handler doesn't return.  If the handler doesn't return
 168              but leaves other signals flagged, they their handlers
 169              will be applied some time later when the async is checked
 170              again.  It would probably be better to reset the flags
 171              after doing a longjmp.  */
 172           got_signal[i] = 0;
 173 #ifndef HAVE_SIGACTION
 174           signal (i, take_signal);
 175 #endif
 176           scm_call_1 (SCM_VELTS (*signal_handlers)[i], SCM_MAKINUM (i));
 177         }
 178     }
 179   return SCM_UNSPECIFIED;
 180 }
 181
 182 /* user interface for installation of signal handlers.  */
 183 SCM_DEFINE (scm_sigaction, "sigaction", 1, 2, 0,
 184            (SCM signum, SCM handler, SCM flags),
 185             "Install or report the signal handler for a specified signal.\n\n"
 186             "@var{signum} is the signal number, which can be specified using the value\n"
 187             "of variables such as @code{SIGINT}.\n\n"
 188             "If @var{action} is omitted, @code{sigaction} returns a pair: the\n"
 189             "CAR is the current\n"
 190             "signal hander, which will be either an integer with the value @code{SIG_DFL}\n"
 191             "(default action) or @code{SIG_IGN} (ignore), or the Scheme procedure which\n"
 192             "handles the signal, or @code{#f} if a non-Scheme procedure handles the\n"
 193             "signal.  The CDR contains the current @code{sigaction} flags for the handler.\n\n"
 194             "If @var{action} is provided, it is installed as the new handler for\n"
 195             "@var{signum}.  @var{action} can be a Scheme procedure taking one\n"
 196             "argument, or the value of @code{SIG_DFL} (default action) or\n"
 197             "@code{SIG_IGN} (ignore), or @code{#f} to restore whatever signal handler\n"
 198             "was installed before @code{sigaction} was first used.  Flags can\n"
 199             "optionally be specified for the new handler (@code{SA_RESTART} will\n"
 200             "always be added if it's available and the system is using restartable\n"
 201             "system calls.)  The return value is a pair with information about the\n"
 202             "old handler as described above.\n\n"
 203             "This interface does not provide access to the \"signal blocking\"\n"
 204             "facility.  Maybe this is not needed, since the thread support may\n"
 205             "provide solutions to the problem of consistent access to data\n"
 206             "structures.")
 207 #define FUNC_NAME s_scm_sigaction
 208 {
 209   int csig;
 210 #ifdef HAVE_SIGACTION
 211   struct sigaction action;
 212   struct sigaction old_action;
 213 #else
 214   SIGRETTYPE (* chandler) (int);
 215   SIGRETTYPE (* old_chandler) (int);
 216 #endif
 217   int query_only = 0;
 218   int save_handler = 0;
 219   SCM *scheme_handlers = SCM_VELTS (*signal_handlers);
 220   SCM old_handler;
 221
 222   SCM_VALIDATE_INUM_COPY (1,signum,csig);
 223 #if defined(HAVE_SIGACTION)
 224 #if defined(SA_RESTART) && defined(HAVE_RESTARTABLE_SYSCALLS)
 225   /* don't allow SA_RESTART to be omitted if HAVE_RESTARTABLE_SYSCALLS
 226      is defined, since libguile would be likely to produce spurious
 227      EINTR errors.  */
 228   action.sa_flags = SA_RESTART;
 229 #else
 230   action.sa_flags = 0;
 231 #endif
 232   if (!SCM_UNBNDP (flags))
 233     {
 234       SCM_VALIDATE_INUM (3,flags);
 235       action.sa_flags |= SCM_INUM (flags);
 236     }
 237   sigemptyset (&action.sa_mask);
 238 #endif
 239   SCM_DEFER_INTS;
 240   old_handler = scheme_handlers[csig];
 241   if (SCM_UNBNDP (handler))
 242     query_only = 1;
 243   else if (SCM_EQ_P (scm_integer_p (handler), SCM_BOOL_T))
 244     {
 245       if (SCM_NUM2LONG (2, handler) == (long) SIG_DFL
 246           || SCM_NUM2LONG (2, handler) == (long) SIG_IGN)
 247         {
 248 #ifdef HAVE_SIGACTION
 249           action.sa_handler = (SIGRETTYPE (*) (int)) SCM_INUM (handler);
 250 #else
 251           chandler = (SIGRETTYPE (*) (int)) SCM_INUM (handler);
 252 #endif
 253           scheme_handlers[csig] = SCM_BOOL_F;
 254         }
 255       else
 256         SCM_OUT_OF_RANGE (2, handler);
 257     }
 258   else if (SCM_FALSEP (handler))
 259     {
 260       /* restore the default handler.  */
 261 #ifdef HAVE_SIGACTION
 262       if (orig_handlers[csig].sa_handler == SIG_ERR)
 263         query_only = 1;
 264       else
 265         {
 266           action = orig_handlers[csig];
 267           orig_handlers[csig].sa_handler = SIG_ERR;
 268           scheme_handlers[csig] = SCM_BOOL_F;
 269         }
 270 #else
 271       if (orig_handlers[csig] == SIG_ERR)
 272         query_only = 1;
 273       else
 274         {
 275           chandler = orig_handlers[csig];
 276           orig_handlers[csig] = SIG_ERR;
 277           scheme_handlers[csig] = SCM_BOOL_F;
 278         }
 279 #endif
 280     }
 281   else
 282     {
 283       SCM_VALIDATE_NIM (2,handler);
 284 #ifdef HAVE_SIGACTION
 285       action.sa_handler = take_signal;
 286       if (orig_handlers[csig].sa_handler == SIG_ERR)
 287         save_handler = 1;
 288 #else
 289       chandler = take_signal;
 290       if (orig_handlers[csig] == SIG_ERR)
 291         save_handler = 1;
 292 #endif
 293       scheme_handlers[csig] = handler;
 294     }
 295
 296   /* XXX - Silently ignore setting handlers for `program error signals'
 297      because they can't currently be handled by Scheme code.
 298   */
 299
 300   switch (csig)
 301     {
 302       /* This list of program error signals is from the GNU Libc
 303          Reference Manual */
 304     case SIGFPE:
 305     case SIGILL:
 306     case SIGSEGV:
 307 #ifdef SIGBUS
 308     case SIGBUS:
 309 #endif
 310     case SIGABRT:
 311 #if defined(SIGIOT) && (SIGIOT != SIGABRT)
 312     case SIGIOT:
 313 #endif
 314 #ifdef SIGTRAP
 315     case SIGTRAP:
 316 #endif
 317 #ifdef SIGEMT
 318     case SIGEMT:
 319 #endif
 320 #ifdef SIGSYS
 321     case SIGSYS:
 322 #endif
 323       query_only = 1;
 324     }
 325
 326 #ifdef HAVE_SIGACTION
 327   if (query_only)
 328     {
 329       if (sigaction (csig, 0, &old_action) == -1)
 330         SCM_SYSERROR;
 331     }
 332   else
 333     {
 334       if (sigaction (csig, &action , &old_action) == -1)
 335         SCM_SYSERROR;
 336       if (save_handler)
 337         orig_handlers[csig] = old_action;
 338     }
 339   if (old_action.sa_handler == SIG_DFL || old_action.sa_handler == SIG_IGN)
 340     old_handler = scm_long2num ((long) old_action.sa_handler);
 341   SCM_ALLOW_INTS;
 342   return scm_cons (old_handler, SCM_MAKINUM (old_action.sa_flags));
 343 #else
 344   if (query_only)
 345     {
 346       if ((old_chandler = signal (csig, SIG_IGN)) == SIG_ERR)
 347         SCM_SYSERROR;
 348       if (signal (csig, old_chandler) == SIG_ERR)
 349         SCM_SYSERROR;
 350     }
 351   else
 352     {
 353       if ((old_chandler = signal (csig, chandler)) == SIG_ERR)
 354         SCM_SYSERROR;
 355       if (save_handler)
 356         orig_handlers[csig] = old_chandler;
 357     }
 358   if (old_chandler == SIG_DFL || old_chandler == SIG_IGN)
 359     old_handler = scm_long2num ((long) old_chandler);
 360   SCM_ALLOW_INTS;
 361   return scm_cons (old_handler, SCM_MAKINUM (0));
 362 #endif
 363 }
 364 #undef FUNC_NAME
 365
 366 SCM_DEFINE (scm_restore_signals, "restore-signals", 0, 0, 0,
 367             (void),
 368             "Return all signal handlers to the values they had before any call to\n"
 369             "@code{sigaction} was made.  The return value is unspecified.")
 370 #define FUNC_NAME s_scm_restore_signals
 371 {
 372   int i;
 373   SCM *scheme_handlers = SCM_VELTS (*signal_handlers);
 374
 375   for (i = 0; i < NSIG; i++)
 376     {
 377 #ifdef HAVE_SIGACTION
 378       if (orig_handlers[i].sa_handler != SIG_ERR)
 379         {
 380           if (sigaction (i, &orig_handlers[i], NULL) == -1)
 381             SCM_SYSERROR;
 382           orig_handlers[i].sa_handler = SIG_ERR;
 383           scheme_handlers[i] = SCM_BOOL_F;
 384         }
 385 #else
 386       if (orig_handlers[i] != SIG_ERR)
 387         {
 388           if (signal (i, orig_handlers[i]) == SIG_ERR)
 389             SCM_SYSERROR;
 390           orig_handlers[i] = SIG_ERR;
 391           scheme_handlers[i] = SCM_BOOL_F;
 392         }
 393 #endif
 394     }
 395   return SCM_UNSPECIFIED;
 396 }
 397 #undef FUNC_NAME
 398
 399 SCM_DEFINE (scm_alarm, "alarm", 1, 0, 0,
 400            (SCM i),
 401             "Set a timer to raise a @code{SIGALRM} signal after the specified\n"
 402             "number of seconds (an integer).  It's advisable to install a signal\n"
 403             "handler for\n"
 404             "@code{SIGALRM} beforehand, since the default action is to terminate\n"
 405             "the process.\n\n"
 406             "The return value indicates the time remaining for the previous alarm,\n"
 407             "if any.  The new value replaces the previous alarm.  If there was\n"
 408             "no previous alarm, the return value is zero.")
 409 #define FUNC_NAME s_scm_alarm
 410 {
 411   unsigned int j;
 412   SCM_VALIDATE_INUM (1,i);
 413   j = alarm (SCM_INUM (i));
 414   return SCM_MAKINUM (j);
 415 }
 416 #undef FUNC_NAME
 417
 418 #ifdef HAVE_PAUSE
 419 SCM_DEFINE (scm_pause, "pause", 0, 0, 0,
 420            (),
 421             "Pause the current process (thread?) until a signal arrives whose\n"
 422             "action is to either terminate the current process or invoke a\n"
 423             "handler procedure.  The return value is unspecified.")
 424 #define FUNC_NAME s_scm_pause
 425 {
 426   pause ();
 427   return SCM_UNSPECIFIED;
 428 }
 429 #undef FUNC_NAME
 430 #endif
 431
 432 SCM_DEFINE (scm_sleep, "sleep", 1, 0, 0,
 433            (SCM i),
 434             "Wait for the given number of seconds (an integer) or until a signal\n"
 435             "arrives.  The return value is zero if the time elapses or the number\n"
 436             "of seconds remaining otherwise.")
 437 #define FUNC_NAME s_scm_sleep
 438 {
 439   unsigned long j;
 440   SCM_VALIDATE_INUM_MIN (1,i,0);
 441 #ifdef USE_THREADS
 442   j = scm_thread_sleep (SCM_INUM(i));
 443 #else
 444   j = sleep (SCM_INUM(i));
 445 #endif
 446   return scm_ulong2num (j);
 447 }
 448 #undef FUNC_NAME
 449
 450 #if defined(USE_THREADS) || defined(HAVE_USLEEP)
 451 SCM_DEFINE (scm_usleep, "usleep", 1, 0, 0,
 452            (SCM i),
 453             "Sleep for I microseconds.  @code{usleep} is not available on\n"
 454             "all platforms.")
 455 #define FUNC_NAME s_scm_usleep
 456 {
 457   SCM_VALIDATE_INUM_MIN (1,i,0);
 458
 459 #ifdef USE_THREADS
 460   /* If we have threads, we use the thread system's sleep function.  */
 461   {
 462     unsigned long j = scm_thread_usleep (SCM_INUM (i));
 463     return scm_ulong2num (j);
 464   }
 465 #else
 466 #ifdef USLEEP_RETURNS_VOID
 467   usleep (SCM_INUM (i));
 468   return SCM_INUM0;
 469 #else
 470   {
 471     int j = usleep (SCM_INUM (i));
 472     return SCM_MAKINUM (j);
 473   }
 474 #endif
 475 #endif
 476 }
 477 #undef FUNC_NAME
 478 #endif /* GUILE_ISELECT || HAVE_USLEEP */
 479
 480 SCM_DEFINE (scm_raise, "raise", 1, 0, 0,
 481            (SCM sig),
 482             "Sends a specified signal @var{sig} to the current process, where\n"
 483             "@var{sig} is as described for the kill procedure.")
 484 #define FUNC_NAME s_scm_raise
 485 {
 486   SCM_VALIDATE_INUM (1,sig);
 487   SCM_DEFER_INTS;
 488   if (kill (getpid (), (int) SCM_INUM (sig)) != 0)
 489     SCM_SYSERROR;
 490   SCM_ALLOW_INTS;
 491   return SCM_UNSPECIFIED;
 492 }
 493 #undef FUNC_NAME
 494
 495 \f
 496
 497 void
 498 scm_init_scmsigs ()
 499 {
 500   SCM thunk;
 501   int i;
 502
 503   signal_handlers =
 504     SCM_VARIABLE_LOC (scm_c_define ("signal-handlers",
 505                                   scm_c_make_vector (NSIG, SCM_BOOL_F)));
 506   /* XXX - use scm_c_make_gsubr here instead of `define'? */
 507   thunk = scm_c_define_gsubr ("%deliver-signals", 0, 0, 0,
 508                               sys_deliver_signals);
 509   signal_async = scm_system_async (thunk);
 510
 511   for (i = 0; i < NSIG; i++)
 512     {
 513       got_signal[i] = 0;
 514 #ifdef HAVE_SIGACTION
 515       orig_handlers[i].sa_handler = SIG_ERR;
 516
 517 #else
 518       orig_handlers[i] = SIG_ERR;
 519 #endif
 520
 521 #ifdef HAVE_RESTARTABLE_SYSCALLS
 522       /* If HAVE_RESTARTABLE_SYSCALLS is defined, it's important that
 523          signals really are restartable.  don't rely on the same
 524          run-time that configure got: reset the default for every signal.
 525       */
 526 #ifdef HAVE_SIGINTERRUPT
 527       siginterrupt (i, 0);
 528 #elif defined(SA_RESTART)
 529       {
 530         struct sigaction action;
 531
 532         sigaction (i, NULL, &action);
 533         if (!(action.sa_flags & SA_RESTART))
 534           {
 535             action.sa_flags |= SA_RESTART;
 536             sigaction (i, &action, NULL);
 537           }
 538       }
 539 #endif
 540       /* if neither siginterrupt nor SA_RESTART are available we may
 541          as well assume that signals are always restartable.  */
 542 #endif
 543     }
 544
 545   scm_c_define ("NSIG", scm_long2num (NSIG));
 546   scm_c_define ("SIG_IGN", scm_long2num ((long) SIG_IGN));
 547   scm_c_define ("SIG_DFL", scm_long2num ((long) SIG_DFL));
 548 #ifdef SA_NOCLDSTOP
 549   scm_c_define ("SA_NOCLDSTOP", scm_long2num (SA_NOCLDSTOP));
 550 #endif
 551 #ifdef SA_RESTART
 552   scm_c_define ("SA_RESTART", scm_long2num (SA_RESTART));
 553 #endif
 554
 555 #ifndef SCM_MAGIC_SNARFER
 556 #include "libguile/scmsigs.x"
 557 #endif
 558 }
 559
 560
 561 /*
 562   Local Variables:
 563   c-file-style: "gnu"
 564   End:
 565 */