libguile/scmsigs.c

   1 /* Copyright (C) 1995, 1996, 1997, 1998, 1999 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 /* Software engineering face-lift by Greg J. Badros, 11-Dec-1999,
  43    gjb@cs.washington.edu, http://www.cs.washington.edu/homes/gjb */
  44
  45 \f
  46
  47 #include <stdio.h>
  48 #include <signal.h>
  49 #include "_scm.h"
  50
  51 #include "async.h"
  52 #include "eval.h"
  53
  54 #include "scm_validate.h"
  55 #include "scmsigs.h"
  56
  57 #ifdef HAVE_UNISTD_H
  58 #include <unistd.h>
  59 #endif
  60
  61 /* The thread system has its own sleep and usleep functions.  */
  62 #ifndef USE_THREADS
  63
  64 #if defined(MISSING_SLEEP_DECL)
  65 int sleep ();
  66 #endif
  67
  68 #if defined(HAVE_USLEEP) && defined(MISSING_USLEEP_DECL)
  69 int usleep ();
  70 #endif
  71
  72 #endif
  73
  74 \f
  75
  76 #ifdef USE_MIT_PTHREADS
  77 #undef signal
  78 #define signal pthread_signal
  79 #endif
  80
  81 \f
  82
  83 /* SIGRETTYPE is the type that signal handlers return.  See <signal.h> */
  84
  85 #ifdef RETSIGTYPE
  86 # define SIGRETTYPE RETSIGTYPE
  87 #else
  88 # ifdef STDC_HEADERS
  89 #  define SIGRETTYPE void
  90 # else
  91 #  define SIGRETTYPE int
  92 # endif
  93 #endif
  94
  95 \f
  96
  97 /* take_signal is installed as the C signal handler whenever a Scheme
  98    handler is set.  when a signal arrives, take_signal marks the corresponding
  99    element of got_signal and marks signal_async.  the thunk in signal_async
 100    (sys_deliver_signals) will be run at the next opportunity, outside a
 101    critical section. sys_deliver_signals runs each Scheme handler for
 102    which got_signal is set.  */
 103
 104 static SCM signal_async;
 105
 106 static char got_signal[NSIG];
 107
 108 /* a Scheme vector of handler procedures.  */
 109 static SCM *signal_handlers;
 110
 111 /* saves the original C handlers, when a new handler is installed.
 112    set to SIG_ERR if the original handler is installed.  */
 113 #ifdef HAVE_SIGACTION
 114 static struct sigaction orig_handlers[NSIG];
 115 #else
 116 static SIGRETTYPE (*orig_handlers)(int)[NSIG];
 117 #endif
 118
 119 static SIGRETTYPE
 120 take_signal (int signum)
 121 {
 122   int saved_errno = errno;
 123   SCM ignored;
 124   if (!scm_ints_disabled)
 125     {
 126       /* For reasons of speed, the SCM_NEWCELL macro doesn't defer
 127          interrupts.  Instead, it first sets its argument to point to
 128          the first cell in the list, and then advances the freelist
 129          pointer to the next cell.  Now, if this procedure is
 130          interrupted, the only anomalous state possible is to have
 131          both SCM_NEWCELL's argument and scm_freelist pointing to the
 132          same cell.  To deal with this case, we always throw away the
 133          first cell in scm_freelist here.
 134
 135          At least, that's the theory.  I'm not convinced that that's
 136          the only anomalous path we need to worry about.  */
 137       SCM_NEWCELL (ignored);
 138     }
 139   got_signal[signum] = 1;
 140 #if HAVE_SIGACTION
 141   /* unblock the signal before the scheme handler gets to run, since
 142      it may use longjmp to escape (i.e., throw an exception).  */
 143   {
 144     sigset_t set;
 145     sigemptyset (&set);
 146     sigaddset (&set, signum);
 147     sigprocmask (SIG_UNBLOCK, &set, NULL);
 148   }
 149 #endif
 150   scm_system_async_mark (signal_async);
 151   errno = saved_errno;
 152 }
 153
 154 static SCM
 155 sys_deliver_signals (void)
 156 {
 157   int i;
 158
 159   for (i = 0; i < NSIG; i++)
 160     {
 161       if (got_signal[i])
 162         {
 163           /* The flag is reset before calling the handler in case the
 164              handler doesn't return.  If the handler doesn't return
 165              but leaves other signals flagged, they their handlers
 166              will be applied some time later when the async is checked
 167              again.  It would probably be better to reset the flags
 168              after doing a longjmp.  */
 169           got_signal[i] = 0;
 170 #ifndef HAVE_SIGACTION
 171           signal (i, take_signal);
 172 #endif
 173           scm_apply (SCM_VELTS (*signal_handlers)[i],
 174                      scm_listify (SCM_MAKINUM (i), SCM_UNDEFINED),
 175                      SCM_EOL);
 176         }
 177     }
 178   return SCM_UNSPECIFIED;
 179 }
 180
 181 /* user interface for installation of signal handlers.  */
 182 SCM_DEFINE (scm_sigaction, "sigaction", 1, 2, 0,
 183            (SCM signum, SCM handler, SCM flags),
 184             "Install or report the signal hander for a specified signal.\n\n"
 185             "@var{signum} is the signal number, which can be specified using the value\n"
 186             "of variables such as @code{SIGINT}.\n\n"
 187             "If @var{action} is omitted, @code{sigaction} returns a pair: the\n"
 188             "CAR is the current\n"
 189             "signal hander, which will be either an integer with the value @code{SIG_DFL}\n"
 190             "(default action) or @code{SIG_IGN} (ignore), or the Scheme procedure which\n"
 191             "handles the signal, or @code{#f} if a non-Scheme procedure handles the\n"
 192             "signal.  The CDR contains the current @code{sigaction} flags for the handler.\n\n"
 193             "If @var{action} is provided, it is installed as the new handler for\n"
 194             "@var{signum}.  @var{action} can be a Scheme procedure taking one\n"
 195             "argument, or the value of @code{SIG_DFL} (default action) or\n"
 196             "@code{SIG_IGN} (ignore), or @code{#f} to restore whatever signal handler\n"
 197             "was installed before @code{sigaction} was first used.  Flags can\n"
 198             "optionally be specified for the new handler (@code{SA_RESTART} will\n"
 199             "always be added if it's available and the system is using rstartable\n"
 200             "system calls.)  The return value is a pair with information about the\n"
 201             "old handler as described above.\n\n"
 202             "This interface does not provide access to the \"signal blocking\"\n"
 203             "facility.  Maybe this is not needed, since the thread support may\n"
 204             "provide solutions to the problem of consistent access to data\n"
 205             "structures.")
 206 #define FUNC_NAME s_scm_sigaction
 207 {
 208   int csig;
 209 #ifdef HAVE_SIGACTION
 210   struct sigaction action;
 211   struct sigaction old_action;
 212 #else
 213   SIGRETTYPE (* chandler) (int);
 214   SIGRETTYPE (* old_chandler) (int);
 215 #endif
 216   int query_only = 0;
 217   int save_handler = 0;
 218   SCM *scheme_handlers = SCM_VELTS (*signal_handlers);
 219   SCM old_handler;
 220
 221   SCM_VALIDATE_INUM_COPY (1,signum,csig);
 222 #if defined(HAVE_SIGACTION)
 223 #if defined(SA_RESTART) && defined(HAVE_RESTARTABLE_SYSCALLS)
 224   /* don't allow SA_RESTART to be omitted if HAVE_RESTARTABLE_SYSCALLS
 225      is defined, since libguile would be likely to produce spurious
 226      EINTR errors.  */
 227   action.sa_flags = SA_RESTART;
 228 #else
 229   action.sa_flags = 0;
 230 #endif
 231   if (!SCM_UNBNDP (flags))
 232     {
 233       SCM_VALIDATE_INUM (3,flags);
 234       action.sa_flags |= SCM_INUM (flags);
 235     }
 236   sigemptyset (&action.sa_mask);
 237 #endif
 238   SCM_DEFER_INTS;
 239   old_handler = scheme_handlers[csig];
 240   if (SCM_UNBNDP (handler))
 241     query_only = 1;
 242   else if (scm_integer_p (handler) == SCM_BOOL_T)
 243     {
 244       if (SCM_NUM2LONG (2,handler) == (long) SIG_DFL
 245           || SCM_NUM2LONG (2,handler) == (long) SIG_IGN)
 246         {
 247 #ifdef HAVE_SIGACTION
 248           action.sa_handler = (SIGRETTYPE (*) (int)) SCM_INUM (handler);
 249 #else
 250           chandler = (SIGRETTYPE (*) (int)) SCM_INUM (handler);
 251 #endif
 252           scheme_handlers[csig] = SCM_BOOL_F;
 253         }
 254       else
 255         SCM_OUT_OF_RANGE (2, handler);
 256     }
 257   else if (SCM_FALSEP (handler))
 258     {
 259       /* restore the default handler.  */
 260 #ifdef HAVE_SIGACTION
 261       if (orig_handlers[csig].sa_handler == SIG_ERR)
 262         query_only = 1;
 263       else
 264         {
 265           action = orig_handlers[csig];
 266           orig_handlers[csig].sa_handler = SIG_ERR;
 267           scheme_handlers[csig] = SCM_BOOL_F;
 268         }
 269 #else
 270       if (orig_handlers[csig] == SIG_ERR)
 271         query_only = 1;
 272       else
 273         {
 274           chandler = orig_handlers[csig];
 275           orig_handlers[csig] = SIG_ERR;
 276           scheme_handlers[csig] = SCM_BOOL_F;
 277         }
 278 #endif
 279     }
 280   else
 281     {
 282       SCM_VALIDATE_NIM (2,handler);
 283 #ifdef HAVE_SIGACTION
 284       action.sa_handler = take_signal;
 285       if (orig_handlers[csig].sa_handler == SIG_ERR)
 286         save_handler = 1;
 287 #else
 288       chandler = take_signal;
 289       if (orig_handlers[csig] == SIG_ERR)
 290         save_handler = 1;
 291 #endif
 292       scheme_handlers[csig] = handler;
 293     }
 294 #ifdef HAVE_SIGACTION
 295   if (query_only)
 296     {
 297       if (sigaction (csig, 0, &old_action) == -1)
 298         SCM_SYSERROR;
 299     }
 300   else
 301     {
 302       if (sigaction (csig, &action , &old_action) == -1)
 303         SCM_SYSERROR;
 304       if (save_handler)
 305         orig_handlers[csig] = old_action;
 306     }
 307   if (old_action.sa_handler == SIG_DFL || old_action.sa_handler == SIG_IGN)
 308     old_handler = scm_long2num ((long) old_action.sa_handler);
 309   SCM_ALLOW_INTS;
 310   return scm_cons (old_handler, SCM_MAKINUM (old_action.sa_flags));
 311 #else
 312   if (query_only)
 313     {
 314       if ((old_chandler = signal (csig, SIG_IGN)) == SIG_ERR)
 315         SCM_SYSERROR;
 316       if (signal (csig, old_chandler) == SIG_ERR)
 317         SCM_SYSERROR;
 318     }
 319   else
 320     {
 321       if ((old_chandler = signal (csig, chandler)) == SIG_ERR)
 322         SCM_SYSERROR;
 323       if (save_handler)
 324         orig_handlers[csig] = old_chandler;
 325     }
 326   if (old_chandler == SIG_DFL || old_chandler == SIG_IGN)
 327     old_handler = scm_long2num (old_chandler);
 328   SCM_ALLOW_INTS;
 329   return scm_cons (old_handler, SCM_MAKINUM (0));
 330 #endif
 331 }
 332 #undef FUNC_NAME
 333
 334 SCM_DEFINE (scm_restore_signals, "restore-signals", 0, 0, 0,
 335             (void),
 336             "Return all signal handlers to the values they had before any call to\n"
 337             "@code{sigaction} was made.  The return value is unspecified.")
 338 #define FUNC_NAME s_scm_restore_signals
 339 {
 340   int i;
 341   SCM *scheme_handlers = SCM_VELTS (*signal_handlers);
 342
 343   for (i = 0; i < NSIG; i++)
 344     {
 345 #ifdef HAVE_SIGACTION
 346       if (orig_handlers[i].sa_handler != SIG_ERR)
 347         {
 348           if (sigaction (i, &orig_handlers[i], NULL) == -1)
 349             SCM_SYSERROR;
 350           orig_handlers[i].sa_handler = SIG_ERR;
 351           scheme_handlers[i] = SCM_BOOL_F;
 352         }
 353 #else
 354       if (orig_handlers[i] != SIG_ERR)
 355         {
 356           if (signal (i, orig_handlers[i]) == SIG_ERR)
 357             SCM_SYSERROR;
 358           orig_handlers[i] = SIG_ERR;
 359           scheme_handlers[i] = SCM_BOOL_F;
 360         }
 361 #endif
 362     }
 363   return SCM_UNSPECIFIED;
 364 }
 365 #undef FUNC_NAME
 366
 367 SCM_DEFINE (scm_alarm, "alarm", 1, 0, 0,
 368            (SCM i),
 369             "Set a timer to raise a @code{SIGALRM} signal after the specified\n"
 370             "number of seconds (an integer).  It's advisable to install a signal\n"
 371             "handler for\n"
 372             "@code{SIGALRM} beforehand, since the default action is to terminate\n"
 373             "the process.\n\n"
 374             "The return value indicates the time remaining for the previous alarm,\n"
 375             "if any.  The new value replaces the previous alarm.  If there was\n"
 376             "no previous alarm, the return value is zero.")
 377 #define FUNC_NAME s_scm_alarm
 378 {
 379   unsigned int j;
 380   SCM_VALIDATE_INUM (1,i);
 381   j = alarm (SCM_INUM (i));
 382   return SCM_MAKINUM (j);
 383 }
 384 #undef FUNC_NAME
 385
 386 #ifdef HAVE_PAUSE
 387 SCM_DEFINE (scm_pause, "pause", 0, 0, 0,
 388            (),
 389             "Pause the current process (thread?) until a signal arrives whose\n"
 390             "action is to either terminate the current process or invoke a\n"
 391             "handler procedure.  The return value is unspecified.")
 392 #define FUNC_NAME s_scm_pause
 393 {
 394   pause ();
 395   return SCM_UNSPECIFIED;
 396 }
 397 #undef FUNC_NAME
 398 #endif
 399
 400 SCM_DEFINE (scm_sleep, "sleep", 1, 0, 0,
 401            (SCM i),
 402             "Wait for the given number of seconds (an integer) or until a signal\n"
 403             "arrives.  The return value is zero if the time elapses or the number\n"
 404             "of seconds remaining otherwise.")
 405 #define FUNC_NAME s_scm_sleep
 406 {
 407   unsigned long j;
 408   SCM_VALIDATE_INUM_MIN (1,i,0);
 409 #ifdef USE_THREADS
 410   j = scm_thread_sleep (SCM_INUM(i));
 411 #else
 412   j = sleep (SCM_INUM(i));
 413 #endif
 414   return scm_ulong2num (j);
 415 }
 416 #undef FUNC_NAME
 417
 418 #if defined(USE_THREADS) || defined(HAVE_USLEEP)
 419 SCM_DEFINE (scm_usleep, "usleep", 1, 0, 0,
 420            (SCM i),
 421             "Sleep for I microseconds.\n"
 422             "`usleep' is not available on all platforms.")
 423 #define FUNC_NAME s_scm_usleep
 424 {
 425   SCM_VALIDATE_INUM_MIN (1,i,0);
 426
 427 #ifdef USE_THREADS
 428   /* If we have threads, we use the thread system's sleep function.  */
 429   {
 430     unsigned long j = scm_thread_usleep (SCM_INUM (i));
 431     return scm_ulong2num (j);
 432   }
 433 #else
 434 #ifdef USLEEP_RETURNS_VOID
 435   usleep (SCM_INUM (i));
 436   return SCM_INUM0;
 437 #else
 438   {
 439     int j = usleep (SCM_INUM (i));
 440     return SCM_MAKINUM (j);
 441   }
 442 #endif
 443 #endif
 444 }
 445 #undef FUNC_NAME
 446 #endif /* GUILE_ISELECT || HAVE_USLEEP */
 447
 448 SCM_DEFINE (scm_raise, "raise", 1, 0, 0,
 449            (SCM sig),
 450             "\n"
 451             "Sends a specified signal @var{sig} to the current process, where\n"
 452             "@var{sig} is as described for the kill procedure.")
 453 #define FUNC_NAME s_scm_raise
 454 {
 455   SCM_VALIDATE_INUM (1,sig);
 456   SCM_DEFER_INTS;
 457   if (kill (getpid (), (int) SCM_INUM (sig)) != 0)
 458     SCM_SYSERROR;
 459   SCM_ALLOW_INTS;
 460   return SCM_UNSPECIFIED;
 461 }
 462 #undef FUNC_NAME
 463
 464 \f
 465
 466 void
 467 scm_init_scmsigs ()
 468 {
 469   SCM thunk;
 470   int i;
 471
 472   signal_handlers =
 473     SCM_CDRLOC (scm_sysintern ("signal-handlers",
 474                                scm_make_vector (SCM_MAKINUM (NSIG),
 475                                                 SCM_BOOL_F)));
 476   thunk = scm_make_gsubr ("%deliver-signals", 0, 0, 0,
 477                           sys_deliver_signals);
 478   signal_async = scm_system_async (thunk);
 479
 480   for (i = 0; i < NSIG; i++)
 481     {
 482       got_signal[i] = 0;
 483 #ifdef HAVE_SIGACTION
 484       orig_handlers[i].sa_handler = SIG_ERR;
 485
 486 #else
 487       orig_handlers[i] = SIG_ERR;
 488 #endif
 489
 490 #ifdef HAVE_RESTARTABLE_SYSCALLS
 491       /* If HAVE_RESTARTABLE_SYSCALLS is defined, it's important that
 492          signals really are restartable.  don't rely on the same
 493          run-time that configure got: reset the default for every signal.
 494       */
 495 #ifdef HAVE_SIGINTERRUPT
 496       siginterrupt (i, 0);
 497 #elif defined(SA_RESTART)
 498       {
 499         struct sigaction action;
 500
 501         sigaction (i, NULL, &action);
 502         if (!(action.sa_flags & SA_RESTART))
 503           {
 504             action.sa_flags &= SA_RESTART;
 505             sigaction (i, &action, NULL);
 506           }
 507       }
 508 #endif
 509       /* if neither siginterrupt nor SA_RESTART are available we may
 510          as well assume that signals are always restartable.  */
 511 #endif
 512     }
 513
 514   scm_sysintern ("NSIG", scm_long2num (NSIG));
 515   scm_sysintern ("SIG_IGN", scm_long2num ((long) SIG_IGN));
 516   scm_sysintern ("SIG_DFL", scm_long2num ((long) SIG_DFL));
 517 #ifdef SA_NOCLDSTOP
 518   scm_sysintern ("SA_NOCLDSTOP", scm_long2num (SA_NOCLDSTOP));
 519 #endif
 520 #ifdef SA_RESTART
 521   scm_sysintern ("SA_RESTART", scm_long2num (SA_RESTART));
 522 #endif
 523
 524 #include "scmsigs.x"
 525 }
 526