Source

xemacs-beta / src / signal.c

Full commit
  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
/* Handling asynchronous signals.
   Copyright (C) 1992, 1993, 1994 Free Software Foundation, Inc.
   Copyright (C) 1995, 1996, 2001, 2002, 2004, 2010 Ben Wing.

This file is part of XEmacs.

XEmacs is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation; either version 2, or (at your option) any
later version.

XEmacs is distributed in the hope that it will be useful, but WITHOUT
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
for more details.

You should have received a copy of the GNU General Public License
along with XEmacs; see the file COPYING.  If not, write to
the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.  */

/* Synched up with: Not synched with FSF.  Split out of keyboard.c. */

#include <config.h>
#include "lisp.h"

#include "console.h"
#include "device-impl.h"
#include "events.h" /* for signal_fake_event() */
#include "frame-impl.h"
#include "process.h"

#include "sysdep.h"
#include "sysfile.h"
#include "syssignal.h"
#include "systime.h"

/* Set to 1 when a quit-check signal (either a SIGIO interrupt or
   the asynch. timeout for poll-for-quit) occurs.  The QUITP
   macro may look at this. */
volatile int quit_check_signal_happened;

/* Count of the number of times a quit-check signal has occurred.
   Some stuff in event-Xt.c looks at this. */
volatile int quit_check_signal_tick_count;

/* Set to 1 when a SIGINT (or SIGQUIT) interrupt is processed.
   maybe_read_quit_event() looks at this. */
volatile int sigint_happened;

/* Set to 1 when an asynch. timeout signal occurs. */
static volatile int async_timeout_happened;

/* Set to 1 when a multiple of SLOWED_DOWN_INTERRUPTS_SECS elapses,
   after slow_down_interrupts() is called. */
static volatile int slowed_interrupt_timeout_happened;

/* This is used to synchronize setting the waiting_for_user_input_p
   flag. */
static volatile int async_timeout_happened_while_emacs_was_blocking;

/* See check_quit() for when this is set. */
int dont_check_for_quit;

static int poll_for_quit_id;
static int poll_for_sigchld_id;

/* This variable is used to communicate to a lisp
   process-filter/sentinel/asynchronous callback (via the function
   Fwaiting_for_user_input_p below) whether XEmacs was waiting for
   user-input when that process-filter was called. */
static int waiting_for_user_input_p;

static int interrupts_slowed_down;

#define SLOWED_DOWN_INTERRUPTS_SECS 15
#define NORMAL_QUIT_CHECK_TIMEOUT_MSECS 250
#define NORMAL_SIGCHLD_CHECK_TIMEOUT_MSECS 250

/* Used so that signals can break out of system calls that aren't
   naturally interruptible. */

JMP_BUF break_system_call_jump;
volatile int can_break_system_calls;

static SIGTYPE alarm_signal (int signo);



/**********************************************************************/
/*                  Asynchronous timeout functions                    */
/**********************************************************************/

/* See the comment in event-stream.c, under major heading "Timeouts",
   for the difference between low-level (one-shot) and high-level
   (periodic/resignaling) timeouts. */

/* The pending timers are stored in an ordered list, where the first timer
   on the list is the first one to fire.  Times recorded here are
   absolute. */
static struct low_level_timeout *async_timer_queue;

/* Nonzero means async timers are temporarily suppressed.  */
static int async_timer_suppress_count;

static void
set_one_shot_timer (EMACS_TIME interval)
{
#ifdef HAVE_SETITIMER
  struct itimerval it;
  it.it_value = interval;
  EMACS_SET_SECS_USECS (it.it_interval, 0, 0);
  qxe_setitimer (ITIMER_REAL, &it, 0);
#else
  int secs;
  EMACS_TIME_TO_INT (interval, secs);
  alarm (secs);
#endif
}

static void
reset_interval_timer (void)
{
  EMACS_TIME interval;

  /* Get the interval to set.  If an interval is available,
     make sure it's not zero (this is a valid return, but it will
     cause the timer to get disabled, so convert it to a very short
     time). */
  if (get_low_level_timeout_interval (async_timer_queue, &interval))
    {
      if (EMACS_SECS (interval) == 0 && EMACS_USECS (interval) == 0)
	EMACS_SET_USECS (interval, 1);
    }
  else
    /* A time of 0 means "disable". */
    EMACS_SET_SECS_USECS (interval, 0, 0);

  set_one_shot_timer (interval);
}


static void
init_async_timeouts (void)
{
  set_timeout_signal (SIGALRM, alarm_signal);
  async_timer_suppress_count = 0;
}

/* Turn off async timeouts.  */

static void
stop_async_timeouts (void)
{
  if (async_timer_suppress_count == 0)
    {
      /* If timer was on, turn it off. */
      EMACS_TIME thyme;
      EMACS_SET_SECS_USECS (thyme, 0, 0);
      set_one_shot_timer (thyme);
    }
  async_timer_suppress_count++;
}

/* Turn on async timeouts again. */

static void
start_async_timeouts (void)
{
  assert (async_timer_suppress_count > 0);
  async_timer_suppress_count--;
  if (async_timer_suppress_count == 0)
    {
      /* Some callers turn off async timeouts and then use the alarm
	 for their own purposes; so reinitialize everything. */
      set_timeout_signal (SIGALRM, alarm_signal);
      reset_interval_timer ();
    }
}

static void
handle_async_timeout_signal (void)
{
  int interval_id;
  int wakeup_id;
  Lisp_Object fun, arg;
  /* Avoid any possibility of GC during QUIT */
  int specco = begin_gc_forbidden ();

  /* No checks for Vinhibit_quit here or anywhere else in this file!!!
     Otherwise critical quit will not work right.
     The only check for Vinhibit_quit is in QUIT itself.

     (#### ???? I don't quite understand this comment.) */
  interval_id = pop_low_level_timeout (&async_timer_queue, 0);

  reset_interval_timer ();
  if (async_timeout_happened_while_emacs_was_blocking)
    {
      async_timeout_happened_while_emacs_was_blocking = 0;
      waiting_for_user_input_p = 1;
    }

  wakeup_id = event_stream_resignal_wakeup (interval_id, 1, &fun, &arg);

  if (wakeup_id == poll_for_quit_id)
    {
      quit_check_signal_happened = 1;
      quit_check_signal_tick_count++;
    }
  else if (wakeup_id == poll_for_sigchld_id)
    {
      kick_status_notify ();
    }
  else
    /* call1 GC-protects its arguments */
    call1_trapping_problems ("Error in asynchronous timeout callback",
			     fun, arg, INHIBIT_GC);

  waiting_for_user_input_p = 0;

  unbind_to (specco);
}

/* The following two functions are the external interface onto
   creating/deleting asynchronous interval timeouts, and are
   called by event-stream.c.  We call back to event-stream.c using
   event_stream_resignal_wakeup(), when an interval goes off. */

int
signal_add_async_interval_timeout (EMACS_TIME thyme)
{
  int id = add_low_level_timeout (&async_timer_queue, thyme);

  /* If this timeout is at the head of the queue, then we need to
     set the timer right now for this timeout.  Otherwise, things
     are fine as-is; after the timers ahead of us are signalled,
     the timer will be set for us. */

  if (async_timer_queue->id == id)
    reset_interval_timer ();

  return id;
}

void
signal_remove_async_interval_timeout (int id)
{
  int first = (async_timer_queue && async_timer_queue->id == id);
  remove_low_level_timeout (&async_timer_queue, id);

  /* If we removed the timeout from the head of the queue, then
     we need to reset the interval timer right now. */
  if (first)
    reset_interval_timer ();
}

/* If alarm() gets called when polling isn't disabled, it will mess up
   the asynchronous timeouts, and then C-g checking won't work again.
   Some libraries call alarm() directly, so we override the standard
   library's alarm() and ABORT() if the caller of the library function
   didn't wrap in stop_interrupts()/start_interrupts().

   NOTE: We could potentially avoid the need to wrap by adding a
   one-shot timeout to simulate the alarm(), smashing our signal
   handler back into place, and calling the library function when the
   alarm goes off.  But do we want to?  We're not going to gain the
   ability to C-g out of library functions this way (unless we forcibly
   longjmp() out of a signal handler, which is likely to lead to a
   crash). --ben */

#ifdef HAVE_SETITIMER

unsigned int
alarm (unsigned int howlong)
{
  struct itimerval old_it, new_it;

  assert (async_timer_suppress_count > 0);

  new_it.it_value.tv_sec = howlong;
  new_it.it_value.tv_usec = 0;
  new_it.it_interval.tv_sec = 0;
  new_it.it_interval.tv_usec = 0;
  qxe_setitimer (ITIMER_REAL, &new_it, &old_it);

  /* Never return zero if there was a timer outstanding. */
  return old_it.it_value.tv_sec + (old_it.it_value.tv_usec > 0 ? 1 : 0);
}

int
qxe_setitimer (int kind, const struct itimerval *itnew,
	       struct itimerval *itold)
{
#ifdef WIN32_ANY
  /* setitimer() does not exist on native MS Windows, and appears broken
     on Cygwin.  See win32.c.
     
     We are emulating the Unix98 setitimer() function, as found in its
     incarnations on modern versions of Unix.  Note however that in
     the win32.c version, ITNEW and ITOLD must be equal if both are
     non-zero, due to limitations in the underlying multimedia-timer
     API. */
  return mswindows_setitimer (kind, itnew, itold);
#else
  /* YUCK!  glibc defines setitimer's first argument as
     enum __itimer_which, not int, which causes compile errors if
     we call setitimer() in the obvious way. */
  switch (kind)
    {
    case ITIMER_REAL: return setitimer (ITIMER_REAL, itnew, itold);
    case ITIMER_VIRTUAL: return setitimer (ITIMER_VIRTUAL, itnew, itold);
    case ITIMER_PROF: return setitimer (ITIMER_PROF, itnew, itold);
    default: ABORT (); return 0;
    }
#endif
}

#endif /* HAVE_SETITIMER */

signal_handler_t
set_timeout_signal (int signal_number, signal_handler_t action)
{
#ifdef CYGWIN_BROKEN_SIGNALS
  return mswindows_sigset (signal_number, action);
#else
  return EMACS_SIGNAL (signal_number, action);
#endif
}

DEFUN ("waiting-for-user-input-p", Fwaiting_for_user_input_p, 0, 0, 0, /*
Return non-nil if XEmacs is waiting for input from the user.
This is intended for use by asynchronous timeout callbacks and by
asynchronous process output filters and sentinels (not yet implemented
in XEmacs).  It will always be nil if XEmacs is not inside of
an asynchronous timeout or process callback.
*/
       ())
{
  return waiting_for_user_input_p ? Qt : Qnil;
}


/**********************************************************************/
/*                     Enabling/disabling signals                     */
/**********************************************************************/

static int interrupts_initted;

void
stop_interrupts (void)
{
  if (!interrupts_initted)
    return;
#if defined(SIGIO) && !defined(BROKEN_SIGIO)
  unrequest_sigio ();
#endif
  stop_async_timeouts ();
}

void
start_interrupts (void)
{
  if (!interrupts_initted)
    return;
#if defined(SIGIO) && !defined(BROKEN_SIGIO)
  request_sigio ();
#endif
  start_async_timeouts ();
}


static void
establish_slow_interrupt_timer (void)
{
  EMACS_TIME thyme;

  EMACS_SET_SECS_USECS (thyme, SLOWED_DOWN_INTERRUPTS_SECS, 0);
  set_one_shot_timer (thyme);
}

/* Some functions don't like being interrupted with SIGALRM or SIGIO.
   Previously we were calling stop_interrupts() / start_interrupts(),
   but then if the program hangs in one of those functions, e.g.
   waiting for a connect(), we're really screwed.  So instead we
   just "slow them down".  We do this by disabling all interrupts
   and then installing a timer of length fairly large, like 5 or
   10 secs.  That way, any "legitimate" connections (which should
   take a fairly short amount of time) go through OK, but we can
   interrupt bogus ones. */

void
slow_down_interrupts (void)
{
  /* We have to set the flag *before* setting the slowed-down timer,
     to avoid a race condition -- if the signal occurs between the
     call to set_one_shot_timer() and the setting of this flag,
     async_timeout_happened will get set, which will be a Bad Thing if
     there were no timeouts on the queue. */
  interrupts_slowed_down++;
  if (interrupts_slowed_down == 1)
    {
      stop_interrupts ();
      establish_slow_interrupt_timer ();
    }
}

void
speed_up_interrupts (void)
{
  if (interrupts_slowed_down > 0)
    {
      start_interrupts ();
      /* Change this flag AFTER fiddling with interrupts, for the same
	 race-condition reasons as above. */
      interrupts_slowed_down--;
    }
}


/**********************************************************************/
/*                 The mechanism that drives it all                   */
/**********************************************************************/

/* called from QUIT when something_happened gets set (as a result of
   a signal) */

void
check_what_happened (void)
{
  /* No GC can happen anywhere here.  handle_async_timeout_signal()
     prevents GC (from asynch timeout handler), so does check_quit()
     (from processing a message such as WM_INITMENU as a result of
     draining the message queue).  establish_slow_interrupt_timer() is
     too low-level to do anything that might invoke QUIT or call Lisp
     code. */

#ifdef ERROR_CHECK_TRAPPING_PROBLEMS
  /* When in a critical section, don't reset something_happened, so that
     every single QUIT will verify proper wrapping. (something_happened
     was set by enter_redisplay_critical_section() and will be reset
     upon exit.) */
  if (!in_display)
#endif
    something_happened = 0;

  /* Don't try to do anything clever if we're called from debug_print()
     or very close to startup or shutdown. */
  if (inhibit_non_essential_conversion_operations)
    return;

  if (async_timeout_happened)
    {
      async_timeout_happened = 0;
      handle_async_timeout_signal ();
    }
  if (slowed_interrupt_timeout_happened)
    {
      slowed_interrupt_timeout_happened = 0;
      establish_slow_interrupt_timer ();
    }

  check_quit ();
}

#ifdef SIGIO

/* Signal handler for SIGIO. */

static void
input_available_signal (int SIG_ARG_MAYBE_UNUSED (signo))
{
  something_happened = 1; /* tell QUIT to wake up */
  quit_check_signal_happened = 1;
  quit_check_signal_tick_count++;
  EMACS_REESTABLISH_SIGNAL (signo, input_available_signal);
  SIGRETURN;
}

#endif /* SIGIO */

/* Actual signal handler for SIGALRM.  Called when:

   -- asynchronous timeouts (added with `add-async-timeout') go off

   -- when the poll-for-quit timer (used for C-g handling; more or
      less when SIGIO is unavailable or BROKEN_SIGIO is defined) or
      poll-for-sigchld timer (used when BROKEN_SIGCHLD is defined) go
      off.  The latter two timers, if set, normally go off every 1/4
      of a second -- see NORMAL_QUIT_CHECK_TIMEOUT_MSECS and
      NORMAL_SIGCHLD_CHECK_TIMEOUT_MSECS. (Both of these timers are
      treated like other asynchronous timeouts, but special-cased
      in handle_async_timeout_signal().)

   -- we called slow_down_interrupts() and SLOWED_DOWN_INTERRUPTS_SECS
      (or a multiple of it) has elapsed.

   Note that under Windows, we have no working setitimer(), so we
   simulate it using the multimedia timeout functions,
   e.g. timeSetEvent().  See setitimer() in nt.c.

   Note also that we don't actually *do* anything here (except in the
   case of can_break_system_calls).  Instead, we just set various
   flags; next time QUIT is called, the flags will cause
   check_what_happened() to be called, at which point we do everything
   indicated by the flags.
*/

static SIGTYPE
alarm_signal (int signo)
{
  something_happened = 1; /* tell QUIT to wake up and call
			     check_what_happened() */

  if (interrupts_slowed_down)
    {
      /* we are in "slowed-down interrupts" mode; the only alarm
	 happening here is the slowed-down quit-check alarm, so
	 we set this flag.

	 Do NOT set async_timeout_happened, because we don't want
	 anyone looking at the timeout queue -- async timeouts
	 are disabled. */
      quit_check_signal_happened = 1;
      quit_check_signal_tick_count++;
      /* make sure we establish the slow timer again. */
      slowed_interrupt_timeout_happened = 1;

      /* can_break_system_calls is set when we want to break out of
	 non-interruptible system calls. */
      if (can_break_system_calls)
	{
	  /* reset the flag for safety and such.  Do this *before*
	     unblocking or reestablishing the signal to avoid potential
	     race conditions. */
	  can_break_system_calls = 0;
#ifndef WIN32_NATIVE
	  /* #### I didn't add this WIN32_NATIVE check.  I'm not sure
	     why it's here.  But then again, someone needs to review
	     this can_break_system_calls stuff and see if it still
	     makes sense. --ben */
	  EMACS_UNBLOCK_SIGNAL (signo);
	  EMACS_REESTABLISH_SIGNAL (signo, alarm_signal);
	  LONGJMP (break_system_call_jump, 0);
#endif
	}
    }
  else
    {
      async_timeout_happened = 1;
      if (emacs_is_blocking)
	async_timeout_happened_while_emacs_was_blocking = 1;
      /* #### This is for QUITP.  When it is run, it may not be the
	 place to do arbitrary stuff like run asynch. handlers, but
	 it needs to know whether the poll-for-quit asynch. timeout
	 went off.  Rather than put the code in to compute this
	 specially, we just set this flag.  Should fix this. */
      quit_check_signal_happened = 1;

#ifdef HAVE_UNIXOID_EVENT_LOOP
      signal_fake_event ();
#endif
    }

  EMACS_REESTABLISH_SIGNAL (signo, alarm_signal);
  SIGRETURN;
}

/* Set this for debugging, to have a way to get out */
int stop_character; /* #### not currently implemented */

/* Signal handler for SIGINT and SIGQUIT.  On TTY's, one of these two
   signals will get generated in response to C-g.  (When running under
   X, C-g is handled using the SIGIO handler, which sets a flag
   telling the QUIT macro to scan the unread events for a ^G.)
   */

static SIGTYPE
interrupt_signal (int sig)
{
  /* This function can call lisp */
  /* #### we should NOT be calling lisp from a signal handler, boys
     and girls */
  /* Must preserve main program's value of errno.  */
  int old_errno = errno;

  EMACS_REESTABLISH_SIGNAL (sig, interrupt_signal);

  if (sigint_happened && CONSOLEP (Vcontrolling_terminal) &&
      CONSOLE_LIVE_P (XCONSOLE (Vcontrolling_terminal)) &&
      !emacs_is_blocking)
    {
      /* #### this is inherited from GNU Emacs.  Do we really want this?
	 --ben */
      char c;
      fflush (stdout);
      reset_initial_console ();
      EMACS_UNBLOCK_SIGNAL (sig);
#ifdef SIGTSTP			/* Support possible in later USG versions */
/*
 * On systems which can suspend the current process and return to the original
 * shell, this command causes the user to end up back at the shell.
 * The "Auto-save" and "Abort" questions are not asked until
 * the user elects to return to emacs, at which point he can save the current
 * job and either dump core or continue.
 */
      sys_suspend ();
#else
      /* Perhaps should really fork an inferior shell?
	 But that would not provide any way to get back
	 to the original shell, ever.  */
      stdout_out ("No support for stopping a process on this operating system;\n");
      stdout_out ("you can continue or abort.\n");
#endif /* not SIGTSTP */
      stdout_out ("Auto-save? (y or n) ");
      if (((c = getc (stdin)) & ~040) == 'Y')
	Fdo_auto_save (Qnil, Qnil);
      while (c != '\n')
        c = getc (stdin);
      stdout_out ("Abort (and dump core)? (y or n) ");
      if (((c = getc (stdin)) & ~040) == 'Y')
	ABORT ();
      while (c != '\n')
        c = getc (stdin);
      stdout_out ("Continuing...\n");
      reinit_initial_console ();
      MARK_FRAME_CHANGED (XFRAME (DEVICE_SELECTED_FRAME
				  (XDEVICE (CONSOLE_SELECTED_DEVICE
					    (XCONSOLE
					     (Vcontrolling_terminal))))));
    }
  else
    {
      /* Else request quit when it's safe */
      Vquit_flag = Qt;
      sigint_happened = 1;
#ifdef HAVE_UNIXOID_EVENT_LOOP
      signal_fake_event ();
#endif
    }
  errno = old_errno;
  SIGRETURN;
}


/**********************************************************************/
/*                        Control-G checking                          */
/**********************************************************************/

/*

Info on Control-G checking:

  (Info-goto-node "(internals)Control-G (Quit) Checking")
*/

/* Defer all checking or processing of C-g.  You can do this, for example,
   if you want to read C-g's as events. (In that case, you should set
   Vquit_flag to Qnil just before you unbind, because it typically gets set
   as a result of reading C-g.) */

int
begin_dont_check_for_quit (void)
{
  int depth = specpdl_depth ();
  /* As an optimization in QUIT_FLAG_SAYS_SHOULD_QUIT, we bind inhibit-quit
     to t -- it has to be checked anyway, and by doing this, we only need
     to check dont_check_for_quit when quit-flag == `critical', which is
     rare. */
  specbind (Qinhibit_quit, Qt);
  internal_bind_int (&dont_check_for_quit, 1);

  return depth;
}

/* If we're inside of a begin_dont_check_for_quit() section, but want
   to temporarily enable quit-checking, call this.  This is used in
   particular when processing menu filters -- some menu filters do
   antisocial things like load large amounts of Lisp code (custom in
   particular), and we obviously want a way of breaking out of any
   problems.  If you do use this, you should really be trapping the
   throw() that comes from the quitting (as does the code that handles
   menus popping up). */

int
begin_do_check_for_quit (void)
{
  int depth = specpdl_depth ();
  specbind (Qinhibit_quit, Qnil);
  internal_bind_int (&dont_check_for_quit, 0);
  /* #### should we set Vquit_flag to Qnil? */
  return depth;
 }

/* The effect of this function is to set Vquit_flag appropriately if the
   user pressed C-g or Sh-C-g.  After this function finishes, Vquit_flag
   will be Qt for C-g, Qcritical for Sh-C-g, and unchanged otherwise.
   The C-g or Sh-C-g is discarded, so it won't be noticed again. 
*/



void
check_quit (void)
{
  int specdepth;
  
  if (dont_check_for_quit)
    return;

  if (quit_check_signal_happened)
    {
#ifdef ERROR_CHECK_TRAPPING_PROBLEMS
      /* Since the code below can call Lisp, make sure that proper wrapping is
	 in place during redisplay. */
#if 0
      assert_with_message
	(proper_redisplay_wrapping_in_place (),
	 "QUIT called from within redisplay without being properly wrapped");
#else
    /* FUCKME!  It looks like we cannot even check for QUIT, *EVER*, during
       redisplay.  Checking for quit can dispatch events, which can enter
       redisplay recursively, which can trip on 

Fatal error: assertion failed, file c:\xemacs\build\src\redisplay.c, line 5532,
!dy->locked

Backtrace given in

  (Info-goto-node "(internals)Critical Redisplay Sections")

    */
      assert_with_message
	(!in_display,
	 "QUIT called from within redisplay without being properly wrapped");
#endif /* 0 */
#endif /* ERROR_CHECK_TRAPPING_PROBLEMS */

      /* Since arbitrary Lisp code may be executed (e.g. through a menu
         filter, see backtrace directly above), GC might happen,
         which would majorly fuck a lot of things, e.g. re_match()
         [string gets relocated] and lots of other code that's not
         prepared to handle GC in QUIT. */
      specdepth = begin_gc_forbidden ();
      quit_check_signal_happened = 0;
      event_stream_quit_p ();
      unbind_to (specdepth);
    }
}



void
init_poll_for_quit (void)
{
#if !defined (SIGIO) && !defined (DONT_POLL_FOR_QUIT)
  /* Check for C-g every 1/4 of a second.

     #### This is just a guess.  Some investigation will have to be
     done to see what the best value is.  The best value is the
     smallest possible value that doesn't cause a significant amount
     of running time to be spent in C-g checking. */
  if (!poll_for_quit_id)
    poll_for_quit_id =
      event_stream_generate_wakeup (NORMAL_QUIT_CHECK_TIMEOUT_MSECS,
				    NORMAL_QUIT_CHECK_TIMEOUT_MSECS,
				    Qnil, Qnil, 1);
#endif /* not SIGIO and not DONT_POLL_FOR_QUIT */
}

#if 0 /* not used anywhere */

void
reset_poll_for_quit (void)
{
#if !defined (SIGIO) && !defined (DONT_POLL_FOR_QUIT)
  if (poll_for_quit_id)
    {
      event_stream_disable_wakeup (poll_for_quit_id, 1);
      poll_for_quit_id = 0;
    }
#endif /* not SIGIO and not DONT_POLL_FOR_QUIT */
}

#endif /* 0 */

#if defined (HAVE_UNIX_PROCESSES) && !defined (SIGCHLD)

static void
init_poll_for_sigchld (void)
{
  /* Check for terminated processes every 1/4 of a second.

     #### This is just a guess.  Some investigation will have to be
     done to see what the best value is.  The best value is the
     smallest possible value that doesn't cause a significant amount
     of running time to be spent in process-termination checking.
     */
  poll_for_sigchld_id =
    event_stream_generate_wakeup (NORMAL_SIGCHLD_CHECK_TIMEOUT_MSECS,
				  NORMAL_SIGCHLD_CHECK_TIMEOUT_MSECS,
				  Qnil, Qnil, 1);
}

#endif /* not SIGCHLD */


/************************************************************************/
/*                            initialization                            */
/************************************************************************/

/* If we've been nohup'ed, keep it that way.
   This allows `nohup xemacs &' to work.
   More generally, if a normally fatal signal has been redirected
   to SIG_IGN by our invocation environment, trust the environment.
   This keeps xemacs from being killed by a SIGQUIT intended for a
   different process after having been backgrounded under a
   non-job-control shell! */
static void
handle_signal_if_fatal (int signo)
{
  if (EMACS_SIGNAL (signo,  fatal_error_signal) == SIG_IGN)
    EMACS_SIGNAL (signo, SIG_IGN);
}

void
init_signals_very_early (void)
{
  /* Catch all signals that would kill us.
     Don't catch these signals in batch mode if not initialized.
     On some machines, this sets static data that would make
     signal fail to work right when the dumped Emacs is run.  */
  if (noninteractive && !initialized)
    return;

  handle_signal_if_fatal (SIGILL);  /* ANSI */
  handle_signal_if_fatal (SIGABRT); /* ANSI */
  handle_signal_if_fatal (SIGFPE);  /* ANSI */
  handle_signal_if_fatal (SIGSEGV); /* ANSI */
  handle_signal_if_fatal (SIGTERM); /* ANSI */


#ifdef SIGHUP
  handle_signal_if_fatal (SIGHUP);  /* POSIX */
#endif
#ifdef SIGQUIT
  handle_signal_if_fatal (SIGQUIT); /* POSIX */
#endif
#ifdef SIGTRAP
  handle_signal_if_fatal (SIGTRAP); /* POSIX */
#endif
#ifdef SIGUSR1
  handle_signal_if_fatal (SIGUSR1); /* POSIX */
#endif
#ifdef SIGUSR2
  handle_signal_if_fatal (SIGUSR2); /* POSIX */
#endif
#ifdef SIGPIPE
  handle_signal_if_fatal (SIGPIPE); /* POSIX */
#endif
#ifdef SIGALRM
  /* This will get reset later, once we're
     capable of handling it properly. */
  handle_signal_if_fatal (SIGALRM); /* POSIX */
#endif


#ifdef SIGBUS
  handle_signal_if_fatal (SIGBUS);  /* XPG5 */
#endif
#ifdef SIGSYS
  handle_signal_if_fatal (SIGSYS);  /* XPG5 */
#endif
#ifdef SIGXCPU
  handle_signal_if_fatal (SIGXCPU); /* XPG5 */
#endif
#ifdef SIGXFSZ
  handle_signal_if_fatal (SIGXFSZ); /* XPG5 */
#endif
#ifdef SIGVTALRM
  handle_signal_if_fatal (SIGVTALRM); /* XPG5 */
#endif
#ifdef SIGPROF
  /* Messes up the REAL profiler */
  /* handle_signal_if_fatal (SIGPROF); */ /* XPG5 */
#endif


#ifdef SIGHWE
  handle_signal_if_fatal (SIGHWE);
#endif
#ifdef SIGPRE
  handle_signal_if_fatal (SIGPRE);
#endif
#ifdef SIGORE
  handle_signal_if_fatal (SIGORE);
#endif
#ifdef SIGUME
  handle_signal_if_fatal (SIGUME);
#endif
#ifdef SIGDLK
  handle_signal_if_fatal (SIGDLK);
#endif
#ifdef SIGCPULIM
  handle_signal_if_fatal (SIGCPULIM);
#endif
#ifdef SIGIOT
  handle_signal_if_fatal (SIGIOT);
#endif
#ifdef SIGEMT
  handle_signal_if_fatal (SIGEMT);
#endif
#ifdef SIGLOST
  handle_signal_if_fatal (SIGLOST);
#endif
#ifdef SIGSTKFLT /* coprocessor stack fault under Linux */
  handle_signal_if_fatal (SIGSTKFLT);
#endif
#ifdef SIGUNUSED /* exists under Linux, and will kill process! */
  handle_signal_if_fatal (SIGUNUSED);
#endif

#ifdef AIX
/* 20 is SIGCHLD, 21 is SIGTTIN, 22 is SIGTTOU.  */
#ifndef _I386
  handle_signal_if_fatal (SIGIOINT);
#endif
  handle_signal_if_fatal (SIGGRANT);
  handle_signal_if_fatal (SIGRETRACT);
  handle_signal_if_fatal (SIGSOUND);
  handle_signal_if_fatal (SIGMSG);
#endif /* AIX */

#ifdef SIGDANGER
  /* This just means available memory is getting low.  */
  EMACS_SIGNAL (SIGDANGER, memory_warning_signal);
#endif
}

void
syms_of_signal (void)
{
  DEFSUBR (Fwaiting_for_user_input_p);
}

void
init_interrupts_late (void)
{
  if (!noninteractive)
    {
      EMACS_SIGNAL (SIGINT, interrupt_signal);
#ifdef HAVE_TERMIO
      /* On  systems with TERMIO, C-g is set up for both SIGINT and SIGQUIT
	 and we can't tell which one it will give us.  */
      EMACS_SIGNAL (SIGQUIT, interrupt_signal);
#endif /* HAVE_TERMIO */
      init_async_timeouts ();
#ifdef SIGIO
      EMACS_SIGNAL (SIGIO, input_available_signal);
# ifdef SIGPOLL /* XPG5 */
      /* Some systems (e.g. Motorola SVR4) losingly have different
	 values for SIGIO and SIGPOLL, and send SIGPOLL instead of
	 SIGIO.  On those same systems, an uncaught SIGPOLL kills the
	 process. */
      EMACS_SIGNAL (SIGPOLL, input_available_signal);
# endif
#elif !defined (DONT_POLL_FOR_QUIT)
      init_poll_for_quit ();
#endif
    }

#if defined (HAVE_UNIX_PROCESSES) && !defined (SIGCHLD)
  init_poll_for_sigchld ();
#endif

  EMACS_UNBLOCK_ALL_SIGNALS ();

  interrupts_initted = 1;
}