gdb/inflow.c

   1 /* Low level interface to ptrace, for GDB when running under Unix.
   2    Copyright 1986-87, 1989, 1991-92, 1995, 1998 Free Software Foundation, Inc.
   3
   4    This file is part of GDB.
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 2 of the License, or
   9    (at your option) any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program; if not, write to the Free Software
  18    Foundation, Inc., 59 Temple Place - Suite 330,
  19    Boston, MA 02111-1307, USA.  */
  20
  21 #include "defs.h"
  22 #include "frame.h"
  23 #include "inferior.h"
  24 #include "command.h"
  25 #include "signals.h"
  26 #include "serial.h"
  27 #include "terminal.h"
  28 #include "target.h"
  29 #include "gdbthread.h"
  30
  31 #include "gdb_string.h"
  32 #include <signal.h>
  33 #include <fcntl.h>
  34 #ifdef HAVE_SYS_SELECT_H
  35 #include <sys/select.h>
  36 #endif
  37
  38 #ifdef HAVE_TERMIOS
  39 #define PROCESS_GROUP_TYPE pid_t
  40 #endif
  41
  42 #ifdef HAVE_TERMIO
  43 #define PROCESS_GROUP_TYPE int
  44 #endif
  45
  46 #ifdef HAVE_SGTTY
  47 #ifdef SHORT_PGRP
  48 /* This is only used for the ultra.  Does it have pid_t?  */
  49 #define PROCESS_GROUP_TYPE short
  50 #else
  51 #define PROCESS_GROUP_TYPE int
  52 #endif
  53 #endif /* sgtty */
  54
  55 #ifdef HAVE_SYS_IOCTL_H
  56 #include <sys/ioctl.h>
  57 #endif
  58
  59 #if defined (SIGIO) && defined (FASYNC) && defined (FD_SET) && defined (F_SETOWN)
  60 static void handle_sigio (int);
  61 #endif
  62
  63 extern void _initialize_inflow (void);
  64
  65 static void pass_signal (int);
  66
  67 static void kill_command (char *, int);
  68
  69 static void terminal_ours_1 (int);
  70 \f
  71 /* Record terminal status separately for debugger and inferior.  */
  72
  73 static serial_t stdin_serial;
  74
  75 /* TTY state for the inferior.  We save it whenever the inferior stops, and
  76    restore it when it resumes.  */
  77 static serial_ttystate inferior_ttystate;
  78
  79 /* Our own tty state, which we restore every time we need to deal with the
  80    terminal.  We only set it once, when GDB first starts.  The settings of
  81    flags which readline saves and restores and unimportant.  */
  82 static serial_ttystate our_ttystate;
  83
  84 /* fcntl flags for us and the inferior.  Saved and restored just like
  85    {our,inferior}_ttystate.  */
  86 static int tflags_inferior;
  87 static int tflags_ours;
  88
  89 #ifdef PROCESS_GROUP_TYPE
  90 /* Process group for us and the inferior.  Saved and restored just like
  91    {our,inferior}_ttystate.  */
  92 PROCESS_GROUP_TYPE our_process_group;
  93 PROCESS_GROUP_TYPE inferior_process_group;
  94 #endif
  95
  96 /* While the inferior is running, we want SIGINT and SIGQUIT to go to the
  97    inferior only.  If we have job control, that takes care of it.  If not,
  98    we save our handlers in these two variables and set SIGINT and SIGQUIT
  99    to SIG_IGN.  */
 100
 101 static void (*sigint_ours) ();
 102 static void (*sigquit_ours) ();
 103
 104 /* The name of the tty (from the `tty' command) that we gave to the inferior
 105    when it was last started.  */
 106
 107 static char *inferior_thisrun_terminal;
 108
 109 /* Nonzero if our terminal settings are in effect.  Zero if the
 110    inferior's settings are in effect.  Ignored if !gdb_has_a_terminal
 111    ().  */
 112
 113 int terminal_is_ours;
 114
 115 enum
 116   {
 117     yes, no, have_not_checked
 118   }
 119 gdb_has_a_terminal_flag = have_not_checked;
 120
 121 /* Does GDB have a terminal (on stdin)?  */
 122 int
 123 gdb_has_a_terminal (void)
 124 {
 125   switch (gdb_has_a_terminal_flag)
 126     {
 127     case yes:
 128       return 1;
 129     case no:
 130       return 0;
 131     case have_not_checked:
 132       /* Get all the current tty settings (including whether we have a tty at
 133          all!).  Can't do this in _initialize_inflow because SERIAL_FDOPEN
 134          won't work until the serial_ops_list is initialized.  */
 135
 136 #ifdef F_GETFL
 137       tflags_ours = fcntl (0, F_GETFL, 0);
 138 #endif
 139
 140       gdb_has_a_terminal_flag = no;
 141       stdin_serial = SERIAL_FDOPEN (0);
 142       if (stdin_serial != NULL)
 143         {
 144           our_ttystate = SERIAL_GET_TTY_STATE (stdin_serial);
 145
 146           if (our_ttystate != NULL)
 147             {
 148               gdb_has_a_terminal_flag = yes;
 149 #ifdef HAVE_TERMIOS
 150               our_process_group = tcgetpgrp (0);
 151 #endif
 152 #ifdef HAVE_TERMIO
 153               our_process_group = getpgrp ();
 154 #endif
 155 #ifdef HAVE_SGTTY
 156               ioctl (0, TIOCGPGRP, &our_process_group);
 157 #endif
 158             }
 159         }
 160
 161       return gdb_has_a_terminal_flag == yes;
 162     default:
 163       /* "Can't happen".  */
 164       return 0;
 165     }
 166 }
 167
 168 /* Macro for printing errors from ioctl operations */
 169
 170 #define OOPSY(what)     \
 171   if (result == -1)     \
 172     fprintf_unfiltered(gdb_stderr, "[%s failed in terminal_inferior: %s]\n", \
 173             what, strerror (errno))
 174
 175 static void terminal_ours_1 (int);
 176
 177 /* Initialize the terminal settings we record for the inferior,
 178    before we actually run the inferior.  */
 179
 180 void
 181 terminal_init_inferior_with_pgrp (int pgrp)
 182 {
 183   if (gdb_has_a_terminal ())
 184     {
 185       /* We could just as well copy our_ttystate (if we felt like adding
 186          a new function SERIAL_COPY_TTY_STATE).  */
 187       if (inferior_ttystate)
 188         free (inferior_ttystate);
 189       inferior_ttystate = SERIAL_GET_TTY_STATE (stdin_serial);
 190
 191 #ifdef PROCESS_GROUP_TYPE
 192       inferior_process_group = pgrp;
 193 #endif
 194
 195       /* Make sure that next time we call terminal_inferior (which will be
 196          before the program runs, as it needs to be), we install the new
 197          process group.  */
 198       terminal_is_ours = 1;
 199     }
 200 }
 201
 202 void
 203 terminal_init_inferior (void)
 204 {
 205 #ifdef PROCESS_GROUP_TYPE
 206   /* This is for Lynx, and should be cleaned up by having Lynx be a separate
 207      debugging target with a version of target_terminal_init_inferior which
 208      passes in the process group to a generic routine which does all the work
 209      (and the non-threaded child_terminal_init_inferior can just pass in
 210      inferior_pid to the same routine).  */
 211   /* We assume INFERIOR_PID is also the child's process group.  */
 212   terminal_init_inferior_with_pgrp (PIDGET (inferior_pid));
 213 #endif /* PROCESS_GROUP_TYPE */
 214 }
 215
 216 /* Put the inferior's terminal settings into effect.
 217    This is preparation for starting or resuming the inferior.  */
 218
 219 void
 220 terminal_inferior (void)
 221 {
 222   if (gdb_has_a_terminal () && terminal_is_ours
 223       && inferior_thisrun_terminal == 0)
 224     {
 225       int result;
 226
 227 #ifdef F_GETFL
 228       /* Is there a reason this is being done twice?  It happens both
 229          places we use F_SETFL, so I'm inclined to think perhaps there
 230          is some reason, however perverse.  Perhaps not though...  */
 231       result = fcntl (0, F_SETFL, tflags_inferior);
 232       result = fcntl (0, F_SETFL, tflags_inferior);
 233       OOPSY ("fcntl F_SETFL");
 234 #endif
 235
 236       /* Because we were careful to not change in or out of raw mode in
 237          terminal_ours, we will not change in our out of raw mode with
 238          this call, so we don't flush any input.  */
 239       result = SERIAL_SET_TTY_STATE (stdin_serial, inferior_ttystate);
 240       OOPSY ("setting tty state");
 241
 242       if (!job_control)
 243         {
 244           sigint_ours = (void (*)()) signal (SIGINT, SIG_IGN);
 245 #ifdef SIGQUIT
 246           sigquit_ours = (void (*)()) signal (SIGQUIT, SIG_IGN);
 247 #endif
 248         }
 249
 250       /* If attach_flag is set, we don't know whether we are sharing a
 251          terminal with the inferior or not.  (attaching a process
 252          without a terminal is one case where we do not; attaching a
 253          process which we ran from the same shell as GDB via `&' is
 254          one case where we do, I think (but perhaps this is not
 255          `sharing' in the sense that we need to save and restore tty
 256          state)).  I don't know if there is any way to tell whether we
 257          are sharing a terminal.  So what we do is to go through all
 258          the saving and restoring of the tty state, but ignore errors
 259          setting the process group, which will happen if we are not
 260          sharing a terminal).  */
 261
 262       if (job_control)
 263         {
 264 #ifdef HAVE_TERMIOS
 265           result = tcsetpgrp (0, inferior_process_group);
 266           if (!attach_flag)
 267             OOPSY ("tcsetpgrp");
 268 #endif
 269
 270 #ifdef HAVE_SGTTY
 271           result = ioctl (0, TIOCSPGRP, &inferior_process_group);
 272           if (!attach_flag)
 273             OOPSY ("TIOCSPGRP");
 274 #endif
 275         }
 276
 277     }
 278   terminal_is_ours = 0;
 279 }
 280
 281 /* Put some of our terminal settings into effect,
 282    enough to get proper results from our output,
 283    but do not change into or out of RAW mode
 284    so that no input is discarded.
 285
 286    After doing this, either terminal_ours or terminal_inferior
 287    should be called to get back to a normal state of affairs.  */
 288
 289 void
 290 terminal_ours_for_output (void)
 291 {
 292   terminal_ours_1 (1);
 293 }
 294
 295 /* Put our terminal settings into effect.
 296    First record the inferior's terminal settings
 297    so they can be restored properly later.  */
 298
 299 void
 300 terminal_ours (void)
 301 {
 302   terminal_ours_1 (0);
 303 }
 304
 305 /* output_only is not used, and should not be used unless we introduce
 306    separate terminal_is_ours and terminal_is_ours_for_output
 307    flags.  */
 308
 309 static void
 310 terminal_ours_1 (int output_only)
 311 {
 312   /* Checking inferior_thisrun_terminal is necessary so that
 313      if GDB is running in the background, it won't block trying
 314      to do the ioctl()'s below.  Checking gdb_has_a_terminal
 315      avoids attempting all the ioctl's when running in batch.  */
 316   if (inferior_thisrun_terminal != 0 || gdb_has_a_terminal () == 0)
 317     return;
 318
 319   if (!terminal_is_ours)
 320     {
 321       /* Ignore this signal since it will happen when we try to set the
 322          pgrp.  */
 323       void (*osigttou) ();
 324       int result;
 325
 326       terminal_is_ours = 1;
 327
 328 #ifdef SIGTTOU
 329       if (job_control)
 330         osigttou = (void (*)()) signal (SIGTTOU, SIG_IGN);
 331 #endif
 332
 333       if (inferior_ttystate)
 334         free (inferior_ttystate);
 335       inferior_ttystate = SERIAL_GET_TTY_STATE (stdin_serial);
 336 #ifdef HAVE_TERMIOS
 337       inferior_process_group = tcgetpgrp (0);
 338 #endif
 339 #ifdef HAVE_TERMIO
 340       inferior_process_group = getpgrp ();
 341 #endif
 342 #ifdef HAVE_SGTTY
 343       ioctl (0, TIOCGPGRP, &inferior_process_group);
 344 #endif
 345
 346       /* Here we used to set ICANON in our ttystate, but I believe this
 347          was an artifact from before when we used readline.  Readline sets
 348          the tty state when it needs to.
 349          FIXME-maybe: However, query() expects non-raw mode and doesn't
 350          use readline.  Maybe query should use readline (on the other hand,
 351          this only matters for HAVE_SGTTY, not termio or termios, I think).  */
 352
 353       /* Set tty state to our_ttystate.  We don't change in our out of raw
 354          mode, to avoid flushing input.  We need to do the same thing
 355          regardless of output_only, because we don't have separate
 356          terminal_is_ours and terminal_is_ours_for_output flags.  It's OK,
 357          though, since readline will deal with raw mode when/if it needs to.
 358        */
 359
 360       SERIAL_NOFLUSH_SET_TTY_STATE (stdin_serial, our_ttystate,
 361                                     inferior_ttystate);
 362
 363       if (job_control)
 364         {
 365 #ifdef HAVE_TERMIOS
 366           result = tcsetpgrp (0, our_process_group);
 367 #if 0
 368           /* This fails on Ultrix with EINVAL if you run the testsuite
 369              in the background with nohup, and then log out.  GDB never
 370              used to check for an error here, so perhaps there are other
 371              such situations as well.  */
 372           if (result == -1)
 373             fprintf_unfiltered (gdb_stderr, "[tcsetpgrp failed in terminal_ours: %s]\n",
 374                                 strerror (errno));
 375 #endif
 376 #endif /* termios */
 377
 378 #ifdef HAVE_SGTTY
 379           result = ioctl (0, TIOCSPGRP, &our_process_group);
 380 #endif
 381         }
 382
 383 #ifdef SIGTTOU
 384       if (job_control)
 385         signal (SIGTTOU, osigttou);
 386 #endif
 387
 388       if (!job_control)
 389         {
 390           signal (SIGINT, sigint_ours);
 391 #ifdef SIGQUIT
 392           signal (SIGQUIT, sigquit_ours);
 393 #endif
 394         }
 395
 396 #ifdef F_GETFL
 397       tflags_inferior = fcntl (0, F_GETFL, 0);
 398
 399       /* Is there a reason this is being done twice?  It happens both
 400          places we use F_SETFL, so I'm inclined to think perhaps there
 401          is some reason, however perverse.  Perhaps not though...  */
 402       result = fcntl (0, F_SETFL, tflags_ours);
 403       result = fcntl (0, F_SETFL, tflags_ours);
 404 #endif
 405
 406       result = result;          /* lint */
 407     }
 408 }
 409
 410 /* ARGSUSED */
 411 void
 412 term_info (char *arg, int from_tty)
 413 {
 414   target_terminal_info (arg, from_tty);
 415 }
 416
 417 /* ARGSUSED */
 418 void
 419 child_terminal_info (char *args, int from_tty)
 420 {
 421   if (!gdb_has_a_terminal ())
 422     {
 423       printf_filtered ("This GDB does not control a terminal.\n");
 424       return;
 425     }
 426
 427   printf_filtered ("Inferior's terminal status (currently saved by GDB):\n");
 428
 429   /* First the fcntl flags.  */
 430   {
 431     int flags;
 432
 433     flags = tflags_inferior;
 434
 435     printf_filtered ("File descriptor flags = ");
 436
 437 #ifndef O_ACCMODE
 438 #define O_ACCMODE (O_RDONLY | O_WRONLY | O_RDWR)
 439 #endif
 440     /* (O_ACCMODE) parens are to avoid Ultrix header file bug */
 441     switch (flags & (O_ACCMODE))
 442       {
 443       case O_RDONLY:
 444         printf_filtered ("O_RDONLY");
 445         break;
 446       case O_WRONLY:
 447         printf_filtered ("O_WRONLY");
 448         break;
 449       case O_RDWR:
 450         printf_filtered ("O_RDWR");
 451         break;
 452       }
 453     flags &= ~(O_ACCMODE);
 454
 455 #ifdef O_NONBLOCK
 456     if (flags & O_NONBLOCK)
 457       printf_filtered (" | O_NONBLOCK");
 458     flags &= ~O_NONBLOCK;
 459 #endif
 460
 461 #if defined (O_NDELAY)
 462     /* If O_NDELAY and O_NONBLOCK are defined to the same thing, we will
 463        print it as O_NONBLOCK, which is good cause that is what POSIX
 464        has, and the flag will already be cleared by the time we get here.  */
 465     if (flags & O_NDELAY)
 466       printf_filtered (" | O_NDELAY");
 467     flags &= ~O_NDELAY;
 468 #endif
 469
 470     if (flags & O_APPEND)
 471       printf_filtered (" | O_APPEND");
 472     flags &= ~O_APPEND;
 473
 474 #if defined (O_BINARY)
 475     if (flags & O_BINARY)
 476       printf_filtered (" | O_BINARY");
 477     flags &= ~O_BINARY;
 478 #endif
 479
 480     if (flags)
 481       printf_filtered (" | 0x%x", flags);
 482     printf_filtered ("\n");
 483   }
 484
 485 #ifdef PROCESS_GROUP_TYPE
 486   printf_filtered ("Process group = %d\n",
 487                    (int) inferior_process_group);
 488 #endif
 489
 490   SERIAL_PRINT_TTY_STATE (stdin_serial, inferior_ttystate, gdb_stdout);
 491 }
 492 \f
 493 /* NEW_TTY_PREFORK is called before forking a new child process,
 494    so we can record the state of ttys in the child to be formed.
 495    TTYNAME is null if we are to share the terminal with gdb;
 496    or points to a string containing the name of the desired tty.
 497
 498    NEW_TTY is called in new child processes under Unix, which will
 499    become debugger target processes.  This actually switches to
 500    the terminal specified in the NEW_TTY_PREFORK call.  */
 501
 502 void
 503 new_tty_prefork (char *ttyname)
 504 {
 505   /* Save the name for later, for determining whether we and the child
 506      are sharing a tty.  */
 507   inferior_thisrun_terminal = ttyname;
 508 }
 509
 510 void
 511 new_tty (void)
 512 {
 513   register int tty;
 514
 515   if (inferior_thisrun_terminal == 0)
 516     return;
 517 #if !defined(__GO32__) && !defined(_WIN32)
 518 #ifdef TIOCNOTTY
 519   /* Disconnect the child process from our controlling terminal.  On some
 520      systems (SVR4 for example), this may cause a SIGTTOU, so temporarily
 521      ignore SIGTTOU. */
 522   tty = open ("/dev/tty", O_RDWR);
 523   if (tty > 0)
 524     {
 525       void (*osigttou) ();
 526
 527       osigttou = (void (*)()) signal (SIGTTOU, SIG_IGN);
 528       ioctl (tty, TIOCNOTTY, 0);
 529       close (tty);
 530       signal (SIGTTOU, osigttou);
 531     }
 532 #endif
 533
 534   /* Now open the specified new terminal.  */
 535
 536 #ifdef USE_O_NOCTTY
 537   tty = open (inferior_thisrun_terminal, O_RDWR | O_NOCTTY);
 538 #else
 539   tty = open (inferior_thisrun_terminal, O_RDWR);
 540 #endif
 541   if (tty == -1)
 542     {
 543       print_sys_errmsg (inferior_thisrun_terminal, errno);
 544       _exit (1);
 545     }
 546
 547   /* Avoid use of dup2; doesn't exist on all systems.  */
 548   if (tty != 0)
 549     {
 550       close (0);
 551       dup (tty);
 552     }
 553   if (tty != 1)
 554     {
 555       close (1);
 556       dup (tty);
 557     }
 558   if (tty != 2)
 559     {
 560       close (2);
 561       dup (tty);
 562     }
 563   if (tty > 2)
 564     close (tty);
 565 #endif /* !go32 && !win32 */
 566 }
 567 \f
 568 /* Kill the inferior process.  Make us have no inferior.  */
 569
 570 /* ARGSUSED */
 571 static void
 572 kill_command (char *arg, int from_tty)
 573 {
 574   /* FIXME:  This should not really be inferior_pid (or target_has_execution).
 575      It should be a distinct flag that indicates that a target is active, cuz
 576      some targets don't have processes! */
 577
 578   if (inferior_pid == 0)
 579     error ("The program is not being run.");
 580   if (!query ("Kill the program being debugged? "))
 581     error ("Not confirmed.");
 582   target_kill ();
 583
 584   init_thread_list ();          /* Destroy thread info */
 585
 586   /* Killing off the inferior can leave us with a core file.  If so,
 587      print the state we are left in.  */
 588   if (target_has_stack)
 589     {
 590       printf_filtered ("In %s,\n", target_longname);
 591       if (selected_frame == NULL)
 592         fputs_filtered ("No selected stack frame.\n", gdb_stdout);
 593       else
 594         print_stack_frame (selected_frame, selected_frame_level, 1);
 595     }
 596 }
 597 \f
 598 /* Call set_sigint_trap when you need to pass a signal on to an attached
 599    process when handling SIGINT */
 600
 601 /* ARGSUSED */
 602 static void
 603 pass_signal (int signo)
 604 {
 605 #ifndef _WIN32
 606   kill (PIDGET (inferior_pid), SIGINT);
 607 #endif
 608 }
 609
 610 static void (*osig) ();
 611
 612 void
 613 set_sigint_trap (void)
 614 {
 615   if (attach_flag || inferior_thisrun_terminal)
 616     {
 617       osig = (void (*)()) signal (SIGINT, pass_signal);
 618     }
 619 }
 620
 621 void
 622 clear_sigint_trap (void)
 623 {
 624   if (attach_flag || inferior_thisrun_terminal)
 625     {
 626       signal (SIGINT, osig);
 627     }
 628 }
 629 \f
 630 #if defined (SIGIO) && defined (FASYNC) && defined (FD_SET) && defined (F_SETOWN)
 631 static void (*old_sigio) ();
 632
 633 static void
 634 handle_sigio (int signo)
 635 {
 636   int numfds;
 637   fd_set readfds;
 638
 639   signal (SIGIO, handle_sigio);
 640
 641   FD_ZERO (&readfds);
 642   FD_SET (target_activity_fd, &readfds);
 643   numfds = select (target_activity_fd + 1, &readfds, NULL, NULL, NULL);
 644   if (numfds >= 0 && FD_ISSET (target_activity_fd, &readfds))
 645     {
 646 #ifndef _WIN32
 647       if ((*target_activity_function) ())
 648         kill (inferior_pid, SIGINT);
 649 #endif
 650     }
 651 }
 652
 653 static int old_fcntl_flags;
 654
 655 void
 656 set_sigio_trap (void)
 657 {
 658   if (target_activity_function)
 659     {
 660       old_sigio = (void (*)()) signal (SIGIO, handle_sigio);
 661       fcntl (target_activity_fd, F_SETOWN, getpid ());
 662       old_fcntl_flags = fcntl (target_activity_fd, F_GETFL, 0);
 663       fcntl (target_activity_fd, F_SETFL, old_fcntl_flags | FASYNC);
 664     }
 665 }
 666
 667 void
 668 clear_sigio_trap (void)
 669 {
 670   if (target_activity_function)
 671     {
 672       signal (SIGIO, old_sigio);
 673       fcntl (target_activity_fd, F_SETFL, old_fcntl_flags);
 674     }
 675 }
 676 #else /* No SIGIO.  */
 677 void
 678 set_sigio_trap (void)
 679 {
 680   if (target_activity_function)
 681     abort ();
 682 }
 683
 684 void
 685 clear_sigio_trap (void)
 686 {
 687   if (target_activity_function)
 688     abort ();
 689 }
 690 #endif /* No SIGIO.  */
 691 \f
 692
 693 /* This is here because this is where we figure out whether we (probably)
 694    have job control.  Just using job_control only does part of it because
 695    setpgid or setpgrp might not exist on a system without job control.
 696    It might be considered misplaced (on the other hand, process groups and
 697    job control are closely related to ttys).
 698
 699    For a more clean implementation, in libiberty, put a setpgid which merely
 700    calls setpgrp and a setpgrp which does nothing (any system with job control
 701    will have one or the other).  */
 702 int
 703 gdb_setpgid (void)
 704 {
 705   int retval = 0;
 706
 707   if (job_control)
 708     {
 709 #if defined (NEED_POSIX_SETPGID) || (defined (HAVE_TERMIOS) && defined (HAVE_SETPGID))
 710       /* setpgid (0, 0) is supposed to work and mean the same thing as
 711          this, but on Ultrix 4.2A it fails with EPERM (and
 712          setpgid (getpid (), getpid ()) succeeds).  */
 713       retval = setpgid (getpid (), getpid ());
 714 #else
 715 #if defined (TIOCGPGRP)
 716 #if defined(USG) && !defined(SETPGRP_ARGS)
 717       retval = setpgrp ();
 718 #else
 719       retval = setpgrp (getpid (), getpid ());
 720 #endif /* USG */
 721 #endif /* TIOCGPGRP.  */
 722 #endif /* NEED_POSIX_SETPGID */
 723     }
 724   return retval;
 725 }
 726
 727 void
 728 _initialize_inflow (void)
 729 {
 730   add_info ("terminal", term_info,
 731             "Print inferior's saved terminal status.");
 732
 733   add_com ("kill", class_run, kill_command,
 734            "Kill execution of program being debugged.");
 735
 736   inferior_pid = 0;
 737
 738   terminal_is_ours = 1;
 739
 740   /* OK, figure out whether we have job control.  If neither termios nor
 741      sgtty (i.e. termio or go32), leave job_control 0.  */
 742
 743 #if defined (HAVE_TERMIOS)
 744   /* Do all systems with termios have the POSIX way of identifying job
 745      control?  I hope so.  */
 746 #ifdef _POSIX_JOB_CONTROL
 747   job_control = 1;
 748 #else
 749 #ifdef _SC_JOB_CONTROL
 750   job_control = sysconf (_SC_JOB_CONTROL);
 751 #else
 752   job_control = 0;              /* have to assume the worst */
 753 #endif /* _SC_JOB_CONTROL */
 754 #endif /* _POSIX_JOB_CONTROL */
 755 #endif /* HAVE_TERMIOS */
 756
 757 #ifdef HAVE_SGTTY
 758 #ifdef TIOCGPGRP
 759   job_control = 1;
 760 #else
 761   job_control = 0;
 762 #endif /* TIOCGPGRP */
 763 #endif /* sgtty */
 764 }