gdb/inflow.c

   1 /* Low level interface to ptrace, for GDB when running under Unix.
   2    Copyright 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995,
   3    1996, 1998, 1999, 2000, 2001 Free Software Foundation, Inc.
   4
   5    This file is part of GDB.
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 2 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program; if not, write to the Free Software
  19    Foundation, Inc., 59 Temple Place - Suite 330,
  20    Boston, MA 02111-1307, USA.  */
  21
  22 #include "defs.h"
  23 #include "frame.h"
  24 #include "inferior.h"
  25 #include "command.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         xfree (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_ptid to the same routine).  */
 211   /* We assume INFERIOR_PID is also the child's process group.  */
 212   terminal_init_inferior_with_pgrp (PIDGET (inferior_ptid));
 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 #ifdef SIGTTOU
 322       /* Ignore this signal since it will happen when we try to set the
 323          pgrp.  */
 324       void (*osigttou) () = NULL;
 325 #endif
 326       int result;
 327
 328       terminal_is_ours = 1;
 329
 330 #ifdef SIGTTOU
 331       if (job_control)
 332         osigttou = (void (*)()) signal (SIGTTOU, SIG_IGN);
 333 #endif
 334
 335       if (inferior_ttystate)
 336         xfree (inferior_ttystate);
 337       inferior_ttystate = SERIAL_GET_TTY_STATE (stdin_serial);
 338 #ifdef HAVE_TERMIOS
 339       inferior_process_group = tcgetpgrp (0);
 340 #endif
 341 #ifdef HAVE_TERMIO
 342       inferior_process_group = getpgrp ();
 343 #endif
 344 #ifdef HAVE_SGTTY
 345       ioctl (0, TIOCGPGRP, &inferior_process_group);
 346 #endif
 347
 348       /* Here we used to set ICANON in our ttystate, but I believe this
 349          was an artifact from before when we used readline.  Readline sets
 350          the tty state when it needs to.
 351          FIXME-maybe: However, query() expects non-raw mode and doesn't
 352          use readline.  Maybe query should use readline (on the other hand,
 353          this only matters for HAVE_SGTTY, not termio or termios, I think).  */
 354
 355       /* Set tty state to our_ttystate.  We don't change in our out of raw
 356          mode, to avoid flushing input.  We need to do the same thing
 357          regardless of output_only, because we don't have separate
 358          terminal_is_ours and terminal_is_ours_for_output flags.  It's OK,
 359          though, since readline will deal with raw mode when/if it needs to.
 360        */
 361
 362       SERIAL_NOFLUSH_SET_TTY_STATE (stdin_serial, our_ttystate,
 363                                     inferior_ttystate);
 364
 365       if (job_control)
 366         {
 367 #ifdef HAVE_TERMIOS
 368           result = tcsetpgrp (0, our_process_group);
 369 #if 0
 370           /* This fails on Ultrix with EINVAL if you run the testsuite
 371              in the background with nohup, and then log out.  GDB never
 372              used to check for an error here, so perhaps there are other
 373              such situations as well.  */
 374           if (result == -1)
 375             fprintf_unfiltered (gdb_stderr, "[tcsetpgrp failed in terminal_ours: %s]\n",
 376                                 strerror (errno));
 377 #endif
 378 #endif /* termios */
 379
 380 #ifdef HAVE_SGTTY
 381           result = ioctl (0, TIOCSPGRP, &our_process_group);
 382 #endif
 383         }
 384
 385 #ifdef SIGTTOU
 386       if (job_control)
 387         signal (SIGTTOU, osigttou);
 388 #endif
 389
 390       if (!job_control)
 391         {
 392           signal (SIGINT, sigint_ours);
 393 #ifdef SIGQUIT
 394           signal (SIGQUIT, sigquit_ours);
 395 #endif
 396         }
 397
 398 #ifdef F_GETFL
 399       tflags_inferior = fcntl (0, F_GETFL, 0);
 400
 401       /* Is there a reason this is being done twice?  It happens both
 402          places we use F_SETFL, so I'm inclined to think perhaps there
 403          is some reason, however perverse.  Perhaps not though...  */
 404       result = fcntl (0, F_SETFL, tflags_ours);
 405       result = fcntl (0, F_SETFL, tflags_ours);
 406 #endif
 407
 408       result = result;          /* lint */
 409     }
 410 }
 411
 412 /* ARGSUSED */
 413 void
 414 term_info (char *arg, int from_tty)
 415 {
 416   target_terminal_info (arg, from_tty);
 417 }
 418
 419 /* ARGSUSED */
 420 void
 421 child_terminal_info (char *args, int from_tty)
 422 {
 423   if (!gdb_has_a_terminal ())
 424     {
 425       printf_filtered ("This GDB does not control a terminal.\n");
 426       return;
 427     }
 428
 429   printf_filtered ("Inferior's terminal status (currently saved by GDB):\n");
 430
 431   /* First the fcntl flags.  */
 432   {
 433     int flags;
 434
 435     flags = tflags_inferior;
 436
 437     printf_filtered ("File descriptor flags = ");
 438
 439 #ifndef O_ACCMODE
 440 #define O_ACCMODE (O_RDONLY | O_WRONLY | O_RDWR)
 441 #endif
 442     /* (O_ACCMODE) parens are to avoid Ultrix header file bug */
 443     switch (flags & (O_ACCMODE))
 444       {
 445       case O_RDONLY:
 446         printf_filtered ("O_RDONLY");
 447         break;
 448       case O_WRONLY:
 449         printf_filtered ("O_WRONLY");
 450         break;
 451       case O_RDWR:
 452         printf_filtered ("O_RDWR");
 453         break;
 454       }
 455     flags &= ~(O_ACCMODE);
 456
 457 #ifdef O_NONBLOCK
 458     if (flags & O_NONBLOCK)
 459       printf_filtered (" | O_NONBLOCK");
 460     flags &= ~O_NONBLOCK;
 461 #endif
 462
 463 #if defined (O_NDELAY)
 464     /* If O_NDELAY and O_NONBLOCK are defined to the same thing, we will
 465        print it as O_NONBLOCK, which is good cause that is what POSIX
 466        has, and the flag will already be cleared by the time we get here.  */
 467     if (flags & O_NDELAY)
 468       printf_filtered (" | O_NDELAY");
 469     flags &= ~O_NDELAY;
 470 #endif
 471
 472     if (flags & O_APPEND)
 473       printf_filtered (" | O_APPEND");
 474     flags &= ~O_APPEND;
 475
 476 #if defined (O_BINARY)
 477     if (flags & O_BINARY)
 478       printf_filtered (" | O_BINARY");
 479     flags &= ~O_BINARY;
 480 #endif
 481
 482     if (flags)
 483       printf_filtered (" | 0x%x", flags);
 484     printf_filtered ("\n");
 485   }
 486
 487 #ifdef PROCESS_GROUP_TYPE
 488   printf_filtered ("Process group = %d\n",
 489                    (int) inferior_process_group);
 490 #endif
 491
 492   SERIAL_PRINT_TTY_STATE (stdin_serial, inferior_ttystate, gdb_stdout);
 493 }
 494 \f
 495 /* NEW_TTY_PREFORK is called before forking a new child process,
 496    so we can record the state of ttys in the child to be formed.
 497    TTYNAME is null if we are to share the terminal with gdb;
 498    or points to a string containing the name of the desired tty.
 499
 500    NEW_TTY is called in new child processes under Unix, which will
 501    become debugger target processes.  This actually switches to
 502    the terminal specified in the NEW_TTY_PREFORK call.  */
 503
 504 void
 505 new_tty_prefork (char *ttyname)
 506 {
 507   /* Save the name for later, for determining whether we and the child
 508      are sharing a tty.  */
 509   inferior_thisrun_terminal = ttyname;
 510 }
 511
 512 void
 513 new_tty (void)
 514 {
 515   register int tty;
 516
 517   if (inferior_thisrun_terminal == 0)
 518     return;
 519 #if !defined(__GO32__) && !defined(_WIN32)
 520 #ifdef TIOCNOTTY
 521   /* Disconnect the child process from our controlling terminal.  On some
 522      systems (SVR4 for example), this may cause a SIGTTOU, so temporarily
 523      ignore SIGTTOU. */
 524   tty = open ("/dev/tty", O_RDWR);
 525   if (tty > 0)
 526     {
 527       void (*osigttou) ();
 528
 529       osigttou = (void (*)()) signal (SIGTTOU, SIG_IGN);
 530       ioctl (tty, TIOCNOTTY, 0);
 531       close (tty);
 532       signal (SIGTTOU, osigttou);
 533     }
 534 #endif
 535
 536   /* Now open the specified new terminal.  */
 537
 538 #ifdef USE_O_NOCTTY
 539   tty = open (inferior_thisrun_terminal, O_RDWR | O_NOCTTY);
 540 #else
 541   tty = open (inferior_thisrun_terminal, O_RDWR);
 542 #endif
 543   if (tty == -1)
 544     {
 545       print_sys_errmsg (inferior_thisrun_terminal, errno);
 546       _exit (1);
 547     }
 548
 549   /* Avoid use of dup2; doesn't exist on all systems.  */
 550   if (tty != 0)
 551     {
 552       close (0);
 553       dup (tty);
 554     }
 555   if (tty != 1)
 556     {
 557       close (1);
 558       dup (tty);
 559     }
 560   if (tty != 2)
 561     {
 562       close (2);
 563       dup (tty);
 564     }
 565   if (tty > 2)
 566     close (tty);
 567 #endif /* !go32 && !win32 */
 568 }
 569 \f
 570 /* Kill the inferior process.  Make us have no inferior.  */
 571
 572 /* ARGSUSED */
 573 static void
 574 kill_command (char *arg, int from_tty)
 575 {
 576   /* FIXME:  This should not really be inferior_ptid (or target_has_execution).
 577      It should be a distinct flag that indicates that a target is active, cuz
 578      some targets don't have processes! */
 579
 580   if (ptid_equal (inferior_ptid, null_ptid))
 581     error ("The program is not being run.");
 582   if (!query ("Kill the program being debugged? "))
 583     error ("Not confirmed.");
 584   target_kill ();
 585
 586   init_thread_list ();          /* Destroy thread info */
 587
 588   /* Killing off the inferior can leave us with a core file.  If so,
 589      print the state we are left in.  */
 590   if (target_has_stack)
 591     {
 592       printf_filtered ("In %s,\n", target_longname);
 593       if (selected_frame == NULL)
 594         fputs_filtered ("No selected stack frame.\n", gdb_stdout);
 595       else
 596         print_stack_frame (selected_frame, selected_frame_level, 1);
 597     }
 598 }
 599 \f
 600 /* Call set_sigint_trap when you need to pass a signal on to an attached
 601    process when handling SIGINT */
 602
 603 /* ARGSUSED */
 604 static void
 605 pass_signal (int signo)
 606 {
 607 #ifndef _WIN32
 608   kill (PIDGET (inferior_ptid), SIGINT);
 609 #endif
 610 }
 611
 612 static void (*osig) ();
 613
 614 void
 615 set_sigint_trap (void)
 616 {
 617   if (attach_flag || inferior_thisrun_terminal)
 618     {
 619       osig = (void (*)()) signal (SIGINT, pass_signal);
 620     }
 621 }
 622
 623 void
 624 clear_sigint_trap (void)
 625 {
 626   if (attach_flag || inferior_thisrun_terminal)
 627     {
 628       signal (SIGINT, osig);
 629     }
 630 }
 631 \f
 632 #if defined (SIGIO) && defined (FASYNC) && defined (FD_SET) && defined (F_SETOWN)
 633 static void (*old_sigio) ();
 634
 635 static void
 636 handle_sigio (int signo)
 637 {
 638   int numfds;
 639   fd_set readfds;
 640
 641   signal (SIGIO, handle_sigio);
 642
 643   FD_ZERO (&readfds);
 644   FD_SET (target_activity_fd, &readfds);
 645   numfds = select (target_activity_fd + 1, &readfds, NULL, NULL, NULL);
 646   if (numfds >= 0 && FD_ISSET (target_activity_fd, &readfds))
 647     {
 648 #ifndef _WIN32
 649       if ((*target_activity_function) ())
 650         kill (PIDGET (inferior_ptid), SIGINT);
 651 #endif
 652     }
 653 }
 654
 655 static int old_fcntl_flags;
 656
 657 void
 658 set_sigio_trap (void)
 659 {
 660   if (target_activity_function)
 661     {
 662       old_sigio = (void (*)()) signal (SIGIO, handle_sigio);
 663       fcntl (target_activity_fd, F_SETOWN, getpid ());
 664       old_fcntl_flags = fcntl (target_activity_fd, F_GETFL, 0);
 665       fcntl (target_activity_fd, F_SETFL, old_fcntl_flags | FASYNC);
 666     }
 667 }
 668
 669 void
 670 clear_sigio_trap (void)
 671 {
 672   if (target_activity_function)
 673     {
 674       signal (SIGIO, old_sigio);
 675       fcntl (target_activity_fd, F_SETFL, old_fcntl_flags);
 676     }
 677 }
 678 #else /* No SIGIO.  */
 679 void
 680 set_sigio_trap (void)
 681 {
 682   if (target_activity_function)
 683     internal_error (__FILE__, __LINE__, "failed internal consistency check");
 684 }
 685
 686 void
 687 clear_sigio_trap (void)
 688 {
 689   if (target_activity_function)
 690     internal_error (__FILE__, __LINE__, "failed internal consistency check");
 691 }
 692 #endif /* No SIGIO.  */
 693 \f
 694
 695 /* This is here because this is where we figure out whether we (probably)
 696    have job control.  Just using job_control only does part of it because
 697    setpgid or setpgrp might not exist on a system without job control.
 698    It might be considered misplaced (on the other hand, process groups and
 699    job control are closely related to ttys).
 700
 701    For a more clean implementation, in libiberty, put a setpgid which merely
 702    calls setpgrp and a setpgrp which does nothing (any system with job control
 703    will have one or the other).  */
 704 int
 705 gdb_setpgid (void)
 706 {
 707   int retval = 0;
 708
 709   if (job_control)
 710     {
 711 #if defined (NEED_POSIX_SETPGID) || (defined (HAVE_TERMIOS) && defined (HAVE_SETPGID))
 712       /* setpgid (0, 0) is supposed to work and mean the same thing as
 713          this, but on Ultrix 4.2A it fails with EPERM (and
 714          setpgid (getpid (), getpid ()) succeeds).  */
 715       retval = setpgid (getpid (), getpid ());
 716 #else
 717 #if defined (TIOCGPGRP)
 718 #if defined(USG) && !defined(SETPGRP_ARGS)
 719       retval = setpgrp ();
 720 #else
 721       retval = setpgrp (getpid (), getpid ());
 722 #endif /* USG */
 723 #endif /* TIOCGPGRP.  */
 724 #endif /* NEED_POSIX_SETPGID */
 725     }
 726   return retval;
 727 }
 728
 729 void
 730 _initialize_inflow (void)
 731 {
 732   add_info ("terminal", term_info,
 733             "Print inferior's saved terminal status.");
 734
 735   add_com ("kill", class_run, kill_command,
 736            "Kill execution of program being debugged.");
 737
 738   inferior_ptid = null_ptid;
 739
 740   terminal_is_ours = 1;
 741
 742   /* OK, figure out whether we have job control.  If neither termios nor
 743      sgtty (i.e. termio or go32), leave job_control 0.  */
 744
 745 #if defined (HAVE_TERMIOS)
 746   /* Do all systems with termios have the POSIX way of identifying job
 747      control?  I hope so.  */
 748 #ifdef _POSIX_JOB_CONTROL
 749   job_control = 1;
 750 #else
 751 #ifdef _SC_JOB_CONTROL
 752   job_control = sysconf (_SC_JOB_CONTROL);
 753 #else
 754   job_control = 0;              /* have to assume the worst */
 755 #endif /* _SC_JOB_CONTROL */
 756 #endif /* _POSIX_JOB_CONTROL */
 757 #endif /* HAVE_TERMIOS */
 758
 759 #ifdef HAVE_SGTTY
 760 #ifdef TIOCGPGRP
 761   job_control = 1;
 762 #else
 763   job_control = 0;
 764 #endif /* TIOCGPGRP */
 765 #endif /* sgtty */
 766 }