gdb/inflow.c

   1 /* Low level interface to ptrace, for GDB when running under Unix.
   2    Copyright 1986, 1987, 1989, 1991, 1992, 1995 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., 675 Mass Ave, Cambridge, MA 02139, USA.  */
  19
  20 #include "defs.h"
  21 #include "frame.h"
  22 #include "inferior.h"
  23 #include "command.h"
  24 #include "signals.h"
  25 #include "serial.h"
  26 #include "terminal.h"
  27 #include "target.h"
  28 #include "thread.h"
  29
  30 #include "gdb_string.h"
  31 #include <signal.h>
  32 #include <fcntl.h>
  33
  34 #if !defined (HAVE_TERMIOS) && !defined (HAVE_TERMIO) && !defined (HAVE_SGTTY) && !defined (__GO32__) && !defined(WIN32)
  35 #define HAVE_SGTTY
  36 #endif
  37
  38 #if defined (HAVE_TERMIOS)
  39 #include <termios.h>
  40 #include <unistd.h>
  41 #endif
  42
  43 #ifdef HAVE_TERMIOS
  44 #define PROCESS_GROUP_TYPE pid_t
  45 #endif
  46
  47 #ifdef HAVE_SGTTY
  48 #ifdef SHORT_PGRP
  49 /* This is only used for the ultra.  Does it have pid_t?  */
  50 #define PROCESS_GROUP_TYPE short
  51 #else
  52 #define PROCESS_GROUP_TYPE int
  53 #endif
  54 #endif /* sgtty */
  55
  56 static void
  57 kill_command PARAMS ((char *, int));
  58
  59 static void
  60 terminal_ours_1 PARAMS ((int));
  61 \f
  62 /* Record terminal status separately for debugger and inferior.  */
  63
  64 static serial_t stdin_serial;
  65
  66 /* TTY state for the inferior.  We save it whenever the inferior stops, and
  67    restore it when it resumes.  */
  68 static serial_ttystate inferior_ttystate;
  69
  70 /* Our own tty state, which we restore every time we need to deal with the
  71    terminal.  We only set it once, when GDB first starts.  The settings of
  72    flags which readline saves and restores and unimportant.  */
  73 static serial_ttystate our_ttystate;
  74
  75 /* fcntl flags for us and the inferior.  Saved and restored just like
  76    {our,inferior}_ttystate.  */
  77 static int tflags_inferior;
  78 static int tflags_ours;
  79
  80 #ifdef PROCESS_GROUP_TYPE
  81 /* Process group for us and the inferior.  Saved and restored just like
  82    {our,inferior}_ttystate.  */
  83 PROCESS_GROUP_TYPE our_process_group;
  84 PROCESS_GROUP_TYPE inferior_process_group;
  85 #endif
  86
  87 /* While the inferior is running, we want SIGINT and SIGQUIT to go to the
  88    inferior only.  If we have job control, that takes care of it.  If not,
  89    we save our handlers in these two variables and set SIGINT and SIGQUIT
  90    to SIG_IGN.  */
  91 static void (*sigint_ours) ();
  92 static void (*sigquit_ours) ();
  93
  94 /* The name of the tty (from the `tty' command) that we gave to the inferior
  95    when it was last started.  */
  96
  97 static char *inferior_thisrun_terminal;
  98
  99 /* Nonzero if our terminal settings are in effect.  Zero if the
 100    inferior's settings are in effect.  Ignored if !gdb_has_a_terminal
 101    ().  */
 102
 103 static int terminal_is_ours;
 104
 105 enum {yes, no, have_not_checked} gdb_has_a_terminal_flag = have_not_checked;
 106
 107 /* Does GDB have a terminal (on stdin)?  */
 108 int
 109 gdb_has_a_terminal ()
 110 {
 111   switch (gdb_has_a_terminal_flag)
 112     {
 113     case yes:
 114       return 1;
 115     case no:
 116       return 0;
 117     case have_not_checked:
 118       /* Get all the current tty settings (including whether we have a tty at
 119          all!).  Can't do this in _initialize_inflow because SERIAL_FDOPEN
 120          won't work until the serial_ops_list is initialized.  */
 121
 122 #ifdef F_GETFL
 123       tflags_ours = fcntl (0, F_GETFL, 0);
 124 #endif
 125
 126       gdb_has_a_terminal_flag = no;
 127       stdin_serial = SERIAL_FDOPEN (0);
 128       if (stdin_serial != NULL)
 129         {
 130           our_ttystate = SERIAL_GET_TTY_STATE (stdin_serial);
 131
 132           if (our_ttystate != NULL)
 133             {
 134               gdb_has_a_terminal_flag = yes;
 135 #ifdef HAVE_TERMIOS
 136               our_process_group = tcgetpgrp (0);
 137 #endif
 138 #ifdef HAVE_SGTTY
 139               ioctl (0, TIOCGPGRP, &our_process_group);
 140 #endif
 141             }
 142         }
 143
 144       return gdb_has_a_terminal_flag == yes;
 145     default:
 146       /* "Can't happen".  */
 147       return 0;
 148     }
 149 }
 150
 151 /* Macro for printing errors from ioctl operations */
 152
 153 #define OOPSY(what)     \
 154   if (result == -1)     \
 155     fprintf_unfiltered(gdb_stderr, "[%s failed in terminal_inferior: %s]\n", \
 156             what, strerror (errno))
 157
 158 static void terminal_ours_1 PARAMS ((int));
 159
 160 /* Initialize the terminal settings we record for the inferior,
 161    before we actually run the inferior.  */
 162
 163 void
 164 terminal_init_inferior ()
 165 {
 166   if (gdb_has_a_terminal ())
 167     {
 168       /* We could just as well copy our_ttystate (if we felt like adding
 169          a new function SERIAL_COPY_TTY_STATE).  */
 170       if (inferior_ttystate)
 171         free (inferior_ttystate);
 172       inferior_ttystate = SERIAL_GET_TTY_STATE (stdin_serial);
 173 #ifdef PROCESS_GROUP_TYPE
 174 #ifdef PIDGET
 175       /* This is for Lynx, and should be cleaned up by having Lynx be
 176          a separate debugging target with a version of
 177          target_terminal_init_inferior which passes in the process
 178          group to a generic routine which does all the work (and the
 179          non-threaded child_terminal_init_inferior can just pass in
 180          inferior_pid to the same routine).  */
 181       inferior_process_group = PIDGET (inferior_pid);
 182 #else
 183       inferior_process_group = inferior_pid;
 184 #endif
 185 #endif
 186
 187       /* Make sure that next time we call terminal_inferior (which will be
 188          before the program runs, as it needs to be), we install the new
 189          process group.  */
 190       terminal_is_ours = 1;
 191     }
 192 }
 193
 194 /* Put the inferior's terminal settings into effect.
 195    This is preparation for starting or resuming the inferior.  */
 196
 197 void
 198 terminal_inferior ()
 199 {
 200   if (gdb_has_a_terminal () && terminal_is_ours
 201       && inferior_thisrun_terminal == 0)
 202     {
 203       int result;
 204
 205 #ifdef F_GETFL
 206       /* Is there a reason this is being done twice?  It happens both
 207          places we use F_SETFL, so I'm inclined to think perhaps there
 208          is some reason, however perverse.  Perhaps not though...  */
 209       result = fcntl (0, F_SETFL, tflags_inferior);
 210       result = fcntl (0, F_SETFL, tflags_inferior);
 211       OOPSY ("fcntl F_SETFL");
 212 #endif
 213
 214       /* Because we were careful to not change in or out of raw mode in
 215          terminal_ours, we will not change in our out of raw mode with
 216          this call, so we don't flush any input.  */
 217       result = SERIAL_SET_TTY_STATE (stdin_serial, inferior_ttystate);
 218       OOPSY ("setting tty state");
 219
 220       if (!job_control)
 221         {
 222           sigint_ours = (void (*) ()) signal (SIGINT, SIG_IGN);
 223           sigquit_ours = (void (*) ()) signal (SIGQUIT, SIG_IGN);
 224         }
 225
 226       /* If attach_flag is set, we don't know whether we are sharing a
 227          terminal with the inferior or not.  (attaching a process
 228          without a terminal is one case where we do not; attaching a
 229          process which we ran from the same shell as GDB via `&' is
 230          one case where we do, I think (but perhaps this is not
 231          `sharing' in the sense that we need to save and restore tty
 232          state)).  I don't know if there is any way to tell whether we
 233          are sharing a terminal.  So what we do is to go through all
 234          the saving and restoring of the tty state, but ignore errors
 235          setting the process group, which will happen if we are not
 236          sharing a terminal).  */
 237
 238       if (job_control)
 239         {
 240 #ifdef HAVE_TERMIOS
 241           result = tcsetpgrp (0, inferior_process_group);
 242           if (!attach_flag)
 243             OOPSY ("tcsetpgrp");
 244 #endif
 245
 246 #ifdef HAVE_SGTTY
 247           result = ioctl (0, TIOCSPGRP, &inferior_process_group);
 248           if (!attach_flag)
 249             OOPSY ("TIOCSPGRP");
 250 #endif
 251         }
 252
 253     }
 254   terminal_is_ours = 0;
 255 }
 256
 257 /* Put some of our terminal settings into effect,
 258    enough to get proper results from our output,
 259    but do not change into or out of RAW mode
 260    so that no input is discarded.
 261
 262    After doing this, either terminal_ours or terminal_inferior
 263    should be called to get back to a normal state of affairs.  */
 264
 265 void
 266 terminal_ours_for_output ()
 267 {
 268   terminal_ours_1 (1);
 269 }
 270
 271 /* Put our terminal settings into effect.
 272    First record the inferior's terminal settings
 273    so they can be restored properly later.  */
 274
 275 void
 276 terminal_ours ()
 277 {
 278   terminal_ours_1 (0);
 279 }
 280
 281 /* output_only is not used, and should not be used unless we introduce
 282    separate terminal_is_ours and terminal_is_ours_for_output
 283    flags.  */
 284
 285 static void
 286 terminal_ours_1 (output_only)
 287      int output_only;
 288 {
 289   /* Checking inferior_thisrun_terminal is necessary so that
 290      if GDB is running in the background, it won't block trying
 291      to do the ioctl()'s below.  Checking gdb_has_a_terminal
 292      avoids attempting all the ioctl's when running in batch.  */
 293   if (inferior_thisrun_terminal != 0 || gdb_has_a_terminal () == 0)
 294     return;
 295
 296   if (!terminal_is_ours)
 297     {
 298       /* Ignore this signal since it will happen when we try to set the
 299          pgrp.  */
 300       void (*osigttou) ();
 301       int result;
 302
 303       terminal_is_ours = 1;
 304
 305 #ifdef SIGTTOU
 306       if (job_control)
 307         osigttou = (void (*) ()) signal (SIGTTOU, SIG_IGN);
 308 #endif
 309
 310       if (inferior_ttystate)
 311         free (inferior_ttystate);
 312       inferior_ttystate = SERIAL_GET_TTY_STATE (stdin_serial);
 313 #ifdef HAVE_TERMIOS
 314       inferior_process_group = tcgetpgrp (0);
 315 #endif
 316 #ifdef HAVE_SGTTY
 317       ioctl (0, TIOCGPGRP, &inferior_process_group);
 318 #endif
 319
 320       /* Here we used to set ICANON in our ttystate, but I believe this
 321          was an artifact from before when we used readline.  Readline sets
 322          the tty state when it needs to.
 323          FIXME-maybe: However, query() expects non-raw mode and doesn't
 324          use readline.  Maybe query should use readline (on the other hand,
 325          this only matters for HAVE_SGTTY, not termio or termios, I think).  */
 326
 327       /* Set tty state to our_ttystate.  We don't change in our out of raw
 328          mode, to avoid flushing input.  We need to do the same thing
 329          regardless of output_only, because we don't have separate
 330          terminal_is_ours and terminal_is_ours_for_output flags.  It's OK,
 331          though, since readline will deal with raw mode when/if it needs to.
 332          */
 333
 334       SERIAL_NOFLUSH_SET_TTY_STATE (stdin_serial, our_ttystate,
 335                                     inferior_ttystate);
 336
 337       if (job_control)
 338         {
 339 #ifdef HAVE_TERMIOS
 340           result = tcsetpgrp (0, our_process_group);
 341 #if 0
 342           /* This fails on Ultrix with EINVAL if you run the testsuite
 343              in the background with nohup, and then log out.  GDB never
 344              used to check for an error here, so perhaps there are other
 345              such situations as well.  */
 346           if (result == -1)
 347             fprintf_unfiltered (gdb_stderr, "[tcsetpgrp failed in terminal_ours: %s]\n",
 348                      strerror (errno));
 349 #endif
 350 #endif /* termios */
 351
 352 #ifdef HAVE_SGTTY
 353           result = ioctl (0, TIOCSPGRP, &our_process_group);
 354 #endif
 355         }
 356
 357 #ifdef SIGTTOU
 358       if (job_control)
 359         signal (SIGTTOU, osigttou);
 360 #endif
 361
 362       if (!job_control)
 363         {
 364           signal (SIGINT, sigint_ours);
 365           signal (SIGQUIT, sigquit_ours);
 366         }
 367
 368 #ifdef F_GETFL
 369       tflags_inferior = fcntl (0, F_GETFL, 0);
 370
 371       /* Is there a reason this is being done twice?  It happens both
 372          places we use F_SETFL, so I'm inclined to think perhaps there
 373          is some reason, however perverse.  Perhaps not though...  */
 374       result = fcntl (0, F_SETFL, tflags_ours);
 375       result = fcntl (0, F_SETFL, tflags_ours);
 376 #endif
 377
 378       result = result;  /* lint */
 379     }
 380 }
 381
 382 /* ARGSUSED */
 383 void
 384 term_info (arg, from_tty)
 385      char *arg;
 386      int from_tty;
 387 {
 388   target_terminal_info (arg, from_tty);
 389 }
 390
 391 /* ARGSUSED */
 392 void
 393 child_terminal_info (args, from_tty)
 394      char *args;
 395      int from_tty;
 396 {
 397   if (!gdb_has_a_terminal ())
 398     {
 399       printf_filtered ("This GDB does not control a terminal.\n");
 400       return;
 401     }
 402
 403   printf_filtered ("Inferior's terminal status (currently saved by GDB):\n");
 404
 405   /* First the fcntl flags.  */
 406   {
 407     int flags;
 408
 409     flags = tflags_inferior;
 410
 411     printf_filtered ("File descriptor flags = ");
 412
 413 #ifndef O_ACCMODE
 414 #define O_ACCMODE (O_RDONLY | O_WRONLY | O_RDWR)
 415 #endif
 416     /* (O_ACCMODE) parens are to avoid Ultrix header file bug */
 417     switch (flags & (O_ACCMODE))
 418       {
 419       case O_RDONLY: printf_filtered ("O_RDONLY"); break;
 420       case O_WRONLY: printf_filtered ("O_WRONLY"); break;
 421       case O_RDWR: printf_filtered ("O_RDWR"); break;
 422       }
 423     flags &= ~(O_ACCMODE);
 424
 425 #ifdef O_NONBLOCK
 426     if (flags & O_NONBLOCK)
 427       printf_filtered (" | O_NONBLOCK");
 428     flags &= ~O_NONBLOCK;
 429 #endif
 430
 431 #if defined (O_NDELAY)
 432     /* If O_NDELAY and O_NONBLOCK are defined to the same thing, we will
 433        print it as O_NONBLOCK, which is good cause that is what POSIX
 434        has, and the flag will already be cleared by the time we get here.  */
 435     if (flags & O_NDELAY)
 436       printf_filtered (" | O_NDELAY");
 437     flags &= ~O_NDELAY;
 438 #endif
 439
 440     if (flags & O_APPEND)
 441       printf_filtered (" | O_APPEND");
 442     flags &= ~O_APPEND;
 443
 444 #if defined (O_BINARY)
 445     if (flags & O_BINARY)
 446       printf_filtered (" | O_BINARY");
 447     flags &= ~O_BINARY;
 448 #endif
 449
 450     if (flags)
 451       printf_filtered (" | 0x%x", flags);
 452     printf_filtered ("\n");
 453   }
 454
 455 #ifdef PROCESS_GROUP_TYPE
 456   printf_filtered ("Process group = %d\n", inferior_process_group);
 457 #endif
 458
 459   SERIAL_PRINT_TTY_STATE (stdin_serial, inferior_ttystate);
 460 }
 461 \f
 462 /* NEW_TTY_PREFORK is called before forking a new child process,
 463    so we can record the state of ttys in the child to be formed.
 464    TTYNAME is null if we are to share the terminal with gdb;
 465    or points to a string containing the name of the desired tty.
 466
 467    NEW_TTY is called in new child processes under Unix, which will
 468    become debugger target processes.  This actually switches to
 469    the terminal specified in the NEW_TTY_PREFORK call.  */
 470
 471 void
 472 new_tty_prefork (ttyname)
 473      char *ttyname;
 474 {
 475   /* Save the name for later, for determining whether we and the child
 476      are sharing a tty.  */
 477   inferior_thisrun_terminal = ttyname;
 478 }
 479
 480 void
 481 new_tty ()
 482 {
 483   register int tty;
 484
 485   if (inferior_thisrun_terminal == 0)
 486     return;
 487 #if !defined(__GO32__) && !defined(WIN32)
 488 #ifdef TIOCNOTTY
 489   /* Disconnect the child process from our controlling terminal.  On some
 490      systems (SVR4 for example), this may cause a SIGTTOU, so temporarily
 491      ignore SIGTTOU. */
 492   tty = open("/dev/tty", O_RDWR);
 493   if (tty > 0)
 494     {
 495       void (*osigttou) ();
 496
 497       osigttou = (void (*)()) signal(SIGTTOU, SIG_IGN);
 498       ioctl(tty, TIOCNOTTY, 0);
 499       close(tty);
 500       signal(SIGTTOU, osigttou);
 501     }
 502 #endif
 503
 504   /* Now open the specified new terminal.  */
 505
 506 #ifdef USE_O_NOCTTY
 507   tty = open(inferior_thisrun_terminal, O_RDWR | O_NOCTTY);
 508 #else
 509   tty = open(inferior_thisrun_terminal, O_RDWR);
 510 #endif
 511   if (tty == -1)
 512     {
 513       print_sys_errmsg (inferior_thisrun_terminal, errno);
 514       _exit(1);
 515     }
 516
 517   /* Avoid use of dup2; doesn't exist on all systems.  */
 518   if (tty != 0)
 519     { close (0); dup (tty); }
 520   if (tty != 1)
 521     { close (1); dup (tty); }
 522   if (tty != 2)
 523     { close (2); dup (tty); }
 524   if (tty > 2)
 525     close(tty);
 526 #endif /* !go32 && !win32*/
 527 }
 528 \f
 529 /* Kill the inferior process.  Make us have no inferior.  */
 530
 531 /* ARGSUSED */
 532 static void
 533 kill_command (arg, from_tty)
 534      char *arg;
 535      int from_tty;
 536 {
 537   /* FIXME:  This should not really be inferior_pid (or target_has_execution).
 538      It should be a distinct flag that indicates that a target is active, cuz
 539      some targets don't have processes! */
 540
 541   if (inferior_pid == 0)
 542     error ("The program is not being run.");
 543   if (!query ("Kill the program being debugged? "))
 544     error ("Not confirmed.");
 545   target_kill ();
 546
 547   init_thread_list();           /* Destroy thread info */
 548
 549   /* Killing off the inferior can leave us with a core file.  If so,
 550      print the state we are left in.  */
 551   if (target_has_stack) {
 552     printf_filtered ("In %s,\n", target_longname);
 553     if (selected_frame == NULL)
 554       fputs_filtered ("No selected stack frame.\n", gdb_stdout);
 555     else
 556       print_stack_frame (selected_frame, selected_frame_level, 1);
 557   }
 558 }
 559 \f
 560 /* Call set_sigint_trap when you need to pass a signal on to an attached
 561    process when handling SIGINT */
 562
 563 /* ARGSUSED */
 564 static void
 565 pass_signal (signo)
 566     int signo;
 567 {
 568   kill (inferior_pid, SIGINT);
 569 }
 570
 571 static void (*osig)();
 572
 573 void
 574 set_sigint_trap()
 575 {
 576   if (attach_flag || inferior_thisrun_terminal)
 577     {
 578       osig = (void (*) ()) signal (SIGINT, pass_signal);
 579     }
 580 }
 581
 582 void
 583 clear_sigint_trap()
 584 {
 585   if (attach_flag || inferior_thisrun_terminal)
 586     {
 587       signal (SIGINT, osig);
 588     }
 589 }
 590 \f
 591 #if defined (SIGIO) && defined (FASYNC) && defined (FD_SET) && defined (F_SETOWN)
 592 static void (*old_sigio) ();
 593
 594 static void
 595 handle_sigio (signo)
 596      int signo;
 597 {
 598   int numfds;
 599   fd_set readfds;
 600
 601   signal (SIGIO, handle_sigio);
 602
 603   FD_ZERO (&readfds);
 604   FD_SET (target_activity_fd, &readfds);
 605   numfds = select (target_activity_fd + 1, &readfds, NULL, NULL, NULL);
 606   if (numfds >= 0 && FD_ISSET (target_activity_fd, &readfds))
 607     {
 608       if ((*target_activity_function) ())
 609         kill (inferior_pid, SIGINT);
 610     }
 611 }
 612
 613 static int old_fcntl_flags;
 614
 615 void
 616 set_sigio_trap ()
 617 {
 618   if (target_activity_function)
 619     {
 620       old_sigio = (void (*) ()) signal (SIGIO, handle_sigio);
 621       fcntl (target_activity_fd, F_SETOWN, getpid());
 622       old_fcntl_flags = fcntl (target_activity_fd, F_GETFL, 0);
 623       fcntl (target_activity_fd, F_SETFL, old_fcntl_flags | FASYNC);
 624     }
 625 }
 626
 627 void
 628 clear_sigio_trap ()
 629 {
 630   if (target_activity_function)
 631     {
 632       signal (SIGIO, old_sigio);
 633       fcntl (target_activity_fd, F_SETFL, old_fcntl_flags);
 634     }
 635 }
 636 #else /* No SIGIO.  */
 637 void
 638 set_sigio_trap ()
 639 {
 640   if (target_activity_function)
 641     abort ();
 642 }
 643
 644 void
 645 clear_sigio_trap ()
 646 {
 647   if (target_activity_function)
 648     abort ();
 649 }
 650 #endif /* No SIGIO.  */
 651 \f
 652
 653 /* This is here because this is where we figure out whether we (probably)
 654    have job control.  Just using job_control only does part of it because
 655    setpgid or setpgrp might not exist on a system without job control.
 656    It might be considered misplaced (on the other hand, process groups and
 657    job control are closely related to ttys).
 658
 659    For a more clean implementation, in libiberty, put a setpgid which merely
 660    calls setpgrp and a setpgrp which does nothing (any system with job control
 661    will have one or the other).  */
 662 int
 663 gdb_setpgid ()
 664 {
 665   int retval = 0;
 666
 667   if (job_control)
 668     {
 669 #if defined (NEED_POSIX_SETPGID) || defined (HAVE_TERMIOS)
 670       /* Do all systems with termios have setpgid?  I hope so.  */
 671       /* setpgid (0, 0) is supposed to work and mean the same thing as
 672          this, but on Ultrix 4.2A it fails with EPERM (and
 673          setpgid (getpid (), getpid ()) succeeds).  */
 674       retval = setpgid (getpid (), getpid ());
 675 #else
 676 #if defined (TIOCGPGRP)
 677 #if defined(USG) && !defined(SETPGRP_ARGS)
 678       retval = setpgrp ();
 679 #else
 680       retval = setpgrp (getpid (), getpid ());
 681 #endif /* USG */
 682 #endif /* TIOCGPGRP.  */
 683 #endif /* NEED_POSIX_SETPGID */
 684     }
 685   return retval;
 686 }
 687
 688 void
 689 _initialize_inflow ()
 690 {
 691   add_info ("terminal", term_info,
 692            "Print inferior's saved terminal status.");
 693
 694   add_com ("kill", class_run, kill_command,
 695            "Kill execution of program being debugged.");
 696
 697   inferior_pid = 0;
 698
 699   terminal_is_ours = 1;
 700
 701   /* OK, figure out whether we have job control.  If neither termios nor
 702      sgtty (i.e. termio or go32), leave job_control 0.  */
 703
 704 #if defined (HAVE_TERMIOS)
 705   /* Do all systems with termios have the POSIX way of identifying job
 706      control?  I hope so.  */
 707 #ifdef _POSIX_JOB_CONTROL
 708   job_control = 1;
 709 #else
 710   job_control = sysconf (_SC_JOB_CONTROL);
 711 #endif
 712 #endif /* termios */
 713
 714 #ifdef HAVE_SGTTY
 715 #ifdef TIOCGPGRP
 716   job_control = 1;
 717 #else
 718   job_control = 0;
 719 #endif /* TIOCGPGRP */
 720 #endif /* sgtty */
 721 }