gdb/inflow.c

   1 /* Low level interface to ptrace, for GDB when running under Unix.
   2    Copyright (C) 1986-2013 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 3 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, see <http://www.gnu.org/licenses/>.  */
  18
  19 #include "defs.h"
  20 #include "frame.h"
  21 #include "inferior.h"
  22 #include "command.h"
  23 #include "serial.h"
  24 #include "terminal.h"
  25 #include "target.h"
  26 #include "gdbthread.h"
  27 #include "observer.h"
  28
  29 #include "gdb_string.h"
  30 #include <signal.h>
  31 #include <fcntl.h>
  32 #include "gdb_select.h"
  33
  34 #include "inflow.h"
  35 #include "gdbcmd.h"
  36
  37 #ifdef HAVE_SYS_IOCTL_H
  38 #include <sys/ioctl.h>
  39 #endif
  40
  41 #ifndef O_NOCTTY
  42 #define O_NOCTTY 0
  43 #endif
  44
  45 extern void _initialize_inflow (void);
  46
  47 static void pass_signal (int);
  48
  49 static void terminal_ours_1 (int);
  50 \f
  51 /* Record terminal status separately for debugger and inferior.  */
  52
  53 static struct serial *stdin_serial;
  54
  55 /* Terminal related info we need to keep track of.  Each inferior
  56    holds an instance of this structure --- we save it whenever the
  57    corresponding inferior stops, and restore it to the foreground
  58    inferior when it resumes.  */
  59 struct terminal_info
  60 {
  61   /* The name of the tty (from the `tty' command) that we gave to the
  62      inferior when it was started.  */
  63   char *run_terminal;
  64
  65   /* TTY state.  We save it whenever the inferior stops, and restore
  66      it when it resumes.  */
  67   serial_ttystate ttystate;
  68
  69 #ifdef PROCESS_GROUP_TYPE
  70   /* Process group.  Saved and restored just like ttystate.  */
  71   PROCESS_GROUP_TYPE process_group;
  72 #endif
  73
  74   /* fcntl flags.  Saved and restored just like ttystate.  */
  75   int tflags;
  76 };
  77
  78 /* Our own tty state, which we restore every time we need to deal with
  79    the terminal.  This is only set once, when GDB first starts.  The
  80    settings of flags which readline saves and restores and
  81    unimportant.  */
  82 static struct terminal_info our_terminal_info;
  83
  84 static struct terminal_info *get_inflow_inferior_data (struct inferior *);
  85
  86 #ifdef PROCESS_GROUP_TYPE
  87
  88 /* Return the process group of the current inferior.  */
  89
  90 PROCESS_GROUP_TYPE
  91 inferior_process_group (void)
  92 {
  93   return get_inflow_inferior_data (current_inferior ())->process_group;
  94 }
  95 #endif
  96
  97 /* While the inferior is running, we want SIGINT and SIGQUIT to go to the
  98    inferior only.  If we have job control, that takes care of it.  If not,
  99    we save our handlers in these two variables and set SIGINT and SIGQUIT
 100    to SIG_IGN.  */
 101
 102 static void (*sigint_ours) ();
 103 static void (*sigquit_ours) ();
 104
 105 /* The name of the tty (from the `tty' command) that we're giving to
 106    the inferior when starting it up.  This is only (and should only
 107    be) used as a transient global by new_tty_prefork,
 108    create_tty_session, new_tty and new_tty_postfork, all called from
 109    fork_inferior, while forking a new child.  */
 110 static const char *inferior_thisrun_terminal;
 111
 112 /* Nonzero if our terminal settings are in effect.  Zero if the
 113    inferior's settings are in effect.  Ignored if !gdb_has_a_terminal
 114    ().  */
 115
 116 int terminal_is_ours;
 117
 118 #ifdef PROCESS_GROUP_TYPE
 119 static PROCESS_GROUP_TYPE
 120 gdb_getpgrp (void)
 121 {
 122   int process_group = -1;
 123
 124 #ifdef HAVE_TERMIOS
 125   process_group = tcgetpgrp (0);
 126 #endif
 127 #ifdef HAVE_TERMIO
 128   process_group = getpgrp ();
 129 #endif
 130 #ifdef HAVE_SGTTY
 131   ioctl (0, TIOCGPGRP, &process_group);
 132 #endif
 133   return process_group;
 134 }
 135 #endif
 136
 137 enum
 138   {
 139     yes, no, have_not_checked
 140   }
 141 gdb_has_a_terminal_flag = have_not_checked;
 142
 143 /* The value of the "interactive-mode" setting.  */
 144 static enum auto_boolean interactive_mode = AUTO_BOOLEAN_AUTO;
 145
 146 /* Implement the "show interactive-mode" option.  */
 147
 148 static void
 149 show_interactive_mode (struct ui_file *file, int from_tty,
 150                        struct cmd_list_element *c,
 151                        const char *value)
 152 {
 153   if (interactive_mode == AUTO_BOOLEAN_AUTO)
 154     fprintf_filtered (file, "Debugger's interactive mode "
 155                             "is %s (currently %s).\n",
 156                       value, gdb_has_a_terminal () ? "on" : "off");
 157   else
 158     fprintf_filtered (file, "Debugger's interactive mode is %s.\n", value);
 159 }
 160
 161 /* Does GDB have a terminal (on stdin)?  */
 162 int
 163 gdb_has_a_terminal (void)
 164 {
 165   if (interactive_mode != AUTO_BOOLEAN_AUTO)
 166     return interactive_mode == AUTO_BOOLEAN_TRUE;
 167
 168   switch (gdb_has_a_terminal_flag)
 169     {
 170     case yes:
 171       return 1;
 172     case no:
 173       return 0;
 174     case have_not_checked:
 175       /* Get all the current tty settings (including whether we have a
 176          tty at all!).  Can't do this in _initialize_inflow because
 177          serial_fdopen() won't work until the serial_ops_list is
 178          initialized.  */
 179
 180 #ifdef F_GETFL
 181       our_terminal_info.tflags = fcntl (0, F_GETFL, 0);
 182 #endif
 183
 184       gdb_has_a_terminal_flag = no;
 185       if (stdin_serial != NULL)
 186         {
 187           our_terminal_info.ttystate = serial_get_tty_state (stdin_serial);
 188
 189           if (our_terminal_info.ttystate != NULL)
 190             {
 191               gdb_has_a_terminal_flag = yes;
 192 #ifdef PROCESS_GROUP_TYPE
 193               our_terminal_info.process_group = gdb_getpgrp ();
 194 #endif
 195             }
 196         }
 197
 198       return gdb_has_a_terminal_flag == yes;
 199     default:
 200       /* "Can't happen".  */
 201       return 0;
 202     }
 203 }
 204
 205 /* Macro for printing errors from ioctl operations */
 206
 207 #define OOPSY(what)     \
 208   if (result == -1)     \
 209     fprintf_unfiltered(gdb_stderr, "[%s failed in terminal_inferior: %s]\n", \
 210             what, safe_strerror (errno))
 211
 212 static void terminal_ours_1 (int);
 213
 214 /* Initialize the terminal settings we record for the inferior,
 215    before we actually run the inferior.  */
 216
 217 void
 218 terminal_init_inferior_with_pgrp (int pgrp)
 219 {
 220   if (gdb_has_a_terminal ())
 221     {
 222       struct inferior *inf = current_inferior ();
 223       struct terminal_info *tinfo = get_inflow_inferior_data (inf);
 224
 225       xfree (tinfo->ttystate);
 226       tinfo->ttystate = serial_copy_tty_state (stdin_serial,
 227                                                our_terminal_info.ttystate);
 228
 229 #ifdef PROCESS_GROUP_TYPE
 230       tinfo->process_group = pgrp;
 231 #endif
 232
 233       /* Make sure that next time we call terminal_inferior (which will be
 234          before the program runs, as it needs to be), we install the new
 235          process group.  */
 236       terminal_is_ours = 1;
 237     }
 238 }
 239
 240 /* Save the terminal settings again.  This is necessary for the TUI
 241    when it switches to TUI or non-TUI mode;  curses changes the terminal
 242    and gdb must be able to restore it correctly.  */
 243
 244 void
 245 terminal_save_ours (void)
 246 {
 247   if (gdb_has_a_terminal ())
 248     {
 249       xfree (our_terminal_info.ttystate);
 250       our_terminal_info.ttystate = serial_get_tty_state (stdin_serial);
 251     }
 252 }
 253
 254 void
 255 terminal_init_inferior (void)
 256 {
 257 #ifdef PROCESS_GROUP_TYPE
 258   /* This is for Lynx, and should be cleaned up by having Lynx be a separate
 259      debugging target with a version of target_terminal_init_inferior which
 260      passes in the process group to a generic routine which does all the work
 261      (and the non-threaded child_terminal_init_inferior can just pass in
 262      inferior_ptid to the same routine).  */
 263   /* We assume INFERIOR_PID is also the child's process group.  */
 264   terminal_init_inferior_with_pgrp (PIDGET (inferior_ptid));
 265 #endif /* PROCESS_GROUP_TYPE */
 266 }
 267
 268 /* Put the inferior's terminal settings into effect.
 269    This is preparation for starting or resuming the inferior.  */
 270
 271 void
 272 terminal_inferior (void)
 273 {
 274   struct inferior *inf;
 275   struct terminal_info *tinfo;
 276
 277   if (!terminal_is_ours)
 278     return;
 279
 280   inf = current_inferior ();
 281   tinfo = get_inflow_inferior_data (inf);
 282
 283   if (gdb_has_a_terminal ()
 284       && tinfo->ttystate != NULL
 285       && tinfo->run_terminal == NULL)
 286     {
 287       int result;
 288
 289 #ifdef F_GETFL
 290       /* Is there a reason this is being done twice?  It happens both
 291          places we use F_SETFL, so I'm inclined to think perhaps there
 292          is some reason, however perverse.  Perhaps not though...  */
 293       result = fcntl (0, F_SETFL, tinfo->tflags);
 294       result = fcntl (0, F_SETFL, tinfo->tflags);
 295       OOPSY ("fcntl F_SETFL");
 296 #endif
 297
 298       /* Because we were careful to not change in or out of raw mode in
 299          terminal_ours, we will not change in our out of raw mode with
 300          this call, so we don't flush any input.  */
 301       result = serial_set_tty_state (stdin_serial,
 302                                      tinfo->ttystate);
 303       OOPSY ("setting tty state");
 304
 305       if (!job_control)
 306         {
 307           sigint_ours = (void (*)()) signal (SIGINT, SIG_IGN);
 308 #ifdef SIGQUIT
 309           sigquit_ours = (void (*)()) signal (SIGQUIT, SIG_IGN);
 310 #endif
 311         }
 312
 313       /* If attach_flag is set, we don't know whether we are sharing a
 314          terminal with the inferior or not.  (attaching a process
 315          without a terminal is one case where we do not; attaching a
 316          process which we ran from the same shell as GDB via `&' is
 317          one case where we do, I think (but perhaps this is not
 318          `sharing' in the sense that we need to save and restore tty
 319          state)).  I don't know if there is any way to tell whether we
 320          are sharing a terminal.  So what we do is to go through all
 321          the saving and restoring of the tty state, but ignore errors
 322          setting the process group, which will happen if we are not
 323          sharing a terminal).  */
 324
 325       if (job_control)
 326         {
 327 #ifdef HAVE_TERMIOS
 328           result = tcsetpgrp (0, tinfo->process_group);
 329           if (!inf->attach_flag)
 330             OOPSY ("tcsetpgrp");
 331 #endif
 332
 333 #ifdef HAVE_SGTTY
 334           result = ioctl (0, TIOCSPGRP, &tinfo->process_group);
 335           if (!inf->attach_flag)
 336             OOPSY ("TIOCSPGRP");
 337 #endif
 338         }
 339
 340     }
 341   terminal_is_ours = 0;
 342 }
 343
 344 /* Put some of our terminal settings into effect,
 345    enough to get proper results from our output,
 346    but do not change into or out of RAW mode
 347    so that no input is discarded.
 348
 349    After doing this, either terminal_ours or terminal_inferior
 350    should be called to get back to a normal state of affairs.  */
 351
 352 void
 353 terminal_ours_for_output (void)
 354 {
 355   terminal_ours_1 (1);
 356 }
 357
 358 /* Put our terminal settings into effect.
 359    First record the inferior's terminal settings
 360    so they can be restored properly later.  */
 361
 362 void
 363 terminal_ours (void)
 364 {
 365   terminal_ours_1 (0);
 366 }
 367
 368 /* output_only is not used, and should not be used unless we introduce
 369    separate terminal_is_ours and terminal_is_ours_for_output
 370    flags.  */
 371
 372 static void
 373 terminal_ours_1 (int output_only)
 374 {
 375   struct inferior *inf;
 376   struct terminal_info *tinfo;
 377
 378   if (terminal_is_ours)
 379     return;
 380
 381   terminal_is_ours = 1;
 382
 383   /* Checking inferior->run_terminal is necessary so that
 384      if GDB is running in the background, it won't block trying
 385      to do the ioctl()'s below.  Checking gdb_has_a_terminal
 386      avoids attempting all the ioctl's when running in batch.  */
 387
 388   inf = current_inferior ();
 389   tinfo = get_inflow_inferior_data (inf);
 390
 391   if (tinfo->run_terminal != NULL || gdb_has_a_terminal () == 0)
 392     return;
 393
 394     {
 395 #ifdef SIGTTOU
 396       /* Ignore this signal since it will happen when we try to set the
 397          pgrp.  */
 398       void (*osigttou) () = NULL;
 399 #endif
 400       int result;
 401
 402 #ifdef SIGTTOU
 403       if (job_control)
 404         osigttou = (void (*)()) signal (SIGTTOU, SIG_IGN);
 405 #endif
 406
 407       xfree (tinfo->ttystate);
 408       tinfo->ttystate = serial_get_tty_state (stdin_serial);
 409
 410 #ifdef PROCESS_GROUP_TYPE
 411       if (!inf->attach_flag)
 412         /* If setpgrp failed in terminal_inferior, this would give us
 413            our process group instead of the inferior's.  See
 414            terminal_inferior for details.  */
 415         tinfo->process_group = gdb_getpgrp ();
 416 #endif
 417
 418       /* Here we used to set ICANON in our ttystate, but I believe this
 419          was an artifact from before when we used readline.  Readline sets
 420          the tty state when it needs to.
 421          FIXME-maybe: However, query() expects non-raw mode and doesn't
 422          use readline.  Maybe query should use readline (on the other hand,
 423          this only matters for HAVE_SGTTY, not termio or termios, I think).  */
 424
 425       /* Set tty state to our_ttystate.  We don't change in our out of raw
 426          mode, to avoid flushing input.  We need to do the same thing
 427          regardless of output_only, because we don't have separate
 428          terminal_is_ours and terminal_is_ours_for_output flags.  It's OK,
 429          though, since readline will deal with raw mode when/if it needs
 430          to.  */
 431
 432       serial_noflush_set_tty_state (stdin_serial, our_terminal_info.ttystate,
 433                                     tinfo->ttystate);
 434
 435       if (job_control)
 436         {
 437 #ifdef HAVE_TERMIOS
 438           result = tcsetpgrp (0, our_terminal_info.process_group);
 439 #if 0
 440           /* This fails on Ultrix with EINVAL if you run the testsuite
 441              in the background with nohup, and then log out.  GDB never
 442              used to check for an error here, so perhaps there are other
 443              such situations as well.  */
 444           if (result == -1)
 445             fprintf_unfiltered (gdb_stderr,
 446                                 "[tcsetpgrp failed in terminal_ours: %s]\n",
 447                                 safe_strerror (errno));
 448 #endif
 449 #endif /* termios */
 450
 451 #ifdef HAVE_SGTTY
 452           result = ioctl (0, TIOCSPGRP, &our_terminal_info.process_group);
 453 #endif
 454         }
 455
 456 #ifdef SIGTTOU
 457       if (job_control)
 458         signal (SIGTTOU, osigttou);
 459 #endif
 460
 461       if (!job_control)
 462         {
 463           signal (SIGINT, sigint_ours);
 464 #ifdef SIGQUIT
 465           signal (SIGQUIT, sigquit_ours);
 466 #endif
 467         }
 468
 469 #ifdef F_GETFL
 470       tinfo->tflags = fcntl (0, F_GETFL, 0);
 471
 472       /* Is there a reason this is being done twice?  It happens both
 473          places we use F_SETFL, so I'm inclined to think perhaps there
 474          is some reason, however perverse.  Perhaps not though...  */
 475       result = fcntl (0, F_SETFL, our_terminal_info.tflags);
 476       result = fcntl (0, F_SETFL, our_terminal_info.tflags);
 477 #endif
 478     }
 479 }
 480
 481 /* Per-inferior data key.  */
 482 static const struct inferior_data *inflow_inferior_data;
 483
 484 static void
 485 inflow_inferior_data_cleanup (struct inferior *inf, void *arg)
 486 {
 487   struct terminal_info *info;
 488
 489   info = inferior_data (inf, inflow_inferior_data);
 490   if (info != NULL)
 491     {
 492       xfree (info->run_terminal);
 493       xfree (info->ttystate);
 494       xfree (info);
 495     }
 496 }
 497
 498 /* Get the current svr4 data.  If none is found yet, add it now.  This
 499    function always returns a valid object.  */
 500
 501 static struct terminal_info *
 502 get_inflow_inferior_data (struct inferior *inf)
 503 {
 504   struct terminal_info *info;
 505
 506   info = inferior_data (inf, inflow_inferior_data);
 507   if (info == NULL)
 508     {
 509       info = XZALLOC (struct terminal_info);
 510       set_inferior_data (inf, inflow_inferior_data, info);
 511     }
 512
 513   return info;
 514 }
 515
 516 /* This is a "inferior_exit" observer.  Releases the TERMINAL_INFO member
 517    of the inferior structure.  This field is private to inflow.c, and
 518    its type is opaque to the rest of GDB.  PID is the target pid of
 519    the inferior that is about to be removed from the inferior
 520    list.  */
 521
 522 static void
 523 inflow_inferior_exit (struct inferior *inf)
 524 {
 525   struct terminal_info *info;
 526
 527   info = inferior_data (inf, inflow_inferior_data);
 528   if (info != NULL)
 529     {
 530       xfree (info->run_terminal);
 531       xfree (info->ttystate);
 532       xfree (info);
 533       set_inferior_data (inf, inflow_inferior_data, NULL);
 534     }
 535 }
 536
 537 void
 538 copy_terminal_info (struct inferior *to, struct inferior *from)
 539 {
 540   struct terminal_info *tinfo_to, *tinfo_from;
 541
 542   tinfo_to = get_inflow_inferior_data (to);
 543   tinfo_from = get_inflow_inferior_data (from);
 544
 545   xfree (tinfo_to->run_terminal);
 546   xfree (tinfo_to->ttystate);
 547
 548   *tinfo_to = *tinfo_from;
 549
 550   if (tinfo_from->run_terminal)
 551     tinfo_to->run_terminal
 552       = xstrdup (tinfo_from->run_terminal);
 553
 554   if (tinfo_from->ttystate)
 555     tinfo_to->ttystate
 556       = serial_copy_tty_state (stdin_serial, tinfo_from->ttystate);
 557 }
 558
 559 void
 560 term_info (char *arg, int from_tty)
 561 {
 562   target_terminal_info (arg, from_tty);
 563 }
 564
 565 void
 566 child_terminal_info (const char *args, int from_tty)
 567 {
 568   struct inferior *inf;
 569   struct terminal_info *tinfo;
 570
 571   if (!gdb_has_a_terminal ())
 572     {
 573       printf_filtered (_("This GDB does not control a terminal.\n"));
 574       return;
 575     }
 576
 577   if (ptid_equal (inferior_ptid, null_ptid))
 578     return;
 579
 580   inf = current_inferior ();
 581   tinfo = get_inflow_inferior_data (inf);
 582
 583   printf_filtered (_("Inferior's terminal status "
 584                      "(currently saved by GDB):\n"));
 585
 586   /* First the fcntl flags.  */
 587   {
 588     int flags;
 589
 590     flags = tinfo->tflags;
 591
 592     printf_filtered ("File descriptor flags = ");
 593
 594 #ifndef O_ACCMODE
 595 #define O_ACCMODE (O_RDONLY | O_WRONLY | O_RDWR)
 596 #endif
 597     /* (O_ACCMODE) parens are to avoid Ultrix header file bug.  */
 598     switch (flags & (O_ACCMODE))
 599       {
 600       case O_RDONLY:
 601         printf_filtered ("O_RDONLY");
 602         break;
 603       case O_WRONLY:
 604         printf_filtered ("O_WRONLY");
 605         break;
 606       case O_RDWR:
 607         printf_filtered ("O_RDWR");
 608         break;
 609       }
 610     flags &= ~(O_ACCMODE);
 611
 612 #ifdef O_NONBLOCK
 613     if (flags & O_NONBLOCK)
 614       printf_filtered (" | O_NONBLOCK");
 615     flags &= ~O_NONBLOCK;
 616 #endif
 617
 618 #if defined (O_NDELAY)
 619     /* If O_NDELAY and O_NONBLOCK are defined to the same thing, we will
 620        print it as O_NONBLOCK, which is good cause that is what POSIX
 621        has, and the flag will already be cleared by the time we get here.  */
 622     if (flags & O_NDELAY)
 623       printf_filtered (" | O_NDELAY");
 624     flags &= ~O_NDELAY;
 625 #endif
 626
 627     if (flags & O_APPEND)
 628       printf_filtered (" | O_APPEND");
 629     flags &= ~O_APPEND;
 630
 631 #if defined (O_BINARY)
 632     if (flags & O_BINARY)
 633       printf_filtered (" | O_BINARY");
 634     flags &= ~O_BINARY;
 635 #endif
 636
 637     if (flags)
 638       printf_filtered (" | 0x%x", flags);
 639     printf_filtered ("\n");
 640   }
 641
 642 #ifdef PROCESS_GROUP_TYPE
 643   printf_filtered ("Process group = %d\n", (int) tinfo->process_group);
 644 #endif
 645
 646   serial_print_tty_state (stdin_serial, tinfo->ttystate, gdb_stdout);
 647 }
 648 \f
 649 /* NEW_TTY_PREFORK is called before forking a new child process,
 650    so we can record the state of ttys in the child to be formed.
 651    TTYNAME is null if we are to share the terminal with gdb;
 652    or points to a string containing the name of the desired tty.
 653
 654    NEW_TTY is called in new child processes under Unix, which will
 655    become debugger target processes.  This actually switches to
 656    the terminal specified in the NEW_TTY_PREFORK call.  */
 657
 658 void
 659 new_tty_prefork (const char *ttyname)
 660 {
 661   /* Save the name for later, for determining whether we and the child
 662      are sharing a tty.  */
 663   inferior_thisrun_terminal = ttyname;
 664 }
 665
 666 #if !defined(__GO32__) && !defined(_WIN32)
 667 /* If RESULT, assumed to be the return value from a system call, is
 668    negative, print the error message indicated by errno and exit.
 669    MSG should identify the operation that failed.  */
 670 static void
 671 check_syscall (const char *msg, int result)
 672 {
 673   if (result < 0)
 674     {
 675       print_sys_errmsg (msg, errno);
 676       _exit (1);
 677     }
 678 }
 679 #endif
 680
 681 void
 682 new_tty (void)
 683 {
 684   int tty;
 685
 686   if (inferior_thisrun_terminal == 0)
 687     return;
 688 #if !defined(__GO32__) && !defined(_WIN32)
 689 #ifdef TIOCNOTTY
 690   /* Disconnect the child process from our controlling terminal.  On some
 691      systems (SVR4 for example), this may cause a SIGTTOU, so temporarily
 692      ignore SIGTTOU.  */
 693   tty = open ("/dev/tty", O_RDWR);
 694   if (tty > 0)
 695     {
 696       void (*osigttou) ();
 697
 698       osigttou = (void (*)()) signal (SIGTTOU, SIG_IGN);
 699       ioctl (tty, TIOCNOTTY, 0);
 700       close (tty);
 701       signal (SIGTTOU, osigttou);
 702     }
 703 #endif
 704
 705   /* Now open the specified new terminal.  */
 706   tty = open (inferior_thisrun_terminal, O_RDWR | O_NOCTTY);
 707   check_syscall (inferior_thisrun_terminal, tty);
 708
 709   /* Avoid use of dup2; doesn't exist on all systems.  */
 710   if (tty != 0)
 711     {
 712       close (0);
 713       check_syscall ("dup'ing tty into fd 0", dup (tty));
 714     }
 715   if (tty != 1)
 716     {
 717       close (1);
 718       check_syscall ("dup'ing tty into fd 1", dup (tty));
 719     }
 720   if (tty != 2)
 721     {
 722       close (2);
 723       check_syscall ("dup'ing tty into fd 2", dup (tty));
 724     }
 725
 726 #ifdef TIOCSCTTY
 727   /* Make tty our new controlling terminal.  */
 728   if (ioctl (tty, TIOCSCTTY, 0) == -1)
 729     /* Mention GDB in warning because it will appear in the inferior's
 730        terminal instead of GDB's.  */
 731     warning (_("GDB: Failed to set controlling terminal: %s"),
 732              safe_strerror (errno));
 733 #endif
 734
 735   if (tty > 2)
 736     close (tty);
 737 #endif /* !go32 && !win32 */
 738 }
 739
 740 /* NEW_TTY_POSTFORK is called after forking a new child process, and
 741    adding it to the inferior table, to store the TTYNAME being used by
 742    the child, or null if it sharing the terminal with gdb.  */
 743
 744 void
 745 new_tty_postfork (void)
 746 {
 747   /* Save the name for later, for determining whether we and the child
 748      are sharing a tty.  */
 749
 750   if (inferior_thisrun_terminal)
 751     {
 752       struct inferior *inf = current_inferior ();
 753       struct terminal_info *tinfo = get_inflow_inferior_data (inf);
 754
 755       tinfo->run_terminal = xstrdup (inferior_thisrun_terminal);
 756     }
 757
 758   inferior_thisrun_terminal = NULL;
 759 }
 760
 761 \f
 762 /* Call set_sigint_trap when you need to pass a signal on to an attached
 763    process when handling SIGINT.  */
 764
 765 static void
 766 pass_signal (int signo)
 767 {
 768 #ifndef _WIN32
 769   kill (PIDGET (inferior_ptid), SIGINT);
 770 #endif
 771 }
 772
 773 static void (*osig) ();
 774 static int osig_set;
 775
 776 void
 777 set_sigint_trap (void)
 778 {
 779   struct inferior *inf = current_inferior ();
 780   struct terminal_info *tinfo = get_inflow_inferior_data (inf);
 781
 782   if (inf->attach_flag || tinfo->run_terminal)
 783     {
 784       osig = (void (*)()) signal (SIGINT, pass_signal);
 785       osig_set = 1;
 786     }
 787   else
 788     osig_set = 0;
 789 }
 790
 791 void
 792 clear_sigint_trap (void)
 793 {
 794   if (osig_set)
 795     {
 796       signal (SIGINT, osig);
 797       osig_set = 0;
 798     }
 799 }
 800 \f
 801
 802 /* Create a new session if the inferior will run in a different tty.
 803    A session is UNIX's way of grouping processes that share a controlling
 804    terminal, so a new one is needed if the inferior terminal will be
 805    different from GDB's.
 806
 807    Returns the session id of the new session, 0 if no session was created
 808    or -1 if an error occurred.  */
 809 pid_t
 810 create_tty_session (void)
 811 {
 812 #ifdef HAVE_SETSID
 813   pid_t ret;
 814
 815   if (!job_control || inferior_thisrun_terminal == 0)
 816     return 0;
 817
 818   ret = setsid ();
 819   if (ret == -1)
 820     warning (_("Failed to create new terminal session: setsid: %s"),
 821              safe_strerror (errno));
 822
 823   return ret;
 824 #else
 825   return 0;
 826 #endif /* HAVE_SETSID */
 827 }
 828
 829 /* This is here because this is where we figure out whether we (probably)
 830    have job control.  Just using job_control only does part of it because
 831    setpgid or setpgrp might not exist on a system without job control.
 832    It might be considered misplaced (on the other hand, process groups and
 833    job control are closely related to ttys).
 834
 835    For a more clean implementation, in libiberty, put a setpgid which merely
 836    calls setpgrp and a setpgrp which does nothing (any system with job control
 837    will have one or the other).  */
 838 int
 839 gdb_setpgid (void)
 840 {
 841   int retval = 0;
 842
 843   if (job_control)
 844     {
 845 #if defined (HAVE_TERMIOS) || defined (TIOCGPGRP)
 846 #ifdef HAVE_SETPGID
 847       /* The call setpgid (0, 0) is supposed to work and mean the same
 848          thing as this, but on Ultrix 4.2A it fails with EPERM (and
 849          setpgid (getpid (), getpid ()) succeeds).  */
 850       retval = setpgid (getpid (), getpid ());
 851 #else
 852 #ifdef HAVE_SETPGRP
 853 #ifdef SETPGRP_VOID
 854       retval = setpgrp ();
 855 #else
 856       retval = setpgrp (getpid (), getpid ());
 857 #endif
 858 #endif /* HAVE_SETPGRP */
 859 #endif /* HAVE_SETPGID */
 860 #endif /* defined (HAVE_TERMIOS) || defined (TIOCGPGRP) */
 861     }
 862
 863   return retval;
 864 }
 865
 866 /* Get all the current tty settings (including whether we have a
 867    tty at all!).  We can't do this in _initialize_inflow because
 868    serial_fdopen() won't work until the serial_ops_list is
 869    initialized, but we don't want to do it lazily either, so
 870    that we can guarantee stdin_serial is opened if there is
 871    a terminal.  */
 872 void
 873 initialize_stdin_serial (void)
 874 {
 875   stdin_serial = serial_fdopen (0);
 876 }
 877
 878 void
 879 _initialize_inflow (void)
 880 {
 881   add_info ("terminal", term_info,
 882             _("Print inferior's saved terminal status."));
 883
 884   add_setshow_auto_boolean_cmd ("interactive-mode", class_support,
 885                                 &interactive_mode, _("\
 886 Set whether GDB's standard input is a terminal."), _("\
 887 Show whether GDB's standard input is a terminal."), _("\
 888 If on, GDB assumes that standard input is a terminal.  In practice, it\n\
 889 means that GDB should wait for the user to answer queries associated to\n\
 890 commands entered at the command prompt.  If off, GDB assumes that standard\n\
 891 input is not a terminal, and uses the default answer to all queries.\n\
 892 If auto (the default), determine which mode to use based on the standard\n\
 893 input settings."),
 894                         NULL,
 895                         show_interactive_mode,
 896                         &setlist, &showlist);
 897
 898   terminal_is_ours = 1;
 899
 900   /* OK, figure out whether we have job control.  If neither termios nor
 901      sgtty (i.e. termio or go32), leave job_control 0.  */
 902
 903 #if defined (HAVE_TERMIOS)
 904   /* Do all systems with termios have the POSIX way of identifying job
 905      control?  I hope so.  */
 906 #ifdef _POSIX_JOB_CONTROL
 907   job_control = 1;
 908 #else
 909 #ifdef _SC_JOB_CONTROL
 910   job_control = sysconf (_SC_JOB_CONTROL);
 911 #else
 912   job_control = 0;              /* Have to assume the worst.  */
 913 #endif /* _SC_JOB_CONTROL */
 914 #endif /* _POSIX_JOB_CONTROL */
 915 #endif /* HAVE_TERMIOS */
 916
 917 #ifdef HAVE_SGTTY
 918 #ifdef TIOCGPGRP
 919   job_control = 1;
 920 #else
 921   job_control = 0;
 922 #endif /* TIOCGPGRP */
 923 #endif /* sgtty */
 924
 925   observer_attach_inferior_exit (inflow_inferior_exit);
 926
 927   inflow_inferior_data
 928     = register_inferior_data_with_cleanup (NULL, inflow_inferior_data_cleanup);
 929 }