gdb/inferior.c

   1 /* Multi-process control for GDB, the GNU debugger.
   2
   3    Copyright (C) 2008-2019 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 3 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, see <http://www.gnu.org/licenses/>.  */
  19
  20 #include "defs.h"
  21 #include "exec.h"
  22 #include "inferior.h"
  23 #include "target.h"
  24 #include "command.h"
  25 #include "completer.h"
  26 #include "gdbcmd.h"
  27 #include "gdbthread.h"
  28 #include "ui-out.h"
  29 #include "observable.h"
  30 #include "gdbcore.h"
  31 #include "symfile.h"
  32 #include "common/environ.h"
  33 #include "cli/cli-utils.h"
  34 #include "continuations.h"
  35 #include "arch-utils.h"
  36 #include "target-descriptions.h"
  37 #include "readline/tilde.h"
  38 #include "progspace-and-thread.h"
  39
  40 /* Keep a registry of per-inferior data-pointers required by other GDB
  41    modules.  */
  42
  43 DEFINE_REGISTRY (inferior, REGISTRY_ACCESS_FIELD)
  44
  45 struct inferior *inferior_list = NULL;
  46 static int highest_inferior_num;
  47
  48 /* See inferior.h.  */
  49 int print_inferior_events = 1;
  50
  51 /* The Current Inferior.  This is a strong reference.  I.e., whenever
  52    an inferior is the current inferior, its refcount is
  53    incremented.  */
  54 static struct inferior *current_inferior_ = NULL;
  55
  56 struct inferior*
  57 current_inferior (void)
  58 {
  59   return current_inferior_;
  60 }
  61
  62 void
  63 set_current_inferior (struct inferior *inf)
  64 {
  65   /* There's always an inferior.  */
  66   gdb_assert (inf != NULL);
  67
  68   inf->incref ();
  69   current_inferior_->decref ();
  70   current_inferior_ = inf;
  71 }
  72
  73 private_inferior::~private_inferior () = default;
  74
  75 inferior::~inferior ()
  76 {
  77   inferior *inf = this;
  78
  79   discard_all_inferior_continuations (inf);
  80   inferior_free_data (inf);
  81   xfree (inf->args);
  82   xfree (inf->terminal);
  83   target_desc_info_free (inf->tdesc_info);
  84 }
  85
  86 inferior::inferior (int pid_)
  87   : num (++highest_inferior_num),
  88     pid (pid_),
  89     environment (gdb_environ::from_host_environ ()),
  90     registry_data ()
  91 {
  92   inferior_alloc_data (this);
  93 }
  94
  95 struct inferior *
  96 add_inferior_silent (int pid)
  97 {
  98   inferior *inf = new inferior (pid);
  99
 100   if (inferior_list == NULL)
 101     inferior_list = inf;
 102   else
 103     {
 104       inferior *last;
 105
 106       for (last = inferior_list; last->next != NULL; last = last->next)
 107         ;
 108       last->next = inf;
 109     }
 110
 111   gdb::observers::inferior_added.notify (inf);
 112
 113   if (pid != 0)
 114     inferior_appeared (inf, pid);
 115
 116   return inf;
 117 }
 118
 119 struct inferior *
 120 add_inferior (int pid)
 121 {
 122   struct inferior *inf = add_inferior_silent (pid);
 123
 124   if (print_inferior_events)
 125     {
 126       if (pid != 0)
 127         printf_unfiltered (_("[New inferior %d (%s)]\n"),
 128                            inf->num,
 129                            target_pid_to_str (ptid_t (pid)).c_str ());
 130       else
 131         printf_unfiltered (_("[New inferior %d]\n"), inf->num);
 132     }
 133
 134   return inf;
 135 }
 136
 137 void
 138 delete_inferior (struct inferior *todel)
 139 {
 140   struct inferior *inf, *infprev;
 141
 142   infprev = NULL;
 143
 144   for (inf = inferior_list; inf; infprev = inf, inf = inf->next)
 145     if (inf == todel)
 146       break;
 147
 148   if (!inf)
 149     return;
 150
 151   for (thread_info *tp : inf->threads_safe ())
 152     delete_thread_silent (tp);
 153
 154   if (infprev)
 155     infprev->next = inf->next;
 156   else
 157     inferior_list = inf->next;
 158
 159   gdb::observers::inferior_removed.notify (inf);
 160
 161   /* If this program space is rendered useless, remove it. */
 162   if (program_space_empty_p (inf->pspace))
 163     delete_program_space (inf->pspace);
 164
 165   delete inf;
 166 }
 167
 168 /* If SILENT then be quiet -- don't announce a inferior exit, or the
 169    exit of its threads.  */
 170
 171 static void
 172 exit_inferior_1 (struct inferior *inftoex, int silent)
 173 {
 174   struct inferior *inf;
 175
 176   for (inf = inferior_list; inf; inf = inf->next)
 177     if (inf == inftoex)
 178       break;
 179
 180   if (!inf)
 181     return;
 182
 183   for (thread_info *tp : inf->threads_safe ())
 184     {
 185       if (silent)
 186         delete_thread_silent (tp);
 187       else
 188         delete_thread (tp);
 189     }
 190
 191   gdb::observers::inferior_exit.notify (inf);
 192
 193   inf->pid = 0;
 194   inf->fake_pid_p = false;
 195   inf->priv = NULL;
 196
 197   if (inf->vfork_parent != NULL)
 198     {
 199       inf->vfork_parent->vfork_child = NULL;
 200       inf->vfork_parent = NULL;
 201     }
 202   if (inf->vfork_child != NULL)
 203     {
 204       inf->vfork_child->vfork_parent = NULL;
 205       inf->vfork_child = NULL;
 206     }
 207
 208   inf->pending_detach = 0;
 209   /* Reset it.  */
 210   inf->control = inferior_control_state (NO_STOP_QUIETLY);
 211
 212   /* Clear the register cache and the frame cache.  */
 213   registers_changed ();
 214   reinit_frame_cache ();
 215 }
 216
 217 void
 218 exit_inferior (inferior *inf)
 219 {
 220   exit_inferior_1 (inf, 0);
 221 }
 222
 223 void
 224 exit_inferior_silent (int pid)
 225 {
 226   struct inferior *inf = find_inferior_pid (pid);
 227
 228   exit_inferior_1 (inf, 1);
 229 }
 230
 231 void
 232 exit_inferior_silent (inferior *inf)
 233 {
 234   exit_inferior_1 (inf, 1);
 235 }
 236
 237 /* See inferior.h.  */
 238
 239 void
 240 detach_inferior (inferior *inf)
 241 {
 242   /* Save the pid, since exit_inferior_1 will reset it.  */
 243   int pid = inf->pid;
 244
 245   exit_inferior_1 (inf, 0);
 246
 247   if (print_inferior_events)
 248     printf_unfiltered (_("[Inferior %d (%s) detached]\n"),
 249                        inf->num,
 250                        target_pid_to_str (ptid_t (pid)).c_str ());
 251 }
 252
 253 void
 254 inferior_appeared (struct inferior *inf, int pid)
 255 {
 256   /* If this is the first inferior with threads, reset the global
 257      thread id.  */
 258   if (!any_thread_p ())
 259     init_thread_list ();
 260
 261   inf->pid = pid;
 262   inf->has_exit_code = 0;
 263   inf->exit_code = 0;
 264
 265   gdb::observers::inferior_appeared.notify (inf);
 266 }
 267
 268 void
 269 discard_all_inferiors (void)
 270 {
 271   for (inferior *inf : all_non_exited_inferiors ())
 272     exit_inferior_silent (inf);
 273 }
 274
 275 struct inferior *
 276 find_inferior_id (int num)
 277 {
 278   for (inferior *inf : all_inferiors ())
 279     if (inf->num == num)
 280       return inf;
 281
 282   return NULL;
 283 }
 284
 285 struct inferior *
 286 find_inferior_pid (int pid)
 287 {
 288   /* Looking for inferior pid == 0 is always wrong, and indicative of
 289      a bug somewhere else.  There may be more than one with pid == 0,
 290      for instance.  */
 291   gdb_assert (pid != 0);
 292
 293   for (inferior *inf : all_inferiors ())
 294     if (inf->pid == pid)
 295       return inf;
 296
 297   return NULL;
 298 }
 299
 300 /* See inferior.h */
 301
 302 struct inferior *
 303 find_inferior_ptid (ptid_t ptid)
 304 {
 305   return find_inferior_pid (ptid.pid ());
 306 }
 307
 308 /* See inferior.h.  */
 309
 310 struct inferior *
 311 find_inferior_for_program_space (struct program_space *pspace)
 312 {
 313   struct inferior *cur_inf = current_inferior ();
 314
 315   if (cur_inf->pspace == pspace)
 316     return cur_inf;
 317
 318   for (inferior *inf : all_inferiors ())
 319     if (inf->pspace == pspace)
 320       return inf;
 321
 322   return NULL;
 323 }
 324
 325 struct inferior *
 326 iterate_over_inferiors (int (*callback) (struct inferior *, void *),
 327                         void *data)
 328 {
 329   for (inferior *inf : all_inferiors_safe ())
 330     if ((*callback) (inf, data))
 331       return inf;
 332
 333   return NULL;
 334 }
 335
 336 int
 337 have_inferiors (void)
 338 {
 339   for (inferior *inf ATTRIBUTE_UNUSED : all_non_exited_inferiors ())
 340     return 1;
 341
 342   return 0;
 343 }
 344
 345 /* Return the number of live inferiors.  We account for the case
 346    where an inferior might have a non-zero pid but no threads, as
 347    in the middle of a 'mourn' operation.  */
 348
 349 int
 350 number_of_live_inferiors (void)
 351 {
 352   int num_inf = 0;
 353
 354   for (inferior *inf : all_non_exited_inferiors ())
 355     if (target_has_execution_1 (ptid_t (inf->pid)))
 356       for (thread_info *tp ATTRIBUTE_UNUSED : inf->non_exited_threads ())
 357         {
 358           /* Found a live thread in this inferior, go to the next
 359              inferior.  */
 360           ++num_inf;
 361           break;
 362         }
 363
 364   return num_inf;
 365 }
 366
 367 /* Return true if there is at least one live inferior.  */
 368
 369 int
 370 have_live_inferiors (void)
 371 {
 372   return number_of_live_inferiors () > 0;
 373 }
 374
 375 /* Prune away any unused inferiors, and then prune away no longer used
 376    program spaces.  */
 377
 378 void
 379 prune_inferiors (void)
 380 {
 381   struct inferior *ss, **ss_link;
 382
 383   ss = inferior_list;
 384   ss_link = &inferior_list;
 385   while (ss)
 386     {
 387       if (!ss->deletable ()
 388           || !ss->removable
 389           || ss->pid != 0)
 390         {
 391           ss_link = &ss->next;
 392           ss = *ss_link;
 393           continue;
 394         }
 395
 396       *ss_link = ss->next;
 397       delete_inferior (ss);
 398       ss = *ss_link;
 399     }
 400 }
 401
 402 /* Simply returns the count of inferiors.  */
 403
 404 int
 405 number_of_inferiors (void)
 406 {
 407   auto rng = all_inferiors ();
 408   return std::distance (rng.begin (), rng.end ());
 409 }
 410
 411 /* Converts an inferior process id to a string.  Like
 412    target_pid_to_str, but special cases the null process.  */
 413
 414 static std::string
 415 inferior_pid_to_str (int pid)
 416 {
 417   if (pid != 0)
 418     return target_pid_to_str (ptid_t (pid));
 419   else
 420     return _("<null>");
 421 }
 422
 423 /* See inferior.h.  */
 424
 425 void
 426 print_selected_inferior (struct ui_out *uiout)
 427 {
 428   struct inferior *inf = current_inferior ();
 429   const char *filename = inf->pspace->pspace_exec_filename;
 430
 431   if (filename == NULL)
 432     filename = _("<noexec>");
 433
 434   uiout->message (_("[Switching to inferior %d [%s] (%s)]\n"),
 435                   inf->num, inferior_pid_to_str (inf->pid).c_str (), filename);
 436 }
 437
 438 /* Prints the list of inferiors and their details on UIOUT.  This is a
 439    version of 'info_inferior_command' suitable for use from MI.
 440
 441    If REQUESTED_INFERIORS is not NULL, it's a list of GDB ids of the
 442    inferiors that should be printed.  Otherwise, all inferiors are
 443    printed.  */
 444
 445 static void
 446 print_inferior (struct ui_out *uiout, const char *requested_inferiors)
 447 {
 448   int inf_count = 0;
 449
 450   /* Compute number of inferiors we will print.  */
 451   for (inferior *inf : all_inferiors ())
 452     {
 453       if (!number_is_in_list (requested_inferiors, inf->num))
 454         continue;
 455
 456       ++inf_count;
 457     }
 458
 459   if (inf_count == 0)
 460     {
 461       uiout->message ("No inferiors.\n");
 462       return;
 463     }
 464
 465   ui_out_emit_table table_emitter (uiout, 4, inf_count, "inferiors");
 466   uiout->table_header (1, ui_left, "current", "");
 467   uiout->table_header (4, ui_left, "number", "Num");
 468   uiout->table_header (17, ui_left, "target-id", "Description");
 469   uiout->table_header (17, ui_left, "exec", "Executable");
 470
 471   uiout->table_body ();
 472   for (inferior *inf : all_inferiors ())
 473     {
 474       if (!number_is_in_list (requested_inferiors, inf->num))
 475         continue;
 476
 477       ui_out_emit_tuple tuple_emitter (uiout, NULL);
 478
 479       if (inf == current_inferior ())
 480         uiout->field_string ("current", "*");
 481       else
 482         uiout->field_skip ("current");
 483
 484       uiout->field_int ("number", inf->num);
 485
 486       uiout->field_string ("target-id", inferior_pid_to_str (inf->pid));
 487
 488       if (inf->pspace->pspace_exec_filename != NULL)
 489         uiout->field_string ("exec", inf->pspace->pspace_exec_filename);
 490       else
 491         uiout->field_skip ("exec");
 492
 493       /* Print extra info that isn't really fit to always present in
 494          tabular form.  Currently we print the vfork parent/child
 495          relationships, if any.  */
 496       if (inf->vfork_parent)
 497         {
 498           uiout->text (_("\n\tis vfork child of inferior "));
 499           uiout->field_int ("vfork-parent", inf->vfork_parent->num);
 500         }
 501       if (inf->vfork_child)
 502         {
 503           uiout->text (_("\n\tis vfork parent of inferior "));
 504           uiout->field_int ("vfork-child", inf->vfork_child->num);
 505         }
 506
 507       uiout->text ("\n");
 508     }
 509 }
 510
 511 static void
 512 detach_inferior_command (const char *args, int from_tty)
 513 {
 514   if (!args || !*args)
 515     error (_("Requires argument (inferior id(s) to detach)"));
 516
 517   number_or_range_parser parser (args);
 518   while (!parser.finished ())
 519     {
 520       int num = parser.get_number ();
 521
 522       inferior *inf = find_inferior_id (num);
 523       if (inf == NULL)
 524         {
 525           warning (_("Inferior ID %d not known."), num);
 526           continue;
 527         }
 528
 529       if (inf->pid == 0)
 530         {
 531           warning (_("Inferior ID %d is not running."), num);
 532           continue;
 533         }
 534
 535       thread_info *tp = any_thread_of_inferior (inf);
 536       if (tp == NULL)
 537         {
 538           warning (_("Inferior ID %d has no threads."), num);
 539           continue;
 540         }
 541
 542       switch_to_thread (tp);
 543
 544       detach_command (NULL, from_tty);
 545     }
 546 }
 547
 548 static void
 549 kill_inferior_command (const char *args, int from_tty)
 550 {
 551   if (!args || !*args)
 552     error (_("Requires argument (inferior id(s) to kill)"));
 553
 554   number_or_range_parser parser (args);
 555   while (!parser.finished ())
 556     {
 557       int num = parser.get_number ();
 558
 559       inferior *inf = find_inferior_id (num);
 560       if (inf == NULL)
 561         {
 562           warning (_("Inferior ID %d not known."), num);
 563           continue;
 564         }
 565
 566       if (inf->pid == 0)
 567         {
 568           warning (_("Inferior ID %d is not running."), num);
 569           continue;
 570         }
 571
 572       thread_info *tp = any_thread_of_inferior (inf);
 573       if (tp == NULL)
 574         {
 575           warning (_("Inferior ID %d has no threads."), num);
 576           continue;
 577         }
 578
 579       switch_to_thread (tp);
 580
 581       target_kill ();
 582     }
 583
 584   bfd_cache_close_all ();
 585 }
 586
 587 static void
 588 inferior_command (const char *args, int from_tty)
 589 {
 590   struct inferior *inf;
 591   int num;
 592
 593   num = parse_and_eval_long (args);
 594
 595   inf = find_inferior_id (num);
 596   if (inf == NULL)
 597     error (_("Inferior ID %d not known."), num);
 598
 599   if (inf->pid != 0)
 600     {
 601       if (inf != current_inferior ())
 602         {
 603           thread_info *tp = any_thread_of_inferior (inf);
 604           if (tp == NULL)
 605             error (_("Inferior has no threads."));
 606
 607           switch_to_thread (tp);
 608         }
 609
 610       gdb::observers::user_selected_context_changed.notify
 611         (USER_SELECTED_INFERIOR
 612          | USER_SELECTED_THREAD
 613          | USER_SELECTED_FRAME);
 614     }
 615   else
 616     {
 617       set_current_inferior (inf);
 618       switch_to_no_thread ();
 619       set_current_program_space (inf->pspace);
 620
 621       gdb::observers::user_selected_context_changed.notify
 622         (USER_SELECTED_INFERIOR);
 623     }
 624 }
 625
 626 /* Print information about currently known inferiors.  */
 627
 628 static void
 629 info_inferiors_command (const char *args, int from_tty)
 630 {
 631   print_inferior (current_uiout, args);
 632 }
 633
 634 /* remove-inferior ID */
 635
 636 static void
 637 remove_inferior_command (const char *args, int from_tty)
 638 {
 639   if (args == NULL || *args == '\0')
 640     error (_("Requires an argument (inferior id(s) to remove)"));
 641
 642   number_or_range_parser parser (args);
 643   while (!parser.finished ())
 644     {
 645       int num = parser.get_number ();
 646       struct inferior *inf = find_inferior_id (num);
 647
 648       if (inf == NULL)
 649         {
 650           warning (_("Inferior ID %d not known."), num);
 651           continue;
 652         }
 653
 654       if (!inf->deletable ())
 655         {
 656           warning (_("Can not remove current inferior %d."), num);
 657           continue;
 658         }
 659
 660       if (inf->pid != 0)
 661         {
 662           warning (_("Can not remove active inferior %d."), num);
 663           continue;
 664         }
 665
 666       delete_inferior (inf);
 667     }
 668 }
 669
 670 struct inferior *
 671 add_inferior_with_spaces (void)
 672 {
 673   struct address_space *aspace;
 674   struct program_space *pspace;
 675   struct inferior *inf;
 676   struct gdbarch_info info;
 677
 678   /* If all inferiors share an address space on this system, this
 679      doesn't really return a new address space; otherwise, it
 680      really does.  */
 681   aspace = maybe_new_address_space ();
 682   pspace = new program_space (aspace);
 683   inf = add_inferior (0);
 684   inf->pspace = pspace;
 685   inf->aspace = pspace->aspace;
 686
 687   /* Setup the inferior's initial arch, based on information obtained
 688      from the global "set ..." options.  */
 689   gdbarch_info_init (&info);
 690   inf->gdbarch = gdbarch_find_by_info (info);
 691   /* The "set ..." options reject invalid settings, so we should
 692      always have a valid arch by now.  */
 693   gdb_assert (inf->gdbarch != NULL);
 694
 695   return inf;
 696 }
 697
 698 /* add-inferior [-copies N] [-exec FILENAME]  */
 699
 700 static void
 701 add_inferior_command (const char *args, int from_tty)
 702 {
 703   int i, copies = 1;
 704   gdb::unique_xmalloc_ptr<char> exec;
 705   symfile_add_flags add_flags = 0;
 706
 707   if (from_tty)
 708     add_flags |= SYMFILE_VERBOSE;
 709
 710   if (args)
 711     {
 712       gdb_argv built_argv (args);
 713
 714       for (char **argv = built_argv.get (); *argv != NULL; argv++)
 715         {
 716           if (**argv == '-')
 717             {
 718               if (strcmp (*argv, "-copies") == 0)
 719                 {
 720                   ++argv;
 721                   if (!*argv)
 722                     error (_("No argument to -copies"));
 723                   copies = parse_and_eval_long (*argv);
 724                 }
 725               else if (strcmp (*argv, "-exec") == 0)
 726                 {
 727                   ++argv;
 728                   if (!*argv)
 729                     error (_("No argument to -exec"));
 730                   exec.reset (tilde_expand (*argv));
 731                 }
 732             }
 733           else
 734             error (_("Invalid argument"));
 735         }
 736     }
 737
 738   scoped_restore_current_pspace_and_thread restore_pspace_thread;
 739
 740   for (i = 0; i < copies; ++i)
 741     {
 742       struct inferior *inf = add_inferior_with_spaces ();
 743
 744       printf_filtered (_("Added inferior %d\n"), inf->num);
 745
 746       if (exec != NULL)
 747         {
 748           /* Switch over temporarily, while reading executable and
 749              symbols.q.  */
 750           set_current_program_space (inf->pspace);
 751           set_current_inferior (inf);
 752           switch_to_no_thread ();
 753
 754           exec_file_attach (exec.get (), from_tty);
 755           symbol_file_add_main (exec.get (), add_flags);
 756         }
 757     }
 758 }
 759
 760 /* clone-inferior [-copies N] [ID] */
 761
 762 static void
 763 clone_inferior_command (const char *args, int from_tty)
 764 {
 765   int i, copies = 1;
 766   struct inferior *orginf = NULL;
 767
 768   if (args)
 769     {
 770       gdb_argv built_argv (args);
 771
 772       char **argv = built_argv.get ();
 773       for (; *argv != NULL; argv++)
 774         {
 775           if (**argv == '-')
 776             {
 777               if (strcmp (*argv, "-copies") == 0)
 778                 {
 779                   ++argv;
 780                   if (!*argv)
 781                     error (_("No argument to -copies"));
 782                   copies = parse_and_eval_long (*argv);
 783
 784                   if (copies < 0)
 785                     error (_("Invalid copies number"));
 786                 }
 787             }
 788           else
 789             {
 790               if (orginf == NULL)
 791                 {
 792                   int num;
 793
 794                   /* The first non-option (-) argument specified the
 795                      program space ID.  */
 796                   num = parse_and_eval_long (*argv);
 797                   orginf = find_inferior_id (num);
 798
 799                   if (orginf == NULL)
 800                     error (_("Inferior ID %d not known."), num);
 801                   continue;
 802                 }
 803               else
 804                 error (_("Invalid argument"));
 805             }
 806         }
 807     }
 808
 809   /* If no inferior id was specified, then the user wants to clone the
 810      current inferior.  */
 811   if (orginf == NULL)
 812     orginf = current_inferior ();
 813
 814   scoped_restore_current_pspace_and_thread restore_pspace_thread;
 815
 816   for (i = 0; i < copies; ++i)
 817     {
 818       struct address_space *aspace;
 819       struct program_space *pspace;
 820       struct inferior *inf;
 821
 822       /* If all inferiors share an address space on this system, this
 823          doesn't really return a new address space; otherwise, it
 824          really does.  */
 825       aspace = maybe_new_address_space ();
 826       pspace = new program_space (aspace);
 827       inf = add_inferior (0);
 828       inf->pspace = pspace;
 829       inf->aspace = pspace->aspace;
 830       inf->gdbarch = orginf->gdbarch;
 831
 832       /* If the original inferior had a user specified target
 833          description, make the clone use it too.  */
 834       if (target_desc_info_from_user_p (inf->tdesc_info))
 835         copy_inferior_target_desc_info (inf, orginf);
 836
 837       printf_filtered (_("Added inferior %d.\n"), inf->num);
 838
 839       set_current_inferior (inf);
 840       switch_to_no_thread ();
 841       clone_program_space (pspace, orginf->pspace);
 842     }
 843 }
 844
 845 /* Print notices when new inferiors are created and die.  */
 846 static void
 847 show_print_inferior_events (struct ui_file *file, int from_tty,
 848                            struct cmd_list_element *c, const char *value)
 849 {
 850   fprintf_filtered (file, _("Printing of inferior events is %s.\n"), value);
 851 }
 852
 853 /* Return a new value for the selected inferior's id.  */
 854
 855 static struct value *
 856 inferior_id_make_value (struct gdbarch *gdbarch, struct internalvar *var,
 857                         void *ignore)
 858 {
 859   struct inferior *inf = current_inferior ();
 860
 861   return value_from_longest (builtin_type (gdbarch)->builtin_int, inf->num);
 862 }
 863
 864 /* Implementation of `$_inferior' variable.  */
 865
 866 static const struct internalvar_funcs inferior_funcs =
 867 {
 868   inferior_id_make_value,
 869   NULL,
 870   NULL
 871 };
 872
 873 \f
 874
 875 void
 876 initialize_inferiors (void)
 877 {
 878   struct cmd_list_element *c = NULL;
 879
 880   /* There's always one inferior.  Note that this function isn't an
 881      automatic _initialize_foo function, since other _initialize_foo
 882      routines may need to install their per-inferior data keys.  We
 883      can only allocate an inferior when all those modules have done
 884      that.  Do this after initialize_progspace, due to the
 885      current_program_space reference.  */
 886   current_inferior_ = add_inferior_silent (0);
 887   current_inferior_->incref ();
 888   current_inferior_->pspace = current_program_space;
 889   current_inferior_->aspace = current_program_space->aspace;
 890   /* The architecture will be initialized shortly, by
 891      initialize_current_architecture.  */
 892
 893   add_info ("inferiors", info_inferiors_command,
 894             _("Print a list of inferiors being managed.\n\
 895 Usage: info inferiors [ID]...\n\
 896 If IDs are specified, the list is limited to just those inferiors.\n\
 897 By default all inferiors are displayed."));
 898
 899   c = add_com ("add-inferior", no_class, add_inferior_command, _("\
 900 Add a new inferior.\n\
 901 Usage: add-inferior [-copies N] [-exec FILENAME]\n\
 902 N is the optional number of inferiors to add, default is 1.\n\
 903 FILENAME is the file name of the executable to use\n\
 904 as main program."));
 905   set_cmd_completer (c, filename_completer);
 906
 907   add_com ("remove-inferiors", no_class, remove_inferior_command, _("\
 908 Remove inferior ID (or list of IDs).\n\
 909 Usage: remove-inferiors ID..."));
 910
 911   add_com ("clone-inferior", no_class, clone_inferior_command, _("\
 912 Clone inferior ID.\n\
 913 Usage: clone-inferior [-copies N] [ID]\n\
 914 Add N copies of inferior ID.  The new inferior has the same\n\
 915 executable loaded as the copied inferior.  If -copies is not specified,\n\
 916 adds 1 copy.  If ID is not specified, it is the current inferior\n\
 917 that is cloned."));
 918
 919   add_cmd ("inferiors", class_run, detach_inferior_command, _("\
 920 Detach from inferior ID (or list of IDS).\n\
 921 Usage; detach inferiors ID..."),
 922            &detachlist);
 923
 924   add_cmd ("inferiors", class_run, kill_inferior_command, _("\
 925 Kill inferior ID (or list of IDs).\n\
 926 Usage: kill inferiors ID..."),
 927            &killlist);
 928
 929   add_cmd ("inferior", class_run, inferior_command, _("\
 930 Use this command to switch between inferiors.\n\
 931 Usage: inferior ID\n\
 932 The new inferior ID must be currently known."),
 933            &cmdlist);
 934
 935   add_setshow_boolean_cmd ("inferior-events", no_class,
 936          &print_inferior_events, _("\
 937 Set printing of inferior events (such as inferior start and exit)."), _("\
 938 Show printing of inferior events (such as inferior start and exit)."), NULL,
 939          NULL,
 940          show_print_inferior_events,
 941          &setprintlist, &showprintlist);
 942
 943   create_internalvar_type_lazy ("_inferior", &inferior_funcs, NULL);
 944 }