gdb/inferior.c

   1 /* Multi-process control for GDB, the GNU debugger.
   2
   3    Copyright (C) 2008-2018 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 "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     printf_unfiltered (_("[New inferior %d (%s)]\n"),
 126                        inf->num,
 127                        target_pid_to_str (ptid_t (pid)));
 128
 129   return inf;
 130 }
 131
 132 struct delete_thread_of_inferior_arg
 133 {
 134   int pid;
 135   int silent;
 136 };
 137
 138 static int
 139 delete_thread_of_inferior (struct thread_info *tp, void *data)
 140 {
 141   struct delete_thread_of_inferior_arg *arg
 142     = (struct delete_thread_of_inferior_arg *) data;
 143
 144   if (tp->ptid.pid () == arg->pid)
 145     {
 146       if (arg->silent)
 147         delete_thread_silent (tp);
 148       else
 149         delete_thread (tp);
 150     }
 151
 152   return 0;
 153 }
 154
 155 void
 156 delete_inferior (struct inferior *todel)
 157 {
 158   struct inferior *inf, *infprev;
 159   struct delete_thread_of_inferior_arg arg;
 160
 161   infprev = NULL;
 162
 163   for (inf = inferior_list; inf; infprev = inf, inf = inf->next)
 164     if (inf == todel)
 165       break;
 166
 167   if (!inf)
 168     return;
 169
 170   arg.pid = inf->pid;
 171   arg.silent = 1;
 172
 173   iterate_over_threads (delete_thread_of_inferior, &arg);
 174
 175   if (infprev)
 176     infprev->next = inf->next;
 177   else
 178     inferior_list = inf->next;
 179
 180   gdb::observers::inferior_removed.notify (inf);
 181
 182   /* If this program space is rendered useless, remove it. */
 183   if (program_space_empty_p (inf->pspace))
 184     delete_program_space (inf->pspace);
 185
 186   delete inf;
 187 }
 188
 189 /* If SILENT then be quiet -- don't announce a inferior exit, or the
 190    exit of its threads.  */
 191
 192 static void
 193 exit_inferior_1 (struct inferior *inftoex, int silent)
 194 {
 195   struct inferior *inf;
 196   struct delete_thread_of_inferior_arg arg;
 197
 198   for (inf = inferior_list; inf; inf = inf->next)
 199     if (inf == inftoex)
 200       break;
 201
 202   if (!inf)
 203     return;
 204
 205   arg.pid = inf->pid;
 206   arg.silent = silent;
 207
 208   iterate_over_threads (delete_thread_of_inferior, &arg);
 209
 210   gdb::observers::inferior_exit.notify (inf);
 211
 212   inf->pid = 0;
 213   inf->fake_pid_p = 0;
 214   inf->priv = NULL;
 215
 216   if (inf->vfork_parent != NULL)
 217     {
 218       inf->vfork_parent->vfork_child = NULL;
 219       inf->vfork_parent = NULL;
 220     }
 221   if (inf->vfork_child != NULL)
 222     {
 223       inf->vfork_child->vfork_parent = NULL;
 224       inf->vfork_child = NULL;
 225     }
 226
 227   inf->pending_detach = 0;
 228   /* Reset it.  */
 229   inf->control = {NO_STOP_QUIETLY};
 230 }
 231
 232 void
 233 exit_inferior (inferior *inf)
 234 {
 235   int pid = inf->pid;
 236   exit_inferior_1 (inf, 0);
 237 }
 238
 239 void
 240 exit_inferior_silent (int pid)
 241 {
 242   struct inferior *inf = find_inferior_pid (pid);
 243
 244   exit_inferior_1 (inf, 1);
 245 }
 246
 247 void
 248 exit_inferior_silent (inferior *inf)
 249 {
 250   exit_inferior_1 (inf, 1);
 251 }
 252
 253 /* See inferior.h.  */
 254
 255 void
 256 detach_inferior (inferior *inf)
 257 {
 258   /* Save the pid, since exit_inferior_1 will reset it.  */
 259   int pid = inf->pid;
 260
 261   exit_inferior_1 (inf, 0);
 262
 263   if (print_inferior_events)
 264     printf_unfiltered (_("[Inferior %d (%s) detached]\n"),
 265                        inf->num,
 266                        target_pid_to_str (ptid_t (pid)));
 267 }
 268
 269 void
 270 inferior_appeared (struct inferior *inf, int pid)
 271 {
 272   inf->pid = pid;
 273   inf->has_exit_code = 0;
 274   inf->exit_code = 0;
 275
 276   gdb::observers::inferior_appeared.notify (inf);
 277 }
 278
 279 void
 280 discard_all_inferiors (void)
 281 {
 282   struct inferior *inf;
 283
 284   for (inf = inferior_list; inf; inf = inf->next)
 285     {
 286       if (inf->pid != 0)
 287         exit_inferior_silent (inf);
 288     }
 289 }
 290
 291 struct inferior *
 292 find_inferior_id (int num)
 293 {
 294   struct inferior *inf;
 295
 296   for (inf = inferior_list; inf; inf = inf->next)
 297     if (inf->num == num)
 298       return inf;
 299
 300   return NULL;
 301 }
 302
 303 struct inferior *
 304 find_inferior_pid (int pid)
 305 {
 306   struct inferior *inf;
 307
 308   /* Looking for inferior pid == 0 is always wrong, and indicative of
 309      a bug somewhere else.  There may be more than one with pid == 0,
 310      for instance.  */
 311   gdb_assert (pid != 0);
 312
 313   for (inf = inferior_list; inf; inf = inf->next)
 314     if (inf->pid == pid)
 315       return inf;
 316
 317   return NULL;
 318 }
 319
 320 /* See inferior.h */
 321
 322 struct inferior *
 323 find_inferior_ptid (ptid_t ptid)
 324 {
 325   return find_inferior_pid (ptid.pid ());
 326 }
 327
 328 /* See inferior.h.  */
 329
 330 struct inferior *
 331 find_inferior_for_program_space (struct program_space *pspace)
 332 {
 333   struct inferior *inf = current_inferior ();
 334
 335   if (inf->pspace == pspace)
 336     return inf;
 337
 338   for (inf = inferior_list; inf != NULL; inf = inf->next)
 339     {
 340       if (inf->pspace == pspace)
 341         return inf;
 342     }
 343
 344   return NULL;
 345 }
 346
 347 struct inferior *
 348 iterate_over_inferiors (int (*callback) (struct inferior *, void *),
 349                         void *data)
 350 {
 351   struct inferior *inf, *infnext;
 352
 353   for (inf = inferior_list; inf; inf = infnext)
 354     {
 355       infnext = inf->next;
 356       if ((*callback) (inf, data))
 357         return inf;
 358     }
 359
 360   return NULL;
 361 }
 362
 363 int
 364 have_inferiors (void)
 365 {
 366   struct inferior *inf;
 367
 368   for (inf = inferior_list; inf; inf = inf->next)
 369     if (inf->pid != 0)
 370       return 1;
 371
 372   return 0;
 373 }
 374
 375 /* Return the number of live inferiors.  We account for the case
 376    where an inferior might have a non-zero pid but no threads, as
 377    in the middle of a 'mourn' operation.  */
 378
 379 int
 380 number_of_live_inferiors (void)
 381 {
 382   struct inferior *inf;
 383   int num_inf = 0;
 384
 385   for (inf = inferior_list; inf; inf = inf->next)
 386     if (inf->pid != 0)
 387       {
 388         struct thread_info *tp;
 389
 390         ALL_NON_EXITED_THREADS (tp)
 391          if (tp && tp->ptid.pid () == inf->pid)
 392            if (target_has_execution_1 (tp->ptid))
 393              {
 394                /* Found a live thread in this inferior, go to the next
 395                   inferior.  */
 396                ++num_inf;
 397                break;
 398              }
 399       }
 400
 401   return num_inf;
 402 }
 403
 404 /* Return true if there is at least one live inferior.  */
 405
 406 int
 407 have_live_inferiors (void)
 408 {
 409   return number_of_live_inferiors () > 0;
 410 }
 411
 412 /* Prune away any unused inferiors, and then prune away no longer used
 413    program spaces.  */
 414
 415 void
 416 prune_inferiors (void)
 417 {
 418   struct inferior *ss, **ss_link;
 419
 420   ss = inferior_list;
 421   ss_link = &inferior_list;
 422   while (ss)
 423     {
 424       if (!ss->deletable ()
 425           || !ss->removable
 426           || ss->pid != 0)
 427         {
 428           ss_link = &ss->next;
 429           ss = *ss_link;
 430           continue;
 431         }
 432
 433       *ss_link = ss->next;
 434       delete_inferior (ss);
 435       ss = *ss_link;
 436     }
 437 }
 438
 439 /* Simply returns the count of inferiors.  */
 440
 441 int
 442 number_of_inferiors (void)
 443 {
 444   struct inferior *inf;
 445   int count = 0;
 446
 447   for (inf = inferior_list; inf != NULL; inf = inf->next)
 448     count++;
 449
 450   return count;
 451 }
 452
 453 /* Converts an inferior process id to a string.  Like
 454    target_pid_to_str, but special cases the null process.  */
 455
 456 static const char *
 457 inferior_pid_to_str (int pid)
 458 {
 459   if (pid != 0)
 460     return target_pid_to_str (ptid_t (pid));
 461   else
 462     return _("<null>");
 463 }
 464
 465 /* See inferior.h.  */
 466
 467 void
 468 print_selected_inferior (struct ui_out *uiout)
 469 {
 470   struct inferior *inf = current_inferior ();
 471   const char *filename = inf->pspace->pspace_exec_filename;
 472
 473   if (filename == NULL)
 474     filename = _("<noexec>");
 475
 476   uiout->message (_("[Switching to inferior %d [%s] (%s)]\n"),
 477                   inf->num, inferior_pid_to_str (inf->pid), filename);
 478 }
 479
 480 /* Prints the list of inferiors and their details on UIOUT.  This is a
 481    version of 'info_inferior_command' suitable for use from MI.
 482
 483    If REQUESTED_INFERIORS is not NULL, it's a list of GDB ids of the
 484    inferiors that should be printed.  Otherwise, all inferiors are
 485    printed.  */
 486
 487 static void
 488 print_inferior (struct ui_out *uiout, const char *requested_inferiors)
 489 {
 490   struct inferior *inf;
 491   int inf_count = 0;
 492
 493   /* Compute number of inferiors we will print.  */
 494   for (inf = inferior_list; inf; inf = inf->next)
 495     {
 496       if (!number_is_in_list (requested_inferiors, inf->num))
 497         continue;
 498
 499       ++inf_count;
 500     }
 501
 502   if (inf_count == 0)
 503     {
 504       uiout->message ("No inferiors.\n");
 505       return;
 506     }
 507
 508   ui_out_emit_table table_emitter (uiout, 4, inf_count, "inferiors");
 509   uiout->table_header (1, ui_left, "current", "");
 510   uiout->table_header (4, ui_left, "number", "Num");
 511   uiout->table_header (17, ui_left, "target-id", "Description");
 512   uiout->table_header (17, ui_left, "exec", "Executable");
 513
 514   uiout->table_body ();
 515   for (inf = inferior_list; inf; inf = inf->next)
 516     {
 517       if (!number_is_in_list (requested_inferiors, inf->num))
 518         continue;
 519
 520       ui_out_emit_tuple tuple_emitter (uiout, NULL);
 521
 522       if (inf == current_inferior ())
 523         uiout->field_string ("current", "*");
 524       else
 525         uiout->field_skip ("current");
 526
 527       uiout->field_int ("number", inf->num);
 528
 529       uiout->field_string ("target-id", inferior_pid_to_str (inf->pid));
 530
 531       if (inf->pspace->pspace_exec_filename != NULL)
 532         uiout->field_string ("exec", inf->pspace->pspace_exec_filename);
 533       else
 534         uiout->field_skip ("exec");
 535
 536       /* Print extra info that isn't really fit to always present in
 537          tabular form.  Currently we print the vfork parent/child
 538          relationships, if any.  */
 539       if (inf->vfork_parent)
 540         {
 541           uiout->text (_("\n\tis vfork child of inferior "));
 542           uiout->field_int ("vfork-parent", inf->vfork_parent->num);
 543         }
 544       if (inf->vfork_child)
 545         {
 546           uiout->text (_("\n\tis vfork parent of inferior "));
 547           uiout->field_int ("vfork-child", inf->vfork_child->num);
 548         }
 549
 550       uiout->text ("\n");
 551     }
 552 }
 553
 554 static void
 555 detach_inferior_command (const char *args, int from_tty)
 556 {
 557   if (!args || !*args)
 558     error (_("Requires argument (inferior id(s) to detach)"));
 559
 560   number_or_range_parser parser (args);
 561   while (!parser.finished ())
 562     {
 563       int num = parser.get_number ();
 564
 565       inferior *inf = find_inferior_id (num);
 566       if (inf == NULL)
 567         {
 568           warning (_("Inferior ID %d not known."), num);
 569           continue;
 570         }
 571
 572       if (inf->pid == 0)
 573         {
 574           warning (_("Inferior ID %d is not running."), num);
 575           continue;
 576         }
 577
 578       thread_info *tp = any_thread_of_inferior (inf);
 579       if (tp == NULL)
 580         {
 581           warning (_("Inferior ID %d has no threads."), num);
 582           continue;
 583         }
 584
 585       switch_to_thread (tp);
 586
 587       detach_command (NULL, from_tty);
 588     }
 589 }
 590
 591 static void
 592 kill_inferior_command (const char *args, int from_tty)
 593 {
 594   if (!args || !*args)
 595     error (_("Requires argument (inferior id(s) to kill)"));
 596
 597   number_or_range_parser parser (args);
 598   while (!parser.finished ())
 599     {
 600       int num = parser.get_number ();
 601
 602       inferior *inf = find_inferior_id (num);
 603       if (inf == NULL)
 604         {
 605           warning (_("Inferior ID %d not known."), num);
 606           continue;
 607         }
 608
 609       if (inf->pid == 0)
 610         {
 611           warning (_("Inferior ID %d is not running."), num);
 612           continue;
 613         }
 614
 615       thread_info *tp = any_thread_of_inferior (inf);
 616       if (tp == NULL)
 617         {
 618           warning (_("Inferior ID %d has no threads."), num);
 619           continue;
 620         }
 621
 622       switch_to_thread (tp);
 623
 624       target_kill ();
 625     }
 626
 627   bfd_cache_close_all ();
 628 }
 629
 630 static void
 631 inferior_command (const char *args, int from_tty)
 632 {
 633   struct inferior *inf;
 634   int num;
 635
 636   num = parse_and_eval_long (args);
 637
 638   inf = find_inferior_id (num);
 639   if (inf == NULL)
 640     error (_("Inferior ID %d not known."), num);
 641
 642   if (inf->pid != 0)
 643     {
 644       if (inf != current_inferior ())
 645         {
 646           thread_info *tp = any_thread_of_inferior (inf);
 647           if (tp == NULL)
 648             error (_("Inferior has no threads."));
 649
 650           switch_to_thread (tp);
 651         }
 652
 653       gdb::observers::user_selected_context_changed.notify
 654         (USER_SELECTED_INFERIOR
 655          | USER_SELECTED_THREAD
 656          | USER_SELECTED_FRAME);
 657     }
 658   else
 659     {
 660       set_current_inferior (inf);
 661       switch_to_no_thread ();
 662       set_current_program_space (inf->pspace);
 663
 664       gdb::observers::user_selected_context_changed.notify
 665         (USER_SELECTED_INFERIOR);
 666     }
 667 }
 668
 669 /* Print information about currently known inferiors.  */
 670
 671 static void
 672 info_inferiors_command (const char *args, int from_tty)
 673 {
 674   print_inferior (current_uiout, args);
 675 }
 676
 677 /* remove-inferior ID */
 678
 679 static void
 680 remove_inferior_command (const char *args, int from_tty)
 681 {
 682   if (args == NULL || *args == '\0')
 683     error (_("Requires an argument (inferior id(s) to remove)"));
 684
 685   number_or_range_parser parser (args);
 686   while (!parser.finished ())
 687     {
 688       int num = parser.get_number ();
 689       struct inferior *inf = find_inferior_id (num);
 690
 691       if (inf == NULL)
 692         {
 693           warning (_("Inferior ID %d not known."), num);
 694           continue;
 695         }
 696
 697       if (!inf->deletable ())
 698         {
 699           warning (_("Can not remove current inferior %d."), num);
 700           continue;
 701         }
 702
 703       if (inf->pid != 0)
 704         {
 705           warning (_("Can not remove active inferior %d."), num);
 706           continue;
 707         }
 708
 709       delete_inferior (inf);
 710     }
 711 }
 712
 713 struct inferior *
 714 add_inferior_with_spaces (void)
 715 {
 716   struct address_space *aspace;
 717   struct program_space *pspace;
 718   struct inferior *inf;
 719   struct gdbarch_info info;
 720
 721   /* If all inferiors share an address space on this system, this
 722      doesn't really return a new address space; otherwise, it
 723      really does.  */
 724   aspace = maybe_new_address_space ();
 725   pspace = new program_space (aspace);
 726   inf = add_inferior (0);
 727   inf->pspace = pspace;
 728   inf->aspace = pspace->aspace;
 729
 730   /* Setup the inferior's initial arch, based on information obtained
 731      from the global "set ..." options.  */
 732   gdbarch_info_init (&info);
 733   inf->gdbarch = gdbarch_find_by_info (info);
 734   /* The "set ..." options reject invalid settings, so we should
 735      always have a valid arch by now.  */
 736   gdb_assert (inf->gdbarch != NULL);
 737
 738   return inf;
 739 }
 740
 741 /* add-inferior [-copies N] [-exec FILENAME]  */
 742
 743 static void
 744 add_inferior_command (const char *args, int from_tty)
 745 {
 746   int i, copies = 1;
 747   gdb::unique_xmalloc_ptr<char> exec;
 748   symfile_add_flags add_flags = 0;
 749
 750   if (from_tty)
 751     add_flags |= SYMFILE_VERBOSE;
 752
 753   if (args)
 754     {
 755       gdb_argv built_argv (args);
 756
 757       for (char **argv = built_argv.get (); *argv != NULL; argv++)
 758         {
 759           if (**argv == '-')
 760             {
 761               if (strcmp (*argv, "-copies") == 0)
 762                 {
 763                   ++argv;
 764                   if (!*argv)
 765                     error (_("No argument to -copies"));
 766                   copies = parse_and_eval_long (*argv);
 767                 }
 768               else if (strcmp (*argv, "-exec") == 0)
 769                 {
 770                   ++argv;
 771                   if (!*argv)
 772                     error (_("No argument to -exec"));
 773                   exec.reset (tilde_expand (*argv));
 774                 }
 775             }
 776           else
 777             error (_("Invalid argument"));
 778         }
 779     }
 780
 781   scoped_restore_current_pspace_and_thread restore_pspace_thread;
 782
 783   for (i = 0; i < copies; ++i)
 784     {
 785       struct inferior *inf = add_inferior_with_spaces ();
 786
 787       printf_filtered (_("Added inferior %d\n"), inf->num);
 788
 789       if (exec != NULL)
 790         {
 791           /* Switch over temporarily, while reading executable and
 792              symbols.q.  */
 793           set_current_program_space (inf->pspace);
 794           set_current_inferior (inf);
 795           switch_to_no_thread ();
 796
 797           exec_file_attach (exec.get (), from_tty);
 798           symbol_file_add_main (exec.get (), add_flags);
 799         }
 800     }
 801 }
 802
 803 /* clone-inferior [-copies N] [ID] */
 804
 805 static void
 806 clone_inferior_command (const char *args, int from_tty)
 807 {
 808   int i, copies = 1;
 809   struct inferior *orginf = NULL;
 810
 811   if (args)
 812     {
 813       gdb_argv built_argv (args);
 814
 815       char **argv = built_argv.get ();
 816       for (; *argv != NULL; argv++)
 817         {
 818           if (**argv == '-')
 819             {
 820               if (strcmp (*argv, "-copies") == 0)
 821                 {
 822                   ++argv;
 823                   if (!*argv)
 824                     error (_("No argument to -copies"));
 825                   copies = parse_and_eval_long (*argv);
 826
 827                   if (copies < 0)
 828                     error (_("Invalid copies number"));
 829                 }
 830             }
 831           else
 832             {
 833               if (orginf == NULL)
 834                 {
 835                   int num;
 836
 837                   /* The first non-option (-) argument specified the
 838                      program space ID.  */
 839                   num = parse_and_eval_long (*argv);
 840                   orginf = find_inferior_id (num);
 841
 842                   if (orginf == NULL)
 843                     error (_("Inferior ID %d not known."), num);
 844                   continue;
 845                 }
 846               else
 847                 error (_("Invalid argument"));
 848             }
 849         }
 850     }
 851
 852   /* If no inferior id was specified, then the user wants to clone the
 853      current inferior.  */
 854   if (orginf == NULL)
 855     orginf = current_inferior ();
 856
 857   scoped_restore_current_pspace_and_thread restore_pspace_thread;
 858
 859   for (i = 0; i < copies; ++i)
 860     {
 861       struct address_space *aspace;
 862       struct program_space *pspace;
 863       struct inferior *inf;
 864
 865       /* If all inferiors share an address space on this system, this
 866          doesn't really return a new address space; otherwise, it
 867          really does.  */
 868       aspace = maybe_new_address_space ();
 869       pspace = new program_space (aspace);
 870       inf = add_inferior (0);
 871       inf->pspace = pspace;
 872       inf->aspace = pspace->aspace;
 873       inf->gdbarch = orginf->gdbarch;
 874
 875       /* If the original inferior had a user specified target
 876          description, make the clone use it too.  */
 877       if (target_desc_info_from_user_p (inf->tdesc_info))
 878         copy_inferior_target_desc_info (inf, orginf);
 879
 880       printf_filtered (_("Added inferior %d.\n"), inf->num);
 881
 882       set_current_inferior (inf);
 883       switch_to_no_thread ();
 884       clone_program_space (pspace, orginf->pspace);
 885     }
 886 }
 887
 888 /* Print notices when new inferiors are created and die.  */
 889 static void
 890 show_print_inferior_events (struct ui_file *file, int from_tty,
 891                            struct cmd_list_element *c, const char *value)
 892 {
 893   fprintf_filtered (file, _("Printing of inferior events is %s.\n"), value);
 894 }
 895
 896 /* Return a new value for the selected inferior's id.  */
 897
 898 static struct value *
 899 inferior_id_make_value (struct gdbarch *gdbarch, struct internalvar *var,
 900                         void *ignore)
 901 {
 902   struct inferior *inf = current_inferior ();
 903
 904   return value_from_longest (builtin_type (gdbarch)->builtin_int, inf->num);
 905 }
 906
 907 /* Implementation of `$_inferior' variable.  */
 908
 909 static const struct internalvar_funcs inferior_funcs =
 910 {
 911   inferior_id_make_value,
 912   NULL,
 913   NULL
 914 };
 915
 916 \f
 917
 918 void
 919 initialize_inferiors (void)
 920 {
 921   struct cmd_list_element *c = NULL;
 922
 923   /* There's always one inferior.  Note that this function isn't an
 924      automatic _initialize_foo function, since other _initialize_foo
 925      routines may need to install their per-inferior data keys.  We
 926      can only allocate an inferior when all those modules have done
 927      that.  Do this after initialize_progspace, due to the
 928      current_program_space reference.  */
 929   current_inferior_ = add_inferior_silent (0);
 930   current_inferior_->incref ();
 931   current_inferior_->pspace = current_program_space;
 932   current_inferior_->aspace = current_program_space->aspace;
 933   /* The architecture will be initialized shortly, by
 934      initialize_current_architecture.  */
 935
 936   add_info ("inferiors", info_inferiors_command,
 937             _("Print a list of inferiors being managed.\n\
 938 Usage: info inferiors [ID]...\n\
 939 If IDs are specified, the list is limited to just those inferiors.\n\
 940 By default all inferiors are displayed."));
 941
 942   c = add_com ("add-inferior", no_class, add_inferior_command, _("\
 943 Add a new inferior.\n\
 944 Usage: add-inferior [-copies N] [-exec FILENAME]\n\
 945 N is the optional number of inferiors to add, default is 1.\n\
 946 FILENAME is the file name of the executable to use\n\
 947 as main program."));
 948   set_cmd_completer (c, filename_completer);
 949
 950   add_com ("remove-inferiors", no_class, remove_inferior_command, _("\
 951 Remove inferior ID (or list of IDs).\n\
 952 Usage: remove-inferiors ID..."));
 953
 954   add_com ("clone-inferior", no_class, clone_inferior_command, _("\
 955 Clone inferior ID.\n\
 956 Usage: clone-inferior [-copies N] [ID]\n\
 957 Add N copies of inferior ID.  The new inferior has the same\n\
 958 executable loaded as the copied inferior.  If -copies is not specified,\n\
 959 adds 1 copy.  If ID is not specified, it is the current inferior\n\
 960 that is cloned."));
 961
 962   add_cmd ("inferiors", class_run, detach_inferior_command, _("\
 963 Detach from inferior ID (or list of IDS).\n\
 964 Usage; detach inferiors ID..."),
 965            &detachlist);
 966
 967   add_cmd ("inferiors", class_run, kill_inferior_command, _("\
 968 Kill inferior ID (or list of IDs).\n\
 969 Usage: kill inferiors ID..."),
 970            &killlist);
 971
 972   add_cmd ("inferior", class_run, inferior_command, _("\
 973 Use this command to switch between inferiors.\n\
 974 Usage: inferior ID\n\
 975 The new inferior ID must be currently known."),
 976            &cmdlist);
 977
 978   add_setshow_boolean_cmd ("inferior-events", no_class,
 979          &print_inferior_events, _("\
 980 Set printing of inferior events (e.g., inferior start and exit)."), _("\
 981 Show printing of inferior events (e.g., inferior start and exit)."), NULL,
 982          NULL,
 983          show_print_inferior_events,
 984          &setprintlist, &showprintlist);
 985
 986   create_internalvar_type_lazy ("_inferior", &inferior_funcs, NULL);
 987 }