gdb/thread.c

   1 /* Multi-process/thread control for GDB, the GNU debugger.
   2
   3    Copyright 1986, 1987, 1988, 1993, 1994, 1995, 1996, 1997, 1998,
   4    1999, 2000, 2001, 2002, 2003 Free Software Foundation, Inc.
   5
   6    Contributed by Lynx Real-Time Systems, Inc.  Los Gatos, CA.
   7
   8    This file is part of GDB.
   9
  10    This program is free software; you can redistribute it and/or modify
  11    it under the terms of the GNU General Public License as published by
  12    the Free Software Foundation; either version 2 of the License, or
  13    (at your option) any later version.
  14
  15    This program is distributed in the hope that it will be useful,
  16    but WITHOUT ANY WARRANTY; without even the implied warranty of
  17    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18    GNU General Public License for more details.
  19
  20    You should have received a copy of the GNU General Public License
  21    along with this program; if not, write to the Free Software
  22    Foundation, Inc., 59 Temple Place - Suite 330,
  23    Boston, MA 02111-1307, USA.  */
  24
  25 #include "defs.h"
  26 #include "symtab.h"
  27 #include "frame.h"
  28 #include "inferior.h"
  29 #include "environ.h"
  30 #include "value.h"
  31 #include "target.h"
  32 #include "gdbthread.h"
  33 #include "command.h"
  34 #include "gdbcmd.h"
  35 #include "regcache.h"
  36 #include "gdb.h"
  37 #include "gdb_string.h"
  38
  39 #include <ctype.h>
  40 #include <sys/types.h>
  41 #include <signal.h>
  42 #include "ui-out.h"
  43
  44 /*#include "lynxos-core.h" */
  45
  46 /* Definition of struct thread_info exported to gdbthread.h */
  47
  48 /* Prototypes for exported functions. */
  49
  50 void _initialize_thread (void);
  51
  52 /* Prototypes for local functions. */
  53
  54 static struct thread_info *thread_list = NULL;
  55 static int highest_thread_num;
  56
  57 static struct thread_info *find_thread_id (int num);
  58
  59 static void thread_command (char *tidstr, int from_tty);
  60 static void thread_apply_all_command (char *, int);
  61 static int thread_alive (struct thread_info *);
  62 static void info_threads_command (char *, int);
  63 static void thread_apply_command (char *, int);
  64 static void restore_current_thread (ptid_t);
  65 static void switch_to_thread (ptid_t ptid);
  66 static void prune_threads (void);
  67
  68 void
  69 delete_step_resume_breakpoint (void *arg)
  70 {
  71   struct breakpoint **breakpointp = (struct breakpoint **) arg;
  72   struct thread_info *tp;
  73
  74   if (*breakpointp != NULL)
  75     {
  76       delete_breakpoint (*breakpointp);
  77       for (tp = thread_list; tp; tp = tp->next)
  78         if (tp->step_resume_breakpoint == *breakpointp)
  79           tp->step_resume_breakpoint = NULL;
  80
  81       *breakpointp = NULL;
  82     }
  83 }
  84
  85 static void
  86 free_thread (struct thread_info *tp)
  87 {
  88   /* NOTE: this will take care of any left-over step_resume breakpoints,
  89      but not any user-specified thread-specific breakpoints. */
  90   if (tp->step_resume_breakpoint)
  91     delete_breakpoint (tp->step_resume_breakpoint);
  92
  93   /* FIXME: do I ever need to call the back-end to give it a
  94      chance at this private data before deleting the thread?  */
  95   if (tp->private)
  96     xfree (tp->private);
  97
  98   xfree (tp);
  99 }
 100
 101 void
 102 init_thread_list (void)
 103 {
 104   struct thread_info *tp, *tpnext;
 105
 106   highest_thread_num = 0;
 107   if (!thread_list)
 108     return;
 109
 110   for (tp = thread_list; tp; tp = tpnext)
 111     {
 112       tpnext = tp->next;
 113       free_thread (tp);
 114     }
 115
 116   thread_list = NULL;
 117 }
 118
 119 /* add_thread now returns a pointer to the new thread_info,
 120    so that back_ends can initialize their private data.  */
 121
 122 struct thread_info *
 123 add_thread (ptid_t ptid)
 124 {
 125   struct thread_info *tp;
 126
 127   tp = (struct thread_info *) xmalloc (sizeof (*tp));
 128   memset (tp, 0, sizeof (*tp));
 129   tp->ptid = ptid;
 130   tp->num = ++highest_thread_num;
 131   tp->next = thread_list;
 132   thread_list = tp;
 133   return tp;
 134 }
 135
 136 void
 137 delete_thread (ptid_t ptid)
 138 {
 139   struct thread_info *tp, *tpprev;
 140
 141   tpprev = NULL;
 142
 143   for (tp = thread_list; tp; tpprev = tp, tp = tp->next)
 144     if (ptid_equal (tp->ptid, ptid))
 145       break;
 146
 147   if (!tp)
 148     return;
 149
 150   if (tpprev)
 151     tpprev->next = tp->next;
 152   else
 153     thread_list = tp->next;
 154
 155   free_thread (tp);
 156 }
 157
 158 static struct thread_info *
 159 find_thread_id (int num)
 160 {
 161   struct thread_info *tp;
 162
 163   for (tp = thread_list; tp; tp = tp->next)
 164     if (tp->num == num)
 165       return tp;
 166
 167   return NULL;
 168 }
 169
 170 /* Find a thread_info by matching PTID.  */
 171 struct thread_info *
 172 find_thread_pid (ptid_t ptid)
 173 {
 174   struct thread_info *tp;
 175
 176   for (tp = thread_list; tp; tp = tp->next)
 177     if (ptid_equal (tp->ptid, ptid))
 178       return tp;
 179
 180   return NULL;
 181 }
 182
 183 /*
 184  * Thread iterator function.
 185  *
 186  * Calls a callback function once for each thread, so long as
 187  * the callback function returns false.  If the callback function
 188  * returns true, the iteration will end and the current thread
 189  * will be returned.  This can be useful for implementing a
 190  * search for a thread with arbitrary attributes, or for applying
 191  * some operation to every thread.
 192  *
 193  * FIXME: some of the existing functionality, such as
 194  * "Thread apply all", might be rewritten using this functionality.
 195  */
 196
 197 struct thread_info *
 198 iterate_over_threads (int (*callback) (struct thread_info *, void *),
 199                       void *data)
 200 {
 201   struct thread_info *tp;
 202
 203   for (tp = thread_list; tp; tp = tp->next)
 204     if ((*callback) (tp, data))
 205       return tp;
 206
 207   return NULL;
 208 }
 209
 210 int
 211 valid_thread_id (int num)
 212 {
 213   struct thread_info *tp;
 214
 215   for (tp = thread_list; tp; tp = tp->next)
 216     if (tp->num == num)
 217       return 1;
 218
 219   return 0;
 220 }
 221
 222 int
 223 pid_to_thread_id (ptid_t ptid)
 224 {
 225   struct thread_info *tp;
 226
 227   for (tp = thread_list; tp; tp = tp->next)
 228     if (ptid_equal (tp->ptid, ptid))
 229       return tp->num;
 230
 231   return 0;
 232 }
 233
 234 ptid_t
 235 thread_id_to_pid (int num)
 236 {
 237   struct thread_info *thread = find_thread_id (num);
 238   if (thread)
 239     return thread->ptid;
 240   else
 241     return pid_to_ptid (-1);
 242 }
 243
 244 int
 245 in_thread_list (ptid_t ptid)
 246 {
 247   struct thread_info *tp;
 248
 249   for (tp = thread_list; tp; tp = tp->next)
 250     if (ptid_equal (tp->ptid, ptid))
 251       return 1;
 252
 253   return 0;                     /* Never heard of 'im */
 254 }
 255
 256 /* Print a list of thread ids currently known, and the total number of
 257    threads. To be used from within catch_errors. */
 258 static int
 259 do_captured_list_thread_ids (struct ui_out *uiout, void *arg)
 260 {
 261   struct thread_info *tp;
 262   int num = 0;
 263   struct cleanup *cleanup_chain;
 264
 265   prune_threads ();
 266   target_find_new_threads ();
 267
 268   cleanup_chain = make_cleanup_ui_out_tuple_begin_end (uiout, "thread-ids");
 269
 270   for (tp = thread_list; tp; tp = tp->next)
 271     {
 272       num++;
 273       ui_out_field_int (uiout, "thread-id", tp->num);
 274     }
 275
 276   do_cleanups (cleanup_chain);
 277   ui_out_field_int (uiout, "number-of-threads", num);
 278   return GDB_RC_OK;
 279 }
 280
 281 /* Official gdblib interface function to get a list of thread ids and
 282    the total number. */
 283 enum gdb_rc
 284 gdb_list_thread_ids (struct ui_out *uiout)
 285 {
 286   return catch_exceptions (uiout, do_captured_list_thread_ids, NULL,
 287                            NULL, RETURN_MASK_ALL);
 288 }
 289
 290 /* Load infrun state for the thread PID.  */
 291
 292 void
 293 load_infrun_state (ptid_t ptid,
 294                    CORE_ADDR *prev_pc,
 295                    int *trap_expected,
 296                    struct breakpoint **step_resume_breakpoint,
 297                    struct breakpoint **through_sigtramp_breakpoint,
 298                    CORE_ADDR *step_range_start,
 299                    CORE_ADDR *step_range_end,
 300                    struct frame_id *step_frame_id,
 301                    int *handling_longjmp,
 302                    int *another_trap,
 303                    int *stepping_through_solib_after_catch,
 304                    bpstat *stepping_through_solib_catchpoints,
 305                    int *stepping_through_sigtramp,
 306                    int *current_line,
 307                    struct symtab **current_symtab, CORE_ADDR *step_sp)
 308 {
 309   struct thread_info *tp;
 310
 311   /* If we can't find the thread, then we're debugging a single threaded
 312      process.  No need to do anything in that case.  */
 313   tp = find_thread_id (pid_to_thread_id (ptid));
 314   if (tp == NULL)
 315     return;
 316
 317   *prev_pc = tp->prev_pc;
 318   *trap_expected = tp->trap_expected;
 319   *step_resume_breakpoint = tp->step_resume_breakpoint;
 320   *through_sigtramp_breakpoint = tp->through_sigtramp_breakpoint;
 321   *step_range_start = tp->step_range_start;
 322   *step_range_end = tp->step_range_end;
 323   *step_frame_id = tp->step_frame_id;
 324   *handling_longjmp = tp->handling_longjmp;
 325   *another_trap = tp->another_trap;
 326   *stepping_through_solib_after_catch =
 327     tp->stepping_through_solib_after_catch;
 328   *stepping_through_solib_catchpoints =
 329     tp->stepping_through_solib_catchpoints;
 330   *stepping_through_sigtramp = tp->stepping_through_sigtramp;
 331   *current_line = tp->current_line;
 332   *current_symtab = tp->current_symtab;
 333   *step_sp = tp->step_sp;
 334 }
 335
 336 /* Save infrun state for the thread PID.  */
 337
 338 void
 339 save_infrun_state (ptid_t ptid,
 340                    CORE_ADDR prev_pc,
 341                    int trap_expected,
 342                    struct breakpoint *step_resume_breakpoint,
 343                    struct breakpoint *through_sigtramp_breakpoint,
 344                    CORE_ADDR step_range_start,
 345                    CORE_ADDR step_range_end,
 346                    const struct frame_id *step_frame_id,
 347                    int handling_longjmp,
 348                    int another_trap,
 349                    int stepping_through_solib_after_catch,
 350                    bpstat stepping_through_solib_catchpoints,
 351                    int stepping_through_sigtramp,
 352                    int current_line,
 353                    struct symtab *current_symtab, CORE_ADDR step_sp)
 354 {
 355   struct thread_info *tp;
 356
 357   /* If we can't find the thread, then we're debugging a single-threaded
 358      process.  Nothing to do in that case.  */
 359   tp = find_thread_id (pid_to_thread_id (ptid));
 360   if (tp == NULL)
 361     return;
 362
 363   tp->prev_pc = prev_pc;
 364   tp->trap_expected = trap_expected;
 365   tp->step_resume_breakpoint = step_resume_breakpoint;
 366   tp->through_sigtramp_breakpoint = through_sigtramp_breakpoint;
 367   tp->step_range_start = step_range_start;
 368   tp->step_range_end = step_range_end;
 369   tp->step_frame_id = (*step_frame_id);
 370   tp->handling_longjmp = handling_longjmp;
 371   tp->another_trap = another_trap;
 372   tp->stepping_through_solib_after_catch = stepping_through_solib_after_catch;
 373   tp->stepping_through_solib_catchpoints = stepping_through_solib_catchpoints;
 374   tp->stepping_through_sigtramp = stepping_through_sigtramp;
 375   tp->current_line = current_line;
 376   tp->current_symtab = current_symtab;
 377   tp->step_sp = step_sp;
 378 }
 379
 380 /* Return true if TP is an active thread. */
 381 static int
 382 thread_alive (struct thread_info *tp)
 383 {
 384   if (PIDGET (tp->ptid) == -1)
 385     return 0;
 386   if (!target_thread_alive (tp->ptid))
 387     {
 388       tp->ptid = pid_to_ptid (-1);      /* Mark it as dead */
 389       return 0;
 390     }
 391   return 1;
 392 }
 393
 394 static void
 395 prune_threads (void)
 396 {
 397   struct thread_info *tp, *next;
 398
 399   for (tp = thread_list; tp; tp = next)
 400     {
 401       next = tp->next;
 402       if (!thread_alive (tp))
 403         delete_thread (tp->ptid);
 404     }
 405 }
 406
 407 /* Print information about currently known threads
 408
 409  * Note: this has the drawback that it _really_ switches
 410  *       threads, which frees the frame cache.  A no-side
 411  *       effects info-threads command would be nicer.
 412  */
 413
 414 static void
 415 info_threads_command (char *arg, int from_tty)
 416 {
 417   struct thread_info *tp;
 418   ptid_t current_ptid;
 419   struct frame_info *cur_frame;
 420   int saved_frame_level = frame_relative_level (deprecated_selected_frame);
 421   int counter;
 422   char *extra_info;
 423
 424   /* Avoid coredumps which would happen if we tried to access a NULL
 425      deprecated_selected_frame.  */
 426   if (!target_has_stack)
 427     error ("No stack.");
 428
 429   prune_threads ();
 430   target_find_new_threads ();
 431   current_ptid = inferior_ptid;
 432   for (tp = thread_list; tp; tp = tp->next)
 433     {
 434       if (ptid_equal (tp->ptid, current_ptid))
 435         printf_filtered ("* ");
 436       else
 437         printf_filtered ("  ");
 438
 439 #ifdef HPUXHPPA
 440       printf_filtered ("%d %s", tp->num, target_tid_to_str (tp->ptid));
 441 #else
 442       printf_filtered ("%d %s", tp->num, target_pid_to_str (tp->ptid));
 443 #endif
 444
 445       extra_info = target_extra_thread_info (tp);
 446       if (extra_info)
 447         printf_filtered (" (%s)", extra_info);
 448       puts_filtered ("  ");
 449
 450       switch_to_thread (tp->ptid);
 451       if (deprecated_selected_frame)
 452         print_stack_frame (deprecated_selected_frame, -1, 0);
 453       else
 454         printf_filtered ("[No stack.]\n");
 455     }
 456
 457   switch_to_thread (current_ptid);
 458
 459   /* Code below copied from "up_silently_base" in "stack.c".
 460    * It restores the frame set by the user before the "info threads"
 461    * command.  We have finished the info-threads display by switching
 462    * back to the current thread.  That switch has put us at the top
 463    * of the stack (leaf frame).
 464    */
 465   counter = saved_frame_level;
 466   cur_frame = find_relative_frame (deprecated_selected_frame, &counter);
 467   if (counter != 0)
 468     {
 469       /* Ooops, can't restore, tell user where we are. */
 470       warning ("Couldn't restore frame in current thread, at frame 0");
 471       print_stack_frame (deprecated_selected_frame, -1, 0);
 472     }
 473   else
 474     {
 475       select_frame (cur_frame);
 476     }
 477
 478   /* re-show current frame. */
 479   show_stack_frame (cur_frame);
 480 }
 481
 482 /* Switch from one thread to another. */
 483
 484 static void
 485 switch_to_thread (ptid_t ptid)
 486 {
 487   if (ptid_equal (ptid, inferior_ptid))
 488     return;
 489
 490   inferior_ptid = ptid;
 491   flush_cached_frames ();
 492   registers_changed ();
 493   stop_pc = read_pc ();
 494   select_frame (get_current_frame ());
 495 }
 496
 497 static void
 498 restore_current_thread (ptid_t ptid)
 499 {
 500   if (!ptid_equal (ptid, inferior_ptid))
 501     {
 502       switch_to_thread (ptid);
 503       print_stack_frame (get_current_frame (), 0, -1);
 504     }
 505 }
 506
 507 struct current_thread_cleanup
 508 {
 509   ptid_t inferior_ptid;
 510 };
 511
 512 static void
 513 do_restore_current_thread_cleanup (void *arg)
 514 {
 515   struct current_thread_cleanup *old = arg;
 516   restore_current_thread (old->inferior_ptid);
 517   xfree (old);
 518 }
 519
 520 static struct cleanup *
 521 make_cleanup_restore_current_thread (ptid_t inferior_ptid)
 522 {
 523   struct current_thread_cleanup *old
 524     = xmalloc (sizeof (struct current_thread_cleanup));
 525   old->inferior_ptid = inferior_ptid;
 526   return make_cleanup (do_restore_current_thread_cleanup, old);
 527 }
 528
 529 /* Apply a GDB command to a list of threads.  List syntax is a whitespace
 530    seperated list of numbers, or ranges, or the keyword `all'.  Ranges consist
 531    of two numbers seperated by a hyphen.  Examples:
 532
 533    thread apply 1 2 7 4 backtrace       Apply backtrace cmd to threads 1,2,7,4
 534    thread apply 2-7 9 p foo(1)  Apply p foo(1) cmd to threads 2->7 & 9
 535    thread apply all p x/i $pc   Apply x/i $pc cmd to all threads
 536  */
 537
 538 static void
 539 thread_apply_all_command (char *cmd, int from_tty)
 540 {
 541   struct thread_info *tp;
 542   struct cleanup *old_chain;
 543   struct cleanup *saved_cmd_cleanup_chain;
 544   char *saved_cmd;
 545
 546   if (cmd == NULL || *cmd == '\000')
 547     error ("Please specify a command following the thread ID list");
 548
 549   old_chain = make_cleanup_restore_current_thread (inferior_ptid);
 550
 551   /* It is safe to update the thread list now, before
 552      traversing it for "thread apply all".  MVS */
 553   target_find_new_threads ();
 554
 555   /* Save a copy of the command in case it is clobbered by
 556      execute_command */
 557   saved_cmd = xstrdup (cmd);
 558   saved_cmd_cleanup_chain = make_cleanup (xfree, (void *) saved_cmd);
 559   for (tp = thread_list; tp; tp = tp->next)
 560     if (thread_alive (tp))
 561       {
 562         switch_to_thread (tp->ptid);
 563 #ifdef HPUXHPPA
 564         printf_filtered ("\nThread %d (%s):\n",
 565                          tp->num, target_tid_to_str (inferior_ptid));
 566 #else
 567         printf_filtered ("\nThread %d (%s):\n", tp->num,
 568                          target_pid_to_str (inferior_ptid));
 569 #endif
 570         execute_command (cmd, from_tty);
 571         strcpy (cmd, saved_cmd);        /* Restore exact command used previously */
 572       }
 573
 574   do_cleanups (saved_cmd_cleanup_chain);
 575   do_cleanups (old_chain);
 576 }
 577
 578 static void
 579 thread_apply_command (char *tidlist, int from_tty)
 580 {
 581   char *cmd;
 582   char *p;
 583   struct cleanup *old_chain;
 584   struct cleanup *saved_cmd_cleanup_chain;
 585   char *saved_cmd;
 586
 587   if (tidlist == NULL || *tidlist == '\000')
 588     error ("Please specify a thread ID list");
 589
 590   for (cmd = tidlist; *cmd != '\000' && !isalpha (*cmd); cmd++);
 591
 592   if (*cmd == '\000')
 593     error ("Please specify a command following the thread ID list");
 594
 595   old_chain = make_cleanup_restore_current_thread (inferior_ptid);
 596
 597   /* Save a copy of the command in case it is clobbered by
 598      execute_command */
 599   saved_cmd = xstrdup (cmd);
 600   saved_cmd_cleanup_chain = make_cleanup (xfree, (void *) saved_cmd);
 601   while (tidlist < cmd)
 602     {
 603       struct thread_info *tp;
 604       int start, end;
 605
 606       start = strtol (tidlist, &p, 10);
 607       if (p == tidlist)
 608         error ("Error parsing %s", tidlist);
 609       tidlist = p;
 610
 611       while (*tidlist == ' ' || *tidlist == '\t')
 612         tidlist++;
 613
 614       if (*tidlist == '-')      /* Got a range of IDs? */
 615         {
 616           tidlist++;            /* Skip the - */
 617           end = strtol (tidlist, &p, 10);
 618           if (p == tidlist)
 619             error ("Error parsing %s", tidlist);
 620           tidlist = p;
 621
 622           while (*tidlist == ' ' || *tidlist == '\t')
 623             tidlist++;
 624         }
 625       else
 626         end = start;
 627
 628       for (; start <= end; start++)
 629         {
 630           tp = find_thread_id (start);
 631
 632           if (!tp)
 633             warning ("Unknown thread %d.", start);
 634           else if (!thread_alive (tp))
 635             warning ("Thread %d has terminated.", start);
 636           else
 637             {
 638               switch_to_thread (tp->ptid);
 639 #ifdef HPUXHPPA
 640               printf_filtered ("\nThread %d (%s):\n", tp->num,
 641                                target_tid_to_str (inferior_ptid));
 642 #else
 643               printf_filtered ("\nThread %d (%s):\n", tp->num,
 644                                target_pid_to_str (inferior_ptid));
 645 #endif
 646               execute_command (cmd, from_tty);
 647               strcpy (cmd, saved_cmd);  /* Restore exact command used previously */
 648             }
 649         }
 650     }
 651
 652   do_cleanups (saved_cmd_cleanup_chain);
 653   do_cleanups (old_chain);
 654 }
 655
 656 /* Switch to the specified thread.  Will dispatch off to thread_apply_command
 657    if prefix of arg is `apply'.  */
 658
 659 static void
 660 thread_command (char *tidstr, int from_tty)
 661 {
 662   if (!tidstr)
 663     {
 664       /* Don't generate an error, just say which thread is current. */
 665       if (target_has_stack)
 666         printf_filtered ("[Current thread is %d (%s)]\n",
 667                          pid_to_thread_id (inferior_ptid),
 668 #if defined(HPUXHPPA)
 669                          target_tid_to_str (inferior_ptid)
 670 #else
 671                          target_pid_to_str (inferior_ptid)
 672 #endif
 673           );
 674       else
 675         error ("No stack.");
 676       return;
 677     }
 678
 679   gdb_thread_select (uiout, tidstr);
 680 }
 681
 682 static int
 683 do_captured_thread_select (struct ui_out *uiout, void *tidstr)
 684 {
 685   int num;
 686   struct thread_info *tp;
 687
 688   num = value_as_long (parse_and_eval (tidstr));
 689
 690   tp = find_thread_id (num);
 691
 692   if (!tp)
 693     error ("Thread ID %d not known.", num);
 694
 695   if (!thread_alive (tp))
 696     error ("Thread ID %d has terminated.\n", num);
 697
 698   switch_to_thread (tp->ptid);
 699
 700   ui_out_text (uiout, "[Switching to thread ");
 701   ui_out_field_int (uiout, "new-thread-id", pid_to_thread_id (inferior_ptid));
 702   ui_out_text (uiout, " (");
 703 #if defined(HPUXHPPA)
 704   ui_out_text (uiout, target_tid_to_str (inferior_ptid));
 705 #else
 706   ui_out_text (uiout, target_pid_to_str (inferior_ptid));
 707 #endif
 708   ui_out_text (uiout, ")]");
 709
 710   print_stack_frame (deprecated_selected_frame,
 711                      frame_relative_level (deprecated_selected_frame), 1);
 712   return GDB_RC_OK;
 713 }
 714
 715 enum gdb_rc
 716 gdb_thread_select (struct ui_out *uiout, char *tidstr)
 717 {
 718   return catch_exceptions (uiout, do_captured_thread_select, tidstr,
 719                            NULL, RETURN_MASK_ALL);
 720 }
 721
 722 /* Commands with a prefix of `thread'.  */
 723 struct cmd_list_element *thread_cmd_list = NULL;
 724
 725 void
 726 _initialize_thread (void)
 727 {
 728   static struct cmd_list_element *thread_apply_list = NULL;
 729
 730   add_info ("threads", info_threads_command,
 731             "IDs of currently known threads.");
 732
 733   add_prefix_cmd ("thread", class_run, thread_command,
 734                   "Use this command to switch between threads.\n\
 735 The new thread ID must be currently known.", &thread_cmd_list, "thread ", 1, &cmdlist);
 736
 737   add_prefix_cmd ("apply", class_run, thread_apply_command,
 738                   "Apply a command to a list of threads.",
 739                   &thread_apply_list, "apply ", 1, &thread_cmd_list);
 740
 741   add_cmd ("all", class_run, thread_apply_all_command,
 742            "Apply a command to all threads.", &thread_apply_list);
 743
 744   if (!xdb_commands)
 745     add_com_alias ("t", "thread", class_run, 1);
 746 }