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 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
  38 #include <ctype.h>
  39 #include <sys/types.h>
  40 #include <signal.h>
  41 #include "ui-out.h"
  42
  43 /*#include "lynxos-core.h" */
  44
  45 /* Definition of struct thread_info exported to gdbthread.h */
  46
  47 /* Prototypes for exported functions. */
  48
  49 void _initialize_thread (void);
  50
  51 /* Prototypes for local functions. */
  52
  53 static struct thread_info *thread_list = NULL;
  54 static int highest_thread_num;
  55
  56 static struct thread_info *find_thread_id (int num);
  57
  58 static void thread_command (char *tidstr, int from_tty);
  59 static void thread_apply_all_command (char *, int);
  60 static int thread_alive (struct thread_info *);
  61 static void info_threads_command (char *, int);
  62 static void thread_apply_command (char *, int);
  63 static void restore_current_thread (ptid_t);
  64 static void switch_to_thread (ptid_t ptid);
  65 static void prune_threads (void);
  66
  67 void
  68 delete_step_resume_breakpoint (void *arg)
  69 {
  70   struct breakpoint **breakpointp = (struct breakpoint **) arg;
  71   struct thread_info *tp;
  72
  73   if (*breakpointp != NULL)
  74     {
  75       delete_breakpoint (*breakpointp);
  76       for (tp = thread_list; tp; tp = tp->next)
  77         if (tp->step_resume_breakpoint == *breakpointp)
  78           tp->step_resume_breakpoint = NULL;
  79
  80       *breakpointp = NULL;
  81     }
  82 }
  83
  84 static void
  85 free_thread (struct thread_info *tp)
  86 {
  87   /* NOTE: this will take care of any left-over step_resume breakpoints,
  88      but not any user-specified thread-specific breakpoints. */
  89   if (tp->step_resume_breakpoint)
  90     delete_breakpoint (tp->step_resume_breakpoint);
  91
  92   /* FIXME: do I ever need to call the back-end to give it a
  93      chance at this private data before deleting the thread?  */
  94   if (tp->private)
  95     xfree (tp->private);
  96
  97   xfree (tp);
  98 }
  99
 100 void
 101 init_thread_list (void)
 102 {
 103   struct thread_info *tp, *tpnext;
 104
 105   highest_thread_num = 0;
 106   if (!thread_list)
 107     return;
 108
 109   for (tp = thread_list; tp; tp = tpnext)
 110     {
 111       tpnext = tp->next;
 112       free_thread (tp);
 113     }
 114
 115   thread_list = NULL;
 116 }
 117
 118 /* add_thread now returns a pointer to the new thread_info,
 119    so that back_ends can initialize their private data.  */
 120
 121 struct thread_info *
 122 add_thread (ptid_t ptid)
 123 {
 124   struct thread_info *tp;
 125
 126   tp = (struct thread_info *) xmalloc (sizeof (*tp));
 127   memset (tp, 0, sizeof (*tp));
 128   tp->ptid = ptid;
 129   tp->num = ++highest_thread_num;
 130   tp->next = thread_list;
 131   thread_list = tp;
 132   return tp;
 133 }
 134
 135 void
 136 delete_thread (ptid_t ptid)
 137 {
 138   struct thread_info *tp, *tpprev;
 139
 140   tpprev = NULL;
 141
 142   for (tp = thread_list; tp; tpprev = tp, tp = tp->next)
 143     if (ptid_equal (tp->ptid, ptid))
 144       break;
 145
 146   if (!tp)
 147     return;
 148
 149   if (tpprev)
 150     tpprev->next = tp->next;
 151   else
 152     thread_list = tp->next;
 153
 154   free_thread (tp);
 155 }
 156
 157 static struct thread_info *
 158 find_thread_id (int num)
 159 {
 160   struct thread_info *tp;
 161
 162   for (tp = thread_list; tp; tp = tp->next)
 163     if (tp->num == num)
 164       return tp;
 165
 166   return NULL;
 167 }
 168
 169 /* Find a thread_info by matching PTID.  */
 170 struct thread_info *
 171 find_thread_pid (ptid_t ptid)
 172 {
 173   struct thread_info *tp;
 174
 175   for (tp = thread_list; tp; tp = tp->next)
 176     if (ptid_equal (tp->ptid, ptid))
 177       return tp;
 178
 179   return NULL;
 180 }
 181
 182 /*
 183  * Thread iterator function.
 184  *
 185  * Calls a callback function once for each thread, so long as
 186  * the callback function returns false.  If the callback function
 187  * returns true, the iteration will end and the current thread
 188  * will be returned.  This can be useful for implementing a
 189  * search for a thread with arbitrary attributes, or for applying
 190  * some operation to every thread.
 191  *
 192  * FIXME: some of the existing functionality, such as
 193  * "Thread apply all", might be rewritten using this functionality.
 194  */
 195
 196 struct thread_info *
 197 iterate_over_threads (int (*callback) (struct thread_info *, void *),
 198                       void *data)
 199 {
 200   struct thread_info *tp;
 201
 202   for (tp = thread_list; tp; tp = tp->next)
 203     if ((*callback) (tp, data))
 204       return tp;
 205
 206   return NULL;
 207 }
 208
 209 int
 210 valid_thread_id (int num)
 211 {
 212   struct thread_info *tp;
 213
 214   for (tp = thread_list; tp; tp = tp->next)
 215     if (tp->num == num)
 216       return 1;
 217
 218   return 0;
 219 }
 220
 221 int
 222 pid_to_thread_id (ptid_t ptid)
 223 {
 224   struct thread_info *tp;
 225
 226   for (tp = thread_list; tp; tp = tp->next)
 227     if (ptid_equal (tp->ptid, ptid))
 228       return tp->num;
 229
 230   return 0;
 231 }
 232
 233 ptid_t
 234 thread_id_to_pid (int num)
 235 {
 236   struct thread_info *thread = find_thread_id (num);
 237   if (thread)
 238     return thread->ptid;
 239   else
 240     return pid_to_ptid (-1);
 241 }
 242
 243 int
 244 in_thread_list (ptid_t ptid)
 245 {
 246   struct thread_info *tp;
 247
 248   for (tp = thread_list; tp; tp = tp->next)
 249     if (ptid_equal (tp->ptid, ptid))
 250       return 1;
 251
 252   return 0;                     /* Never heard of 'im */
 253 }
 254
 255 /* Print a list of thread ids currently known, and the total number of
 256    threads. To be used from within catch_errors. */
 257 static int
 258 do_captured_list_thread_ids (struct ui_out *uiout,
 259                              void *arg)
 260 {
 261   struct thread_info *tp;
 262   int num = 0;
 263
 264   ui_out_tuple_begin (uiout, "thread-ids");
 265
 266   for (tp = thread_list; tp; tp = tp->next)
 267     {
 268       num++;
 269       ui_out_field_int (uiout, "thread-id", tp->num);
 270     }
 271
 272   ui_out_tuple_end (uiout);
 273   ui_out_field_int (uiout, "number-of-threads", num);
 274   return GDB_RC_OK;
 275 }
 276
 277 /* Official gdblib interface function to get a list of thread ids and
 278    the total number. */
 279 enum gdb_rc
 280 gdb_list_thread_ids (struct ui_out *uiout)
 281 {
 282   return catch_exceptions (uiout, do_captured_list_thread_ids, NULL,
 283                            NULL, RETURN_MASK_ALL);
 284 }
 285
 286 /* Load infrun state for the thread PID.  */
 287
 288 void
 289 load_infrun_state (ptid_t ptid,
 290                    CORE_ADDR *prev_pc,
 291                    CORE_ADDR *prev_func_start,
 292                    char **prev_func_name,
 293                    int *trap_expected,
 294                    struct breakpoint **step_resume_breakpoint,
 295                    struct breakpoint **through_sigtramp_breakpoint,
 296                    CORE_ADDR *step_range_start,
 297                    CORE_ADDR *step_range_end,
 298                    CORE_ADDR *step_frame_address,
 299                    int *handling_longjmp,
 300                    int *another_trap,
 301                    int *stepping_through_solib_after_catch,
 302                    bpstat *stepping_through_solib_catchpoints,
 303                    int *stepping_through_sigtramp,
 304                    int *current_line,
 305                    struct symtab **current_symtab,
 306                    CORE_ADDR *step_sp)
 307 {
 308   struct thread_info *tp;
 309
 310   /* If we can't find the thread, then we're debugging a single threaded
 311      process.  No need to do anything in that case.  */
 312   tp = find_thread_id (pid_to_thread_id (ptid));
 313   if (tp == NULL)
 314     return;
 315
 316   *prev_pc = tp->prev_pc;
 317   *prev_func_start = tp->prev_func_start;
 318   *prev_func_name = tp->prev_func_name;
 319   *trap_expected = tp->trap_expected;
 320   *step_resume_breakpoint = tp->step_resume_breakpoint;
 321   *through_sigtramp_breakpoint = tp->through_sigtramp_breakpoint;
 322   *step_range_start = tp->step_range_start;
 323   *step_range_end = tp->step_range_end;
 324   *step_frame_address = tp->step_frame_address;
 325   *handling_longjmp = tp->handling_longjmp;
 326   *another_trap = tp->another_trap;
 327   *stepping_through_solib_after_catch = tp->stepping_through_solib_after_catch;
 328   *stepping_through_solib_catchpoints = tp->stepping_through_solib_catchpoints;
 329   *stepping_through_sigtramp = tp->stepping_through_sigtramp;
 330   *current_line = tp->current_line;
 331   *current_symtab = tp->current_symtab;
 332   *step_sp = tp->step_sp;
 333 }
 334
 335 /* Save infrun state for the thread PID.  */
 336
 337 void
 338 save_infrun_state (ptid_t ptid,
 339                    CORE_ADDR prev_pc,
 340                    CORE_ADDR prev_func_start,
 341                    char *prev_func_name,
 342                    int trap_expected,
 343                    struct breakpoint *step_resume_breakpoint,
 344                    struct breakpoint *through_sigtramp_breakpoint,
 345                    CORE_ADDR step_range_start,
 346                    CORE_ADDR step_range_end,
 347                    CORE_ADDR step_frame_address,
 348                    int handling_longjmp,
 349                    int another_trap,
 350                    int stepping_through_solib_after_catch,
 351                    bpstat stepping_through_solib_catchpoints,
 352                    int stepping_through_sigtramp,
 353                    int current_line,
 354                    struct symtab *current_symtab,
 355                    CORE_ADDR step_sp)
 356 {
 357   struct thread_info *tp;
 358
 359   /* If we can't find the thread, then we're debugging a single-threaded
 360      process.  Nothing to do in that case.  */
 361   tp = find_thread_id (pid_to_thread_id (ptid));
 362   if (tp == NULL)
 363     return;
 364
 365   tp->prev_pc = prev_pc;
 366   tp->prev_func_start = prev_func_start;
 367   tp->prev_func_name = prev_func_name;
 368   tp->trap_expected = trap_expected;
 369   tp->step_resume_breakpoint = step_resume_breakpoint;
 370   tp->through_sigtramp_breakpoint = through_sigtramp_breakpoint;
 371   tp->step_range_start = step_range_start;
 372   tp->step_range_end = step_range_end;
 373   tp->step_frame_address = step_frame_address;
 374   tp->handling_longjmp = handling_longjmp;
 375   tp->another_trap = another_trap;
 376   tp->stepping_through_solib_after_catch = stepping_through_solib_after_catch;
 377   tp->stepping_through_solib_catchpoints = stepping_through_solib_catchpoints;
 378   tp->stepping_through_sigtramp = stepping_through_sigtramp;
 379   tp->current_line = current_line;
 380   tp->current_symtab = current_symtab;
 381   tp->step_sp = step_sp;
 382 }
 383
 384 /* Return true if TP is an active thread. */
 385 static int
 386 thread_alive (struct thread_info *tp)
 387 {
 388   if (PIDGET (tp->ptid) == -1)
 389     return 0;
 390   if (!target_thread_alive (tp->ptid))
 391     {
 392       tp->ptid = pid_to_ptid (-1);      /* Mark it as dead */
 393       return 0;
 394     }
 395   return 1;
 396 }
 397
 398 static void
 399 prune_threads (void)
 400 {
 401   struct thread_info *tp, *next;
 402
 403   for (tp = thread_list; tp; tp = next)
 404     {
 405       next = tp->next;
 406       if (!thread_alive (tp))
 407         delete_thread (tp->ptid);
 408     }
 409 }
 410
 411 /* Print information about currently known threads
 412
 413  * Note: this has the drawback that it _really_ switches
 414  *       threads, which frees the frame cache.  A no-side
 415  *       effects info-threads command would be nicer.
 416  */
 417
 418 static void
 419 info_threads_command (char *arg, int from_tty)
 420 {
 421   struct thread_info *tp;
 422   ptid_t current_ptid;
 423   struct frame_info *cur_frame;
 424   int saved_frame_level = selected_frame_level;
 425   int counter;
 426   char *extra_info;
 427
 428   /* Avoid coredumps which would happen if we tried to access a NULL
 429      selected_frame.  */
 430   if (!target_has_stack)
 431     error ("No stack.");
 432
 433   prune_threads ();
 434   target_find_new_threads ();
 435   current_ptid = inferior_ptid;
 436   for (tp = thread_list; tp; tp = tp->next)
 437     {
 438       if (ptid_equal (tp->ptid, current_ptid))
 439         printf_filtered ("* ");
 440       else
 441         printf_filtered ("  ");
 442
 443 #ifdef HPUXHPPA
 444       printf_filtered ("%d %s", tp->num, target_tid_to_str (tp->ptid));
 445 #else
 446       printf_filtered ("%d %s", tp->num, target_pid_to_str (tp->ptid));
 447 #endif
 448
 449       extra_info = target_extra_thread_info (tp);
 450       if (extra_info)
 451         printf_filtered (" (%s)", extra_info);
 452       puts_filtered ("  ");
 453
 454       switch_to_thread (tp->ptid);
 455       if (selected_frame)
 456         print_only_stack_frame (selected_frame, -1, 0);
 457       else
 458         printf_filtered ("[No stack.]\n");
 459     }
 460
 461   switch_to_thread (current_ptid);
 462
 463   /* Code below copied from "up_silently_base" in "stack.c".
 464    * It restores the frame set by the user before the "info threads"
 465    * command.  We have finished the info-threads display by switching
 466    * back to the current thread.  That switch has put us at the top
 467    * of the stack (leaf frame).
 468    */
 469   counter = saved_frame_level;
 470   cur_frame = find_relative_frame (selected_frame, &counter);
 471   if (counter != 0)
 472     {
 473       /* Ooops, can't restore, tell user where we are. */
 474       warning ("Couldn't restore frame in current thread, at frame 0");
 475       print_stack_frame (selected_frame, -1, 0);
 476     }
 477   else
 478     {
 479       select_frame (cur_frame, saved_frame_level);
 480     }
 481
 482   /* re-show current frame. */
 483   show_stack_frame (cur_frame);
 484 }
 485
 486 /* Switch from one thread to another. */
 487
 488 static void
 489 switch_to_thread (ptid_t ptid)
 490 {
 491   if (ptid_equal (ptid, inferior_ptid))
 492     return;
 493
 494   inferior_ptid = ptid;
 495   flush_cached_frames ();
 496   registers_changed ();
 497   stop_pc = read_pc ();
 498   select_frame (get_current_frame (), 0);
 499 }
 500
 501 static void
 502 restore_current_thread (ptid_t ptid)
 503 {
 504   if (! ptid_equal (ptid, inferior_ptid))
 505     {
 506       switch_to_thread (ptid);
 507       print_stack_frame (get_current_frame (), 0, -1);
 508     }
 509 }
 510
 511 struct current_thread_cleanup
 512 {
 513   ptid_t inferior_ptid;
 514 };
 515
 516 static void
 517 do_restore_current_thread_cleanup (void *arg)
 518 {
 519   struct current_thread_cleanup *old = arg;
 520   restore_current_thread (old->inferior_ptid);
 521   xfree (old);
 522 }
 523
 524 static struct cleanup *
 525 make_cleanup_restore_current_thread (ptid_t inferior_ptid)
 526 {
 527   struct current_thread_cleanup *old
 528     = xmalloc (sizeof (struct current_thread_cleanup));
 529   old->inferior_ptid = inferior_ptid;
 530   return make_cleanup (do_restore_current_thread_cleanup, old);
 531 }
 532
 533 /* Apply a GDB command to a list of threads.  List syntax is a whitespace
 534    seperated list of numbers, or ranges, or the keyword `all'.  Ranges consist
 535    of two numbers seperated by a hyphen.  Examples:
 536
 537    thread apply 1 2 7 4 backtrace       Apply backtrace cmd to threads 1,2,7,4
 538    thread apply 2-7 9 p foo(1)  Apply p foo(1) cmd to threads 2->7 & 9
 539    thread apply all p x/i $pc   Apply x/i $pc cmd to all threads
 540  */
 541
 542 static void
 543 thread_apply_all_command (char *cmd, int from_tty)
 544 {
 545   struct thread_info *tp;
 546   struct cleanup *old_chain;
 547   struct cleanup *saved_cmd_cleanup_chain;
 548   char *saved_cmd;
 549
 550   if (cmd == NULL || *cmd == '\000')
 551     error ("Please specify a command following the thread ID list");
 552
 553   old_chain = make_cleanup_restore_current_thread (inferior_ptid);
 554
 555   /* It is safe to update the thread list now, before
 556      traversing it for "thread apply all".  MVS */
 557   target_find_new_threads ();
 558
 559   /* Save a copy of the command in case it is clobbered by
 560      execute_command */
 561   saved_cmd = xstrdup (cmd);
 562   saved_cmd_cleanup_chain = make_cleanup (xfree, (void *) saved_cmd);
 563   for (tp = thread_list; tp; tp = tp->next)
 564     if (thread_alive (tp))
 565       {
 566         switch_to_thread (tp->ptid);
 567 #ifdef HPUXHPPA
 568         printf_filtered ("\nThread %d (%s):\n",
 569                          tp->num,
 570                          target_tid_to_str (inferior_ptid));
 571 #else
 572         printf_filtered ("\nThread %d (%s):\n", tp->num,
 573                          target_pid_to_str (inferior_ptid));
 574 #endif
 575         execute_command (cmd, from_tty);
 576         strcpy (cmd, saved_cmd); /* Restore exact command used previously */
 577       }
 578
 579   do_cleanups (saved_cmd_cleanup_chain);
 580   do_cleanups (old_chain);
 581 }
 582
 583 static void
 584 thread_apply_command (char *tidlist, int from_tty)
 585 {
 586   char *cmd;
 587   char *p;
 588   struct cleanup *old_chain;
 589   struct cleanup *saved_cmd_cleanup_chain;
 590   char *saved_cmd;
 591
 592   if (tidlist == NULL || *tidlist == '\000')
 593     error ("Please specify a thread ID list");
 594
 595   for (cmd = tidlist; *cmd != '\000' && !isalpha (*cmd); cmd++);
 596
 597   if (*cmd == '\000')
 598     error ("Please specify a command following the thread ID list");
 599
 600   old_chain = make_cleanup_restore_current_thread (inferior_ptid);
 601
 602   /* Save a copy of the command in case it is clobbered by
 603      execute_command */
 604   saved_cmd = xstrdup (cmd);
 605   saved_cmd_cleanup_chain = make_cleanup (xfree, (void *) saved_cmd);
 606   while (tidlist < cmd)
 607     {
 608       struct thread_info *tp;
 609       int start, end;
 610
 611       start = strtol (tidlist, &p, 10);
 612       if (p == tidlist)
 613         error ("Error parsing %s", tidlist);
 614       tidlist = p;
 615
 616       while (*tidlist == ' ' || *tidlist == '\t')
 617         tidlist++;
 618
 619       if (*tidlist == '-')      /* Got a range of IDs? */
 620         {
 621           tidlist++;            /* Skip the - */
 622           end = strtol (tidlist, &p, 10);
 623           if (p == tidlist)
 624             error ("Error parsing %s", tidlist);
 625           tidlist = p;
 626
 627           while (*tidlist == ' ' || *tidlist == '\t')
 628             tidlist++;
 629         }
 630       else
 631         end = start;
 632
 633       for (; start <= end; start++)
 634         {
 635           tp = find_thread_id (start);
 636
 637           if (!tp)
 638             warning ("Unknown thread %d.", start);
 639           else if (!thread_alive (tp))
 640             warning ("Thread %d has terminated.", start);
 641           else
 642             {
 643               switch_to_thread (tp->ptid);
 644 #ifdef HPUXHPPA
 645               printf_filtered ("\nThread %d (%s):\n", tp->num,
 646                                target_tid_to_str (inferior_ptid));
 647 #else
 648               printf_filtered ("\nThread %d (%s):\n", tp->num,
 649                                target_pid_to_str (inferior_ptid));
 650 #endif
 651               execute_command (cmd, from_tty);
 652               strcpy (cmd, saved_cmd);  /* Restore exact command used previously */
 653             }
 654         }
 655     }
 656
 657   do_cleanups (saved_cmd_cleanup_chain);
 658   do_cleanups (old_chain);
 659 }
 660
 661 /* Switch to the specified thread.  Will dispatch off to thread_apply_command
 662    if prefix of arg is `apply'.  */
 663
 664 static void
 665 thread_command (char *tidstr, int from_tty)
 666 {
 667   if (!tidstr)
 668     {
 669       /* Don't generate an error, just say which thread is current. */
 670       if (target_has_stack)
 671         printf_filtered ("[Current thread is %d (%s)]\n",
 672                          pid_to_thread_id (inferior_ptid),
 673 #if defined(HPUXHPPA)
 674                          target_tid_to_str (inferior_ptid)
 675 #else
 676                          target_pid_to_str (inferior_ptid)
 677 #endif
 678           );
 679       else
 680         error ("No stack.");
 681       return;
 682     }
 683
 684   gdb_thread_select (uiout, tidstr);
 685 }
 686
 687 static int
 688 do_captured_thread_select (struct ui_out *uiout,
 689                            void *tidstr)
 690 {
 691   int num;
 692   struct thread_info *tp;
 693
 694   num = value_as_long (parse_and_eval (tidstr));
 695
 696   tp = find_thread_id (num);
 697
 698   if (!tp)
 699     error ("Thread ID %d not known.", num);
 700
 701   if (!thread_alive (tp))
 702     error ("Thread ID %d has terminated.\n", num);
 703
 704   switch_to_thread (tp->ptid);
 705
 706   ui_out_text (uiout, "[Switching to thread ");
 707   ui_out_field_int (uiout, "new-thread-id", pid_to_thread_id (inferior_ptid));
 708   ui_out_text (uiout, " (");
 709 #if defined(HPUXHPPA)
 710   ui_out_text (uiout, target_tid_to_str (inferior_ptid));
 711 #else
 712   ui_out_text (uiout, target_pid_to_str (inferior_ptid));
 713 #endif
 714   ui_out_text (uiout, ")]");
 715
 716   print_stack_frame (selected_frame, selected_frame_level, 1);
 717   return GDB_RC_OK;
 718 }
 719
 720 enum gdb_rc
 721 gdb_thread_select (struct ui_out *uiout,
 722                    char *tidstr)
 723 {
 724   return catch_exceptions (uiout, do_captured_thread_select, tidstr,
 725                            NULL, RETURN_MASK_ALL);
 726 }
 727
 728 /* Commands with a prefix of `thread'.  */
 729 struct cmd_list_element *thread_cmd_list = NULL;
 730
 731 void
 732 _initialize_thread (void)
 733 {
 734   static struct cmd_list_element *thread_apply_list = NULL;
 735
 736   add_info ("threads", info_threads_command,
 737             "IDs of currently known threads.");
 738
 739   add_prefix_cmd ("thread", class_run, thread_command,
 740                   "Use this command to switch between threads.\n\
 741 The new thread ID must be currently known.", &thread_cmd_list, "thread ", 1,
 742                   &cmdlist);
 743
 744   add_prefix_cmd ("apply", class_run, thread_apply_command,
 745                   "Apply a command to a list of threads.",
 746                   &thread_apply_list, "apply ", 1, &thread_cmd_list);
 747
 748   add_cmd ("all", class_run, thread_apply_all_command,
 749            "Apply a command to all threads.",
 750            &thread_apply_list);
 751
 752   if (!xdb_commands)
 753     add_com_alias ("t", "thread", class_run, 1);
 754 }