gdb/break-catch-throw.c

   1 /* Everything about catch/throw catchpoints, for GDB.
   2
   3    Copyright (C) 1986-2022 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 "arch-utils.h"
  22 #include <ctype.h>
  23 #include "breakpoint.h"
  24 #include "gdbcmd.h"
  25 #include "inferior.h"
  26 #include "annotate.h"
  27 #include "valprint.h"
  28 #include "cli/cli-utils.h"
  29 #include "completer.h"
  30 #include "gdbsupport/gdb_obstack.h"
  31 #include "mi/mi-common.h"
  32 #include "linespec.h"
  33 #include "probe.h"
  34 #include "objfiles.h"
  35 #include "cp-abi.h"
  36 #include "gdbsupport/gdb_regex.h"
  37 #include "cp-support.h"
  38 #include "location.h"
  39 #include "cli/cli-decode.h"
  40
  41 /* Each spot where we may place an exception-related catchpoint has
  42    two names: the SDT probe point and the function name.  This
  43    structure holds both.  */
  44
  45 struct exception_names
  46 {
  47   /* The name of the probe point to try, in the form accepted by
  48      'parse_probes'.  */
  49
  50   const char *probe;
  51
  52   /* The name of the corresponding function.  */
  53
  54   const char *function;
  55 };
  56
  57 /* Names of the probe points and functions on which to break.  This is
  58    indexed by exception_event_kind.  */
  59 static const struct exception_names exception_functions[] =
  60 {
  61   { "-probe-stap libstdcxx:throw", "__cxa_throw" },
  62   { "-probe-stap libstdcxx:rethrow", "__cxa_rethrow" },
  63   { "-probe-stap libstdcxx:catch", "__cxa_begin_catch" }
  64 };
  65
  66 /* The type of an exception catchpoint.  */
  67
  68 struct exception_catchpoint : public base_breakpoint
  69 {
  70   void re_set () override;
  71   enum print_stop_action print_it (struct bpstat *bs) override;
  72   bool print_one (struct bp_location **) override;
  73   void print_mention () override;
  74   void print_recreate (struct ui_file *fp) override;
  75   void print_one_detail (struct ui_out *) const override;
  76   void check_status (struct bpstat *bs) override;
  77   struct bp_location *allocate_location () override;
  78
  79   /* FIXME this is temporary - until ordinary breakpoints have been
  80      converted.  */
  81   int resources_needed (const struct bp_location *) override
  82   {
  83     return 1;
  84   }
  85
  86   /* The kind of exception catchpoint.  */
  87
  88   enum exception_event_kind kind;
  89
  90   /* If not empty, a string holding the source form of the regular
  91      expression to match against.  */
  92
  93   std::string exception_rx;
  94
  95   /* If non-NULL, a compiled regular expression which is used to
  96      determine which exceptions to stop on.  */
  97
  98   std::unique_ptr<compiled_regex> pattern;
  99 };
 100
 101 /* See breakpoint.h.  */
 102
 103 bool
 104 is_exception_catchpoint (breakpoint *bp)
 105 {
 106   return dynamic_cast<exception_catchpoint *> (bp) != nullptr;
 107 }
 108
 109 \f
 110
 111 /* A helper function that fetches exception probe arguments.  This
 112    fills in *ARG0 (if non-NULL) and *ARG1 (which must be non-NULL).
 113    It will throw an exception on any kind of failure.  */
 114
 115 static void
 116 fetch_probe_arguments (struct value **arg0, struct value **arg1)
 117 {
 118   struct frame_info *frame = get_selected_frame (_("No frame selected"));
 119   CORE_ADDR pc = get_frame_pc (frame);
 120   struct bound_probe pc_probe;
 121   unsigned n_args;
 122
 123   pc_probe = find_probe_by_pc (pc);
 124   if (pc_probe.prob == NULL)
 125     error (_("did not find exception probe (does libstdcxx have SDT probes?)"));
 126
 127   if (pc_probe.prob->get_provider () != "libstdcxx"
 128       || (pc_probe.prob->get_name () != "catch"
 129           && pc_probe.prob->get_name () != "throw"
 130           && pc_probe.prob->get_name () != "rethrow"))
 131     error (_("not stopped at a C++ exception catchpoint"));
 132
 133   n_args = pc_probe.prob->get_argument_count (get_frame_arch (frame));
 134   if (n_args < 2)
 135     error (_("C++ exception catchpoint has too few arguments"));
 136
 137   if (arg0 != NULL)
 138     *arg0 = pc_probe.prob->evaluate_argument (0, frame);
 139   *arg1 = pc_probe.prob->evaluate_argument (1, frame);
 140
 141   if ((arg0 != NULL && *arg0 == NULL) || *arg1 == NULL)
 142     error (_("error computing probe argument at c++ exception catchpoint"));
 143 }
 144
 145 \f
 146
 147 /* Implement the 'check_status' method.  */
 148
 149 void
 150 exception_catchpoint::check_status (struct bpstat *bs)
 151 {
 152   struct exception_catchpoint *self
 153     = (struct exception_catchpoint *) bs->breakpoint_at;
 154   std::string type_name;
 155
 156   this->breakpoint::check_status (bs);
 157   if (bs->stop == 0)
 158     return;
 159
 160   if (self->pattern == NULL)
 161     return;
 162
 163   const char *name = nullptr;
 164   gdb::unique_xmalloc_ptr<char> canon;
 165   try
 166     {
 167       struct value *typeinfo_arg;
 168
 169       fetch_probe_arguments (NULL, &typeinfo_arg);
 170       type_name = cplus_typename_from_type_info (typeinfo_arg);
 171
 172       canon = cp_canonicalize_string (type_name.c_str ());
 173       name = (canon != nullptr
 174               ? canon.get ()
 175               : type_name.c_str ());
 176     }
 177   catch (const gdb_exception_error &e)
 178     {
 179       exception_print (gdb_stderr, e);
 180     }
 181
 182   if (name != nullptr)
 183     {
 184       if (self->pattern->exec (name, 0, NULL, 0) != 0)
 185         bs->stop = 0;
 186     }
 187 }
 188
 189 /* Implement the 're_set' method.  */
 190
 191 void
 192 exception_catchpoint::re_set ()
 193 {
 194   std::vector<symtab_and_line> sals;
 195   struct program_space *filter_pspace = current_program_space;
 196
 197   /* We first try to use the probe interface.  */
 198   try
 199     {
 200       event_location_up location
 201         = new_probe_location (exception_functions[kind].probe);
 202       sals = parse_probes (location.get (), filter_pspace, NULL);
 203     }
 204   catch (const gdb_exception_error &e)
 205     {
 206       /* Using the probe interface failed.  Let's fallback to the normal
 207          catchpoint mode.  */
 208       try
 209         {
 210           struct explicit_location explicit_loc;
 211
 212           initialize_explicit_location (&explicit_loc);
 213           explicit_loc.function_name
 214             = ASTRDUP (exception_functions[kind].function);
 215           event_location_up location = new_explicit_location (&explicit_loc);
 216           sals = this->decode_location (location.get (), filter_pspace);
 217         }
 218       catch (const gdb_exception_error &ex)
 219         {
 220           /* NOT_FOUND_ERROR just means the breakpoint will be
 221              pending, so let it through.  */
 222           if (ex.error != NOT_FOUND_ERROR)
 223             throw;
 224         }
 225     }
 226
 227   update_breakpoint_locations (this, filter_pspace, sals, {});
 228 }
 229
 230 enum print_stop_action
 231 exception_catchpoint::print_it (bpstat *bs)
 232 {
 233   struct ui_out *uiout = current_uiout;
 234   int bp_temp;
 235
 236   annotate_catchpoint (number);
 237   maybe_print_thread_hit_breakpoint (uiout);
 238
 239   bp_temp = disposition == disp_del;
 240   uiout->text (bp_temp ? "Temporary catchpoint "
 241                        : "Catchpoint ");
 242   uiout->field_signed ("bkptno", number);
 243   uiout->text ((kind == EX_EVENT_THROW ? " (exception thrown), "
 244                 : (kind == EX_EVENT_CATCH ? " (exception caught), "
 245                    : " (exception rethrown), ")));
 246   if (uiout->is_mi_like_p ())
 247     {
 248       uiout->field_string ("reason",
 249                            async_reason_lookup (EXEC_ASYNC_BREAKPOINT_HIT));
 250       uiout->field_string ("disp", bpdisp_text (disposition));
 251     }
 252   return PRINT_SRC_AND_LOC;
 253 }
 254
 255 bool
 256 exception_catchpoint::print_one (struct bp_location **last_loc)
 257 {
 258   struct value_print_options opts;
 259   struct ui_out *uiout = current_uiout;
 260
 261   get_user_print_options (&opts);
 262
 263   if (opts.addressprint)
 264     uiout->field_skip ("addr");
 265   annotate_field (5);
 266
 267   switch (kind)
 268     {
 269     case EX_EVENT_THROW:
 270       uiout->field_string ("what", "exception throw");
 271       if (uiout->is_mi_like_p ())
 272         uiout->field_string ("catch-type", "throw");
 273       break;
 274
 275     case EX_EVENT_RETHROW:
 276       uiout->field_string ("what", "exception rethrow");
 277       if (uiout->is_mi_like_p ())
 278         uiout->field_string ("catch-type", "rethrow");
 279       break;
 280
 281     case EX_EVENT_CATCH:
 282       uiout->field_string ("what", "exception catch");
 283       if (uiout->is_mi_like_p ())
 284         uiout->field_string ("catch-type", "catch");
 285       break;
 286     }
 287
 288   return true;
 289 }
 290
 291 /* Implement the 'print_one_detail' method.  */
 292
 293 void
 294 exception_catchpoint::print_one_detail (struct ui_out *uiout) const
 295 {
 296   if (!exception_rx.empty ())
 297     {
 298       uiout->text (_("\tmatching: "));
 299       uiout->field_string ("regexp", exception_rx);
 300       uiout->text ("\n");
 301     }
 302 }
 303
 304 void
 305 exception_catchpoint::print_mention ()
 306 {
 307   struct ui_out *uiout = current_uiout;
 308   int bp_temp;
 309
 310   bp_temp = disposition == disp_del;
 311   uiout->message ("%s %d %s",
 312                   (bp_temp ? _("Temporary catchpoint ") : _("Catchpoint")),
 313                   number,
 314                   (kind == EX_EVENT_THROW
 315                    ? _("(throw)") : (kind == EX_EVENT_CATCH
 316                                      ? _("(catch)") : _("(rethrow)"))));
 317 }
 318
 319 /* Implement the "print_recreate" method for throw and catch
 320    catchpoints.  */
 321
 322 void
 323 exception_catchpoint::print_recreate (struct ui_file *fp)
 324 {
 325   int bp_temp;
 326
 327   bp_temp = disposition == disp_del;
 328   gdb_printf (fp, bp_temp ? "tcatch " : "catch ");
 329   switch (kind)
 330     {
 331     case EX_EVENT_THROW:
 332       gdb_printf (fp, "throw");
 333       break;
 334     case EX_EVENT_CATCH:
 335       gdb_printf (fp, "catch");
 336       break;
 337     case EX_EVENT_RETHROW:
 338       gdb_printf (fp, "rethrow");
 339       break;
 340     }
 341   print_recreate_thread (this, fp);
 342 }
 343
 344 /* Implement the "allocate_location" method for throw and catch
 345    catchpoints.  */
 346
 347 bp_location *
 348 exception_catchpoint::allocate_location ()
 349 {
 350   return new bp_location (this, bp_loc_software_breakpoint);
 351 }
 352
 353 static void
 354 handle_gnu_v3_exceptions (int tempflag, std::string &&except_rx,
 355                           const char *cond_string,
 356                           enum exception_event_kind ex_event, int from_tty)
 357 {
 358   std::unique_ptr<compiled_regex> pattern;
 359
 360   if (!except_rx.empty ())
 361     {
 362       pattern.reset (new compiled_regex (except_rx.c_str (), REG_NOSUB,
 363                                          _("invalid type-matching regexp")));
 364     }
 365
 366   std::unique_ptr<exception_catchpoint> cp (new exception_catchpoint ());
 367
 368   init_catchpoint (cp.get (), get_current_arch (), tempflag, cond_string,
 369                    &vtable_breakpoint_ops);
 370   cp->kind = ex_event;
 371   cp->exception_rx = std::move (except_rx);
 372   cp->pattern = std::move (pattern);
 373
 374   cp->re_set ();
 375
 376   install_breakpoint (0, std::move (cp), 1);
 377 }
 378
 379 /* Look for an "if" token in *STRING.  The "if" token must be preceded
 380    by whitespace.
 381
 382    If there is any non-whitespace text between *STRING and the "if"
 383    token, then it is returned in a newly-xmalloc'd string.  Otherwise,
 384    this returns NULL.
 385
 386    STRING is updated to point to the "if" token, if it exists, or to
 387    the end of the string.  */
 388
 389 static std::string
 390 extract_exception_regexp (const char **string)
 391 {
 392   const char *start;
 393   const char *last, *last_space;
 394
 395   start = skip_spaces (*string);
 396
 397   last = start;
 398   last_space = start;
 399   while (*last != '\0')
 400     {
 401       const char *if_token = last;
 402
 403       /* Check for the "if".  */
 404       if (check_for_argument (&if_token, "if", 2))
 405         break;
 406
 407       /* No "if" token here.  Skip to the next word start.  */
 408       last_space = skip_to_space (last);
 409       last = skip_spaces (last_space);
 410     }
 411
 412   *string = last;
 413   if (last_space > start)
 414     return std::string (start, last_space - start);
 415   return std::string ();
 416 }
 417
 418 /* See breakpoint.h.  */
 419
 420 void
 421 catch_exception_event (enum exception_event_kind ex_event,
 422                        const char *arg, bool tempflag, int from_tty)
 423 {
 424   const char *cond_string = NULL;
 425
 426   if (!arg)
 427     arg = "";
 428   arg = skip_spaces (arg);
 429
 430   std::string except_rx = extract_exception_regexp (&arg);
 431
 432   cond_string = ep_parse_optional_if_clause (&arg);
 433
 434   if ((*arg != '\0') && !isspace (*arg))
 435     error (_("Junk at end of arguments."));
 436
 437   if (ex_event != EX_EVENT_THROW
 438       && ex_event != EX_EVENT_CATCH
 439       && ex_event != EX_EVENT_RETHROW)
 440     error (_("Unsupported or unknown exception event; cannot catch it"));
 441
 442   handle_gnu_v3_exceptions (tempflag, std::move (except_rx), cond_string,
 443                             ex_event, from_tty);
 444 }
 445
 446 /* Implementation of "catch catch" command.  */
 447
 448 static void
 449 catch_catch_command (const char *arg, int from_tty,
 450                      struct cmd_list_element *command)
 451 {
 452   bool tempflag = command->context () == CATCH_TEMPORARY;
 453
 454   catch_exception_event (EX_EVENT_CATCH, arg, tempflag, from_tty);
 455 }
 456
 457 /* Implementation of "catch throw" command.  */
 458
 459 static void
 460 catch_throw_command (const char *arg, int from_tty,
 461                      struct cmd_list_element *command)
 462 {
 463   bool tempflag = command->context () == CATCH_TEMPORARY;
 464
 465   catch_exception_event (EX_EVENT_THROW, arg, tempflag, from_tty);
 466 }
 467
 468 /* Implementation of "catch rethrow" command.  */
 469
 470 static void
 471 catch_rethrow_command (const char *arg, int from_tty,
 472                        struct cmd_list_element *command)
 473 {
 474   bool tempflag = command->context () == CATCH_TEMPORARY;
 475
 476   catch_exception_event (EX_EVENT_RETHROW, arg, tempflag, from_tty);
 477 }
 478
 479 \f
 480
 481 /* Implement the 'make_value' method for the $_exception
 482    internalvar.  */
 483
 484 static struct value *
 485 compute_exception (struct gdbarch *argc, struct internalvar *var, void *ignore)
 486 {
 487   struct value *arg0, *arg1;
 488   struct type *obj_type;
 489
 490   fetch_probe_arguments (&arg0, &arg1);
 491
 492   /* ARG0 is a pointer to the exception object.  ARG1 is a pointer to
 493      the std::type_info for the exception.  Now we find the type from
 494      the type_info and cast the result.  */
 495   obj_type = cplus_type_from_type_info (arg1);
 496   return value_ind (value_cast (make_pointer_type (obj_type, NULL), arg0));
 497 }
 498
 499 /* Implementation of the '$_exception' variable.  */
 500
 501 static const struct internalvar_funcs exception_funcs =
 502 {
 503   compute_exception,
 504   NULL,
 505 };
 506
 507 \f
 508
 509 void _initialize_break_catch_throw ();
 510 void
 511 _initialize_break_catch_throw ()
 512 {
 513   /* Add catch and tcatch sub-commands.  */
 514   add_catch_command ("catch", _("\
 515 Catch an exception, when caught."),
 516                      catch_catch_command,
 517                      NULL,
 518                      CATCH_PERMANENT,
 519                      CATCH_TEMPORARY);
 520   add_catch_command ("throw", _("\
 521 Catch an exception, when thrown."),
 522                      catch_throw_command,
 523                      NULL,
 524                      CATCH_PERMANENT,
 525                      CATCH_TEMPORARY);
 526   add_catch_command ("rethrow", _("\
 527 Catch an exception, when rethrown."),
 528                      catch_rethrow_command,
 529                      NULL,
 530                      CATCH_PERMANENT,
 531                      CATCH_TEMPORARY);
 532
 533   create_internalvar_type_lazy ("_exception", &exception_funcs, NULL);
 534 }