gdb/guile/scm-exception.c

   1 /* GDB/Scheme exception support.
   2
   3    Copyright (C) 2014-2020 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 /* See README file in this directory for implementation notes, coding
  21    conventions, et.al.  */
  22
  23 /* Notes:
  24
  25    IWBN to support SRFI 34/35.  At the moment we follow Guile's own
  26    exception mechanism.
  27
  28    The non-static functions in this file have prefix gdbscm_ and
  29    not exscm_ on purpose.  */
  30
  31 #include "defs.h"
  32 #include <signal.h>
  33 #include "guile-internal.h"
  34
  35 /* The <gdb:exception> smob.
  36    This is used to record and handle Scheme exceptions.
  37    One important invariant is that <gdb:exception> smobs are never a valid
  38    result of a function, other than to signify an exception occurred.  */
  39
  40 struct exception_smob
  41 {
  42   /* This always appears first.  */
  43   gdb_smob base;
  44
  45   /* The key and args parameters to "throw".  */
  46   SCM key;
  47   SCM args;
  48 };
  49
  50 static const char exception_smob_name[] = "gdb:exception";
  51
  52 /* The tag Guile knows the exception smob by.  */
  53 static scm_t_bits exception_smob_tag;
  54
  55 /* A generic error in struct gdb_exception.
  56    I.e., not RETURN_QUIT and not MEMORY_ERROR.  */
  57 static SCM error_symbol;
  58
  59 /* An error occurred accessing inferior memory.
  60    This is not a Scheme programming error.  */
  61 static SCM memory_error_symbol;
  62
  63 /* User interrupt, e.g., RETURN_QUIT in struct gdb_exception.  */
  64 static SCM signal_symbol;
  65
  66 /* A user error, e.g., bad arg to gdb command.  */
  67 static SCM user_error_symbol;
  68
  69 /* Printing the stack is done by first capturing the stack and recording it in
  70    a <gdb:exception> object with this key and with the ARGS field set to
  71    (cons real-key (cons stack real-args)).
  72    See gdbscm_make_exception_with_stack.  */
  73 static SCM with_stack_error_symbol;
  74
  75 /* The key to use for an invalid object exception.  An invalid object is one
  76    where the underlying object has been removed from GDB.  */
  77 SCM gdbscm_invalid_object_error_symbol;
  78
  79 /* Values for "guile print-stack" as symbols.  */
  80 static SCM none_symbol;
  81 static SCM message_symbol;
  82 static SCM full_symbol;
  83
  84 static const char percent_print_exception_message_name[] =
  85   "%print-exception-message";
  86
  87 /* Variable containing %print-exception-message.
  88    It is not defined until late in initialization, after our init routine
  89    has run.  Cope by looking it up lazily.  */
  90 static SCM percent_print_exception_message_var = SCM_BOOL_F;
  91
  92 static const char percent_print_exception_with_stack_name[] =
  93   "%print-exception-with-stack";
  94
  95 /* Variable containing %print-exception-with-stack.
  96    It is not defined until late in initialization, after our init routine
  97    has run.  Cope by looking it up lazily.  */
  98 static SCM percent_print_exception_with_stack_var = SCM_BOOL_F;
  99
 100 /* Counter to keep track of the number of times we create a <gdb:exception>
 101    object, for performance monitoring purposes.  */
 102 static unsigned long gdbscm_exception_count = 0;
 103 \f
 104 /* Administrivia for exception smobs.  */
 105
 106 /* The smob "print" function for <gdb:exception>.  */
 107
 108 static int
 109 exscm_print_exception_smob (SCM self, SCM port, scm_print_state *pstate)
 110 {
 111   exception_smob *e_smob = (exception_smob *) SCM_SMOB_DATA (self);
 112
 113   gdbscm_printf (port, "#<%s ", exception_smob_name);
 114   scm_write (e_smob->key, port);
 115   scm_puts (" ", port);
 116   scm_write (e_smob->args, port);
 117   scm_puts (">", port);
 118
 119   scm_remember_upto_here_1 (self);
 120
 121   /* Non-zero means success.  */
 122   return 1;
 123 }
 124
 125 /* (make-exception key args) -> <gdb:exception> */
 126
 127 SCM
 128 gdbscm_make_exception (SCM key, SCM args)
 129 {
 130   exception_smob *e_smob = (exception_smob *)
 131     scm_gc_malloc (sizeof (exception_smob), exception_smob_name);
 132   SCM smob;
 133
 134   e_smob->key = key;
 135   e_smob->args = args;
 136   smob = scm_new_smob (exception_smob_tag, (scm_t_bits) e_smob);
 137   gdbscm_init_gsmob (&e_smob->base);
 138
 139   ++gdbscm_exception_count;
 140
 141   return smob;
 142 }
 143
 144 /* Return non-zero if SCM is a <gdb:exception> object.  */
 145
 146 int
 147 gdbscm_is_exception (SCM scm)
 148 {
 149   return SCM_SMOB_PREDICATE (exception_smob_tag, scm);
 150 }
 151
 152 /* (exception? scm) -> boolean */
 153
 154 static SCM
 155 gdbscm_exception_p (SCM scm)
 156 {
 157   return scm_from_bool (gdbscm_is_exception (scm));
 158 }
 159
 160 /* (exception-key <gdb:exception>) -> key */
 161
 162 SCM
 163 gdbscm_exception_key (SCM self)
 164 {
 165   exception_smob *e_smob;
 166
 167   SCM_ASSERT_TYPE (gdbscm_is_exception (self), self, SCM_ARG1, FUNC_NAME,
 168                    "gdb:exception");
 169
 170   e_smob = (exception_smob *) SCM_SMOB_DATA (self);
 171   return e_smob->key;
 172 }
 173
 174 /* (exception-args <gdb:exception>) -> arg-list */
 175
 176 SCM
 177 gdbscm_exception_args (SCM self)
 178 {
 179   exception_smob *e_smob;
 180
 181   SCM_ASSERT_TYPE (gdbscm_is_exception (self), self, SCM_ARG1, FUNC_NAME,
 182                    "gdb:exception");
 183
 184   e_smob = (exception_smob *) SCM_SMOB_DATA (self);
 185   return e_smob->args;
 186 }
 187 \f
 188 /* Wrap an exception in a <gdb:exception> object that includes STACK.
 189    gdbscm_print_exception_with_stack knows how to unwrap it.  */
 190
 191 SCM
 192 gdbscm_make_exception_with_stack (SCM key, SCM args, SCM stack)
 193 {
 194   return gdbscm_make_exception (with_stack_error_symbol,
 195                                 scm_cons (key, scm_cons (stack, args)));
 196 }
 197
 198 /* Version of scm_error_scm that creates a gdb:exception object that can later
 199    be passed to gdbscm_throw.
 200    KEY is a symbol denoting the kind of error.
 201    SUBR is either #f or a string marking the function in which the error
 202    occurred.
 203    MESSAGE is either #f or the error message string.  It may contain ~a and ~s
 204    modifiers, provided by ARGS.
 205    ARGS is a list of args to MESSAGE.
 206    DATA is an arbitrary object, its value depends on KEY.  The value to pass
 207    here is a bit underspecified by Guile.  */
 208
 209 SCM
 210 gdbscm_make_error_scm (SCM key, SCM subr, SCM message, SCM args, SCM data)
 211 {
 212   return gdbscm_make_exception (key, scm_list_4 (subr, message, args, data));
 213 }
 214
 215 /* Version of scm_error that creates a gdb:exception object that can later
 216    be passed to gdbscm_throw.
 217    See gdbscm_make_error_scm for a description of the arguments.  */
 218
 219 SCM
 220 gdbscm_make_error (SCM key, const char *subr, const char *message,
 221                    SCM args, SCM data)
 222 {
 223   return gdbscm_make_error_scm
 224     (key,
 225      subr == NULL ? SCM_BOOL_F : scm_from_latin1_string (subr),
 226      message == NULL ? SCM_BOOL_F : scm_from_latin1_string (message),
 227      args, data);
 228 }
 229
 230 /* Version of SCM_ASSERT_TYPE/scm_wrong_type_arg_msg that creates a
 231    gdb:exception object that can later be passed to gdbscm_throw.  */
 232
 233 SCM
 234 gdbscm_make_type_error (const char *subr, int arg_pos, SCM bad_value,
 235                         const char *expected_type)
 236 {
 237   char *msg;
 238   SCM result;
 239
 240   if (arg_pos > 0)
 241     {
 242       if (expected_type != NULL)
 243         {
 244           msg = xstrprintf (_("Wrong type argument in position %d"
 245                               " (expecting %s): ~S"),
 246                             arg_pos, expected_type);
 247         }
 248       else
 249         {
 250           msg = xstrprintf (_("Wrong type argument in position %d: ~S"),
 251                             arg_pos);
 252         }
 253     }
 254   else
 255     {
 256       if (expected_type != NULL)
 257         {
 258           msg = xstrprintf (_("Wrong type argument (expecting %s): ~S"),
 259                             expected_type);
 260         }
 261       else
 262         msg = xstrprintf (_("Wrong type argument: ~S"));
 263     }
 264
 265   result = gdbscm_make_error (scm_arg_type_key, subr, msg,
 266                               scm_list_1 (bad_value), scm_list_1 (bad_value));
 267   xfree (msg);
 268   return result;
 269 }
 270
 271 /* A variant of gdbscm_make_type_error for non-type argument errors.
 272    ERROR_PREFIX and ERROR are combined to build the error message.
 273    Care needs to be taken so that the i18n composed form is still
 274    reasonable, but no one is going to translate these anyway so we don't
 275    worry too much.
 276    ERROR_PREFIX may be NULL, ERROR may not be NULL.  */
 277
 278 static SCM
 279 gdbscm_make_arg_error (SCM key, const char *subr, int arg_pos, SCM bad_value,
 280                        const char *error_prefix, const char *error)
 281 {
 282   char *msg;
 283   SCM result;
 284
 285   if (error_prefix != NULL)
 286     {
 287       if (arg_pos > 0)
 288         {
 289           msg = xstrprintf (_("%s %s in position %d: ~S"),
 290                             error_prefix, error, arg_pos);
 291         }
 292       else
 293         msg = xstrprintf (_("%s %s: ~S"), error_prefix, error);
 294     }
 295   else
 296     {
 297       if (arg_pos > 0)
 298         msg = xstrprintf (_("%s in position %d: ~S"), error, arg_pos);
 299       else
 300         msg = xstrprintf (_("%s: ~S"), error);
 301     }
 302
 303   result = gdbscm_make_error (key, subr, msg,
 304                               scm_list_1 (bad_value), scm_list_1 (bad_value));
 305   xfree (msg);
 306   return result;
 307 }
 308
 309 /* Make an invalid-object error <gdb:exception> object.
 310    OBJECT is the name of the kind of object that is invalid.  */
 311
 312 SCM
 313 gdbscm_make_invalid_object_error (const char *subr, int arg_pos, SCM bad_value,
 314                                   const char *object)
 315 {
 316   return gdbscm_make_arg_error (gdbscm_invalid_object_error_symbol,
 317                                 subr, arg_pos, bad_value,
 318                                 _("Invalid object:"), object);
 319 }
 320
 321 /* Throw an invalid-object error.
 322    OBJECT is the name of the kind of object that is invalid.  */
 323
 324 void
 325 gdbscm_invalid_object_error (const char *subr, int arg_pos, SCM bad_value,
 326                              const char *object)
 327 {
 328   SCM exception
 329     = gdbscm_make_invalid_object_error (subr, arg_pos, bad_value, object);
 330
 331   gdbscm_throw (exception);
 332 }
 333
 334 /* Make an out-of-range error <gdb:exception> object.  */
 335
 336 SCM
 337 gdbscm_make_out_of_range_error (const char *subr, int arg_pos, SCM bad_value,
 338                                 const char *error)
 339 {
 340   return gdbscm_make_arg_error (scm_out_of_range_key,
 341                                 subr, arg_pos, bad_value,
 342                                 _("Out of range:"), error);
 343 }
 344
 345 /* Throw an out-of-range error.
 346    This is the standard Guile out-of-range exception.  */
 347
 348 void
 349 gdbscm_out_of_range_error (const char *subr, int arg_pos, SCM bad_value,
 350                            const char *error)
 351 {
 352   SCM exception
 353     = gdbscm_make_out_of_range_error (subr, arg_pos, bad_value, error);
 354
 355   gdbscm_throw (exception);
 356 }
 357
 358 /* Make a misc-error <gdb:exception> object.  */
 359
 360 SCM
 361 gdbscm_make_misc_error (const char *subr, int arg_pos, SCM bad_value,
 362                         const char *error)
 363 {
 364   return gdbscm_make_arg_error (scm_misc_error_key,
 365                                 subr, arg_pos, bad_value, NULL, error);
 366 }
 367
 368 /* Throw a misc-error error.  */
 369
 370 void
 371 gdbscm_misc_error (const char *subr, int arg_pos, SCM bad_value,
 372                    const char *error)
 373 {
 374   SCM exception = gdbscm_make_misc_error (subr, arg_pos, bad_value, error);
 375
 376   gdbscm_throw (exception);
 377 }
 378
 379 /* Return a <gdb:exception> object for gdb:memory-error.  */
 380
 381 SCM
 382 gdbscm_make_memory_error (const char *subr, const char *msg, SCM args)
 383 {
 384   return gdbscm_make_error (memory_error_symbol, subr, msg, args,
 385                             SCM_EOL);
 386 }
 387
 388 /* Throw a gdb:memory-error exception.  */
 389
 390 void
 391 gdbscm_memory_error (const char *subr, const char *msg, SCM args)
 392 {
 393   SCM exception = gdbscm_make_memory_error (subr, msg, args);
 394
 395   gdbscm_throw (exception);
 396 }
 397
 398 /* Return non-zero if KEY is gdb:memory-error.
 399    Note: This is an excp_matcher_func function.  */
 400
 401 int
 402 gdbscm_memory_error_p (SCM key)
 403 {
 404   return scm_is_eq (key, memory_error_symbol);
 405 }
 406
 407 /* Return non-zero if KEY is gdb:user-error.
 408    Note: This is an excp_matcher_func function.  */
 409
 410 int
 411 gdbscm_user_error_p (SCM key)
 412 {
 413   return scm_is_eq (key, user_error_symbol);
 414 }
 415
 416 /* Wrapper around scm_throw to throw a gdb:exception.
 417    This function does not return.
 418    This function cannot be called from inside TRY_CATCH.  */
 419
 420 void
 421 gdbscm_throw (SCM exception)
 422 {
 423   scm_throw (gdbscm_exception_key (exception),
 424              gdbscm_exception_args (exception));
 425   gdb_assert_not_reached ("scm_throw returned");
 426 }
 427
 428 /* Convert a GDB exception to a <gdb:exception> object.  */
 429
 430 SCM
 431 gdbscm_scm_from_gdb_exception (const gdbscm_gdb_exception &exception)
 432 {
 433   SCM key;
 434
 435   if (exception.reason == RETURN_QUIT)
 436     {
 437       /* Handle this specially to be consistent with top-repl.scm.  */
 438       return gdbscm_make_error (signal_symbol, NULL, _("User interrupt"),
 439                                 SCM_EOL, scm_list_1 (scm_from_int (SIGINT)));
 440     }
 441
 442   if (exception.error == MEMORY_ERROR)
 443     key = memory_error_symbol;
 444   else
 445     key = error_symbol;
 446
 447   return gdbscm_make_error (key, NULL, "~A",
 448                             scm_list_1 (gdbscm_scm_from_c_string
 449                                         (exception.message)),
 450                             SCM_BOOL_F);
 451 }
 452
 453 /* Convert a GDB exception to the appropriate Scheme exception and throw it.
 454    This function does not return.  */
 455
 456 void
 457 gdbscm_throw_gdb_exception (gdbscm_gdb_exception exception)
 458 {
 459   SCM scm_exception = gdbscm_scm_from_gdb_exception (exception);
 460   xfree (exception.message);
 461   gdbscm_throw (scm_exception);
 462 }
 463
 464 /* Print the error message portion of an exception.
 465    If PORT is #f, use the standard error port.
 466    KEY cannot be gdb:with-stack.
 467
 468    Basically this function is just a wrapper around calling
 469    %print-exception-message.  */
 470
 471 static void
 472 gdbscm_print_exception_message (SCM port, SCM frame, SCM key, SCM args)
 473 {
 474   SCM printer, status;
 475
 476   if (gdbscm_is_false (port))
 477     port = scm_current_error_port ();
 478
 479   gdb_assert (!scm_is_eq (key, with_stack_error_symbol));
 480
 481   /* This does not use scm_print_exception because we tweak the output a bit.
 482      Compare Guile's print-exception with our %print-exception-message for
 483      details.  */
 484   if (gdbscm_is_false (percent_print_exception_message_var))
 485     {
 486       percent_print_exception_message_var
 487         = scm_c_private_variable (gdbscm_init_module_name,
 488                                   percent_print_exception_message_name);
 489       /* If we can't find %print-exception-message, there's a problem on the
 490          Scheme side.  Don't kill GDB, just flag an error and leave it at
 491          that.  */
 492       if (gdbscm_is_false (percent_print_exception_message_var))
 493         {
 494           gdbscm_printf (port, _("Error in Scheme exception printing,"
 495                                  " can't find %s.\n"),
 496                          percent_print_exception_message_name);
 497           return;
 498         }
 499     }
 500   printer = scm_variable_ref (percent_print_exception_message_var);
 501
 502   status = gdbscm_safe_call_4 (printer, port, frame, key, args, NULL);
 503
 504   /* If that failed still tell the user something.
 505      But don't use the exception printing machinery!  */
 506   if (gdbscm_is_exception (status))
 507     {
 508       gdbscm_printf (port, _("Error in Scheme exception printing:\n"));
 509       scm_display (status, port);
 510       scm_newline (port);
 511     }
 512 }
 513
 514 /* Print the description of exception KEY, ARGS to PORT, according to the
 515    setting of "set guile print-stack".
 516    If PORT is #f, use the standard error port.
 517    If STACK is #f, never print the stack, regardless of whether printing it
 518    is enabled.  If STACK is #t, then print it if it is contained in ARGS
 519    (i.e., KEY is gdb:with-stack).  Otherwise STACK is the result of calling
 520    scm_make_stack (which will be ignored in favor of the stack in ARGS if
 521    KEY is gdb:with-stack).
 522    KEY, ARGS are the standard arguments to scm_throw, et.al.
 523
 524    Basically this function is just a wrapper around calling
 525    %print-exception-with-stack.  */
 526
 527 void
 528 gdbscm_print_exception_with_stack (SCM port, SCM stack, SCM key, SCM args)
 529 {
 530   SCM printer, status;
 531
 532   if (gdbscm_is_false (port))
 533     port = scm_current_error_port ();
 534
 535   if (gdbscm_is_false (percent_print_exception_with_stack_var))
 536     {
 537       percent_print_exception_with_stack_var
 538         = scm_c_private_variable (gdbscm_init_module_name,
 539                                   percent_print_exception_with_stack_name);
 540       /* If we can't find %print-exception-with-stack, there's a problem on the
 541          Scheme side.  Don't kill GDB, just flag an error and leave it at
 542          that.  */
 543       if (gdbscm_is_false (percent_print_exception_with_stack_var))
 544         {
 545           gdbscm_printf (port, _("Error in Scheme exception printing,"
 546                                  " can't find %s.\n"),
 547                          percent_print_exception_with_stack_name);
 548           return;
 549         }
 550     }
 551   printer = scm_variable_ref (percent_print_exception_with_stack_var);
 552
 553   status = gdbscm_safe_call_4 (printer, port, stack, key, args, NULL);
 554
 555   /* If that failed still tell the user something.
 556      But don't use the exception printing machinery!  */
 557   if (gdbscm_is_exception (status))
 558     {
 559       gdbscm_printf (port, _("Error in Scheme exception printing:\n"));
 560       scm_display (status, port);
 561       scm_newline (port);
 562     }
 563 }
 564
 565 /* Print EXCEPTION, a <gdb:exception> object, to PORT.
 566    If PORT is #f, use the standard error port.  */
 567
 568 void
 569 gdbscm_print_gdb_exception (SCM port, SCM exception)
 570 {
 571   gdb_assert (gdbscm_is_exception (exception));
 572
 573   gdbscm_print_exception_with_stack (port, SCM_BOOL_T,
 574                                      gdbscm_exception_key (exception),
 575                                      gdbscm_exception_args (exception));
 576 }
 577
 578 /* Return a string description of <gdb:exception> EXCEPTION.
 579    If EXCEPTION is a gdb:with-stack exception, unwrap it, a backtrace
 580    is never returned as part of the result.  */
 581
 582 gdb::unique_xmalloc_ptr<char>
 583 gdbscm_exception_message_to_string (SCM exception)
 584 {
 585   SCM port = scm_open_output_string ();
 586   SCM key, args;
 587
 588   gdb_assert (gdbscm_is_exception (exception));
 589
 590   key = gdbscm_exception_key (exception);
 591   args = gdbscm_exception_args (exception);
 592
 593   if (scm_is_eq (key, with_stack_error_symbol)
 594       /* Don't crash on a badly generated gdb:with-stack exception.  */
 595       && scm_is_pair (args)
 596       && scm_is_pair (scm_cdr (args)))
 597     {
 598       key = scm_car (args);
 599       args = scm_cddr (args);
 600     }
 601
 602   gdbscm_print_exception_message (port, SCM_BOOL_F, key, args);
 603   gdb::unique_xmalloc_ptr<char> result
 604     = gdbscm_scm_to_c_string (scm_get_output_string (port));
 605   scm_close_port (port);
 606   return result;
 607 }
 608
 609 /* Return the value of the "guile print-stack" option as one of:
 610    'none, 'message, 'full.  */
 611
 612 static SCM
 613 gdbscm_percent_exception_print_style (void)
 614 {
 615   if (gdbscm_print_excp == gdbscm_print_excp_none)
 616     return none_symbol;
 617   if (gdbscm_print_excp == gdbscm_print_excp_message)
 618     return message_symbol;
 619   if (gdbscm_print_excp == gdbscm_print_excp_full)
 620     return full_symbol;
 621   gdb_assert_not_reached ("bad value for \"guile print-stack\"");
 622 }
 623
 624 /* Return the current <gdb:exception> counter.
 625    This is for debugging purposes.  */
 626
 627 static SCM
 628 gdbscm_percent_exception_count (void)
 629 {
 630   return scm_from_ulong (gdbscm_exception_count);
 631 }
 632 \f
 633 /* Initialize the Scheme exception support.  */
 634
 635 static const scheme_function exception_functions[] =
 636 {
 637   { "make-exception", 2, 0, 0, as_a_scm_t_subr (gdbscm_make_exception),
 638     "\
 639 Create a <gdb:exception> object.\n\
 640 \n\
 641   Arguments: key args\n\
 642     These are the standard key,args arguments of \"throw\"." },
 643
 644   { "exception?", 1, 0, 0, as_a_scm_t_subr (gdbscm_exception_p),
 645     "\
 646 Return #t if the object is a <gdb:exception> object." },
 647
 648   { "exception-key", 1, 0, 0, as_a_scm_t_subr (gdbscm_exception_key),
 649     "\
 650 Return the exception's key." },
 651
 652   { "exception-args", 1, 0, 0, as_a_scm_t_subr (gdbscm_exception_args),
 653     "\
 654 Return the exception's arg list." },
 655
 656   END_FUNCTIONS
 657 };
 658
 659 static const scheme_function private_exception_functions[] =
 660 {
 661   { "%exception-print-style", 0, 0, 0,
 662     as_a_scm_t_subr (gdbscm_percent_exception_print_style),
 663     "\
 664 Return the value of the \"guile print-stack\" option." },
 665
 666   { "%exception-count", 0, 0, 0,
 667     as_a_scm_t_subr (gdbscm_percent_exception_count),
 668     "\
 669 Return a count of the number of <gdb:exception> objects created.\n\
 670 This is for debugging purposes." },
 671
 672   END_FUNCTIONS
 673 };
 674
 675 void
 676 gdbscm_initialize_exceptions (void)
 677 {
 678   exception_smob_tag = gdbscm_make_smob_type (exception_smob_name,
 679                                               sizeof (exception_smob));
 680   scm_set_smob_print (exception_smob_tag, exscm_print_exception_smob);
 681
 682   gdbscm_define_functions (exception_functions, 1);
 683   gdbscm_define_functions (private_exception_functions, 0);
 684
 685   error_symbol = scm_from_latin1_symbol ("gdb:error");
 686
 687   memory_error_symbol = scm_from_latin1_symbol ("gdb:memory-error");
 688
 689   user_error_symbol = scm_from_latin1_symbol ("gdb:user-error");
 690
 691   gdbscm_invalid_object_error_symbol
 692     = scm_from_latin1_symbol ("gdb:invalid-object-error");
 693
 694   with_stack_error_symbol = scm_from_latin1_symbol ("gdb:with-stack");
 695
 696   /* The text of this symbol is taken from Guile's top-repl.scm.  */
 697   signal_symbol = scm_from_latin1_symbol ("signal");
 698
 699   none_symbol = scm_from_latin1_symbol ("none");
 700   message_symbol = scm_from_latin1_symbol ("message");
 701   full_symbol = scm_from_latin1_symbol ("full");
 702 }