libguile/backtrace.c

   1 /* Printing of backtraces and error messages
   2  * Copyright (C) 1996,1997,1998,1999,2000,2001, 2003, 2004, 2006 Free Software Foundation
   3  *
   4  * This library is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU Lesser General Public
   6  * License as published by the Free Software Foundation; either
   7  * version 2.1 of the License, or (at your option) any later version.
   8  *
   9  * This library is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * Lesser General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU Lesser General Public
  15  * License along with this library; if not, write to the Free Software
  16  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  17  */
  18
  19 #ifdef HAVE_CONFIG_H
  20 #  include <config.h>
  21 #endif
  22
  23 #include <stdio.h>
  24 #include <ctype.h>
  25 #include <assert.h>
  26
  27 #include "libguile/_scm.h"
  28
  29 #ifdef HAVE_UNISTD_H
  30 #include <unistd.h>
  31 #endif
  32 #ifdef HAVE_IO_H
  33 #include <io.h>
  34 #endif
  35
  36 #include "libguile/stacks.h"
  37 #include "libguile/srcprop.h"
  38 #include "libguile/struct.h"
  39 #include "libguile/strports.h"
  40 #include "libguile/throw.h"
  41 #include "libguile/fluids.h"
  42 #include "libguile/ports.h"
  43 #include "libguile/strings.h"
  44 #include "libguile/dynwind.h"
  45
  46 #include "libguile/validate.h"
  47 #include "libguile/lang.h"
  48 #include "libguile/backtrace.h"
  49 #include "libguile/filesys.h"
  50 #include "libguile/private-options.h"
  51
  52 /* {Error reporting and backtraces}
  53  *
  54  * Note that these functions shouldn't generate errors themselves.
  55  */
  56
  57 /* Print parameters for error messages. */
  58
  59 #define DISPLAY_ERROR_MESSAGE_MAX_LEVEL   7
  60 #define DISPLAY_ERROR_MESSAGE_MAX_LENGTH 10
  61
  62 /* Print parameters for failing expressions in error messages.
  63  * (See also `print_params' below for backtrace print parameters.)
  64  */
  65
  66 #define DISPLAY_EXPRESSION_MAX_LEVEL      2
  67 #define DISPLAY_EXPRESSION_MAX_LENGTH     3
  68
  69 #undef SCM_ASSERT
  70 #define SCM_ASSERT(_cond, _arg, _pos, _subr) \
  71         if (!(_cond)) \
  72           return SCM_BOOL_F;
  73
  74 SCM scm_the_last_stack_fluid_var;
  75
  76 static void
  77 display_header (SCM source, SCM port)
  78 {
  79   if (SCM_MEMOIZEDP (source))
  80     {
  81       SCM fname = scm_source_property (source, scm_sym_filename);
  82       SCM line = scm_source_property (source, scm_sym_line);
  83       SCM col = scm_source_property (source, scm_sym_column);
  84
  85       /* Dirk:FIXME:: Maybe we should store the _port_ rather than the
  86        * filename with the source properties?  Then we could in case of
  87        * non-file ports give at least some more details than just
  88        * "<unnamed port>". */
  89       if (scm_is_true (fname))
  90         scm_prin1 (fname, port, 0);
  91       else
  92         scm_puts ("<unnamed port>", port);
  93
  94       if (scm_is_true (line) && scm_is_true (col))
  95         {
  96           scm_putc (':', port);
  97           scm_intprint (scm_to_long (line) + 1, 10, port);
  98           scm_putc (':', port);
  99           scm_intprint (scm_to_long (col) + 1, 10, port);
 100         }
 101     }
 102   else
 103     scm_puts ("ERROR", port);
 104   scm_puts (": ", port);
 105 }
 106
 107
 108 struct display_error_message_data {
 109   SCM message;
 110   SCM args;
 111   SCM port;
 112   scm_print_state *pstate;
 113   int old_fancyp;
 114   int old_level;
 115   int old_length;
 116 };
 117
 118 static SCM
 119 display_error_message (struct display_error_message_data *d)
 120 {
 121   if (scm_is_string (d->message) && scm_is_true (scm_list_p (d->args)))
 122     scm_simple_format (d->port, d->message, d->args);
 123   else
 124     scm_display (d->message, d->port);
 125   scm_newline (d->port);
 126   return SCM_UNSPECIFIED;
 127 }
 128
 129 static void
 130 before_display_error_message (struct display_error_message_data *d)
 131 {
 132   scm_print_state *pstate = d->pstate;
 133   d->old_fancyp = pstate->fancyp;
 134   d->old_level  = pstate->level;
 135   d->old_length = pstate->length;
 136   pstate->fancyp = 1;
 137   pstate->level  = DISPLAY_ERROR_MESSAGE_MAX_LEVEL;
 138   pstate->length = DISPLAY_ERROR_MESSAGE_MAX_LENGTH;
 139 }
 140
 141 static void
 142 after_display_error_message (struct display_error_message_data *d)
 143 {
 144   scm_print_state *pstate = d->pstate;
 145   pstate->fancyp = d->old_fancyp;
 146   pstate->level  = d->old_level;
 147   pstate->length = d->old_length;
 148 }
 149
 150 void
 151 scm_display_error_message (SCM message, SCM args, SCM port)
 152 {
 153   struct display_error_message_data d;
 154   SCM print_state;
 155   scm_print_state *pstate;
 156
 157   port = scm_i_port_with_print_state (port, SCM_UNDEFINED);
 158   print_state = SCM_PORT_WITH_PS_PS (port);
 159   pstate = SCM_PRINT_STATE (print_state);
 160
 161   d.message = message;
 162   d.args = args;
 163   d.port = port;
 164   d.pstate = pstate;
 165   scm_internal_dynamic_wind ((scm_t_guard) before_display_error_message,
 166                              (scm_t_inner) display_error_message,
 167                              (scm_t_guard) after_display_error_message,
 168                              &d,
 169                              &d);
 170 }
 171
 172 static void
 173 display_expression (SCM frame, SCM pname, SCM source, SCM port)
 174 {
 175   SCM print_state = scm_make_print_state ();
 176   scm_print_state *pstate = SCM_PRINT_STATE (print_state);
 177   pstate->writingp = 0;
 178   pstate->fancyp = 1;
 179   pstate->level  = DISPLAY_EXPRESSION_MAX_LEVEL;
 180   pstate->length = DISPLAY_EXPRESSION_MAX_LENGTH;
 181   if (scm_is_symbol (pname) || scm_is_string (pname))
 182     {
 183       if (SCM_FRAMEP (frame)
 184           && SCM_FRAME_EVAL_ARGS_P (frame))
 185         scm_puts ("While evaluating arguments to ", port);
 186       else
 187         scm_puts ("In procedure ", port);
 188       scm_iprin1 (pname, port, pstate);
 189       if (SCM_MEMOIZEDP (source))
 190         {
 191           scm_puts (" in expression ", port);
 192           pstate->writingp = 1;
 193           scm_iprin1 (scm_i_unmemoize_expr (source), port, pstate);
 194         }
 195     }
 196   else if (SCM_MEMOIZEDP (source))
 197     {
 198       scm_puts ("In expression ", port);
 199       pstate->writingp = 1;
 200       scm_iprin1 (scm_i_unmemoize_expr (source), port, pstate);
 201     }
 202   scm_puts (":\n", port);
 203   scm_free_print_state (print_state);
 204 }
 205
 206 struct display_error_args {
 207   SCM stack;
 208   SCM port;
 209   SCM subr;
 210   SCM message;
 211   SCM args;
 212   SCM rest;
 213 };
 214
 215 static SCM
 216 display_error_body (struct display_error_args *a)
 217 {
 218   SCM current_frame = SCM_BOOL_F;
 219   SCM source = SCM_BOOL_F;
 220   SCM prev_frame = SCM_BOOL_F;
 221   SCM pname = a->subr;
 222
 223   if (scm_debug_mode_p
 224       && SCM_STACKP (a->stack)
 225       && SCM_STACK_LENGTH (a->stack) > 0)
 226     {
 227       current_frame = scm_stack_ref (a->stack, SCM_INUM0);
 228       source = SCM_FRAME_SOURCE (current_frame);
 229       prev_frame = SCM_FRAME_PREV (current_frame);
 230       if (!SCM_MEMOIZEDP (source) && scm_is_true (prev_frame))
 231         source = SCM_FRAME_SOURCE (prev_frame);
 232       if (!scm_is_symbol (pname)
 233           && !scm_is_string (pname)
 234           && SCM_FRAME_PROC_P (current_frame)
 235           && scm_is_true (scm_procedure_p (SCM_FRAME_PROC (current_frame))))
 236         pname = scm_procedure_name (SCM_FRAME_PROC (current_frame));
 237     }
 238   if (scm_is_symbol (pname) || scm_is_string (pname) || SCM_MEMOIZEDP (source))
 239     {
 240       display_header (source, a->port);
 241       display_expression (current_frame, pname, source, a->port);
 242     }
 243   display_header (source, a->port);
 244   scm_display_error_message (a->message, a->args, a->port);
 245   return SCM_UNSPECIFIED;
 246 }
 247
 248 struct display_error_handler_data {
 249   char *mode;
 250   SCM port;
 251 };
 252
 253 /* This is the exception handler for error reporting routines.
 254    Note that it is very important that this handler *doesn't* try to
 255    print more than the error tag, since the error very probably is
 256    caused by an erroneous print call-back routine.  If we would
 257    try to print all objects, we would enter an infinite loop. */
 258 static SCM
 259 display_error_handler (struct display_error_handler_data *data,
 260                        SCM tag, SCM args SCM_UNUSED)
 261 {
 262   SCM print_state = scm_make_print_state ();
 263   scm_puts ("\nException during displaying of ", data->port);
 264   scm_puts (data->mode, data->port);
 265   scm_puts (": ", data->port);
 266   scm_iprin1 (tag, data->port, SCM_PRINT_STATE (print_state));
 267   scm_putc ('\n', data->port);
 268   return SCM_UNSPECIFIED;
 269 }
 270
 271
 272 /* The function scm_i_display_error prints out a detailed error message.  This
 273  * function will be called directly within libguile to signal error messages.
 274  * No parameter checks will be performed by scm_i_display_error.  Thus, User
 275  * code should rather use the function scm_display_error.
 276  */
 277 void
 278 scm_i_display_error (SCM stack, SCM port, SCM subr, SCM message, SCM args, SCM rest)
 279 {
 280   struct display_error_args a;
 281   struct display_error_handler_data data;
 282   a.stack = stack;
 283   a.port  = port;
 284   a.subr  = subr;
 285   a.message = message;
 286   a.args  = args;
 287   a.rest  = rest;
 288   data.mode = "error";
 289   data.port = port;
 290   scm_internal_catch (SCM_BOOL_T,
 291                       (scm_t_catch_body) display_error_body, &a,
 292                       (scm_t_catch_handler) display_error_handler, &data);
 293 }
 294
 295
 296 SCM_DEFINE (scm_display_error, "display-error", 6, 0, 0,
 297             (SCM stack, SCM port, SCM subr, SCM message, SCM args, SCM rest),
 298             "Display an error message to the output port @var{port}.\n"
 299             "@var{stack} is the saved stack for the error, @var{subr} is\n"
 300             "the name of the procedure in which the error occurred and\n"
 301             "@var{message} is the actual error message, which may contain\n"
 302             "formatting instructions. These will format the arguments in\n"
 303             "the list @var{args} accordingly.  @var{rest} is currently\n"
 304             "ignored.")
 305 #define FUNC_NAME s_scm_display_error
 306 {
 307   SCM_VALIDATE_OUTPUT_PORT (2, port);
 308
 309   scm_i_display_error (stack, port, subr, message, args, rest);
 310
 311   return SCM_UNSPECIFIED;
 312 }
 313 #undef FUNC_NAME
 314
 315
 316 typedef struct {
 317   int level;
 318   int length;
 319 } print_params_t;
 320
 321 static int n_print_params = 9;
 322 static print_params_t default_print_params[] = {
 323   { 4, 9 }, { 4, 3 },
 324   { 3, 4 }, { 3, 3 },
 325   { 2, 4 }, { 2, 3 },
 326   { 1, 4 }, { 1, 3 }, { 1, 2 }
 327 };
 328 static print_params_t *print_params = default_print_params;
 329
 330 #ifdef GUILE_DEBUG
 331 SCM_DEFINE (scm_set_print_params_x, "set-print-params!", 1, 0, 0,
 332            (SCM params),
 333             "Set the print parameters to the values from @var{params}.\n"
 334             "@var{params} must be a list of two-element lists which must\n"
 335             "hold two integer values.")
 336 #define FUNC_NAME s_scm_set_print_params_x
 337 {
 338   int i;
 339   int n;
 340   SCM ls;
 341   print_params_t *new_params;
 342
 343   SCM_VALIDATE_NONEMPTYLIST_COPYLEN (2, params, n);
 344   for (ls = params; !SCM_NULL_OR_NIL_P (ls); ls = SCM_CDR (ls))
 345     SCM_ASSERT (scm_ilength (SCM_CAR (params)) == 2
 346                 && scm_is_unsigned_integer (SCM_CAAR (ls), 0, INT_MAX)
 347                 && scm_is_unsigned_integer (SCM_CADAR (ls), 0, INT_MAX),
 348                 params,
 349                 SCM_ARG2,
 350                 s_scm_set_print_params_x);
 351   new_params = scm_malloc (n * sizeof (print_params_t));
 352   if (print_params != default_print_params)
 353     free (print_params);
 354   print_params = new_params;
 355   for (i = 0; i < n; ++i)
 356     {
 357       print_params[i].level = scm_to_int (SCM_CAAR (params));
 358       print_params[i].length = scm_to_int (SCM_CADAR (params));
 359       params = SCM_CDR (params);
 360     }
 361   n_print_params = n;
 362   return SCM_UNSPECIFIED;
 363 }
 364 #undef FUNC_NAME
 365 #endif
 366
 367 static void
 368 indent (int n, SCM port)
 369 {
 370   int i;
 371   for (i = 0; i < n; ++i)
 372     scm_putc (' ', port);
 373 }
 374
 375 static void
 376 display_frame_expr (char *hdr, SCM exp, char *tlr, int indentation, SCM sport, SCM port, scm_print_state *pstate)
 377 {
 378   int i = 0, n;
 379   scm_t_ptob_descriptor *ptob = scm_ptobs + SCM_PTOBNUM (sport);
 380   do
 381     {
 382       pstate->length = print_params[i].length;
 383       ptob->seek (sport, 0, SEEK_SET);
 384       if (scm_is_pair (exp))
 385         {
 386           pstate->level = print_params[i].level - 1;
 387           scm_iprlist (hdr, exp, tlr[0], sport, pstate);
 388           scm_puts (&tlr[1], sport);
 389         }
 390       else
 391         {
 392           pstate->level = print_params[i].level;
 393           scm_iprin1 (exp, sport, pstate);
 394         }
 395       ptob->flush (sport);
 396       n = ptob->seek (sport, 0, SEEK_CUR);
 397       ++i;
 398     }
 399   while (indentation + n > SCM_BACKTRACE_WIDTH && i < n_print_params);
 400   ptob->truncate (sport, n);
 401
 402   scm_display (scm_strport_to_string (sport), port);
 403 }
 404
 405 static void
 406 display_application (SCM frame, int indentation, SCM sport, SCM port, scm_print_state *pstate)
 407 {
 408   SCM proc = SCM_FRAME_PROC (frame);
 409   SCM name = (scm_is_true (scm_procedure_p (proc))
 410               ? scm_procedure_name (proc)
 411               : SCM_BOOL_F);
 412   display_frame_expr ("[",
 413                       scm_cons (scm_is_true (name) ? name : proc,
 414                                 SCM_FRAME_ARGS (frame)),
 415                       SCM_FRAME_EVAL_ARGS_P (frame) ? " ..." : "]",
 416                       indentation,
 417                       sport,
 418                       port,
 419                       pstate);
 420 }
 421
 422 SCM_DEFINE (scm_display_application, "display-application", 1, 2, 0,
 423            (SCM frame, SCM port, SCM indent),
 424             "Display a procedure application @var{frame} to the output port\n"
 425             "@var{port}. @var{indent} specifies the indentation of the\n"
 426             "output.")
 427 #define FUNC_NAME s_scm_display_application
 428 {
 429   SCM_VALIDATE_FRAME (1, frame);
 430   if (SCM_UNBNDP (port))
 431     port = scm_current_output_port ();
 432   else
 433     SCM_VALIDATE_OPOUTPORT (2, port);
 434   if (SCM_UNBNDP (indent))
 435     indent = SCM_INUM0;
 436
 437   if (SCM_FRAME_PROC_P (frame))
 438     /* Display an application. */
 439     {
 440       SCM sport, print_state;
 441       scm_print_state *pstate;
 442
 443       /* Create a string port used for adaptation of printing parameters. */
 444       sport = scm_mkstrport (SCM_INUM0,
 445                              scm_make_string (scm_from_int (240),
 446                                               SCM_UNDEFINED),
 447                              SCM_OPN | SCM_WRTNG,
 448                              FUNC_NAME);
 449
 450       /* Create a print state for printing of frames. */
 451       print_state = scm_make_print_state ();
 452       pstate = SCM_PRINT_STATE (print_state);
 453       pstate->writingp = 1;
 454       pstate->fancyp = 1;
 455
 456       display_application (frame, scm_to_int (indent), sport, port, pstate);
 457       return SCM_BOOL_T;
 458     }
 459   else
 460     return SCM_BOOL_F;
 461 }
 462 #undef FUNC_NAME
 463
 464 SCM_SYMBOL (sym_base, "base");
 465
 466 static void
 467 display_backtrace_get_file_line (SCM frame, SCM *file, SCM *line)
 468 {
 469   SCM source = SCM_FRAME_SOURCE (frame);
 470   *file = *line = SCM_BOOL_F;
 471   if (SCM_MEMOIZEDP (source))
 472     {
 473       *file = scm_source_property (source, scm_sym_filename);
 474       *line = scm_source_property (source, scm_sym_line);
 475     }
 476   else if (scm_is_pair (source)
 477            && scm_is_pair (scm_cdr (source))
 478            && scm_is_pair (scm_cddr (source))
 479            && !scm_is_pair (scm_cdddr (source)))
 480     {
 481       /* (addr . (filename . (line . column))), from vm compilation */
 482       *file = scm_cadr (source);
 483       *line = scm_caddr (source);
 484     }
 485 }
 486
 487 static void
 488 display_backtrace_file (frame, last_file, port, pstate)
 489      SCM frame;
 490      SCM *last_file;
 491      SCM port;
 492      scm_print_state *pstate;
 493 {
 494   SCM file, line;
 495
 496   display_backtrace_get_file_line (frame, &file, &line);
 497
 498   if (scm_is_eq (file, *last_file))
 499     return;
 500
 501   *last_file = file;
 502
 503   scm_puts ("In ", port);
 504   if (scm_is_false (file))
 505     if (scm_is_false (line))
 506       scm_puts ("unknown file", port);
 507     else
 508       scm_puts ("current input", port);
 509   else
 510     {
 511       pstate->writingp = 0;
 512       scm_iprin1 (file, port, pstate);
 513       pstate->writingp = 1;
 514     }
 515   scm_puts (":\n", port);
 516 }
 517
 518 static void
 519 display_backtrace_file_and_line (SCM frame, SCM port, scm_print_state *pstate)
 520 {
 521   SCM file, line;
 522
 523   display_backtrace_get_file_line (frame, &file, &line);
 524
 525   if (scm_is_eq (SCM_PACK (SCM_SHOW_FILE_NAME), sym_base))
 526     {
 527       if (scm_is_false (file))
 528         {
 529           if (scm_is_false (line))
 530             scm_putc ('?', port);
 531           else
 532             scm_puts ("<stdin>", port);
 533         }
 534       else
 535         {
 536           pstate -> writingp = 0;
 537 #ifdef HAVE_POSIX
 538           scm_iprin1 ((scm_is_string (file)?
 539                        scm_basename (file, SCM_UNDEFINED) : file),
 540                       port, pstate);
 541 #else
 542           scm_iprin1 (file, port, pstate);
 543 #endif
 544           pstate -> writingp = 1;
 545         }
 546
 547       scm_putc (':', port);
 548     }
 549   else if (scm_is_true (line))
 550     {
 551       int i, j=0;
 552       for (i = scm_to_int (line)+1; i > 0; i = i/10, j++)
 553         ;
 554       indent (4-j, port);
 555     }
 556
 557   if (scm_is_false (line))
 558     scm_puts ("   ?", port);
 559   else
 560     scm_intprint (scm_to_int (line) + 1, 10, port);
 561   scm_puts (": ", port);
 562 }
 563
 564 static void
 565 display_frame (SCM frame, int nfield, int indentation, SCM sport, SCM port, scm_print_state *pstate)
 566 {
 567   int n, i, j;
 568
 569   /* Announce missing frames? */
 570   if (!SCM_BACKWARDS_P && SCM_FRAME_OVERFLOW_P (frame))
 571     {
 572       indent (nfield + 1 + indentation, port);
 573       scm_puts ("...\n", port);
 574     }
 575
 576   /* display file name and line number */
 577   if (scm_is_true (SCM_PACK (SCM_SHOW_FILE_NAME)))
 578     display_backtrace_file_and_line (frame, port, pstate);
 579
 580   /* Check size of frame number. */
 581   n = SCM_FRAME_NUMBER (frame);
 582   for (i = 0, j = n; j > 0; ++i) j /= 10;
 583
 584   /* Number indentation. */
 585   indent (nfield - (i ? i : 1), port);
 586
 587   /* Frame number. */
 588   scm_iprin1 (scm_from_int (n), port, pstate);
 589
 590   /* Real frame marker */
 591   scm_putc (SCM_FRAME_REAL_P (frame) ? '*' : ' ', port);
 592
 593   /* Indentation. */
 594   indent (indentation, port);
 595
 596   if (SCM_FRAME_PROC_P (frame))
 597     /* Display an application. */
 598     display_application (frame, nfield + 1 + indentation, sport, port, pstate);
 599   else
 600     /* Display a special form. */
 601     {
 602       SCM source = SCM_FRAME_SOURCE (frame);
 603       SCM copy = (scm_is_pair (source)
 604                   ? scm_source_property (source, scm_sym_copy)
 605                   : SCM_BOOL_F);
 606       SCM umcopy = (SCM_MEMOIZEDP (source)
 607                     ? scm_i_unmemoize_expr (source)
 608                     : SCM_BOOL_F);
 609       display_frame_expr ("(",
 610                           scm_is_pair (copy) ? copy : umcopy,
 611                           ")",
 612                           nfield + 1 + indentation,
 613                           sport,
 614                           port,
 615                           pstate);
 616     }
 617   scm_putc ('\n', port);
 618
 619   /* Announce missing frames? */
 620   if (SCM_BACKWARDS_P && SCM_FRAME_OVERFLOW_P (frame))
 621     {
 622       indent (nfield + 1 + indentation, port);
 623       scm_puts ("...\n", port);
 624     }
 625 }
 626
 627 struct display_backtrace_args {
 628   SCM stack;
 629   SCM port;
 630   SCM first;
 631   SCM depth;
 632   SCM highlight_objects;
 633 };
 634
 635 static SCM
 636 display_backtrace_body (struct display_backtrace_args *a)
 637 #define FUNC_NAME "display_backtrace_body"
 638 {
 639   int n_frames, beg, end, n, i, j;
 640   int nfield, indent_p, indentation;
 641   SCM frame, sport, print_state;
 642   SCM last_file;
 643   scm_print_state *pstate;
 644
 645   a->port = SCM_COERCE_OUTPORT (a->port);
 646
 647   /* Argument checking and extraction. */
 648   SCM_VALIDATE_STACK (1, a->stack);
 649   SCM_VALIDATE_OPOUTPORT (2, a->port);
 650   n_frames = scm_to_int (scm_stack_length (a->stack));
 651   n = scm_is_integer (a->depth) ? scm_to_int (a->depth) : SCM_BACKTRACE_DEPTH;
 652   if (SCM_BACKWARDS_P)
 653     {
 654       beg = scm_is_integer (a->first) ? scm_to_int (a->first) : 0;
 655       end = beg + n - 1;
 656       if (end >= n_frames)
 657         end = n_frames - 1;
 658       n = end - beg + 1;
 659     }
 660   else
 661     {
 662       if (scm_is_integer (a->first))
 663         {
 664           beg = scm_to_int (a->first);
 665           end = beg - n + 1;
 666           if (end < 0)
 667             end = 0;
 668         }
 669       else
 670         {
 671           beg = n - 1;
 672           end = 0;
 673           if (beg >= n_frames)
 674             beg = n_frames - 1;
 675         }
 676       n = beg - end + 1;
 677     }
 678   SCM_ASSERT (beg >= 0 && beg < n_frames, a->first, SCM_ARG3, s_display_backtrace);
 679   SCM_ASSERT (n > 0, a->depth, SCM_ARG4, s_display_backtrace);
 680
 681   /* Create a string port used for adaptation of printing parameters. */
 682   sport = scm_mkstrport (SCM_INUM0,
 683                          scm_make_string (scm_from_int (240), SCM_UNDEFINED),
 684                          SCM_OPN | SCM_WRTNG,
 685                          FUNC_NAME);
 686
 687   /* Create a print state for printing of frames. */
 688   print_state = scm_make_print_state ();
 689   pstate = SCM_PRINT_STATE (print_state);
 690   pstate->writingp = 1;
 691   pstate->fancyp = 1;
 692   pstate->highlight_objects = a->highlight_objects;
 693
 694   /* First find out if it's reasonable to do indentation. */
 695   if (SCM_BACKWARDS_P)
 696     indent_p = 0;
 697   else
 698     {
 699       unsigned int j;
 700
 701       indent_p = 1;
 702       frame = scm_stack_ref (a->stack, scm_from_int (beg));
 703       for (i = 0, j = 0; i < n; ++i)
 704         {
 705           if (SCM_FRAME_REAL_P (frame))
 706             ++j;
 707           if (j > SCM_BACKTRACE_INDENT)
 708             {
 709               indent_p = 0;
 710               break;
 711             }
 712           frame = (SCM_BACKWARDS_P
 713                    ? SCM_FRAME_PREV (frame)
 714                    : SCM_FRAME_NEXT (frame));
 715         }
 716     }
 717
 718   /* Determine size of frame number field. */
 719   j = SCM_FRAME_NUMBER (scm_stack_ref (a->stack, scm_from_int (end)));
 720   for (i = 0; j > 0; ++i) j /= 10;
 721   nfield = i ? i : 1;
 722
 723   /* Print frames. */
 724   frame = scm_stack_ref (a->stack, scm_from_int (beg));
 725   indentation = 1;
 726   last_file = SCM_UNDEFINED;
 727   for (i = 0; i < n; ++i)
 728     {
 729       if (!scm_is_eq (SCM_PACK (SCM_SHOW_FILE_NAME), sym_base))
 730         display_backtrace_file (frame, &last_file, a->port, pstate);
 731
 732       display_frame (frame, nfield, indentation, sport, a->port, pstate);
 733       if (indent_p && SCM_FRAME_EVAL_ARGS_P (frame))
 734         ++indentation;
 735       frame = (SCM_BACKWARDS_P ?
 736                SCM_FRAME_PREV (frame) : SCM_FRAME_NEXT (frame));
 737     }
 738
 739   scm_remember_upto_here_1 (print_state);
 740
 741   return SCM_UNSPECIFIED;
 742 }
 743 #undef FUNC_NAME
 744
 745 SCM_DEFINE (scm_display_backtrace_with_highlights, "display-backtrace", 2, 3, 0,
 746             (SCM stack, SCM port, SCM first, SCM depth, SCM highlights),
 747             "Display a backtrace to the output port @var{port}.  @var{stack}\n"
 748             "is the stack to take the backtrace from, @var{first} specifies\n"
 749             "where in the stack to start and @var{depth} how many frames\n"
 750             "to display.  @var{first} and @var{depth} can be @code{#f},\n"
 751             "which means that default values will be used.\n"
 752             "If @var{highlights} is given it should be a list; the elements\n"
 753             "of this list will be highlighted wherever they appear in the\n"
 754             "backtrace.")
 755 #define FUNC_NAME s_scm_display_backtrace_with_highlights
 756 {
 757   struct display_backtrace_args a;
 758   struct display_error_handler_data data;
 759   a.stack = stack;
 760   a.port  = port;
 761   a.first = first;
 762   a.depth = depth;
 763   if (SCM_UNBNDP (highlights))
 764     a.highlight_objects = SCM_EOL;
 765   else
 766     a.highlight_objects = highlights;
 767   data.mode = "backtrace";
 768   data.port = port;
 769   scm_internal_catch (SCM_BOOL_T,
 770                       (scm_t_catch_body) display_backtrace_body, &a,
 771                       (scm_t_catch_handler) display_error_handler, &data);
 772   return SCM_UNSPECIFIED;
 773 }
 774 #undef FUNC_NAME
 775
 776 SCM
 777 scm_display_backtrace (SCM stack, SCM port, SCM first, SCM depth)
 778 {
 779   return scm_display_backtrace_with_highlights (stack, port, first, depth,
 780                                                 SCM_EOL);
 781 }
 782
 783 SCM_VARIABLE (scm_has_shown_backtrace_hint_p_var, "has-shown-backtrace-hint?");
 784
 785 SCM_DEFINE (scm_backtrace_with_highlights, "backtrace", 0, 1, 0,
 786             (SCM highlights),
 787             "Display a backtrace of the stack saved by the last error\n"
 788             "to the current output port.  If @var{highlights} is given\n"
 789             "it should be a list; the elements of this list will be\n"
 790             "highlighted wherever they appear in the backtrace.")
 791 #define FUNC_NAME s_scm_backtrace_with_highlights
 792 {
 793   SCM port = scm_current_output_port ();
 794   SCM the_last_stack =
 795     scm_fluid_ref (SCM_VARIABLE_REF (scm_the_last_stack_fluid_var));
 796
 797   if (SCM_UNBNDP (highlights))
 798     highlights = SCM_EOL;
 799
 800   if (scm_is_true (the_last_stack))
 801     {
 802       scm_newline (port);
 803       scm_puts ("Backtrace:\n", port);
 804       scm_display_backtrace_with_highlights (the_last_stack,
 805                                              port,
 806                                              SCM_BOOL_F,
 807                                              SCM_BOOL_F,
 808                                              highlights);
 809       scm_newline (port);
 810       if (scm_is_false (SCM_VARIABLE_REF (scm_has_shown_backtrace_hint_p_var))
 811           && !SCM_BACKTRACE_P)
 812         {
 813           scm_puts ("Type \"(debug-enable 'backtrace)\" if you would like "
 814                     "a backtrace\n"
 815                     "automatically if an error occurs in the future.\n",
 816                     port);
 817           SCM_VARIABLE_SET (scm_has_shown_backtrace_hint_p_var, SCM_BOOL_T);
 818         }
 819     }
 820   else
 821     {
 822       scm_puts ("No backtrace available.\n", port);
 823     }
 824   return SCM_UNSPECIFIED;
 825 }
 826 #undef FUNC_NAME
 827
 828 SCM
 829 scm_backtrace (void)
 830 {
 831   return scm_backtrace_with_highlights (SCM_EOL);
 832 }
 833
 834 \f
 835
 836 void
 837 scm_init_backtrace ()
 838 {
 839   SCM f = scm_make_fluid ();
 840   scm_the_last_stack_fluid_var = scm_c_define ("the-last-stack", f);
 841
 842 #include "libguile/backtrace.x"
 843 }
 844
 845 /*
 846   Local Variables:
 847   c-file-style: "gnu"
 848   End:
 849 */