libguile/backtrace.c

   1 /* Printing of backtraces and error messages
   2  * Copyright (C) 1996,1997,1998,1999,2000,2001, 2003, 2004 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
  17  */
  18
  19 #if 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
  51 /* {Error reporting and backtraces}
  52  *
  53  * Note that these functions shouldn't generate errors themselves.
  54  */
  55
  56 /* Print parameters for error messages. */
  57
  58 #define DISPLAY_ERROR_MESSAGE_MAX_LEVEL   7
  59 #define DISPLAY_ERROR_MESSAGE_MAX_LENGTH 10
  60
  61 /* Print parameters for failing expressions in error messages.
  62  * (See also `print_params' below for backtrace print parameters.)
  63  */
  64
  65 #define DISPLAY_EXPRESSION_MAX_LEVEL      2
  66 #define DISPLAY_EXPRESSION_MAX_LENGTH     3
  67
  68 #undef SCM_ASSERT
  69 #define SCM_ASSERT(_cond, _arg, _pos, _subr) \
  70         if (!(_cond)) \
  71           return SCM_BOOL_F;
  72
  73 SCM scm_the_last_stack_fluid_var;
  74
  75 static void
  76 display_header (SCM source, SCM port)
  77 {
  78   if (SCM_MEMOIZEDP (source))
  79     {
  80       SCM fname = scm_source_property (source, scm_sym_filename);
  81       SCM line = scm_source_property (source, scm_sym_line);
  82       SCM col = scm_source_property (source, scm_sym_column);
  83
  84       /* Dirk:FIXME:: Maybe we should store the _port_ rather than the
  85        * filename with the source properties?  Then we could in case of
  86        * non-file ports give at least some more details than just
  87        * "<unnamed port>". */
  88       if (scm_is_true (fname))
  89         scm_prin1 (fname, port, 0);
  90       else
  91         scm_puts ("<unnamed port>", port);
  92
  93       if (scm_is_true (line) && scm_is_true (col))
  94         {
  95           scm_putc (':', port);
  96           scm_intprint (scm_to_long (line) + 1, 10, port);
  97           scm_putc (':', port);
  98           scm_intprint (scm_to_long (col) + 1, 10, port);
  99         }
 100     }
 101   else
 102     scm_puts ("ERROR", port);
 103   scm_puts (": ", port);
 104 }
 105
 106
 107 struct display_error_message_data {
 108   SCM message;
 109   SCM args;
 110   SCM port;
 111   scm_print_state *pstate;
 112   int old_fancyp;
 113   int old_level;
 114   int old_length;
 115 };
 116
 117 static SCM
 118 display_error_message (struct display_error_message_data *d)
 119 {
 120   if (scm_is_string (d->message) && scm_is_true (scm_list_p (d->args)))
 121     scm_simple_format (d->port, d->message, d->args);
 122   else
 123     scm_display (d->message, d->port);
 124   scm_newline (d->port);
 125   return SCM_UNSPECIFIED;
 126 }
 127
 128 static void
 129 before_display_error_message (struct display_error_message_data *d)
 130 {
 131   scm_print_state *pstate = d->pstate;
 132   d->old_fancyp = pstate->fancyp;
 133   d->old_level  = pstate->level;
 134   d->old_length = pstate->length;
 135   pstate->fancyp = 1;
 136   pstate->level  = DISPLAY_ERROR_MESSAGE_MAX_LEVEL;
 137   pstate->length = DISPLAY_ERROR_MESSAGE_MAX_LENGTH;
 138 }
 139
 140 static void
 141 after_display_error_message (struct display_error_message_data *d)
 142 {
 143   scm_print_state *pstate = d->pstate;
 144   pstate->fancyp = d->old_fancyp;
 145   pstate->level  = d->old_level;
 146   pstate->length = d->old_length;
 147 }
 148
 149 void
 150 scm_display_error_message (SCM message, SCM args, SCM port)
 151 {
 152   struct display_error_message_data d;
 153   SCM print_state;
 154   scm_print_state *pstate;
 155
 156   port = scm_i_port_with_print_state (port, SCM_UNDEFINED);
 157   print_state = SCM_PORT_WITH_PS_PS (port);
 158   pstate = SCM_PRINT_STATE (print_state);
 159
 160   d.message = message;
 161   d.args = args;
 162   d.port = port;
 163   d.pstate = pstate;
 164   scm_internal_dynamic_wind ((scm_t_guard) before_display_error_message,
 165                              (scm_t_inner) display_error_message,
 166                              (scm_t_guard) after_display_error_message,
 167                              &d,
 168                              &d);
 169 }
 170
 171 static void
 172 display_expression (SCM frame, SCM pname, SCM source, SCM port)
 173 {
 174   SCM print_state = scm_make_print_state ();
 175   scm_print_state *pstate = SCM_PRINT_STATE (print_state);
 176   pstate->writingp = 0;
 177   pstate->fancyp = 1;
 178   pstate->level  = DISPLAY_EXPRESSION_MAX_LEVEL;
 179   pstate->length = DISPLAY_EXPRESSION_MAX_LENGTH;
 180   if (scm_is_symbol (pname) || scm_is_string (pname))
 181     {
 182       if (SCM_FRAMEP (frame)
 183           && SCM_FRAME_EVAL_ARGS_P (frame))
 184         scm_puts ("While evaluating arguments to ", port);
 185       else
 186         scm_puts ("In procedure ", port);
 187       scm_iprin1 (pname, port, pstate);
 188       if (SCM_MEMOIZEDP (source))
 189         {
 190           scm_puts (" in expression ", port);
 191           pstate->writingp = 1;
 192           scm_iprin1 (scm_i_unmemoize_expr (source), port, pstate);
 193         }
 194     }
 195   else if (SCM_MEMOIZEDP (source))
 196     {
 197       scm_puts ("In expression ", port);
 198       pstate->writingp = 1;
 199       scm_iprin1 (scm_i_unmemoize_expr (source), port, pstate);
 200     }
 201   scm_puts (":\n", port);
 202   scm_free_print_state (print_state);
 203 }
 204
 205 struct display_error_args {
 206   SCM stack;
 207   SCM port;
 208   SCM subr;
 209   SCM message;
 210   SCM args;
 211   SCM rest;
 212 };
 213
 214 static SCM
 215 display_error_body (struct display_error_args *a)
 216 {
 217   SCM current_frame = SCM_BOOL_F;
 218   SCM source = SCM_BOOL_F;
 219   SCM prev_frame = SCM_BOOL_F;
 220   SCM pname = a->subr;
 221
 222   if (scm_debug_mode_p
 223       && SCM_STACKP (a->stack)
 224       && SCM_STACK_LENGTH (a->stack) > 0)
 225     {
 226       current_frame = scm_stack_ref (a->stack, SCM_INUM0);
 227       source = SCM_FRAME_SOURCE (current_frame);
 228       prev_frame = SCM_FRAME_PREV (current_frame);
 229       if (!SCM_MEMOIZEDP (source) && scm_is_true (prev_frame))
 230         source = SCM_FRAME_SOURCE (prev_frame);
 231       if (!scm_is_symbol (pname)
 232           && !scm_is_string (pname)
 233           && SCM_FRAME_PROC_P (current_frame)
 234           && scm_is_true (scm_procedure_p (SCM_FRAME_PROC (current_frame))))
 235         pname = scm_procedure_name (SCM_FRAME_PROC (current_frame));
 236     }
 237   if (scm_is_symbol (pname) || scm_is_string (pname) || SCM_MEMOIZEDP (source))
 238     {
 239       display_header (source, a->port);
 240       display_expression (current_frame, pname, source, a->port);
 241     }
 242   display_header (source, a->port);
 243   scm_display_error_message (a->message, a->args, a->port);
 244   return SCM_UNSPECIFIED;
 245 }
 246
 247 struct display_error_handler_data {
 248   char *mode;
 249   SCM port;
 250 };
 251
 252 /* This is the exception handler for error reporting routines.
 253    Note that it is very important that this handler *doesn't* try to
 254    print more than the error tag, since the error very probably is
 255    caused by an erroneous print call-back routine.  If we would
 256    try to print all objects, we would enter an infinite loop. */
 257 static SCM
 258 display_error_handler (struct display_error_handler_data *data,
 259                        SCM tag, SCM args SCM_UNUSED)
 260 {
 261   SCM print_state = scm_make_print_state ();
 262   scm_puts ("\nException during displaying of ", data->port);
 263   scm_puts (data->mode, data->port);
 264   scm_puts (": ", data->port);
 265   scm_iprin1 (tag, data->port, SCM_PRINT_STATE (print_state));
 266   scm_putc ('\n', data->port);
 267   return SCM_UNSPECIFIED;
 268 }
 269
 270
 271 /* The function scm_i_display_error prints out a detailed error message.  This
 272  * function will be called directly within libguile to signal error messages.
 273  * No parameter checks will be performed by scm_i_display_error.  Thus, User
 274  * code should rather use the function scm_display_error.
 275  */
 276 void
 277 scm_i_display_error (SCM stack, SCM port, SCM subr, SCM message, SCM args, SCM rest)
 278 {
 279   struct display_error_args a;
 280   struct display_error_handler_data data;
 281   a.stack = stack;
 282   a.port  = port;
 283   a.subr  = subr;
 284   a.message = message;
 285   a.args  = args;
 286   a.rest  = rest;
 287   data.mode = "error";
 288   data.port = port;
 289   scm_internal_catch (SCM_BOOL_T,
 290                       (scm_t_catch_body) display_error_body, &a,
 291                       (scm_t_catch_handler) display_error_handler, &data);
 292 }
 293
 294
 295 SCM_DEFINE (scm_display_error, "display-error", 6, 0, 0,
 296             (SCM stack, SCM port, SCM subr, SCM message, SCM args, SCM rest),
 297             "Display an error message to the output port @var{port}.\n"
 298             "@var{stack} is the saved stack for the error, @var{subr} is\n"
 299             "the name of the procedure in which the error occurred and\n"
 300             "@var{message} is the actual error message, which may contain\n"
 301             "formatting instructions. These will format the arguments in\n"
 302             "the list @var{args} accordingly.  @var{rest} is currently\n"
 303             "ignored.")
 304 #define FUNC_NAME s_scm_display_error
 305 {
 306   SCM_VALIDATE_OUTPUT_PORT (2, port);
 307
 308   scm_i_display_error (stack, port, subr, message, args, rest);
 309
 310   return SCM_UNSPECIFIED;
 311 }
 312 #undef FUNC_NAME
 313
 314
 315 typedef struct {
 316   int level;
 317   int length;
 318 } print_params_t;
 319
 320 static int n_print_params = 9;
 321 static print_params_t default_print_params[] = {
 322   { 4, 9 }, { 4, 3 },
 323   { 3, 4 }, { 3, 3 },
 324   { 2, 4 }, { 2, 3 },
 325   { 1, 4 }, { 1, 3 }, { 1, 2 }
 326 };
 327 static print_params_t *print_params = default_print_params;
 328
 329 #ifdef GUILE_DEBUG
 330 SCM_DEFINE (scm_set_print_params_x, "set-print-params!", 1, 0, 0,
 331            (SCM params),
 332             "Set the print parameters to the values from @var{params}.\n"
 333             "@var{params} must be a list of two-element lists which must\n"
 334             "hold two integer values.")
 335 #define FUNC_NAME s_scm_set_print_params_x
 336 {
 337   int i;
 338   int n;
 339   SCM ls;
 340   print_params_t *new_params;
 341
 342   SCM_VALIDATE_NONEMPTYLIST_COPYLEN (2, params, n);
 343   for (ls = params; !SCM_NULL_OR_NIL_P (ls); ls = SCM_CDR (ls))
 344     SCM_ASSERT (scm_ilength (SCM_CAR (params)) == 2
 345                 && scm_is_unsigned_integer (SCM_CAAR (ls), 0, INT_MAX)
 346                 && scm_is_unsigned_integer (SCM_CADAR (ls), 0, INT_MAX),
 347                 params,
 348                 SCM_ARG2,
 349                 s_scm_set_print_params_x);
 350   new_params = scm_malloc (n * sizeof (print_params_t));
 351   if (print_params != default_print_params)
 352     free (print_params);
 353   print_params = new_params;
 354   for (i = 0; i < n; ++i)
 355     {
 356       print_params[i].level = scm_to_int (SCM_CAAR (params));
 357       print_params[i].length = scm_to_int (SCM_CADAR (params));
 358       params = SCM_CDR (params);
 359     }
 360   n_print_params = n;
 361   return SCM_UNSPECIFIED;
 362 }
 363 #undef FUNC_NAME
 364 #endif
 365
 366 static void
 367 indent (int n, SCM port)
 368 {
 369   int i;
 370   for (i = 0; i < n; ++i)
 371     scm_putc (' ', port);
 372 }
 373
 374 static void
 375 display_frame_expr (char *hdr, SCM exp, char *tlr, int indentation, SCM sport, SCM port, scm_print_state *pstate)
 376 {
 377   int i = 0, n;
 378   scm_t_ptob_descriptor *ptob = scm_ptobs + SCM_PTOBNUM (sport);
 379   do
 380     {
 381       pstate->length = print_params[i].length;
 382       ptob->seek (sport, 0, SEEK_SET);
 383       if (scm_is_pair (exp))
 384         {
 385           pstate->level = print_params[i].level - 1;
 386           scm_iprlist (hdr, exp, tlr[0], sport, pstate);
 387           scm_puts (&tlr[1], sport);
 388         }
 389       else
 390         {
 391           pstate->level = print_params[i].level;
 392           scm_iprin1 (exp, sport, pstate);
 393         }
 394       ptob->flush (sport);
 395       n = ptob->seek (sport, 0, SEEK_CUR);
 396       ++i;
 397     }
 398   while (indentation + n > SCM_BACKTRACE_WIDTH && i < n_print_params);
 399   ptob->truncate (sport, n);
 400
 401   scm_display (scm_strport_to_string (sport), port);
 402 }
 403
 404 static void
 405 display_application (SCM frame, int indentation, SCM sport, SCM port, scm_print_state *pstate)
 406 {
 407   SCM proc = SCM_FRAME_PROC (frame);
 408   SCM name = (scm_is_true (scm_procedure_p (proc))
 409               ? scm_procedure_name (proc)
 410               : SCM_BOOL_F);
 411   display_frame_expr ("[",
 412                       scm_cons (scm_is_true (name) ? name : proc,
 413                                 SCM_FRAME_ARGS (frame)),
 414                       SCM_FRAME_EVAL_ARGS_P (frame) ? " ..." : "]",
 415                       indentation,
 416                       sport,
 417                       port,
 418                       pstate);
 419 }
 420
 421 SCM_DEFINE (scm_display_application, "display-application", 1, 2, 0,
 422            (SCM frame, SCM port, SCM indent),
 423             "Display a procedure application @var{frame} to the output port\n"
 424             "@var{port}. @var{indent} specifies the indentation of the\n"
 425             "output.")
 426 #define FUNC_NAME s_scm_display_application
 427 {
 428   SCM_VALIDATE_FRAME (1, frame);
 429   if (SCM_UNBNDP (port))
 430     port = scm_current_output_port ();
 431   else
 432     SCM_VALIDATE_OPOUTPORT (2, port);
 433   if (SCM_UNBNDP (indent))
 434     indent = SCM_INUM0;
 435
 436   if (SCM_FRAME_PROC_P (frame))
 437     /* Display an application. */
 438     {
 439       SCM sport, print_state;
 440       scm_print_state *pstate;
 441
 442       /* Create a string port used for adaptation of printing parameters. */
 443       sport = scm_mkstrport (SCM_INUM0,
 444                              scm_make_string (scm_from_int (240),
 445                                               SCM_UNDEFINED),
 446                              SCM_OPN | SCM_WRTNG,
 447                              FUNC_NAME);
 448
 449       /* Create a print state for printing of frames. */
 450       print_state = scm_make_print_state ();
 451       pstate = SCM_PRINT_STATE (print_state);
 452       pstate->writingp = 1;
 453       pstate->fancyp = 1;
 454
 455       display_application (frame, scm_to_int (indent), sport, port, pstate);
 456       return SCM_BOOL_T;
 457     }
 458   else
 459     return SCM_BOOL_F;
 460 }
 461 #undef FUNC_NAME
 462
 463 SCM_SYMBOL (sym_base, "base");
 464
 465 static void
 466 display_backtrace_get_file_line (SCM frame, SCM *file, SCM *line)
 467 {
 468   SCM source = SCM_FRAME_SOURCE (frame);
 469   *file = SCM_MEMOIZEDP (source) ? scm_source_property (source, scm_sym_filename) : SCM_BOOL_F;
 470   *line = (SCM_MEMOIZEDP (source)) ? scm_source_property (source, scm_sym_line) : SCM_BOOL_F;
 471 }
 472
 473 static void
 474 display_backtrace_file (frame, last_file, port, pstate)
 475      SCM frame;
 476      SCM *last_file;
 477      SCM port;
 478      scm_print_state *pstate;
 479 {
 480   SCM file, line;
 481
 482   display_backtrace_get_file_line (frame, &file, &line);
 483
 484   if (scm_is_eq (file, *last_file))
 485     return;
 486
 487   *last_file = file;
 488
 489   scm_puts ("In ", port);
 490   if (scm_is_false (file))
 491     if (scm_is_false (line))
 492       scm_puts ("unknown file", port);
 493     else
 494       scm_puts ("current input", port);
 495   else
 496     {
 497       pstate->writingp = 0;
 498       scm_iprin1 (file, port, pstate);
 499       pstate->writingp = 1;
 500     }
 501   scm_puts (":\n", port);
 502 }
 503
 504 static void
 505 display_backtrace_file_and_line (SCM frame, SCM port, scm_print_state *pstate)
 506 {
 507   SCM file, line;
 508
 509   display_backtrace_get_file_line (frame, &file, &line);
 510
 511   if (scm_is_eq (SCM_PACK (SCM_SHOW_FILE_NAME), sym_base))
 512     {
 513       if (scm_is_false (file))
 514         {
 515           if (scm_is_false (line))
 516             scm_putc ('?', port);
 517           else
 518             scm_puts ("<stdin>", port);
 519         }
 520       else
 521         {
 522           pstate -> writingp = 0;
 523 #ifdef HAVE_POSIX
 524           scm_iprin1 ((scm_is_string (file)?
 525                        scm_basename (file, SCM_UNDEFINED) : file),
 526                       port, pstate);
 527 #else
 528           scm_iprin1 (file, port, pstate);
 529 #endif
 530           pstate -> writingp = 1;
 531         }
 532
 533       scm_putc (':', port);
 534     }
 535   else if (scm_is_true (line))
 536     {
 537       int i, j=0;
 538       for (i = scm_to_int (line)+1; i > 0; i = i/10, j++)
 539         ;
 540       indent (4-j, port);
 541     }
 542
 543   if (scm_is_false (line))
 544     scm_puts ("   ?", port);
 545   else
 546     scm_intprint (scm_to_int (line) + 1, 10, port);
 547   scm_puts (": ", port);
 548 }
 549
 550 static void
 551 display_frame (SCM frame, int nfield, int indentation, SCM sport, SCM port, scm_print_state *pstate)
 552 {
 553   int n, i, j;
 554
 555   /* Announce missing frames? */
 556   if (!SCM_BACKWARDS_P && SCM_FRAME_OVERFLOW_P (frame))
 557     {
 558       indent (nfield + 1 + indentation, port);
 559       scm_puts ("...\n", port);
 560     }
 561
 562   /* display file name and line number */
 563   if (scm_is_true (SCM_PACK (SCM_SHOW_FILE_NAME)))
 564     display_backtrace_file_and_line (frame, port, pstate);
 565
 566   /* Check size of frame number. */
 567   n = SCM_FRAME_NUMBER (frame);
 568   for (i = 0, j = n; j > 0; ++i) j /= 10;
 569
 570   /* Number indentation. */
 571   indent (nfield - (i ? i : 1), port);
 572
 573   /* Frame number. */
 574   scm_iprin1 (scm_from_int (n), port, pstate);
 575
 576   /* Real frame marker */
 577   scm_putc (SCM_FRAME_REAL_P (frame) ? '*' : ' ', port);
 578
 579   /* Indentation. */
 580   indent (indentation, port);
 581
 582   if (SCM_FRAME_PROC_P (frame))
 583     /* Display an application. */
 584     display_application (frame, nfield + 1 + indentation, sport, port, pstate);
 585   else
 586     /* Display a special form. */
 587     {
 588       SCM source = SCM_FRAME_SOURCE (frame);
 589       SCM copy = (scm_is_pair (source)
 590                   ? scm_source_property (source, scm_sym_copy)
 591                   : SCM_BOOL_F);
 592       SCM umcopy = (SCM_MEMOIZEDP (source)
 593                     ? scm_i_unmemoize_expr (source)
 594                     : SCM_BOOL_F);
 595       display_frame_expr ("(",
 596                           scm_is_pair (copy) ? copy : umcopy,
 597                           ")",
 598                           nfield + 1 + indentation,
 599                           sport,
 600                           port,
 601                           pstate);
 602     }
 603   scm_putc ('\n', port);
 604
 605   /* Announce missing frames? */
 606   if (SCM_BACKWARDS_P && SCM_FRAME_OVERFLOW_P (frame))
 607     {
 608       indent (nfield + 1 + indentation, port);
 609       scm_puts ("...\n", port);
 610     }
 611 }
 612
 613 struct display_backtrace_args {
 614   SCM stack;
 615   SCM port;
 616   SCM first;
 617   SCM depth;
 618   SCM highlight_objects;
 619 };
 620
 621 static SCM
 622 display_backtrace_body (struct display_backtrace_args *a)
 623 #define FUNC_NAME "display_backtrace_body"
 624 {
 625   int n_frames, beg, end, n, i, j;
 626   int nfield, indent_p, indentation;
 627   SCM frame, sport, print_state;
 628   SCM last_file;
 629   scm_print_state *pstate;
 630
 631   a->port = SCM_COERCE_OUTPORT (a->port);
 632
 633   /* Argument checking and extraction. */
 634   SCM_VALIDATE_STACK (1, a->stack);
 635   SCM_VALIDATE_OPOUTPORT (2, a->port);
 636   n_frames = scm_to_int (scm_stack_length (a->stack));
 637   n = scm_is_integer (a->depth) ? scm_to_int (a->depth) : SCM_BACKTRACE_DEPTH;
 638   if (SCM_BACKWARDS_P)
 639     {
 640       beg = scm_is_integer (a->first) ? scm_to_int (a->first) : 0;
 641       end = beg + n - 1;
 642       if (end >= n_frames)
 643         end = n_frames - 1;
 644       n = end - beg + 1;
 645     }
 646   else
 647     {
 648       if (scm_is_integer (a->first))
 649         {
 650           beg = scm_to_int (a->first);
 651           end = beg - n + 1;
 652           if (end < 0)
 653             end = 0;
 654         }
 655       else
 656         {
 657           beg = n - 1;
 658           end = 0;
 659           if (beg >= n_frames)
 660             beg = n_frames - 1;
 661         }
 662       n = beg - end + 1;
 663     }
 664   SCM_ASSERT (beg >= 0 && beg < n_frames, a->first, SCM_ARG3, s_display_backtrace);
 665   SCM_ASSERT (n > 0, a->depth, SCM_ARG4, s_display_backtrace);
 666
 667   /* Create a string port used for adaptation of printing parameters. */
 668   sport = scm_mkstrport (SCM_INUM0,
 669                          scm_make_string (scm_from_int (240), SCM_UNDEFINED),
 670                          SCM_OPN | SCM_WRTNG,
 671                          FUNC_NAME);
 672
 673   /* Create a print state for printing of frames. */
 674   print_state = scm_make_print_state ();
 675   pstate = SCM_PRINT_STATE (print_state);
 676   pstate->writingp = 1;
 677   pstate->fancyp = 1;
 678   pstate->highlight_objects = a->highlight_objects;
 679
 680   /* First find out if it's reasonable to do indentation. */
 681   if (SCM_BACKWARDS_P)
 682     indent_p = 0;
 683   else
 684     {
 685       unsigned int j;
 686
 687       indent_p = 1;
 688       frame = scm_stack_ref (a->stack, scm_from_int (beg));
 689       for (i = 0, j = 0; i < n; ++i)
 690         {
 691           if (SCM_FRAME_REAL_P (frame))
 692             ++j;
 693           if (j > SCM_BACKTRACE_INDENT)
 694             {
 695               indent_p = 0;
 696               break;
 697             }
 698           frame = (SCM_BACKWARDS_P
 699                    ? SCM_FRAME_PREV (frame)
 700                    : SCM_FRAME_NEXT (frame));
 701         }
 702     }
 703
 704   /* Determine size of frame number field. */
 705   j = SCM_FRAME_NUMBER (scm_stack_ref (a->stack, scm_from_int (end)));
 706   for (i = 0; j > 0; ++i) j /= 10;
 707   nfield = i ? i : 1;
 708
 709   /* Print frames. */
 710   frame = scm_stack_ref (a->stack, scm_from_int (beg));
 711   indentation = 1;
 712   last_file = SCM_UNDEFINED;
 713   for (i = 0; i < n; ++i)
 714     {
 715       if (!scm_is_eq (SCM_PACK (SCM_SHOW_FILE_NAME), sym_base))
 716         display_backtrace_file (frame, &last_file, a->port, pstate);
 717
 718       display_frame (frame, nfield, indentation, sport, a->port, pstate);
 719       if (indent_p && SCM_FRAME_EVAL_ARGS_P (frame))
 720         ++indentation;
 721       frame = (SCM_BACKWARDS_P ?
 722                SCM_FRAME_PREV (frame) : SCM_FRAME_NEXT (frame));
 723     }
 724
 725   scm_remember_upto_here_1 (print_state);
 726
 727   return SCM_UNSPECIFIED;
 728 }
 729 #undef FUNC_NAME
 730
 731 SCM_DEFINE (scm_display_backtrace_with_highlights, "display-backtrace", 2, 3, 0,
 732             (SCM stack, SCM port, SCM first, SCM depth, SCM highlights),
 733             "Display a backtrace to the output port @var{port}. @var{stack}\n"
 734             "is the stack to take the backtrace from, @var{first} specifies\n"
 735             "where in the stack to start and @var{depth} how much frames\n"
 736             "to display. Both @var{first} and @var{depth} can be @code{#f},\n"
 737             "which means that default values will be used.\n"
 738             "When @var{highlights} is given,\n"
 739             "it should be a list and all members of it are highligthed in\n"
 740             "the backtrace.")
 741 #define FUNC_NAME s_scm_display_backtrace_with_highlights
 742 {
 743   struct display_backtrace_args a;
 744   struct display_error_handler_data data;
 745   a.stack = stack;
 746   a.port  = port;
 747   a.first = first;
 748   a.depth = depth;
 749   if (SCM_UNBNDP (highlights))
 750     a.highlight_objects = SCM_EOL;
 751   else
 752     a.highlight_objects = highlights;
 753   data.mode = "backtrace";
 754   data.port = port;
 755   scm_internal_catch (SCM_BOOL_T,
 756                       (scm_t_catch_body) display_backtrace_body, &a,
 757                       (scm_t_catch_handler) display_error_handler, &data);
 758   return SCM_UNSPECIFIED;
 759 }
 760 #undef FUNC_NAME
 761
 762 SCM
 763 scm_display_backtrace (SCM stack, SCM port, SCM first, SCM depth)
 764 {
 765   return scm_display_backtrace_with_highlights (stack, port, first, depth,
 766                                                 SCM_EOL);
 767 }
 768
 769 SCM_VARIABLE (scm_has_shown_backtrace_hint_p_var, "has-shown-backtrace-hint?");
 770
 771 SCM_DEFINE (scm_backtrace_with_highlights, "backtrace", 0, 1, 0,
 772             (SCM highlights),
 773             "Display a backtrace of the stack saved by the last error\n"
 774             "to the current output port.  When @var{highlights} is given,\n"
 775             "it should be a list and all members of it are highligthed in\n"
 776             "the backtrace.")
 777 #define FUNC_NAME s_scm_backtrace_with_highlights
 778 {
 779   SCM port = scm_current_output_port ();
 780   SCM the_last_stack =
 781     scm_fluid_ref (SCM_VARIABLE_REF (scm_the_last_stack_fluid_var));
 782
 783   if (SCM_UNBNDP (highlights))
 784     highlights = SCM_EOL;
 785
 786   if (scm_is_true (the_last_stack))
 787     {
 788       scm_newline (port);
 789       scm_puts ("Backtrace:\n", port);
 790       scm_display_backtrace_with_highlights (the_last_stack,
 791                                              port,
 792                                              SCM_BOOL_F,
 793                                              SCM_BOOL_F,
 794                                              highlights);
 795       scm_newline (port);
 796       if (scm_is_false (SCM_VARIABLE_REF (scm_has_shown_backtrace_hint_p_var))
 797           && !SCM_BACKTRACE_P)
 798         {
 799           scm_puts ("Type \"(debug-enable 'backtrace)\" if you would like "
 800                     "a backtrace\n"
 801                     "automatically if an error occurs in the future.\n",
 802                     port);
 803           SCM_VARIABLE_SET (scm_has_shown_backtrace_hint_p_var, SCM_BOOL_T);
 804         }
 805     }
 806   else
 807     {
 808       scm_puts ("No backtrace available.\n", port);
 809     }
 810   return SCM_UNSPECIFIED;
 811 }
 812 #undef FUNC_NAME
 813
 814 SCM
 815 scm_backtrace (void)
 816 {
 817   return scm_backtrace_with_highlights (SCM_EOL);
 818 }
 819
 820 \f
 821
 822 void
 823 scm_init_backtrace ()
 824 {
 825   SCM f = scm_make_fluid ();
 826   scm_the_last_stack_fluid_var = scm_c_define ("the-last-stack", f);
 827
 828 #include "libguile/backtrace.x"
 829 }
 830
 831 /*
 832   Local Variables:
 833   c-file-style: "gnu"
 834   End:
 835 */