libguile/gc.c

   1 /* Copyright (C) 1995,1996,1997,1998,1999,2000,2001, 2002, 2003, 2006, 2008 Free Software Foundation, Inc.
   2  *
   3  * This library is free software; you can redistribute it and/or
   4  * modify it under the terms of the GNU Lesser General Public
   5  * License as published by the Free Software Foundation; either
   6  * version 2.1 of the License, or (at your option) any later version.
   7  *
   8  * This library is distributed in the hope that it will be useful,
   9  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  11  * Lesser General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU Lesser General Public
  14  * License along with this library; if not, write to the Free Software
  15  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  16  */
  17
  18 /* #define DEBUGINFO */
  19
  20 #ifdef HAVE_CONFIG_H
  21 #  include <config.h>
  22 #endif
  23
  24 #include "libguile/gen-scmconfig.h"
  25
  26 #include <stdio.h>
  27 #include <errno.h>
  28 #include <string.h>
  29 #include <assert.h>
  30
  31 #ifdef __ia64__
  32 #include <ucontext.h>
  33 extern unsigned long * __libc_ia64_register_backing_store_base;
  34 #endif
  35
  36 #include "libguile/_scm.h"
  37 #include "libguile/eval.h"
  38 #include "libguile/stime.h"
  39 #include "libguile/stackchk.h"
  40 #include "libguile/struct.h"
  41 #include "libguile/smob.h"
  42 #include "libguile/unif.h"
  43 #include "libguile/async.h"
  44 #include "libguile/ports.h"
  45 #include "libguile/root.h"
  46 #include "libguile/strings.h"
  47 #include "libguile/vectors.h"
  48 #include "libguile/weaks.h"
  49 #include "libguile/hashtab.h"
  50 #include "libguile/tags.h"
  51
  52 #include "libguile/private-gc.h"
  53 #include "libguile/validate.h"
  54 #include "libguile/deprecation.h"
  55 #include "libguile/gc.h"
  56 #include "libguile/dynwind.h"
  57
  58 #include "libguile/boehm-gc.h"
  59
  60 #ifdef GUILE_DEBUG_MALLOC
  61 #include "libguile/debug-malloc.h"
  62 #endif
  63
  64 #ifdef HAVE_MALLOC_H
  65 #include <malloc.h>
  66 #endif
  67
  68 #ifdef HAVE_UNISTD_H
  69 #include <unistd.h>
  70 #endif
  71
  72 /* Lock this mutex before doing lazy sweeping.
  73  */
  74 scm_i_pthread_mutex_t scm_i_sweep_mutex = SCM_I_PTHREAD_MUTEX_INITIALIZER;
  75
  76 /* Set this to != 0 if every cell that is accessed shall be checked:
  77  */
  78 int scm_debug_cell_accesses_p = 0;
  79 int scm_expensive_debug_cell_accesses_p = 0;
  80
  81 /* Set this to 0 if no additional gc's shall be performed, otherwise set it to
  82  * the number of cell accesses after which a gc shall be called.
  83  */
  84 int scm_debug_cells_gc_interval = 0;
  85
  86 /*
  87   Global variable, so you can switch it off at runtime by setting
  88   scm_i_cell_validation_already_running.
  89  */
  90 int scm_i_cell_validation_already_running ;
  91
  92 #if (SCM_DEBUG_CELL_ACCESSES == 1)
  93
  94
  95 /*
  96
  97   Assert that the given object is a valid reference to a valid cell.  This
  98   test involves to determine whether the object is a cell pointer, whether
  99   this pointer actually points into a heap segment and whether the cell
 100   pointed to is not a free cell.  Further, additional garbage collections may
 101   get executed after a user defined number of cell accesses.  This helps to
 102   find places in the C code where references are dropped for extremely short
 103   periods.
 104
 105 */
 106 void
 107 scm_i_expensive_validation_check (SCM cell)
 108 {
 109   if (!scm_in_heap_p (cell))
 110     {
 111       fprintf (stderr, "scm_assert_cell_valid: this object does not live in the heap: %lux\n",
 112                (unsigned long) SCM_UNPACK (cell));
 113       abort ();
 114     }
 115
 116   /* If desired, perform additional garbage collections after a user
 117    * defined number of cell accesses.
 118    */
 119   if (scm_debug_cells_gc_interval)
 120     {
 121       static unsigned int counter = 0;
 122
 123       if (counter != 0)
 124         {
 125           --counter;
 126         }
 127       else
 128         {
 129           counter = scm_debug_cells_gc_interval;
 130           scm_gc ();
 131         }
 132     }
 133 }
 134
 135 void
 136 scm_assert_cell_valid (SCM cell)
 137 {
 138   if (!scm_i_cell_validation_already_running && scm_debug_cell_accesses_p)
 139     {
 140       scm_i_cell_validation_already_running = 1;  /* set to avoid recursion */
 141
 142       /*
 143         During GC, no user-code should be run, and the guile core
 144         should use non-protected accessors.
 145       */
 146       if (scm_gc_running_p)
 147         return;
 148
 149       /*
 150         Only scm_in_heap_p and rescanning the heap is wildly
 151         expensive.
 152       */
 153       if (scm_expensive_debug_cell_accesses_p)
 154         scm_i_expensive_validation_check (cell);
 155 #if (SCM_DEBUG_MARKING_API == 0)
 156       if (!SCM_GC_MARK_P (cell))
 157         {
 158           fprintf (stderr,
 159                    "scm_assert_cell_valid: this object is unmarked. \n"
 160                    "It has been garbage-collected in the last GC run: "
 161                    "%lux\n",
 162                    (unsigned long) SCM_UNPACK (cell));
 163           abort ();
 164         }
 165 #endif /* SCM_DEBUG_MARKING_API */
 166
 167       scm_i_cell_validation_already_running = 0;  /* re-enable */
 168     }
 169 }
 170
 171
 172
 173 SCM_DEFINE (scm_set_debug_cell_accesses_x, "set-debug-cell-accesses!", 1, 0, 0,
 174             (SCM flag),
 175             "If @var{flag} is @code{#f}, cell access checking is disabled.\n"
 176             "If @var{flag} is @code{#t}, cheap cell access checking is enabled,\n"
 177             "but no additional calls to garbage collection are issued.\n"
 178             "If @var{flag} is a number, strict cell access checking is enabled,\n"
 179             "with an additional garbage collection after the given\n"
 180             "number of cell accesses.\n"
 181             "This procedure only exists when the compile-time flag\n"
 182             "@code{SCM_DEBUG_CELL_ACCESSES} was set to 1.")
 183 #define FUNC_NAME s_scm_set_debug_cell_accesses_x
 184 {
 185   if (scm_is_false (flag))
 186     {
 187       scm_debug_cell_accesses_p = 0;
 188     }
 189   else if (scm_is_eq (flag, SCM_BOOL_T))
 190     {
 191       scm_debug_cells_gc_interval = 0;
 192       scm_debug_cell_accesses_p = 1;
 193       scm_expensive_debug_cell_accesses_p = 0;
 194     }
 195   else
 196     {
 197       scm_debug_cells_gc_interval = scm_to_signed_integer (flag, 0, INT_MAX);
 198       scm_debug_cell_accesses_p = 1;
 199       scm_expensive_debug_cell_accesses_p = 1;
 200     }
 201   return SCM_UNSPECIFIED;
 202 }
 203 #undef FUNC_NAME
 204
 205
 206 #endif  /* SCM_DEBUG_CELL_ACCESSES == 1 */
 207
 208 \f
 209 /* Hooks.  */
 210 scm_t_c_hook scm_before_gc_c_hook;
 211 scm_t_c_hook scm_before_mark_c_hook;
 212 scm_t_c_hook scm_before_sweep_c_hook;
 213 scm_t_c_hook scm_after_sweep_c_hook;
 214 scm_t_c_hook scm_after_gc_c_hook;
 215
 216
 217 /* scm_mtrigger
 218  * is the number of bytes of malloc allocation needed to trigger gc.
 219  */
 220 unsigned long scm_mtrigger;
 221
 222 /* GC Statistics Keeping
 223  */
 224 unsigned long scm_mallocated = 0;
 225 unsigned long scm_gc_ports_collected = 0;
 226
 227
 228 static unsigned long protected_obj_count = 0;
 229
 230
 231 SCM_SYMBOL (sym_cells_allocated, "cells-allocated");
 232 SCM_SYMBOL (sym_heap_size, "heap-size");
 233 SCM_SYMBOL (sym_heap_free_size, "heap-free-size");
 234 SCM_SYMBOL (sym_heap_total_allocated, "heap-total-allocated");
 235 SCM_SYMBOL (sym_mallocated, "bytes-malloced");
 236 SCM_SYMBOL (sym_mtrigger, "gc-malloc-threshold");
 237 SCM_SYMBOL (sym_heap_segments, "cell-heap-segments");
 238 SCM_SYMBOL (sym_gc_time_taken, "gc-time-taken");
 239 SCM_SYMBOL (sym_gc_mark_time_taken, "gc-mark-time-taken");
 240 SCM_SYMBOL (sym_times, "gc-times");
 241 SCM_SYMBOL (sym_cells_marked, "cells-marked");
 242 SCM_SYMBOL (sym_cells_marked_conservatively, "cells-marked-conservatively");
 243 SCM_SYMBOL (sym_cells_swept, "cells-swept");
 244 SCM_SYMBOL (sym_malloc_yield, "malloc-yield");
 245 SCM_SYMBOL (sym_cell_yield, "cell-yield");
 246 SCM_SYMBOL (sym_protected_objects, "protected-objects");
 247 SCM_SYMBOL (sym_total_cells_allocated, "total-cells-allocated");
 248
 249
 250 /* Number of calls to SCM_NEWCELL since startup.  */
 251 unsigned scm_newcell_count;
 252 unsigned scm_newcell2_count;
 253
 254
 255 /* {Scheme Interface to GC}
 256  */
 257 static SCM
 258 tag_table_to_type_alist (void *closure, SCM key, SCM val, SCM acc)
 259 {
 260   if (scm_is_integer (key))
 261     {
 262       int c_tag = scm_to_int (key);
 263
 264       char const * name = scm_i_tag_name (c_tag);
 265       if (name != NULL)
 266         {
 267           key = scm_from_locale_string (name);
 268         }
 269       else
 270         {
 271           char s[100];
 272           sprintf (s, "tag %d", c_tag);
 273           key = scm_from_locale_string (s);
 274         }
 275     }
 276
 277   return scm_cons (scm_cons (key, val), acc);
 278 }
 279
 280 SCM_DEFINE (scm_gc_live_object_stats, "gc-live-object-stats", 0, 0, 0,
 281             (),
 282             "Return an alist of statistics of the current live objects. ")
 283 #define FUNC_NAME s_scm_gc_live_object_stats
 284 {
 285   SCM tab = scm_make_hash_table (scm_from_int (57));
 286   SCM alist;
 287
 288   alist
 289     = scm_internal_hash_fold (&tag_table_to_type_alist, NULL, SCM_EOL, tab);
 290
 291   return alist;
 292 }
 293 #undef FUNC_NAME
 294
 295 extern int scm_gc_malloc_yield_percentage;
 296 SCM_DEFINE (scm_gc_stats, "gc-stats", 0, 0, 0,
 297             (),
 298             "Return an association list of statistics about Guile's current\n"
 299             "use of storage.\n")
 300 #define FUNC_NAME s_scm_gc_stats
 301 {
 302   SCM answer;
 303   size_t heap_size, free_bytes, bytes_since_gc, total_bytes;
 304   size_t gc_times;
 305
 306   heap_size      = GC_get_heap_size ();
 307   free_bytes     = GC_get_free_bytes ();
 308   bytes_since_gc = GC_get_bytes_since_gc ();
 309   total_bytes    = GC_get_total_bytes ();
 310   gc_times       = GC_gc_no;
 311
 312   /* njrev: can any of these scm_cons's or scm_list_n signal a memory
 313      error?  If so we need a frame here. */
 314   answer =
 315     scm_list_n (scm_cons (sym_gc_time_taken, SCM_INUM0),
 316 #if 0
 317                 scm_cons (sym_cells_allocated,
 318                           scm_from_ulong (local_scm_cells_allocated)),
 319                 scm_cons (sym_mallocated,
 320                           scm_from_ulong (local_scm_mallocated)),
 321                 scm_cons (sym_mtrigger,
 322                           scm_from_ulong (local_scm_mtrigger)),
 323                 scm_cons (sym_gc_mark_time_taken,
 324                           scm_from_ulong (local_scm_gc_mark_time_taken)),
 325                 scm_cons (sym_cells_marked,
 326                           scm_from_double (local_scm_gc_cells_marked)),
 327                 scm_cons (sym_cells_swept,
 328                           scm_from_double (local_scm_gc_cells_swept)),
 329                 scm_cons (sym_malloc_yield,
 330                           scm_from_long (local_scm_gc_malloc_yield_percentage)),
 331                 scm_cons (sym_cell_yield,
 332                           scm_from_long (local_scm_gc_cell_yield_percentage)),
 333                 scm_cons (sym_heap_segments, heap_segs),
 334 #endif
 335                 scm_cons (sym_heap_size, scm_from_size_t (heap_size)),
 336                 scm_cons (sym_heap_free_size, scm_from_size_t (free_bytes)),
 337                 scm_cons (sym_heap_total_allocated,
 338                           scm_from_size_t (total_bytes)),
 339                 scm_cons (sym_protected_objects,
 340                           scm_from_ulong (protected_obj_count)),
 341                 scm_cons (sym_times, scm_from_size_t (gc_times)),
 342                 SCM_UNDEFINED);
 343
 344   return answer;
 345 }
 346 #undef FUNC_NAME
 347
 348
 349 SCM_DEFINE (scm_gc_dump, "gc-dump", 0, 0, 0,
 350             (void),
 351             "Dump information about the garbage collector's internal data "
 352             "structures and memory usage to the standard output.")
 353 #define FUNC_NAME s_scm_gc_dump
 354 {
 355   GC_dump ();
 356
 357   return SCM_UNSPECIFIED;
 358 }
 359 #undef FUNC_NAME
 360
 361
 362 SCM_DEFINE (scm_object_address, "object-address", 1, 0, 0,
 363             (SCM obj),
 364             "Return an integer that for the lifetime of @var{obj} is uniquely\n"
 365             "returned by this function for @var{obj}")
 366 #define FUNC_NAME s_scm_object_address
 367 {
 368   return scm_from_ulong (SCM_UNPACK (obj));
 369 }
 370 #undef FUNC_NAME
 371
 372
 373 SCM_DEFINE (scm_gc_disable, "gc-disable", 0, 0, 0,
 374             (),
 375             "Disables the garbage collector.  Nested calls are permitted.  "
 376             "GC is re-enabled once @code{gc-enable} has been called the "
 377             "same number of times @code{gc-disable} was called.")
 378 #define FUNC_NAME s_scm_gc_disable
 379 {
 380   GC_disable ();
 381   return SCM_UNSPECIFIED;
 382 }
 383 #undef FUNC_NAME
 384
 385 SCM_DEFINE (scm_gc_enable, "gc-enable", 0, 0, 0,
 386             (),
 387             "Enables the garbage collector.")
 388 #define FUNC_NAME s_scm_gc_enable
 389 {
 390   GC_enable ();
 391   return SCM_UNSPECIFIED;
 392 }
 393 #undef FUNC_NAME
 394
 395
 396 SCM_DEFINE (scm_gc, "gc", 0, 0, 0,
 397            (),
 398             "Scans all of SCM objects and reclaims for further use those that are\n"
 399             "no longer accessible.")
 400 #define FUNC_NAME s_scm_gc
 401 {
 402   scm_i_scm_pthread_mutex_lock (&scm_i_sweep_mutex);
 403   scm_i_gc ("call");
 404   /* njrev: It looks as though other places, e.g. scm_realloc,
 405      can call scm_i_gc without acquiring the sweep mutex.  Does this
 406      matter?  Also scm_i_gc (or its descendants) touch the
 407      scm_sys_protects, which are protected in some cases
 408      (e.g. scm_permobjs above in scm_gc_stats) by a critical section,
 409      not by the sweep mutex.  Shouldn't all the GC-relevant objects be
 410      protected in the same way? */
 411   scm_i_pthread_mutex_unlock (&scm_i_sweep_mutex);
 412   scm_c_hook_run (&scm_after_gc_c_hook, 0);
 413   return SCM_UNSPECIFIED;
 414 }
 415 #undef FUNC_NAME
 416
 417 void
 418 scm_i_gc (const char *what)
 419 {
 420   GC_gcollect ();
 421 }
 422
 423
 424 \f
 425 /* {GC Protection Helper Functions}
 426  */
 427
 428
 429 /*
 430  * If within a function you need to protect one or more scheme objects from
 431  * garbage collection, pass them as parameters to one of the
 432  * scm_remember_upto_here* functions below.  These functions don't do
 433  * anything, but since the compiler does not know that they are actually
 434  * no-ops, it will generate code that calls these functions with the given
 435  * parameters.  Therefore, you can be sure that the compiler will keep those
 436  * scheme values alive (on the stack or in a register) up to the point where
 437  * scm_remember_upto_here* is called.  In other words, place the call to
 438  * scm_remember_upto_here* _behind_ the last code in your function, that
 439  * depends on the scheme object to exist.
 440  *
 441  * Example: We want to make sure that the string object str does not get
 442  * garbage collected during the execution of 'some_function' in the code
 443  * below, because otherwise the characters belonging to str would be freed and
 444  * 'some_function' might access freed memory.  To make sure that the compiler
 445  * keeps str alive on the stack or in a register such that it is visible to
 446  * the conservative gc we add the call to scm_remember_upto_here_1 _after_ the
 447  * call to 'some_function'.  Note that this would not be necessary if str was
 448  * used anyway after the call to 'some_function'.
 449  *   char *chars = scm_i_string_chars (str);
 450  *   some_function (chars);
 451  *   scm_remember_upto_here_1 (str);  // str will be alive up to this point.
 452  */
 453
 454 /* Remove any macro versions of these while defining the functions.
 455    Functions are always included in the library, for upward binary
 456    compatibility and in case combinations of GCC and non-GCC are used.  */
 457 #undef scm_remember_upto_here_1
 458 #undef scm_remember_upto_here_2
 459
 460 void
 461 scm_remember_upto_here_1 (SCM obj SCM_UNUSED)
 462 {
 463   /* Empty.  Protects a single object from garbage collection. */
 464 }
 465
 466 void
 467 scm_remember_upto_here_2 (SCM obj1 SCM_UNUSED, SCM obj2 SCM_UNUSED)
 468 {
 469   /* Empty.  Protects two objects from garbage collection. */
 470 }
 471
 472 void
 473 scm_remember_upto_here (SCM obj SCM_UNUSED, ...)
 474 {
 475   /* Empty.  Protects any number of objects from garbage collection. */
 476 }
 477
 478 /*
 479   These crazy functions prevent garbage collection
 480   of arguments after the first argument by
 481   ensuring they remain live throughout the
 482   function because they are used in the last
 483   line of the code block.
 484   It'd be better to have a nice compiler hint to
 485   aid the conservative stack-scanning GC. --03/09/00 gjb */
 486 SCM
 487 scm_return_first (SCM elt, ...)
 488 {
 489   return elt;
 490 }
 491
 492 int
 493 scm_return_first_int (int i, ...)
 494 {
 495   return i;
 496 }
 497
 498
 499 SCM
 500 scm_permanent_object (SCM obj)
 501 {
 502   return (scm_gc_protect_object (obj));
 503 }
 504
 505
 506 /* Protect OBJ from the garbage collector.  OBJ will not be freed, even if all
 507    other references are dropped, until the object is unprotected by calling
 508    scm_gc_unprotect_object (OBJ).  Calls to scm_gc_protect/unprotect_object nest,
 509    i. e. it is possible to protect the same object several times, but it is
 510    necessary to unprotect the object the same number of times to actually get
 511    the object unprotected.  It is an error to unprotect an object more often
 512    than it has been protected before.  The function scm_protect_object returns
 513    OBJ.
 514 */
 515
 516 /* Implementation note:  For every object X, there is a counter which
 517    scm_gc_protect_object (X) increments and scm_gc_unprotect_object (X) decrements.
 518 */
 519
 520
 521
 522 SCM
 523 scm_gc_protect_object (SCM obj)
 524 {
 525   SCM handle;
 526
 527   /* This critical section barrier will be replaced by a mutex. */
 528   /* njrev: Indeed; if my comment above is correct, there is the same
 529      critsec/mutex inconsistency here. */
 530   SCM_CRITICAL_SECTION_START;
 531
 532   handle = scm_hashq_create_handle_x (scm_protects, obj, scm_from_int (0));
 533   SCM_SETCDR (handle, scm_sum (SCM_CDR (handle), scm_from_int (1)));
 534
 535   protected_obj_count ++;
 536
 537   SCM_CRITICAL_SECTION_END;
 538
 539   return obj;
 540 }
 541
 542
 543 /* Remove any protection for OBJ established by a prior call to
 544    scm_protect_object.  This function returns OBJ.
 545
 546    See scm_protect_object for more information.  */
 547 SCM
 548 scm_gc_unprotect_object (SCM obj)
 549 {
 550   SCM handle;
 551
 552   /* This critical section barrier will be replaced by a mutex. */
 553   /* njrev: and again. */
 554   SCM_CRITICAL_SECTION_START;
 555
 556   if (scm_gc_running_p)
 557     {
 558       fprintf (stderr, "scm_unprotect_object called during GC.\n");
 559       abort ();
 560     }
 561
 562   handle = scm_hashq_get_handle (scm_protects, obj);
 563
 564   if (scm_is_false (handle))
 565     {
 566       fprintf (stderr, "scm_unprotect_object called on unprotected object\n");
 567       abort ();
 568     }
 569   else
 570     {
 571       SCM count = scm_difference (SCM_CDR (handle), scm_from_int (1));
 572       if (scm_is_eq (count, scm_from_int (0)))
 573         scm_hashq_remove_x (scm_protects, obj);
 574       else
 575         SCM_SETCDR (handle, count);
 576     }
 577   protected_obj_count --;
 578
 579   SCM_CRITICAL_SECTION_END;
 580
 581   return obj;
 582 }
 583
 584 void
 585 scm_gc_register_root (SCM *p)
 586 {
 587   /* Nothing.  */
 588 }
 589
 590 void
 591 scm_gc_unregister_root (SCM *p)
 592 {
 593   /* Nothing.  */
 594 }
 595
 596 void
 597 scm_gc_register_roots (SCM *b, unsigned long n)
 598 {
 599   SCM *p = b;
 600   for (; p < b + n; ++p)
 601     scm_gc_register_root (p);
 602 }
 603
 604 void
 605 scm_gc_unregister_roots (SCM *b, unsigned long n)
 606 {
 607   SCM *p = b;
 608   for (; p < b + n; ++p)
 609     scm_gc_unregister_root (p);
 610 }
 611
 612 int scm_i_terminating;
 613
 614 \f
 615
 616
 617 /*
 618   MOVE THIS FUNCTION. IT DOES NOT HAVE ANYTHING TODO WITH GC.
 619  */
 620
 621 /* Get an integer from an environment variable.  */
 622 int
 623 scm_getenv_int (const char *var, int def)
 624 {
 625   char *end = 0;
 626   char *val = getenv (var);
 627   long res = def;
 628   if (!val)
 629     return def;
 630   res = strtol (val, &end, 10);
 631   if (end == val)
 632     return def;
 633   return res;
 634 }
 635
 636 void
 637 scm_storage_prehistory ()
 638 {
 639   GC_all_interior_pointers = 0;
 640   GC_set_free_space_divisor (scm_getenv_int ("GC_FREE_SPACE_DIVISOR", 3));
 641
 642   GC_INIT ();
 643
 644 #if (! ((defined GC_VERSION_MAJOR) && (GC_VERSION_MAJOR >= 7))) \
 645     && (defined SCM_I_GSC_USE_PTHREAD_THREADS)
 646   /* When using GC 6.8, this call is required to initialize thread-local
 647      freelists (shouldn't be necessary with GC 7.0).  */
 648   GC_init ();
 649 #endif
 650
 651   GC_expand_hp (SCM_DEFAULT_INIT_HEAP_SIZE_2);
 652
 653   /* We only need to register a displacement for those types for which the
 654      higher bits of the type tag are used to store a pointer (that is, a
 655      pointer to an 8-octet aligned region).  For `scm_tc3_struct', this is
 656      handled in `scm_alloc_struct ()'.  */
 657   GC_REGISTER_DISPLACEMENT (scm_tc3_cons);
 658   GC_REGISTER_DISPLACEMENT (scm_tc3_closure);
 659
 660   /* Sanity check.  */
 661   if (!GC_is_visible (scm_sys_protects))
 662     abort ();
 663
 664   scm_c_hook_init (&scm_before_gc_c_hook, 0, SCM_C_HOOK_NORMAL);
 665   scm_c_hook_init (&scm_before_mark_c_hook, 0, SCM_C_HOOK_NORMAL);
 666   scm_c_hook_init (&scm_before_sweep_c_hook, 0, SCM_C_HOOK_NORMAL);
 667   scm_c_hook_init (&scm_after_sweep_c_hook, 0, SCM_C_HOOK_NORMAL);
 668   scm_c_hook_init (&scm_after_gc_c_hook, 0, SCM_C_HOOK_NORMAL);
 669 }
 670
 671 scm_i_pthread_mutex_t scm_i_gc_admin_mutex = SCM_I_PTHREAD_MUTEX_INITIALIZER;
 672
 673 int
 674 scm_init_storage ()
 675 {
 676   size_t j;
 677
 678   j = SCM_NUM_PROTECTS;
 679   while (j)
 680     scm_sys_protects[--j] = SCM_BOOL_F;
 681
 682   j = SCM_HEAP_SEG_SIZE;
 683
 684 #if 0
 685   /* We can't have a cleanup handler since we have no thread to run it
 686      in. */
 687
 688 #ifdef HAVE_ATEXIT
 689   atexit (cleanup);
 690 #else
 691 #ifdef HAVE_ON_EXIT
 692   on_exit (cleanup, 0);
 693 #endif
 694 #endif
 695
 696 #endif
 697
 698   scm_stand_in_procs = scm_make_weak_key_hash_table (scm_from_int (257));
 699   scm_protects = scm_c_make_hash_table (31);
 700
 701   return 0;
 702 }
 703
 704 \f
 705
 706 SCM scm_after_gc_hook;
 707
 708 static SCM gc_async;
 709
 710 /* The function gc_async_thunk causes the execution of the after-gc-hook.  It
 711  * is run after the gc, as soon as the asynchronous events are handled by the
 712  * evaluator.
 713  */
 714 static SCM
 715 gc_async_thunk (void)
 716 {
 717   scm_c_run_hook (scm_after_gc_hook, SCM_EOL);
 718   return SCM_UNSPECIFIED;
 719 }
 720
 721
 722 /* The function mark_gc_async is run by the scm_after_gc_c_hook at the end of
 723  * the garbage collection.  The only purpose of this function is to mark the
 724  * gc_async (which will eventually lead to the execution of the
 725  * gc_async_thunk).
 726  */
 727 static void *
 728 mark_gc_async (void * hook_data SCM_UNUSED,
 729                void *fn_data SCM_UNUSED,
 730                void *data SCM_UNUSED)
 731 {
 732   /* If cell access debugging is enabled, the user may choose to perform
 733    * additional garbage collections after an arbitrary number of cell
 734    * accesses.  We don't want the scheme level after-gc-hook to be performed
 735    * for each of these garbage collections for the following reason: The
 736    * execution of the after-gc-hook causes cell accesses itself.  Thus, if the
 737    * after-gc-hook was performed with every gc, and if the gc was performed
 738    * after a very small number of cell accesses, then the number of cell
 739    * accesses during the execution of the after-gc-hook will suffice to cause
 740    * the execution of the next gc.  Then, guile would keep executing the
 741    * after-gc-hook over and over again, and would never come to do other
 742    * things.
 743    *
 744    * To overcome this problem, if cell access debugging with additional
 745    * garbage collections is enabled, the after-gc-hook is never run by the
 746    * garbage collecter.  When running guile with cell access debugging and the
 747    * execution of the after-gc-hook is desired, then it is necessary to run
 748    * the hook explicitly from the user code.  This has the effect, that from
 749    * the scheme level point of view it seems that garbage collection is
 750    * performed with a much lower frequency than it actually is.  Obviously,
 751    * this will not work for code that depends on a fixed one to one
 752    * relationship between the execution counts of the C level garbage
 753    * collection hooks and the execution count of the scheme level
 754    * after-gc-hook.
 755    */
 756
 757 #if (SCM_DEBUG_CELL_ACCESSES == 1)
 758   if (scm_debug_cells_gc_interval == 0)
 759     scm_system_async_mark (gc_async);
 760 #else
 761   scm_system_async_mark (gc_async);
 762 #endif
 763
 764   return NULL;
 765 }
 766
 767 char const *
 768 scm_i_tag_name (scm_t_bits tag)
 769 {
 770   if (tag >= 255)
 771     {
 772       if (tag == scm_tc_free_cell)
 773         return "free cell";
 774
 775       {
 776         int k = 0xff & (tag >> 8);
 777         return (scm_smobs[k].name);
 778       }
 779     }
 780
 781   switch (tag) /* 7 bits */
 782     {
 783     case scm_tcs_struct:
 784       return "struct";
 785     case scm_tcs_cons_imcar:
 786       return "cons (immediate car)";
 787     case scm_tcs_cons_nimcar:
 788       return "cons (non-immediate car)";
 789     case scm_tcs_closures:
 790       return "closures";
 791     case scm_tc7_pws:
 792       return "pws";
 793     case scm_tc7_wvect:
 794       return "weak vector";
 795     case scm_tc7_vector:
 796       return "vector";
 797 #ifdef CCLO
 798     case scm_tc7_cclo:
 799       return "compiled closure";
 800 #endif
 801     case scm_tc7_number:
 802       switch (tag)
 803         {
 804         case scm_tc16_real:
 805           return "real";
 806           break;
 807         case scm_tc16_big:
 808           return "bignum";
 809           break;
 810         case scm_tc16_complex:
 811           return "complex number";
 812           break;
 813         case scm_tc16_fraction:
 814           return "fraction";
 815           break;
 816         }
 817       break;
 818     case scm_tc7_string:
 819       return "string";
 820       break;
 821     case scm_tc7_stringbuf:
 822       return "string buffer";
 823       break;
 824     case scm_tc7_symbol:
 825       return "symbol";
 826       break;
 827     case scm_tc7_variable:
 828       return "variable";
 829       break;
 830     case scm_tcs_subrs:
 831       return "subrs";
 832       break;
 833     case scm_tc7_port:
 834       return "port";
 835       break;
 836     case scm_tc7_smob:
 837       return "smob";            /* should not occur. */
 838       break;
 839     }
 840
 841   return NULL;
 842 }
 843
 844
 845
 846 \f
 847 void
 848 scm_init_gc ()
 849 {
 850   /* `GC_INIT ()' was invoked in `scm_storage_prehistory ()'.  */
 851
 852   scm_after_gc_hook = scm_permanent_object (scm_make_hook (SCM_INUM0));
 853   scm_c_define ("after-gc-hook", scm_after_gc_hook);
 854
 855   gc_async = scm_c_make_subr ("%gc-thunk", scm_tc7_subr_0,
 856                               gc_async_thunk);
 857
 858   scm_c_hook_add (&scm_after_gc_c_hook, mark_gc_async, NULL, 0);
 859
 860 #include "libguile/gc.x"
 861 }
 862
 863
 864 void
 865 scm_gc_sweep (void)
 866 #define FUNC_NAME "scm_gc_sweep"
 867 {
 868   /* FIXME */
 869   fprintf (stderr, "%s: doing nothing\n", __FUNCTION__);
 870 }
 871
 872 #undef FUNC_NAME
 873
 874
 875
 876 /*
 877   Local Variables:
 878   c-file-style: "gnu"
 879   End:
 880 */