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
 350 SCM_DEFINE (scm_object_address, "object-address", 1, 0, 0,
 351             (SCM obj),
 352             "Return an integer that for the lifetime of @var{obj} is uniquely\n"
 353             "returned by this function for @var{obj}")
 354 #define FUNC_NAME s_scm_object_address
 355 {
 356   return scm_from_ulong (SCM_UNPACK (obj));
 357 }
 358 #undef FUNC_NAME
 359
 360
 361 SCM_DEFINE (scm_gc_disable, "gc-disable", 0, 0, 0,
 362             (),
 363             "Disables the garbage collector.  Nested calls are permitted.  "
 364             "GC is re-enabled once @code{gc-enable} has been called the "
 365             "same number of times @code{gc-disable} was called.")
 366 #define FUNC_NAME s_scm_gc_disable
 367 {
 368   GC_disable ();
 369   return SCM_UNSPECIFIED;
 370 }
 371 #undef FUNC_NAME
 372
 373 SCM_DEFINE (scm_gc_enable, "gc-enable", 0, 0, 0,
 374             (),
 375             "Enables the garbage collector.")
 376 #define FUNC_NAME s_scm_gc_enable
 377 {
 378   GC_enable ();
 379   return SCM_UNSPECIFIED;
 380 }
 381 #undef FUNC_NAME
 382
 383
 384 SCM_DEFINE (scm_gc, "gc", 0, 0, 0,
 385            (),
 386             "Scans all of SCM objects and reclaims for further use those that are\n"
 387             "no longer accessible.")
 388 #define FUNC_NAME s_scm_gc
 389 {
 390   scm_i_scm_pthread_mutex_lock (&scm_i_sweep_mutex);
 391   scm_i_gc ("call");
 392   /* njrev: It looks as though other places, e.g. scm_realloc,
 393      can call scm_i_gc without acquiring the sweep mutex.  Does this
 394      matter?  Also scm_i_gc (or its descendants) touch the
 395      scm_sys_protects, which are protected in some cases
 396      (e.g. scm_permobjs above in scm_gc_stats) by a critical section,
 397      not by the sweep mutex.  Shouldn't all the GC-relevant objects be
 398      protected in the same way? */
 399   scm_i_pthread_mutex_unlock (&scm_i_sweep_mutex);
 400   scm_c_hook_run (&scm_after_gc_c_hook, 0);
 401   return SCM_UNSPECIFIED;
 402 }
 403 #undef FUNC_NAME
 404
 405 void
 406 scm_i_gc (const char *what)
 407 {
 408   GC_gcollect ();
 409 }
 410
 411
 412 \f
 413 /* {GC Protection Helper Functions}
 414  */
 415
 416
 417 /*
 418  * If within a function you need to protect one or more scheme objects from
 419  * garbage collection, pass them as parameters to one of the
 420  * scm_remember_upto_here* functions below.  These functions don't do
 421  * anything, but since the compiler does not know that they are actually
 422  * no-ops, it will generate code that calls these functions with the given
 423  * parameters.  Therefore, you can be sure that the compiler will keep those
 424  * scheme values alive (on the stack or in a register) up to the point where
 425  * scm_remember_upto_here* is called.  In other words, place the call to
 426  * scm_remember_upto_here* _behind_ the last code in your function, that
 427  * depends on the scheme object to exist.
 428  *
 429  * Example: We want to make sure that the string object str does not get
 430  * garbage collected during the execution of 'some_function' in the code
 431  * below, because otherwise the characters belonging to str would be freed and
 432  * 'some_function' might access freed memory.  To make sure that the compiler
 433  * keeps str alive on the stack or in a register such that it is visible to
 434  * the conservative gc we add the call to scm_remember_upto_here_1 _after_ the
 435  * call to 'some_function'.  Note that this would not be necessary if str was
 436  * used anyway after the call to 'some_function'.
 437  *   char *chars = scm_i_string_chars (str);
 438  *   some_function (chars);
 439  *   scm_remember_upto_here_1 (str);  // str will be alive up to this point.
 440  */
 441
 442 /* Remove any macro versions of these while defining the functions.
 443    Functions are always included in the library, for upward binary
 444    compatibility and in case combinations of GCC and non-GCC are used.  */
 445 #undef scm_remember_upto_here_1
 446 #undef scm_remember_upto_here_2
 447
 448 void
 449 scm_remember_upto_here_1 (SCM obj SCM_UNUSED)
 450 {
 451   /* Empty.  Protects a single object from garbage collection. */
 452 }
 453
 454 void
 455 scm_remember_upto_here_2 (SCM obj1 SCM_UNUSED, SCM obj2 SCM_UNUSED)
 456 {
 457   /* Empty.  Protects two objects from garbage collection. */
 458 }
 459
 460 void
 461 scm_remember_upto_here (SCM obj SCM_UNUSED, ...)
 462 {
 463   /* Empty.  Protects any number of objects from garbage collection. */
 464 }
 465
 466 /*
 467   These crazy functions prevent garbage collection
 468   of arguments after the first argument by
 469   ensuring they remain live throughout the
 470   function because they are used in the last
 471   line of the code block.
 472   It'd be better to have a nice compiler hint to
 473   aid the conservative stack-scanning GC. --03/09/00 gjb */
 474 SCM
 475 scm_return_first (SCM elt, ...)
 476 {
 477   return elt;
 478 }
 479
 480 int
 481 scm_return_first_int (int i, ...)
 482 {
 483   return i;
 484 }
 485
 486
 487 SCM
 488 scm_permanent_object (SCM obj)
 489 {
 490   return (scm_gc_protect_object (obj));
 491 }
 492
 493
 494 /* Protect OBJ from the garbage collector.  OBJ will not be freed, even if all
 495    other references are dropped, until the object is unprotected by calling
 496    scm_gc_unprotect_object (OBJ).  Calls to scm_gc_protect/unprotect_object nest,
 497    i. e. it is possible to protect the same object several times, but it is
 498    necessary to unprotect the object the same number of times to actually get
 499    the object unprotected.  It is an error to unprotect an object more often
 500    than it has been protected before.  The function scm_protect_object returns
 501    OBJ.
 502 */
 503
 504 /* Implementation note:  For every object X, there is a counter which
 505    scm_gc_protect_object (X) increments and scm_gc_unprotect_object (X) decrements.
 506 */
 507
 508
 509
 510 SCM
 511 scm_gc_protect_object (SCM obj)
 512 {
 513   SCM handle;
 514
 515   /* This critical section barrier will be replaced by a mutex. */
 516   /* njrev: Indeed; if my comment above is correct, there is the same
 517      critsec/mutex inconsistency here. */
 518   SCM_CRITICAL_SECTION_START;
 519
 520   handle = scm_hashq_create_handle_x (scm_protects, obj, scm_from_int (0));
 521   SCM_SETCDR (handle, scm_sum (SCM_CDR (handle), scm_from_int (1)));
 522
 523   protected_obj_count ++;
 524
 525   SCM_CRITICAL_SECTION_END;
 526
 527   return obj;
 528 }
 529
 530
 531 /* Remove any protection for OBJ established by a prior call to
 532    scm_protect_object.  This function returns OBJ.
 533
 534    See scm_protect_object for more information.  */
 535 SCM
 536 scm_gc_unprotect_object (SCM obj)
 537 {
 538   SCM handle;
 539
 540   /* This critical section barrier will be replaced by a mutex. */
 541   /* njrev: and again. */
 542   SCM_CRITICAL_SECTION_START;
 543
 544   if (scm_gc_running_p)
 545     {
 546       fprintf (stderr, "scm_unprotect_object called during GC.\n");
 547       abort ();
 548     }
 549
 550   handle = scm_hashq_get_handle (scm_protects, obj);
 551
 552   if (scm_is_false (handle))
 553     {
 554       fprintf (stderr, "scm_unprotect_object called on unprotected object\n");
 555       abort ();
 556     }
 557   else
 558     {
 559       SCM count = scm_difference (SCM_CDR (handle), scm_from_int (1));
 560       if (scm_is_eq (count, scm_from_int (0)))
 561         scm_hashq_remove_x (scm_protects, obj);
 562       else
 563         SCM_SETCDR (handle, count);
 564     }
 565   protected_obj_count --;
 566
 567   SCM_CRITICAL_SECTION_END;
 568
 569   return obj;
 570 }
 571
 572 void
 573 scm_gc_register_root (SCM *p)
 574 {
 575   /* Nothing.  */
 576 }
 577
 578 void
 579 scm_gc_unregister_root (SCM *p)
 580 {
 581   /* Nothing.  */
 582 }
 583
 584 void
 585 scm_gc_register_roots (SCM *b, unsigned long n)
 586 {
 587   SCM *p = b;
 588   for (; p < b + n; ++p)
 589     scm_gc_register_root (p);
 590 }
 591
 592 void
 593 scm_gc_unregister_roots (SCM *b, unsigned long n)
 594 {
 595   SCM *p = b;
 596   for (; p < b + n; ++p)
 597     scm_gc_unregister_root (p);
 598 }
 599
 600 int scm_i_terminating;
 601
 602 \f
 603
 604
 605 /*
 606   MOVE THIS FUNCTION. IT DOES NOT HAVE ANYTHING TODO WITH GC.
 607  */
 608
 609 /* Get an integer from an environment variable.  */
 610 int
 611 scm_getenv_int (const char *var, int def)
 612 {
 613   char *end = 0;
 614   char *val = getenv (var);
 615   long res = def;
 616   if (!val)
 617     return def;
 618   res = strtol (val, &end, 10);
 619   if (end == val)
 620     return def;
 621   return res;
 622 }
 623
 624 void
 625 scm_storage_prehistory ()
 626 {
 627   GC_all_interior_pointers = 0;
 628   GC_set_free_space_divisor (scm_getenv_int ("GC_FREE_SPACE_DIVISOR", 3));
 629
 630   GC_INIT ();
 631
 632 #if (! ((defined GC_VERSION_MAJOR) && (GC_VERSION_MAJOR >= 7))) \
 633     && (defined SCM_I_GSC_USE_PTHREAD_THREADS)
 634   /* When using GC 6.8, this call is required to initialize thread-local
 635      freelists (shouldn't be necessary with GC 7.0).  */
 636   GC_init ();
 637 #endif
 638
 639   GC_expand_hp (SCM_DEFAULT_INIT_HEAP_SIZE_2);
 640
 641   /* We only need to register a displacement for those types for which the
 642      higher bits of the type tag are used to store a pointer (that is, a
 643      pointer to an 8-octet aligned region).  For `scm_tc3_struct', this is
 644      handled in `scm_alloc_struct ()'.  */
 645   GC_REGISTER_DISPLACEMENT (scm_tc3_cons);
 646   GC_REGISTER_DISPLACEMENT (scm_tc3_closure);
 647
 648   /* Sanity check.  */
 649   if (!GC_is_visible (scm_sys_protects))
 650     abort ();
 651
 652   scm_c_hook_init (&scm_before_gc_c_hook, 0, SCM_C_HOOK_NORMAL);
 653   scm_c_hook_init (&scm_before_mark_c_hook, 0, SCM_C_HOOK_NORMAL);
 654   scm_c_hook_init (&scm_before_sweep_c_hook, 0, SCM_C_HOOK_NORMAL);
 655   scm_c_hook_init (&scm_after_sweep_c_hook, 0, SCM_C_HOOK_NORMAL);
 656   scm_c_hook_init (&scm_after_gc_c_hook, 0, SCM_C_HOOK_NORMAL);
 657 }
 658
 659 scm_i_pthread_mutex_t scm_i_gc_admin_mutex = SCM_I_PTHREAD_MUTEX_INITIALIZER;
 660
 661 int
 662 scm_init_storage ()
 663 {
 664   size_t j;
 665
 666   j = SCM_NUM_PROTECTS;
 667   while (j)
 668     scm_sys_protects[--j] = SCM_BOOL_F;
 669
 670   j = SCM_HEAP_SEG_SIZE;
 671
 672 #if 0
 673   /* We can't have a cleanup handler since we have no thread to run it
 674      in. */
 675
 676 #ifdef HAVE_ATEXIT
 677   atexit (cleanup);
 678 #else
 679 #ifdef HAVE_ON_EXIT
 680   on_exit (cleanup, 0);
 681 #endif
 682 #endif
 683
 684 #endif
 685
 686   scm_stand_in_procs = scm_make_weak_key_hash_table (scm_from_int (257));
 687   scm_protects = scm_c_make_hash_table (31);
 688
 689   return 0;
 690 }
 691
 692 \f
 693
 694 SCM scm_after_gc_hook;
 695
 696 static SCM gc_async;
 697
 698 /* The function gc_async_thunk causes the execution of the after-gc-hook.  It
 699  * is run after the gc, as soon as the asynchronous events are handled by the
 700  * evaluator.
 701  */
 702 static SCM
 703 gc_async_thunk (void)
 704 {
 705   scm_c_run_hook (scm_after_gc_hook, SCM_EOL);
 706   return SCM_UNSPECIFIED;
 707 }
 708
 709
 710 /* The function mark_gc_async is run by the scm_after_gc_c_hook at the end of
 711  * the garbage collection.  The only purpose of this function is to mark the
 712  * gc_async (which will eventually lead to the execution of the
 713  * gc_async_thunk).
 714  */
 715 static void *
 716 mark_gc_async (void * hook_data SCM_UNUSED,
 717                void *fn_data SCM_UNUSED,
 718                void *data SCM_UNUSED)
 719 {
 720   /* If cell access debugging is enabled, the user may choose to perform
 721    * additional garbage collections after an arbitrary number of cell
 722    * accesses.  We don't want the scheme level after-gc-hook to be performed
 723    * for each of these garbage collections for the following reason: The
 724    * execution of the after-gc-hook causes cell accesses itself.  Thus, if the
 725    * after-gc-hook was performed with every gc, and if the gc was performed
 726    * after a very small number of cell accesses, then the number of cell
 727    * accesses during the execution of the after-gc-hook will suffice to cause
 728    * the execution of the next gc.  Then, guile would keep executing the
 729    * after-gc-hook over and over again, and would never come to do other
 730    * things.
 731    *
 732    * To overcome this problem, if cell access debugging with additional
 733    * garbage collections is enabled, the after-gc-hook is never run by the
 734    * garbage collecter.  When running guile with cell access debugging and the
 735    * execution of the after-gc-hook is desired, then it is necessary to run
 736    * the hook explicitly from the user code.  This has the effect, that from
 737    * the scheme level point of view it seems that garbage collection is
 738    * performed with a much lower frequency than it actually is.  Obviously,
 739    * this will not work for code that depends on a fixed one to one
 740    * relationship between the execution counts of the C level garbage
 741    * collection hooks and the execution count of the scheme level
 742    * after-gc-hook.
 743    */
 744
 745 #if (SCM_DEBUG_CELL_ACCESSES == 1)
 746   if (scm_debug_cells_gc_interval == 0)
 747     scm_system_async_mark (gc_async);
 748 #else
 749   scm_system_async_mark (gc_async);
 750 #endif
 751
 752   return NULL;
 753 }
 754
 755 char const *
 756 scm_i_tag_name (scm_t_bits tag)
 757 {
 758   if (tag >= 255)
 759     {
 760       if (tag == scm_tc_free_cell)
 761         return "free cell";
 762
 763       {
 764         int k = 0xff & (tag >> 8);
 765         return (scm_smobs[k].name);
 766       }
 767     }
 768
 769   switch (tag) /* 7 bits */
 770     {
 771     case scm_tcs_struct:
 772       return "struct";
 773     case scm_tcs_cons_imcar:
 774       return "cons (immediate car)";
 775     case scm_tcs_cons_nimcar:
 776       return "cons (non-immediate car)";
 777     case scm_tcs_closures:
 778       return "closures";
 779     case scm_tc7_pws:
 780       return "pws";
 781     case scm_tc7_wvect:
 782       return "weak vector";
 783     case scm_tc7_vector:
 784       return "vector";
 785 #ifdef CCLO
 786     case scm_tc7_cclo:
 787       return "compiled closure";
 788 #endif
 789     case scm_tc7_number:
 790       switch (tag)
 791         {
 792         case scm_tc16_real:
 793           return "real";
 794           break;
 795         case scm_tc16_big:
 796           return "bignum";
 797           break;
 798         case scm_tc16_complex:
 799           return "complex number";
 800           break;
 801         case scm_tc16_fraction:
 802           return "fraction";
 803           break;
 804         }
 805       break;
 806     case scm_tc7_string:
 807       return "string";
 808       break;
 809     case scm_tc7_stringbuf:
 810       return "string buffer";
 811       break;
 812     case scm_tc7_symbol:
 813       return "symbol";
 814       break;
 815     case scm_tc7_variable:
 816       return "variable";
 817       break;
 818     case scm_tcs_subrs:
 819       return "subrs";
 820       break;
 821     case scm_tc7_port:
 822       return "port";
 823       break;
 824     case scm_tc7_smob:
 825       return "smob";            /* should not occur. */
 826       break;
 827     }
 828
 829   return NULL;
 830 }
 831
 832
 833
 834 \f
 835 void
 836 scm_init_gc ()
 837 {
 838   /* `GC_INIT ()' was invoked in `scm_storage_prehistory ()'.  */
 839
 840   scm_after_gc_hook = scm_permanent_object (scm_make_hook (SCM_INUM0));
 841   scm_c_define ("after-gc-hook", scm_after_gc_hook);
 842
 843   gc_async = scm_c_make_subr ("%gc-thunk", scm_tc7_subr_0,
 844                               gc_async_thunk);
 845
 846   scm_c_hook_add (&scm_after_gc_c_hook, mark_gc_async, NULL, 0);
 847
 848 #include "libguile/gc.x"
 849 }
 850
 851
 852 void
 853 scm_gc_sweep (void)
 854 #define FUNC_NAME "scm_gc_sweep"
 855 {
 856   /* FIXME */
 857   fprintf (stderr, "%s: doing nothing\n", __FUNCTION__);
 858 }
 859
 860 #undef FUNC_NAME
 861
 862
 863
 864 /*
 865   Local Variables:
 866   c-file-style: "gnu"
 867   End:
 868 */