libguile/gc.c

   1 /* Copyright (C) 1995,1996,1997,1998,1999,2000,2001, 2002, 2003, 2006 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 _GNU_SOURCE
  19
  20 /* #define DEBUGINFO */
  21
  22 #if HAVE_CONFIG_H
  23 #  include <config.h>
  24 #endif
  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 <gc/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
 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
 166       scm_i_cell_validation_already_running = 0;  /* re-enable */
 167     }
 168 }
 169
 170
 171
 172 SCM_DEFINE (scm_set_debug_cell_accesses_x, "set-debug-cell-accesses!", 1, 0, 0,
 173             (SCM flag),
 174             "If @var{flag} is @code{#f}, cell access checking is disabled.\n"
 175             "If @var{flag} is @code{#t}, cheap cell access checking is enabled,\n"
 176             "but no additional calls to garbage collection are issued.\n"
 177             "If @var{flag} is a number, strict cell access checking is enabled,\n"
 178             "with an additional garbage collection after the given\n"
 179             "number of cell accesses.\n"
 180             "This procedure only exists when the compile-time flag\n"
 181             "@code{SCM_DEBUG_CELL_ACCESSES} was set to 1.")
 182 #define FUNC_NAME s_scm_set_debug_cell_accesses_x
 183 {
 184   if (scm_is_false (flag))
 185     {
 186       scm_debug_cell_accesses_p = 0;
 187     }
 188   else if (scm_is_eq (flag, SCM_BOOL_T))
 189     {
 190       scm_debug_cells_gc_interval = 0;
 191       scm_debug_cell_accesses_p = 1;
 192       scm_expensive_debug_cell_accesses_p = 0;
 193     }
 194   else
 195     {
 196       scm_debug_cells_gc_interval = scm_to_signed_integer (flag, 0, INT_MAX);
 197       scm_debug_cell_accesses_p = 1;
 198       scm_expensive_debug_cell_accesses_p = 1;
 199     }
 200   return SCM_UNSPECIFIED;
 201 }
 202 #undef FUNC_NAME
 203
 204
 205 #endif  /* SCM_DEBUG_CELL_ACCESSES == 1 */
 206
 207 \f
 208 /* Hooks.  */
 209 scm_t_c_hook scm_before_gc_c_hook;
 210 scm_t_c_hook scm_before_mark_c_hook;
 211 scm_t_c_hook scm_before_sweep_c_hook;
 212 scm_t_c_hook scm_after_sweep_c_hook;
 213 scm_t_c_hook scm_after_gc_c_hook;
 214
 215
 216 /* scm_mtrigger
 217  * is the number of bytes of malloc allocation needed to trigger gc.
 218  */
 219 unsigned long scm_mtrigger;
 220
 221 /* GC Statistics Keeping
 222  */
 223 unsigned long scm_cells_allocated = 0;
 224 unsigned long scm_mallocated = 0;
 225 unsigned long scm_gc_cells_collected;
 226 unsigned long scm_gc_cells_collected_1 = 0; /* previous GC yield */
 227 unsigned long scm_gc_malloc_collected;
 228 unsigned long scm_gc_ports_collected;
 229 unsigned long scm_gc_time_taken = 0;
 230 static unsigned long t_before_gc;
 231 unsigned long scm_gc_mark_time_taken = 0;
 232 unsigned long scm_gc_times = 0;
 233 unsigned long scm_gc_cells_swept = 0;
 234 double scm_gc_cells_marked_acc = 0.;
 235 double scm_gc_cells_swept_acc = 0.;
 236 int scm_gc_cell_yield_percentage =0;
 237 int scm_gc_malloc_yield_percentage = 0;
 238 unsigned long protected_obj_count = 0;
 239
 240
 241 SCM_SYMBOL (sym_cells_allocated, "cells-allocated");
 242 SCM_SYMBOL (sym_heap_size, "cell-heap-size");
 243 SCM_SYMBOL (sym_mallocated, "bytes-malloced");
 244 SCM_SYMBOL (sym_mtrigger, "gc-malloc-threshold");
 245 SCM_SYMBOL (sym_heap_segments, "cell-heap-segments");
 246 SCM_SYMBOL (sym_gc_time_taken, "gc-time-taken");
 247 SCM_SYMBOL (sym_gc_mark_time_taken, "gc-mark-time-taken");
 248 SCM_SYMBOL (sym_times, "gc-times");
 249 SCM_SYMBOL (sym_cells_marked, "cells-marked");
 250 SCM_SYMBOL (sym_cells_swept, "cells-swept");
 251 SCM_SYMBOL (sym_malloc_yield, "malloc-yield");
 252 SCM_SYMBOL (sym_cell_yield, "cell-yield");
 253 SCM_SYMBOL (sym_protected_objects, "protected-objects");
 254
 255
 256
 257
 258 /* Number of calls to SCM_NEWCELL since startup.  */
 259 unsigned scm_newcell_count;
 260 unsigned scm_newcell2_count;
 261
 262
 263 /* {Scheme Interface to GC}
 264  */
 265 static SCM
 266 tag_table_to_type_alist (void *closure, SCM key, SCM val, SCM acc)
 267 {
 268   if (scm_is_integer (key))
 269     {
 270       int c_tag = scm_to_int (key);
 271
 272       char const * name = scm_i_tag_name (c_tag);
 273       if (name != NULL)
 274         {
 275           key = scm_from_locale_string (name);
 276         }
 277       else
 278         {
 279           char s[100];
 280           sprintf (s, "tag %d", c_tag);
 281           key = scm_from_locale_string (s);
 282         }
 283     }
 284
 285   return scm_cons (scm_cons (key, val), acc);
 286 }
 287
 288 SCM_DEFINE (scm_gc_live_object_stats, "gc-live-object-stats", 0, 0, 0,
 289             (),
 290             "Return an alist of statistics of the current live objects. ")
 291 #define FUNC_NAME s_scm_gc_live_object_stats
 292 {
 293   SCM tab = scm_make_hash_table (scm_from_int (57));
 294   SCM alist;
 295
 296   alist
 297     = scm_internal_hash_fold (&tag_table_to_type_alist, NULL, SCM_EOL, tab);
 298
 299   return alist;
 300 }
 301 #undef FUNC_NAME
 302
 303 extern int scm_gc_malloc_yield_percentage;
 304 SCM_DEFINE (scm_gc_stats, "gc-stats", 0, 0, 0,
 305             (),
 306             "Return an association list of statistics about Guile's current\n"
 307             "use of storage.\n")
 308 #define FUNC_NAME s_scm_gc_stats
 309 {
 310   long i = 0;
 311   SCM heap_segs = SCM_EOL ;
 312   unsigned long int local_scm_mtrigger;
 313   unsigned long int local_scm_mallocated;
 314   unsigned long int local_scm_heap_size;
 315   int local_scm_gc_cell_yield_percentage;
 316   int local_scm_gc_malloc_yield_percentage;
 317   unsigned long int local_scm_cells_allocated;
 318   unsigned long int local_scm_gc_time_taken;
 319   unsigned long int local_scm_gc_times;
 320   unsigned long int local_scm_gc_mark_time_taken;
 321   unsigned long int local_protected_obj_count;
 322   double local_scm_gc_cells_swept;
 323   double local_scm_gc_cells_marked;
 324   SCM answer;
 325   unsigned long *bounds = 0;
 326   SCM_CRITICAL_SECTION_START;
 327
 328   /*
 329     temporarily store the numbers, so as not to cause GC.
 330    */
 331 #if 0
 332   bounds = malloc (sizeof (unsigned long)  * table_size * 2);
 333   if (!bounds)
 334     abort();
 335 #endif
 336
 337   /* Below, we cons to produce the resulting list.  We want a snapshot of
 338    * the heap situation before consing.
 339    */
 340   local_scm_mtrigger = scm_mtrigger;
 341   local_scm_mallocated = scm_mallocated;
 342   local_scm_heap_size = GC_get_heap_size ();
 343
 344   local_scm_cells_allocated = scm_cells_allocated;
 345
 346   local_scm_gc_time_taken = scm_gc_time_taken;
 347   local_scm_gc_mark_time_taken = scm_gc_mark_time_taken;
 348   local_scm_gc_times = scm_gc_times;
 349   local_scm_gc_malloc_yield_percentage = scm_gc_malloc_yield_percentage;
 350   local_scm_gc_cell_yield_percentage=  scm_gc_cell_yield_percentage;
 351   local_protected_obj_count = protected_obj_count;
 352   local_scm_gc_cells_swept =
 353     (double) scm_gc_cells_swept_acc
 354     + (double) scm_gc_cells_swept;
 355   local_scm_gc_cells_marked = scm_gc_cells_marked_acc
 356     +(double) scm_gc_cells_swept
 357     -(double) scm_gc_cells_collected;
 358
 359 #if 0
 360   for (i = table_size; i--;)
 361     {
 362       heap_segs = scm_cons (scm_cons (scm_from_ulong (bounds[2*i]),
 363                                       scm_from_ulong (bounds[2*i+1])),
 364                             heap_segs);
 365     }
 366 #else
 367   heap_segs = scm_list (SCM_INUM0); /* FIXME */
 368 #endif
 369
 370   /* njrev: can any of these scm_cons's or scm_list_n signal a memory
 371      error?  If so we need a frame here. */
 372   answer =
 373     scm_list_n (scm_cons (sym_gc_time_taken,
 374                           scm_from_ulong (local_scm_gc_time_taken)),
 375                 scm_cons (sym_cells_allocated,
 376                           scm_from_ulong (local_scm_cells_allocated)),
 377                 scm_cons (sym_heap_size,
 378                           scm_from_ulong (local_scm_heap_size)),
 379                 scm_cons (sym_mallocated,
 380                           scm_from_ulong (local_scm_mallocated)),
 381                 scm_cons (sym_mtrigger,
 382                           scm_from_ulong (local_scm_mtrigger)),
 383                 scm_cons (sym_times,
 384                           scm_from_ulong (local_scm_gc_times)),
 385                 scm_cons (sym_gc_mark_time_taken,
 386                           scm_from_ulong (local_scm_gc_mark_time_taken)),
 387                 scm_cons (sym_cells_marked,
 388                           scm_from_double (local_scm_gc_cells_marked)),
 389                 scm_cons (sym_cells_swept,
 390                           scm_from_double (local_scm_gc_cells_swept)),
 391                 scm_cons (sym_malloc_yield,
 392                           scm_from_long(local_scm_gc_malloc_yield_percentage)),
 393                 scm_cons (sym_cell_yield,
 394                           scm_from_long (local_scm_gc_cell_yield_percentage)),
 395                 scm_cons (sym_protected_objects,
 396                           scm_from_ulong (local_protected_obj_count)),
 397                 scm_cons (sym_heap_segments, heap_segs),
 398                 SCM_UNDEFINED);
 399   SCM_CRITICAL_SECTION_END;
 400
 401 /*   free (bounds); */
 402   return answer;
 403 }
 404 #undef FUNC_NAME
 405
 406
 407
 408
 409 SCM_DEFINE (scm_object_address, "object-address", 1, 0, 0,
 410             (SCM obj),
 411             "Return an integer that for the lifetime of @var{obj} is uniquely\n"
 412             "returned by this function for @var{obj}")
 413 #define FUNC_NAME s_scm_object_address
 414 {
 415   return scm_from_ulong (SCM_UNPACK (obj));
 416 }
 417 #undef FUNC_NAME
 418
 419
 420 SCM_DEFINE (scm_gc, "gc", 0, 0, 0,
 421            (),
 422             "Scans all of SCM objects and reclaims for further use those that are\n"
 423             "no longer accessible.")
 424 #define FUNC_NAME s_scm_gc
 425 {
 426   scm_i_scm_pthread_mutex_lock (&scm_i_sweep_mutex);
 427   scm_gc_running_p = 1;
 428   scm_i_gc ("call");
 429   /* njrev: It looks as though other places, e.g. scm_realloc,
 430      can call scm_i_gc without acquiring the sweep mutex.  Does this
 431      matter?  Also scm_i_gc (or its descendants) touch the
 432      scm_sys_protects, which are protected in some cases
 433      (e.g. scm_permobjs above in scm_gc_stats) by a critical section,
 434      not by the sweep mutex.  Shouldn't all the GC-relevant objects be
 435      protected in the same way? */
 436   scm_gc_running_p = 0;
 437   scm_i_pthread_mutex_unlock (&scm_i_sweep_mutex);
 438   scm_c_hook_run (&scm_after_gc_c_hook, 0);
 439   return SCM_UNSPECIFIED;
 440 }
 441 #undef FUNC_NAME
 442
 443 void
 444 scm_i_gc (const char *what)
 445 {
 446   GC_gcollect ();
 447 }
 448
 449
 450 \f
 451 /* {GC Protection Helper Functions}
 452  */
 453
 454
 455 /*
 456  * If within a function you need to protect one or more scheme objects from
 457  * garbage collection, pass them as parameters to one of the
 458  * scm_remember_upto_here* functions below.  These functions don't do
 459  * anything, but since the compiler does not know that they are actually
 460  * no-ops, it will generate code that calls these functions with the given
 461  * parameters.  Therefore, you can be sure that the compiler will keep those
 462  * scheme values alive (on the stack or in a register) up to the point where
 463  * scm_remember_upto_here* is called.  In other words, place the call to
 464  * scm_remember_upto_here* _behind_ the last code in your function, that
 465  * depends on the scheme object to exist.
 466  *
 467  * Example: We want to make sure that the string object str does not get
 468  * garbage collected during the execution of 'some_function' in the code
 469  * below, because otherwise the characters belonging to str would be freed and
 470  * 'some_function' might access freed memory.  To make sure that the compiler
 471  * keeps str alive on the stack or in a register such that it is visible to
 472  * the conservative gc we add the call to scm_remember_upto_here_1 _after_ the
 473  * call to 'some_function'.  Note that this would not be necessary if str was
 474  * used anyway after the call to 'some_function'.
 475  *   char *chars = scm_i_string_chars (str);
 476  *   some_function (chars);
 477  *   scm_remember_upto_here_1 (str);  // str will be alive up to this point.
 478  */
 479
 480 /* Remove any macro versions of these while defining the functions.
 481    Functions are always included in the library, for upward binary
 482    compatibility and in case combinations of GCC and non-GCC are used.  */
 483 #undef scm_remember_upto_here_1
 484 #undef scm_remember_upto_here_2
 485
 486 void
 487 scm_remember_upto_here_1 (SCM obj SCM_UNUSED)
 488 {
 489   /* Empty.  Protects a single object from garbage collection. */
 490 }
 491
 492 void
 493 scm_remember_upto_here_2 (SCM obj1 SCM_UNUSED, SCM obj2 SCM_UNUSED)
 494 {
 495   /* Empty.  Protects two objects from garbage collection. */
 496 }
 497
 498 void
 499 scm_remember_upto_here (SCM obj SCM_UNUSED, ...)
 500 {
 501   /* Empty.  Protects any number of objects from garbage collection. */
 502 }
 503
 504 /*
 505   These crazy functions prevent garbage collection
 506   of arguments after the first argument by
 507   ensuring they remain live throughout the
 508   function because they are used in the last
 509   line of the code block.
 510   It'd be better to have a nice compiler hint to
 511   aid the conservative stack-scanning GC. --03/09/00 gjb */
 512 SCM
 513 scm_return_first (SCM elt, ...)
 514 {
 515   return elt;
 516 }
 517
 518 int
 519 scm_return_first_int (int i, ...)
 520 {
 521   return i;
 522 }
 523
 524
 525 SCM
 526 scm_permanent_object (SCM obj)
 527 {
 528   SCM cell = scm_cons (obj, SCM_EOL);
 529   SCM_CRITICAL_SECTION_START;
 530   SCM_SETCDR (cell, scm_permobjs);
 531   scm_permobjs = cell;
 532   SCM_CRITICAL_SECTION_END;
 533   return obj;
 534 }
 535
 536
 537 /* Protect OBJ from the garbage collector.  OBJ will not be freed, even if all
 538    other references are dropped, until the object is unprotected by calling
 539    scm_gc_unprotect_object (OBJ).  Calls to scm_gc_protect/unprotect_object nest,
 540    i. e. it is possible to protect the same object several times, but it is
 541    necessary to unprotect the object the same number of times to actually get
 542    the object unprotected.  It is an error to unprotect an object more often
 543    than it has been protected before.  The function scm_protect_object returns
 544    OBJ.
 545 */
 546
 547 /* Implementation note:  For every object X, there is a counter which
 548    scm_gc_protect_object(X) increments and scm_gc_unprotect_object(X) decrements.
 549 */
 550
 551
 552
 553 SCM
 554 scm_gc_protect_object (SCM obj)
 555 {
 556   SCM handle;
 557
 558   /* This critical section barrier will be replaced by a mutex. */
 559   /* njrev: Indeed; if my comment above is correct, there is the same
 560      critsec/mutex inconsistency here. */
 561   SCM_CRITICAL_SECTION_START;
 562
 563   handle = scm_hashq_create_handle_x (scm_protects, obj, scm_from_int (0));
 564   SCM_SETCDR (handle, scm_sum (SCM_CDR (handle), scm_from_int (1)));
 565
 566   protected_obj_count ++;
 567
 568   SCM_CRITICAL_SECTION_END;
 569
 570   return obj;
 571 }
 572
 573
 574 /* Remove any protection for OBJ established by a prior call to
 575    scm_protect_object.  This function returns OBJ.
 576
 577    See scm_protect_object for more information.  */
 578 SCM
 579 scm_gc_unprotect_object (SCM obj)
 580 {
 581   SCM handle;
 582
 583   /* This critical section barrier will be replaced by a mutex. */
 584   /* njrev: and again. */
 585   SCM_CRITICAL_SECTION_START;
 586
 587   if (scm_gc_running_p)
 588     {
 589       fprintf (stderr, "scm_unprotect_object called during GC.\n");
 590       abort ();
 591     }
 592
 593   handle = scm_hashq_get_handle (scm_protects, obj);
 594
 595   if (scm_is_false (handle))
 596     {
 597       fprintf (stderr, "scm_unprotect_object called on unprotected object\n");
 598       abort ();
 599     }
 600   else
 601     {
 602       SCM count = scm_difference (SCM_CDR (handle), scm_from_int (1));
 603       if (scm_is_eq (count, scm_from_int (0)))
 604         scm_hashq_remove_x (scm_protects, obj);
 605       else
 606         SCM_SETCDR (handle, count);
 607     }
 608   protected_obj_count --;
 609
 610   SCM_CRITICAL_SECTION_END;
 611
 612   return obj;
 613 }
 614
 615 void
 616 scm_gc_register_root (SCM *p)
 617 {
 618   SCM handle;
 619   SCM key = scm_from_ulong ((unsigned long) p);
 620
 621   /* This critical section barrier will be replaced by a mutex. */
 622   /* njrev: and again. */
 623   SCM_CRITICAL_SECTION_START;
 624
 625   handle = scm_hashv_create_handle_x (scm_gc_registered_roots, key,
 626                                       scm_from_int (0));
 627   /* njrev: note also that the above can probably signal an error */
 628   SCM_SETCDR (handle, scm_sum (SCM_CDR (handle), scm_from_int (1)));
 629
 630   SCM_CRITICAL_SECTION_END;
 631 }
 632
 633 void
 634 scm_gc_unregister_root (SCM *p)
 635 {
 636   SCM handle;
 637   SCM key = scm_from_ulong ((unsigned long) p);
 638
 639   /* This critical section barrier will be replaced by a mutex. */
 640   /* njrev: and again. */
 641   SCM_CRITICAL_SECTION_START;
 642
 643   handle = scm_hashv_get_handle (scm_gc_registered_roots, key);
 644
 645   if (scm_is_false (handle))
 646     {
 647       fprintf (stderr, "scm_gc_unregister_root called on unregistered root\n");
 648       abort ();
 649     }
 650   else
 651     {
 652       SCM count = scm_difference (SCM_CDR (handle), scm_from_int (1));
 653       if (scm_is_eq (count, scm_from_int (0)))
 654         scm_hashv_remove_x (scm_gc_registered_roots, key);
 655       else
 656         SCM_SETCDR (handle, count);
 657     }
 658
 659   SCM_CRITICAL_SECTION_END;
 660 }
 661
 662 void
 663 scm_gc_register_roots (SCM *b, unsigned long n)
 664 {
 665   SCM *p = b;
 666   for (; p < b + n; ++p)
 667     scm_gc_register_root (p);
 668 }
 669
 670 void
 671 scm_gc_unregister_roots (SCM *b, unsigned long n)
 672 {
 673   SCM *p = b;
 674   for (; p < b + n; ++p)
 675     scm_gc_unregister_root (p);
 676 }
 677
 678 int scm_i_terminating;
 679
 680 \f
 681
 682
 683 /*
 684   MOVE THIS FUNCTION. IT DOES NOT HAVE ANYTHING TODO WITH GC.
 685  */
 686
 687 /* Get an integer from an environment variable.  */
 688 int
 689 scm_getenv_int (const char *var, int def)
 690 {
 691   char *end = 0;
 692   char *val = getenv (var);
 693   long res = def;
 694   if (!val)
 695     return def;
 696   res = strtol (val, &end, 10);
 697   if (end == val)
 698     return def;
 699   return res;
 700 }
 701
 702 void
 703 scm_storage_prehistory ()
 704 {
 705   GC_INIT ();
 706   GC_add_roots ((char *)scm_sys_protects,
 707                 (char *)(scm_sys_protects + SCM_NUM_PROTECTS));
 708
 709   scm_c_hook_init (&scm_before_gc_c_hook, 0, SCM_C_HOOK_NORMAL);
 710   scm_c_hook_init (&scm_before_mark_c_hook, 0, SCM_C_HOOK_NORMAL);
 711   scm_c_hook_init (&scm_before_sweep_c_hook, 0, SCM_C_HOOK_NORMAL);
 712   scm_c_hook_init (&scm_after_sweep_c_hook, 0, SCM_C_HOOK_NORMAL);
 713   scm_c_hook_init (&scm_after_gc_c_hook, 0, SCM_C_HOOK_NORMAL);
 714 }
 715
 716 scm_i_pthread_mutex_t scm_i_gc_admin_mutex = SCM_I_PTHREAD_MUTEX_INITIALIZER;
 717
 718 int
 719 scm_init_storage ()
 720 {
 721   size_t j;
 722
 723   j = SCM_NUM_PROTECTS;
 724   while (j)
 725     scm_sys_protects[--j] = SCM_BOOL_F;
 726
 727   j = SCM_HEAP_SEG_SIZE;
 728
 729 #if 0
 730   /* We can't have a cleanup handler since we have no thread to run it
 731      in. */
 732
 733 #ifdef HAVE_ATEXIT
 734   atexit (cleanup);
 735 #else
 736 #ifdef HAVE_ON_EXIT
 737   on_exit (cleanup, 0);
 738 #endif
 739 #endif
 740
 741 #endif
 742
 743   scm_stand_in_procs = scm_make_weak_key_hash_table (scm_from_int (257));
 744   scm_permobjs = SCM_EOL;
 745   scm_protects = scm_c_make_hash_table (31);
 746   scm_gc_registered_roots = scm_c_make_hash_table (31);
 747
 748   return 0;
 749 }
 750
 751 \f
 752
 753 SCM scm_after_gc_hook;
 754
 755 static SCM gc_async;
 756
 757 /* The function gc_async_thunk causes the execution of the after-gc-hook.  It
 758  * is run after the gc, as soon as the asynchronous events are handled by the
 759  * evaluator.
 760  */
 761 static SCM
 762 gc_async_thunk (void)
 763 {
 764   scm_c_run_hook (scm_after_gc_hook, SCM_EOL);
 765   return SCM_UNSPECIFIED;
 766 }
 767
 768
 769 /* The function mark_gc_async is run by the scm_after_gc_c_hook at the end of
 770  * the garbage collection.  The only purpose of this function is to mark the
 771  * gc_async (which will eventually lead to the execution of the
 772  * gc_async_thunk).
 773  */
 774 static void *
 775 mark_gc_async (void * hook_data SCM_UNUSED,
 776                void *func_data SCM_UNUSED,
 777                void *data SCM_UNUSED)
 778 {
 779   /* If cell access debugging is enabled, the user may choose to perform
 780    * additional garbage collections after an arbitrary number of cell
 781    * accesses.  We don't want the scheme level after-gc-hook to be performed
 782    * for each of these garbage collections for the following reason: The
 783    * execution of the after-gc-hook causes cell accesses itself.  Thus, if the
 784    * after-gc-hook was performed with every gc, and if the gc was performed
 785    * after a very small number of cell accesses, then the number of cell
 786    * accesses during the execution of the after-gc-hook will suffice to cause
 787    * the execution of the next gc.  Then, guile would keep executing the
 788    * after-gc-hook over and over again, and would never come to do other
 789    * things.
 790    *
 791    * To overcome this problem, if cell access debugging with additional
 792    * garbage collections is enabled, the after-gc-hook is never run by the
 793    * garbage collecter.  When running guile with cell access debugging and the
 794    * execution of the after-gc-hook is desired, then it is necessary to run
 795    * the hook explicitly from the user code.  This has the effect, that from
 796    * the scheme level point of view it seems that garbage collection is
 797    * performed with a much lower frequency than it actually is.  Obviously,
 798    * this will not work for code that depends on a fixed one to one
 799    * relationship between the execution counts of the C level garbage
 800    * collection hooks and the execution count of the scheme level
 801    * after-gc-hook.
 802    */
 803
 804 #if (SCM_DEBUG_CELL_ACCESSES == 1)
 805   if (scm_debug_cells_gc_interval == 0)
 806     scm_system_async_mark (gc_async);
 807 #else
 808   scm_system_async_mark (gc_async);
 809 #endif
 810
 811   return NULL;
 812 }
 813
 814 char const *
 815 scm_i_tag_name (scm_t_bits tag)
 816 {
 817   if (tag >= 255)
 818     {
 819       if (tag == scm_tc_free_cell)
 820         return "free cell";
 821
 822       {
 823         int k = 0xff & (tag >> 8);
 824         return (scm_smobs[k].name);
 825       }
 826     }
 827
 828   switch (tag) /* 7 bits */
 829     {
 830     case scm_tcs_struct:
 831       return "struct";
 832     case scm_tcs_cons_imcar:
 833       return "cons (immediate car)";
 834     case scm_tcs_cons_nimcar:
 835       return "cons (non-immediate car)";
 836     case scm_tcs_closures:
 837       return "closures";
 838     case scm_tc7_pws:
 839       return "pws";
 840     case scm_tc7_wvect:
 841       return "weak vector";
 842     case scm_tc7_vector:
 843       return "vector";
 844 #ifdef CCLO
 845     case scm_tc7_cclo:
 846       return "compiled closure";
 847 #endif
 848     case scm_tc7_number:
 849       switch (tag)
 850         {
 851         case scm_tc16_real:
 852           return "real";
 853           break;
 854         case scm_tc16_big:
 855           return "bignum";
 856           break;
 857         case scm_tc16_complex:
 858           return "complex number";
 859           break;
 860         case scm_tc16_fraction:
 861           return "fraction";
 862           break;
 863         }
 864       break;
 865     case scm_tc7_string:
 866       return "string";
 867       break;
 868     case scm_tc7_stringbuf:
 869       return "string buffer";
 870       break;
 871     case scm_tc7_symbol:
 872       return "symbol";
 873       break;
 874     case scm_tc7_variable:
 875       return "variable";
 876       break;
 877     case scm_tcs_subrs:
 878       return "subrs";
 879       break;
 880     case scm_tc7_port:
 881       return "port";
 882       break;
 883     case scm_tc7_smob:
 884       return "smob";            /* should not occur. */
 885       break;
 886     }
 887
 888   return NULL;
 889 }
 890
 891
 892
 893 \f
 894 void
 895 scm_init_gc ()
 896 {
 897   /* `GC_INIT ()' was invoked in `scm_storage_prehistory ()'.  */
 898
 899   scm_after_gc_hook = scm_permanent_object (scm_make_hook (SCM_INUM0));
 900   scm_c_define ("after-gc-hook", scm_after_gc_hook);
 901
 902   gc_async = scm_c_make_subr ("%gc-thunk", scm_tc7_subr_0,
 903                               gc_async_thunk);
 904
 905   scm_c_hook_add (&scm_after_gc_c_hook, mark_gc_async, NULL, 0);
 906
 907 #include "libguile/gc.x"
 908 }
 909
 910
 911 void
 912 scm_gc_sweep (void)
 913 #define FUNC_NAME "scm_gc_sweep"
 914 {
 915   /* FIXME */
 916   fprintf (stderr, "%s: doing nothing\n", __FUNCTION__);
 917 }
 918
 919 #undef FUNC_NAME
 920
 921
 922
 923 /*
 924   Local Variables:
 925   c-file-style: "gnu"
 926   End:
 927 */