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 #ifdef GUILE_DEBUG_MALLOC
  59 #include "libguile/debug-malloc.h"
  60 #endif
  61
  62 #ifdef HAVE_MALLOC_H
  63 #include <malloc.h>
  64 #endif
  65
  66 #ifdef HAVE_UNISTD_H
  67 #include <unistd.h>
  68 #endif
  69
  70 /* Lock this mutex before doing lazy sweeping.
  71  */
  72 scm_i_pthread_mutex_t scm_i_sweep_mutex = SCM_I_PTHREAD_MUTEX_INITIALIZER;
  73
  74 /* Set this to != 0 if every cell that is accessed shall be checked:
  75  */
  76 int scm_debug_cell_accesses_p = 0;
  77 int scm_expensive_debug_cell_accesses_p = 0;
  78
  79 /* Set this to 0 if no additional gc's shall be performed, otherwise set it to
  80  * the number of cell accesses after which a gc shall be called.
  81  */
  82 int scm_debug_cells_gc_interval = 0;
  83
  84 /*
  85   Global variable, so you can switch it off at runtime by setting
  86   scm_i_cell_validation_already_running.
  87  */
  88 int scm_i_cell_validation_already_running ;
  89
  90 #if (SCM_DEBUG_CELL_ACCESSES == 1)
  91
  92
  93 /*
  94
  95   Assert that the given object is a valid reference to a valid cell.  This
  96   test involves to determine whether the object is a cell pointer, whether
  97   this pointer actually points into a heap segment and whether the cell
  98   pointed to is not a free cell.  Further, additional garbage collections may
  99   get executed after a user defined number of cell accesses.  This helps to
 100   find places in the C code where references are dropped for extremely short
 101   periods.
 102
 103 */
 104 void
 105 scm_i_expensive_validation_check (SCM cell)
 106 {
 107   if (!scm_in_heap_p (cell))
 108     {
 109       fprintf (stderr, "scm_assert_cell_valid: this object does not live in the heap: %lux\n",
 110                (unsigned long) SCM_UNPACK (cell));
 111       abort ();
 112     }
 113
 114   /* If desired, perform additional garbage collections after a user
 115    * defined number of cell accesses.
 116    */
 117   if (scm_debug_cells_gc_interval)
 118     {
 119       static unsigned int counter = 0;
 120
 121       if (counter != 0)
 122         {
 123           --counter;
 124         }
 125       else
 126         {
 127           counter = scm_debug_cells_gc_interval;
 128           scm_gc ();
 129         }
 130     }
 131 }
 132
 133 void
 134 scm_assert_cell_valid (SCM cell)
 135 {
 136   if (!scm_i_cell_validation_already_running && scm_debug_cell_accesses_p)
 137     {
 138       scm_i_cell_validation_already_running = 1;  /* set to avoid recursion */
 139
 140       /*
 141         During GC, no user-code should be run, and the guile core
 142         should use non-protected accessors.
 143       */
 144       if (scm_gc_running_p)
 145         return;
 146
 147       /*
 148         Only scm_in_heap_p and rescanning the heap is wildly
 149         expensive.
 150       */
 151       if (scm_expensive_debug_cell_accesses_p)
 152         scm_i_expensive_validation_check (cell);
 153
 154       if (!SCM_GC_MARK_P (cell))
 155         {
 156           fprintf (stderr,
 157                    "scm_assert_cell_valid: this object is unmarked. \n"
 158                    "It has been garbage-collected in the last GC run: "
 159                    "%lux\n",
 160                    (unsigned long) SCM_UNPACK (cell));
 161           abort ();
 162         }
 163
 164       scm_i_cell_validation_already_running = 0;  /* re-enable */
 165     }
 166 }
 167
 168
 169
 170 SCM_DEFINE (scm_set_debug_cell_accesses_x, "set-debug-cell-accesses!", 1, 0, 0,
 171             (SCM flag),
 172             "If @var{flag} is @code{#f}, cell access checking is disabled.\n"
 173             "If @var{flag} is @code{#t}, cheap cell access checking is enabled,\n"
 174             "but no additional calls to garbage collection are issued.\n"
 175             "If @var{flag} is a number, strict cell access checking is enabled,\n"
 176             "with an additional garbage collection after the given\n"
 177             "number of cell accesses.\n"
 178             "This procedure only exists when the compile-time flag\n"
 179             "@code{SCM_DEBUG_CELL_ACCESSES} was set to 1.")
 180 #define FUNC_NAME s_scm_set_debug_cell_accesses_x
 181 {
 182   if (scm_is_false (flag))
 183     {
 184       scm_debug_cell_accesses_p = 0;
 185     }
 186   else if (scm_is_eq (flag, SCM_BOOL_T))
 187     {
 188       scm_debug_cells_gc_interval = 0;
 189       scm_debug_cell_accesses_p = 1;
 190       scm_expensive_debug_cell_accesses_p = 0;
 191     }
 192   else
 193     {
 194       scm_debug_cells_gc_interval = scm_to_signed_integer (flag, 0, INT_MAX);
 195       scm_debug_cell_accesses_p = 1;
 196       scm_expensive_debug_cell_accesses_p = 1;
 197     }
 198   return SCM_UNSPECIFIED;
 199 }
 200 #undef FUNC_NAME
 201
 202
 203 #endif  /* SCM_DEBUG_CELL_ACCESSES == 1 */
 204
 205 \f
 206 /* Hooks.  */
 207 scm_t_c_hook scm_before_gc_c_hook;
 208 scm_t_c_hook scm_before_mark_c_hook;
 209 scm_t_c_hook scm_before_sweep_c_hook;
 210 scm_t_c_hook scm_after_sweep_c_hook;
 211 scm_t_c_hook scm_after_gc_c_hook;
 212
 213
 214 /* scm_mtrigger
 215  * is the number of bytes of malloc allocation needed to trigger gc.
 216  */
 217 unsigned long scm_mtrigger;
 218
 219 /* GC Statistics Keeping
 220  */
 221 unsigned long scm_cells_allocated = 0;
 222 unsigned long scm_mallocated = 0;
 223 unsigned long scm_gc_cells_collected;
 224 unsigned long scm_gc_cells_collected_1 = 0; /* previous GC yield */
 225 unsigned long scm_gc_malloc_collected;
 226 unsigned long scm_gc_ports_collected;
 227 unsigned long scm_gc_time_taken = 0;
 228 static unsigned long t_before_gc;
 229 unsigned long scm_gc_mark_time_taken = 0;
 230 unsigned long scm_gc_times = 0;
 231 unsigned long scm_gc_cells_swept = 0;
 232 double scm_gc_cells_marked_acc = 0.;
 233 double scm_gc_cells_swept_acc = 0.;
 234 int scm_gc_cell_yield_percentage =0;
 235 int scm_gc_malloc_yield_percentage = 0;
 236 unsigned long protected_obj_count = 0;
 237
 238
 239 SCM_SYMBOL (sym_cells_allocated, "cells-allocated");
 240 SCM_SYMBOL (sym_heap_size, "cell-heap-size");
 241 SCM_SYMBOL (sym_mallocated, "bytes-malloced");
 242 SCM_SYMBOL (sym_mtrigger, "gc-malloc-threshold");
 243 SCM_SYMBOL (sym_heap_segments, "cell-heap-segments");
 244 SCM_SYMBOL (sym_gc_time_taken, "gc-time-taken");
 245 SCM_SYMBOL (sym_gc_mark_time_taken, "gc-mark-time-taken");
 246 SCM_SYMBOL (sym_times, "gc-times");
 247 SCM_SYMBOL (sym_cells_marked, "cells-marked");
 248 SCM_SYMBOL (sym_cells_swept, "cells-swept");
 249 SCM_SYMBOL (sym_malloc_yield, "malloc-yield");
 250 SCM_SYMBOL (sym_cell_yield, "cell-yield");
 251 SCM_SYMBOL (sym_protected_objects, "protected-objects");
 252
 253
 254
 255
 256 /* Number of calls to SCM_NEWCELL since startup.  */
 257 unsigned scm_newcell_count;
 258 unsigned scm_newcell2_count;
 259
 260
 261 /* {Scheme Interface to GC}
 262  */
 263 static SCM
 264 tag_table_to_type_alist (void *closure, SCM key, SCM val, SCM acc)
 265 {
 266   if (scm_is_integer (key))
 267     {
 268       int c_tag = scm_to_int (key);
 269
 270       char const * name = scm_i_tag_name (c_tag);
 271       if (name != NULL)
 272         {
 273           key = scm_from_locale_string (name);
 274         }
 275       else
 276         {
 277           char s[100];
 278           sprintf (s, "tag %d", c_tag);
 279           key = scm_from_locale_string (s);
 280         }
 281     }
 282
 283   return scm_cons (scm_cons (key, val), acc);
 284 }
 285
 286 SCM_DEFINE (scm_gc_live_object_stats, "gc-live-object-stats", 0, 0, 0,
 287             (),
 288             "Return an alist of statistics of the current live objects. ")
 289 #define FUNC_NAME s_scm_gc_live_object_stats
 290 {
 291   SCM tab = scm_make_hash_table (scm_from_int (57));
 292   SCM alist;
 293
 294   alist
 295     = scm_internal_hash_fold (&tag_table_to_type_alist, NULL, SCM_EOL, tab);
 296
 297   return alist;
 298 }
 299 #undef FUNC_NAME
 300
 301 extern int scm_gc_malloc_yield_percentage;
 302 SCM_DEFINE (scm_gc_stats, "gc-stats", 0, 0, 0,
 303             (),
 304             "Return an association list of statistics about Guile's current\n"
 305             "use of storage.\n")
 306 #define FUNC_NAME s_scm_gc_stats
 307 {
 308   long i = 0;
 309   SCM heap_segs = SCM_EOL ;
 310   unsigned long int local_scm_mtrigger;
 311   unsigned long int local_scm_mallocated;
 312   unsigned long int local_scm_heap_size;
 313   int local_scm_gc_cell_yield_percentage;
 314   int local_scm_gc_malloc_yield_percentage;
 315   unsigned long int local_scm_cells_allocated;
 316   unsigned long int local_scm_gc_time_taken;
 317   unsigned long int local_scm_gc_times;
 318   unsigned long int local_scm_gc_mark_time_taken;
 319   unsigned long int local_protected_obj_count;
 320   double local_scm_gc_cells_swept;
 321   double local_scm_gc_cells_marked;
 322   SCM answer;
 323   unsigned long *bounds = 0;
 324   SCM_CRITICAL_SECTION_START;
 325
 326   /*
 327     temporarily store the numbers, so as not to cause GC.
 328    */
 329 #if 0
 330   bounds = malloc (sizeof (unsigned long)  * table_size * 2);
 331   if (!bounds)
 332     abort();
 333 #endif
 334
 335   return SCM_EOL;  /* FIXME */
 336 #if 0
 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 = 0; /* SCM_HEAP_SIZE; */ /* FIXME */
 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   for (i = table_size; i--;)
 360     {
 361       heap_segs = scm_cons (scm_cons (scm_from_ulong (bounds[2*i]),
 362                                       scm_from_ulong (bounds[2*i+1])),
 363                             heap_segs);
 364     }
 365   /* njrev: can any of these scm_cons's or scm_list_n signal a memory
 366      error?  If so we need a frame here. */
 367   answer =
 368     scm_list_n (scm_cons (sym_gc_time_taken,
 369                           scm_from_ulong (local_scm_gc_time_taken)),
 370                 scm_cons (sym_cells_allocated,
 371                           scm_from_ulong (local_scm_cells_allocated)),
 372                 scm_cons (sym_heap_size,
 373                           scm_from_ulong (local_scm_heap_size)),
 374                 scm_cons (sym_mallocated,
 375                           scm_from_ulong (local_scm_mallocated)),
 376                 scm_cons (sym_mtrigger,
 377                           scm_from_ulong (local_scm_mtrigger)),
 378                 scm_cons (sym_times,
 379                           scm_from_ulong (local_scm_gc_times)),
 380                 scm_cons (sym_gc_mark_time_taken,
 381                           scm_from_ulong (local_scm_gc_mark_time_taken)),
 382                 scm_cons (sym_cells_marked,
 383                           scm_from_double (local_scm_gc_cells_marked)),
 384                 scm_cons (sym_cells_swept,
 385                           scm_from_double (local_scm_gc_cells_swept)),
 386                 scm_cons (sym_malloc_yield,
 387                           scm_from_long(local_scm_gc_malloc_yield_percentage)),
 388                 scm_cons (sym_cell_yield,
 389                           scm_from_long (local_scm_gc_cell_yield_percentage)),
 390                 scm_cons (sym_protected_objects,
 391                           scm_from_ulong (local_protected_obj_count)),
 392                 scm_cons (sym_heap_segments, heap_segs),
 393                 SCM_UNDEFINED);
 394   SCM_CRITICAL_SECTION_END;
 395
 396   free (bounds);
 397   return answer;
 398 #endif
 399 }
 400 #undef FUNC_NAME
 401
 402
 403
 404
 405 SCM_DEFINE (scm_object_address, "object-address", 1, 0, 0,
 406             (SCM obj),
 407             "Return an integer that for the lifetime of @var{obj} is uniquely\n"
 408             "returned by this function for @var{obj}")
 409 #define FUNC_NAME s_scm_object_address
 410 {
 411   return scm_from_ulong (SCM_UNPACK (obj));
 412 }
 413 #undef FUNC_NAME
 414
 415
 416 SCM_DEFINE (scm_gc, "gc", 0, 0, 0,
 417            (),
 418             "Scans all of SCM objects and reclaims for further use those that are\n"
 419             "no longer accessible.")
 420 #define FUNC_NAME s_scm_gc
 421 {
 422   scm_i_scm_pthread_mutex_lock (&scm_i_sweep_mutex);
 423   scm_gc_running_p = 1;
 424   scm_i_gc ("call");
 425   /* njrev: It looks as though other places, e.g. scm_realloc,
 426      can call scm_i_gc without acquiring the sweep mutex.  Does this
 427      matter?  Also scm_i_gc (or its descendants) touch the
 428      scm_sys_protects, which are protected in some cases
 429      (e.g. scm_permobjs above in scm_gc_stats) by a critical section,
 430      not by the sweep mutex.  Shouldn't all the GC-relevant objects be
 431      protected in the same way? */
 432   scm_gc_running_p = 0;
 433   scm_i_pthread_mutex_unlock (&scm_i_sweep_mutex);
 434   scm_c_hook_run (&scm_after_gc_c_hook, 0);
 435   return SCM_UNSPECIFIED;
 436 }
 437 #undef FUNC_NAME
 438
 439 void
 440 scm_i_gc (const char *what)
 441 {
 442   GC_gcollect ();
 443 }
 444
 445
 446 \f
 447 /* {GC Protection Helper Functions}
 448  */
 449
 450
 451 /*
 452  * If within a function you need to protect one or more scheme objects from
 453  * garbage collection, pass them as parameters to one of the
 454  * scm_remember_upto_here* functions below.  These functions don't do
 455  * anything, but since the compiler does not know that they are actually
 456  * no-ops, it will generate code that calls these functions with the given
 457  * parameters.  Therefore, you can be sure that the compiler will keep those
 458  * scheme values alive (on the stack or in a register) up to the point where
 459  * scm_remember_upto_here* is called.  In other words, place the call to
 460  * scm_remember_upto_here* _behind_ the last code in your function, that
 461  * depends on the scheme object to exist.
 462  *
 463  * Example: We want to make sure that the string object str does not get
 464  * garbage collected during the execution of 'some_function' in the code
 465  * below, because otherwise the characters belonging to str would be freed and
 466  * 'some_function' might access freed memory.  To make sure that the compiler
 467  * keeps str alive on the stack or in a register such that it is visible to
 468  * the conservative gc we add the call to scm_remember_upto_here_1 _after_ the
 469  * call to 'some_function'.  Note that this would not be necessary if str was
 470  * used anyway after the call to 'some_function'.
 471  *   char *chars = scm_i_string_chars (str);
 472  *   some_function (chars);
 473  *   scm_remember_upto_here_1 (str);  // str will be alive up to this point.
 474  */
 475
 476 /* Remove any macro versions of these while defining the functions.
 477    Functions are always included in the library, for upward binary
 478    compatibility and in case combinations of GCC and non-GCC are used.  */
 479 #undef scm_remember_upto_here_1
 480 #undef scm_remember_upto_here_2
 481
 482 void
 483 scm_remember_upto_here_1 (SCM obj SCM_UNUSED)
 484 {
 485   /* Empty.  Protects a single object from garbage collection. */
 486 }
 487
 488 void
 489 scm_remember_upto_here_2 (SCM obj1 SCM_UNUSED, SCM obj2 SCM_UNUSED)
 490 {
 491   /* Empty.  Protects two objects from garbage collection. */
 492 }
 493
 494 void
 495 scm_remember_upto_here (SCM obj SCM_UNUSED, ...)
 496 {
 497   /* Empty.  Protects any number of objects from garbage collection. */
 498 }
 499
 500 /*
 501   These crazy functions prevent garbage collection
 502   of arguments after the first argument by
 503   ensuring they remain live throughout the
 504   function because they are used in the last
 505   line of the code block.
 506   It'd be better to have a nice compiler hint to
 507   aid the conservative stack-scanning GC. --03/09/00 gjb */
 508 SCM
 509 scm_return_first (SCM elt, ...)
 510 {
 511   return elt;
 512 }
 513
 514 int
 515 scm_return_first_int (int i, ...)
 516 {
 517   return i;
 518 }
 519
 520
 521 SCM
 522 scm_permanent_object (SCM obj)
 523 {
 524   SCM cell = scm_cons (obj, SCM_EOL);
 525   SCM_CRITICAL_SECTION_START;
 526   SCM_SETCDR (cell, scm_permobjs);
 527   scm_permobjs = cell;
 528   SCM_CRITICAL_SECTION_END;
 529   return obj;
 530 }
 531
 532
 533 /* Protect OBJ from the garbage collector.  OBJ will not be freed, even if all
 534    other references are dropped, until the object is unprotected by calling
 535    scm_gc_unprotect_object (OBJ).  Calls to scm_gc_protect/unprotect_object nest,
 536    i. e. it is possible to protect the same object several times, but it is
 537    necessary to unprotect the object the same number of times to actually get
 538    the object unprotected.  It is an error to unprotect an object more often
 539    than it has been protected before.  The function scm_protect_object returns
 540    OBJ.
 541 */
 542
 543 /* Implementation note:  For every object X, there is a counter which
 544    scm_gc_protect_object(X) increments and scm_gc_unprotect_object(X) decrements.
 545 */
 546
 547
 548
 549 SCM
 550 scm_gc_protect_object (SCM obj)
 551 {
 552   SCM handle;
 553
 554   /* This critical section barrier will be replaced by a mutex. */
 555   /* njrev: Indeed; if my comment above is correct, there is the same
 556      critsec/mutex inconsistency here. */
 557   SCM_CRITICAL_SECTION_START;
 558
 559   handle = scm_hashq_create_handle_x (scm_protects, obj, scm_from_int (0));
 560   SCM_SETCDR (handle, scm_sum (SCM_CDR (handle), scm_from_int (1)));
 561
 562   protected_obj_count ++;
 563
 564   SCM_CRITICAL_SECTION_END;
 565
 566   return obj;
 567 }
 568
 569
 570 /* Remove any protection for OBJ established by a prior call to
 571    scm_protect_object.  This function returns OBJ.
 572
 573    See scm_protect_object for more information.  */
 574 SCM
 575 scm_gc_unprotect_object (SCM obj)
 576 {
 577   SCM handle;
 578
 579   /* This critical section barrier will be replaced by a mutex. */
 580   /* njrev: and again. */
 581   SCM_CRITICAL_SECTION_START;
 582
 583   if (scm_gc_running_p)
 584     {
 585       fprintf (stderr, "scm_unprotect_object called during GC.\n");
 586       abort ();
 587     }
 588
 589   handle = scm_hashq_get_handle (scm_protects, obj);
 590
 591   if (scm_is_false (handle))
 592     {
 593       fprintf (stderr, "scm_unprotect_object called on unprotected object\n");
 594       abort ();
 595     }
 596   else
 597     {
 598       SCM count = scm_difference (SCM_CDR (handle), scm_from_int (1));
 599       if (scm_is_eq (count, scm_from_int (0)))
 600         scm_hashq_remove_x (scm_protects, obj);
 601       else
 602         SCM_SETCDR (handle, count);
 603     }
 604   protected_obj_count --;
 605
 606   SCM_CRITICAL_SECTION_END;
 607
 608   return obj;
 609 }
 610
 611 void
 612 scm_gc_register_root (SCM *p)
 613 {
 614   SCM handle;
 615   SCM key = scm_from_ulong ((unsigned long) p);
 616
 617   /* This critical section barrier will be replaced by a mutex. */
 618   /* njrev: and again. */
 619   SCM_CRITICAL_SECTION_START;
 620
 621   handle = scm_hashv_create_handle_x (scm_gc_registered_roots, key,
 622                                       scm_from_int (0));
 623   /* njrev: note also that the above can probably signal an error */
 624   SCM_SETCDR (handle, scm_sum (SCM_CDR (handle), scm_from_int (1)));
 625
 626   SCM_CRITICAL_SECTION_END;
 627 }
 628
 629 void
 630 scm_gc_unregister_root (SCM *p)
 631 {
 632   SCM handle;
 633   SCM key = scm_from_ulong ((unsigned long) p);
 634
 635   /* This critical section barrier will be replaced by a mutex. */
 636   /* njrev: and again. */
 637   SCM_CRITICAL_SECTION_START;
 638
 639   handle = scm_hashv_get_handle (scm_gc_registered_roots, key);
 640
 641   if (scm_is_false (handle))
 642     {
 643       fprintf (stderr, "scm_gc_unregister_root called on unregistered root\n");
 644       abort ();
 645     }
 646   else
 647     {
 648       SCM count = scm_difference (SCM_CDR (handle), scm_from_int (1));
 649       if (scm_is_eq (count, scm_from_int (0)))
 650         scm_hashv_remove_x (scm_gc_registered_roots, key);
 651       else
 652         SCM_SETCDR (handle, count);
 653     }
 654
 655   SCM_CRITICAL_SECTION_END;
 656 }
 657
 658 void
 659 scm_gc_register_roots (SCM *b, unsigned long n)
 660 {
 661   SCM *p = b;
 662   for (; p < b + n; ++p)
 663     scm_gc_register_root (p);
 664 }
 665
 666 void
 667 scm_gc_unregister_roots (SCM *b, unsigned long n)
 668 {
 669   SCM *p = b;
 670   for (; p < b + n; ++p)
 671     scm_gc_unregister_root (p);
 672 }
 673
 674 int scm_i_terminating;
 675
 676 \f
 677
 678
 679 /*
 680   MOVE THIS FUNCTION. IT DOES NOT HAVE ANYTHING TODO WITH GC.
 681  */
 682
 683 /* Get an integer from an environment variable.  */
 684 int
 685 scm_getenv_int (const char *var, int def)
 686 {
 687   char *end = 0;
 688   char *val = getenv (var);
 689   long res = def;
 690   if (!val)
 691     return def;
 692   res = strtol (val, &end, 10);
 693   if (end == val)
 694     return def;
 695   return res;
 696 }
 697
 698 void
 699 scm_storage_prehistory ()
 700 {
 701   scm_c_hook_init (&scm_before_gc_c_hook, 0, SCM_C_HOOK_NORMAL);
 702   scm_c_hook_init (&scm_before_mark_c_hook, 0, SCM_C_HOOK_NORMAL);
 703   scm_c_hook_init (&scm_before_sweep_c_hook, 0, SCM_C_HOOK_NORMAL);
 704   scm_c_hook_init (&scm_after_sweep_c_hook, 0, SCM_C_HOOK_NORMAL);
 705   scm_c_hook_init (&scm_after_gc_c_hook, 0, SCM_C_HOOK_NORMAL);
 706 }
 707
 708 scm_i_pthread_mutex_t scm_i_gc_admin_mutex = SCM_I_PTHREAD_MUTEX_INITIALIZER;
 709
 710 int
 711 scm_init_storage ()
 712 {
 713   size_t j;
 714
 715   j = SCM_NUM_PROTECTS;
 716   while (j)
 717     scm_sys_protects[--j] = SCM_BOOL_F;
 718
 719   j = SCM_HEAP_SEG_SIZE;
 720
 721   /* Initialise the list of ports.  */
 722   scm_i_port_table = (scm_t_port **)
 723     malloc (sizeof (scm_t_port *) * scm_i_port_table_room);
 724   if (!scm_i_port_table)
 725     return 1;
 726
 727 #if 0
 728   /* We can't have a cleanup handler since we have no thread to run it
 729      in. */
 730
 731 #ifdef HAVE_ATEXIT
 732   atexit (cleanup);
 733 #else
 734 #ifdef HAVE_ON_EXIT
 735   on_exit (cleanup, 0);
 736 #endif
 737 #endif
 738
 739 #endif
 740
 741   scm_stand_in_procs = scm_make_weak_key_hash_table (scm_from_int (257));
 742   scm_permobjs = SCM_EOL;
 743   scm_protects = scm_c_make_hash_table (31);
 744   scm_gc_registered_roots = scm_c_make_hash_table (31);
 745
 746   return 0;
 747 }
 748
 749 \f
 750
 751 SCM scm_after_gc_hook;
 752
 753 static SCM gc_async;
 754
 755 /* The function gc_async_thunk causes the execution of the after-gc-hook.  It
 756  * is run after the gc, as soon as the asynchronous events are handled by the
 757  * evaluator.
 758  */
 759 static SCM
 760 gc_async_thunk (void)
 761 {
 762   scm_c_run_hook (scm_after_gc_hook, SCM_EOL);
 763   return SCM_UNSPECIFIED;
 764 }
 765
 766
 767 /* The function mark_gc_async is run by the scm_after_gc_c_hook at the end of
 768  * the garbage collection.  The only purpose of this function is to mark the
 769  * gc_async (which will eventually lead to the execution of the
 770  * gc_async_thunk).
 771  */
 772 static void *
 773 mark_gc_async (void * hook_data SCM_UNUSED,
 774                void *func_data SCM_UNUSED,
 775                void *data SCM_UNUSED)
 776 {
 777   /* If cell access debugging is enabled, the user may choose to perform
 778    * additional garbage collections after an arbitrary number of cell
 779    * accesses.  We don't want the scheme level after-gc-hook to be performed
 780    * for each of these garbage collections for the following reason: The
 781    * execution of the after-gc-hook causes cell accesses itself.  Thus, if the
 782    * after-gc-hook was performed with every gc, and if the gc was performed
 783    * after a very small number of cell accesses, then the number of cell
 784    * accesses during the execution of the after-gc-hook will suffice to cause
 785    * the execution of the next gc.  Then, guile would keep executing the
 786    * after-gc-hook over and over again, and would never come to do other
 787    * things.
 788    *
 789    * To overcome this problem, if cell access debugging with additional
 790    * garbage collections is enabled, the after-gc-hook is never run by the
 791    * garbage collecter.  When running guile with cell access debugging and the
 792    * execution of the after-gc-hook is desired, then it is necessary to run
 793    * the hook explicitly from the user code.  This has the effect, that from
 794    * the scheme level point of view it seems that garbage collection is
 795    * performed with a much lower frequency than it actually is.  Obviously,
 796    * this will not work for code that depends on a fixed one to one
 797    * relationship between the execution counts of the C level garbage
 798    * collection hooks and the execution count of the scheme level
 799    * after-gc-hook.
 800    */
 801
 802 #if (SCM_DEBUG_CELL_ACCESSES == 1)
 803   if (scm_debug_cells_gc_interval == 0)
 804     scm_system_async_mark (gc_async);
 805 #else
 806   scm_system_async_mark (gc_async);
 807 #endif
 808
 809   return NULL;
 810 }
 811
 812 char const *
 813 scm_i_tag_name (scm_t_bits tag)
 814 {
 815   if (tag >= 255)
 816     {
 817       if (tag == scm_tc_free_cell)
 818         return "free cell";
 819
 820       {
 821         int k = 0xff & (tag >> 8);
 822         return (scm_smobs[k].name);
 823       }
 824     }
 825
 826   switch (tag) /* 7 bits */
 827     {
 828     case scm_tcs_struct:
 829       return "struct";
 830     case scm_tcs_cons_imcar:
 831       return "cons (immediate car)";
 832     case scm_tcs_cons_nimcar:
 833       return "cons (non-immediate car)";
 834     case scm_tcs_closures:
 835       return "closures";
 836     case scm_tc7_pws:
 837       return "pws";
 838     case scm_tc7_wvect:
 839       return "weak vector";
 840     case scm_tc7_vector:
 841       return "vector";
 842 #ifdef CCLO
 843     case scm_tc7_cclo:
 844       return "compiled closure";
 845 #endif
 846     case scm_tc7_number:
 847       switch (tag)
 848         {
 849         case scm_tc16_real:
 850           return "real";
 851           break;
 852         case scm_tc16_big:
 853           return "bignum";
 854           break;
 855         case scm_tc16_complex:
 856           return "complex number";
 857           break;
 858         case scm_tc16_fraction:
 859           return "fraction";
 860           break;
 861         }
 862       break;
 863     case scm_tc7_string:
 864       return "string";
 865       break;
 866     case scm_tc7_stringbuf:
 867       return "string buffer";
 868       break;
 869     case scm_tc7_symbol:
 870       return "symbol";
 871       break;
 872     case scm_tc7_variable:
 873       return "variable";
 874       break;
 875     case scm_tcs_subrs:
 876       return "subrs";
 877       break;
 878     case scm_tc7_port:
 879       return "port";
 880       break;
 881     case scm_tc7_smob:
 882       return "smob";            /* should not occur. */
 883       break;
 884     }
 885
 886   return NULL;
 887 }
 888
 889
 890 /*
 891    FIXME: Unimplemented procs!
 892
 893 */
 894
 895 void
 896 scm_gc_mark (SCM o)
 897 {
 898 }
 899
 900 void
 901 scm_gc_mark_dependencies (SCM o)
 902 {
 903 }
 904
 905 void
 906 scm_mark_locations (SCM_STACKITEM x[], unsigned long n)
 907 {
 908 }
 909
 910 \f
 911 void
 912 scm_init_gc ()
 913 {
 914   GC_init ();
 915
 916   scm_after_gc_hook = scm_permanent_object (scm_make_hook (SCM_INUM0));
 917   scm_c_define ("after-gc-hook", scm_after_gc_hook);
 918
 919   gc_async = scm_c_make_subr ("%gc-thunk", scm_tc7_subr_0,
 920                               gc_async_thunk);
 921
 922   scm_c_hook_add (&scm_after_gc_c_hook, mark_gc_async, NULL, 0);
 923
 924 #include "libguile/gc.x"
 925 }
 926
 927
 928 void
 929 scm_gc_sweep (void)
 930 #define FUNC_NAME "scm_gc_sweep"
 931 {
 932   /* FIXME */
 933   fprintf (stderr, "%s: doing nothing\n", __FUNCTION__);
 934 }
 935
 936 #undef FUNC_NAME
 937
 938
 939
 940 /*
 941   Local Variables:
 942   c-file-style: "gnu"
 943   End:
 944 */