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 <stdio.h>
  25 #include <errno.h>
  26 #include <string.h>
  27 #include <assert.h>
  28
  29 #include "libguile/_scm.h"
  30 #include "libguile/eval.h"
  31 #include "libguile/stime.h"
  32 #include "libguile/stackchk.h"
  33 #include "libguile/struct.h"
  34 #include "libguile/smob.h"
  35 #include "libguile/unif.h"
  36 #include "libguile/async.h"
  37 #include "libguile/ports.h"
  38 #include "libguile/root.h"
  39 #include "libguile/strings.h"
  40 #include "libguile/vectors.h"
  41 #include "libguile/weaks.h"
  42 #include "libguile/hashtab.h"
  43 #include "libguile/tags.h"
  44
  45 #include "libguile/private-gc.h"
  46 #include "libguile/validate.h"
  47 #include "libguile/deprecation.h"
  48 #include "libguile/gc.h"
  49 #include "libguile/dynwind.h"
  50
  51 #ifdef GUILE_DEBUG_MALLOC
  52 #include "libguile/debug-malloc.h"
  53 #endif
  54
  55 #ifdef HAVE_MALLOC_H
  56 #include <malloc.h>
  57 #endif
  58
  59 #ifdef HAVE_UNISTD_H
  60 #include <unistd.h>
  61 #endif
  62
  63 /* Lock this mutex before doing lazy sweeping.
  64  */
  65 scm_i_pthread_mutex_t scm_i_sweep_mutex = SCM_I_PTHREAD_MUTEX_INITIALIZER;
  66
  67 /* Set this to != 0 if every cell that is accessed shall be checked:
  68  */
  69 int scm_debug_cell_accesses_p = 0;
  70 int scm_expensive_debug_cell_accesses_p = 0;
  71
  72 /* Set this to 0 if no additional gc's shall be performed, otherwise set it to
  73  * the number of cell accesses after which a gc shall be called.
  74  */
  75 int scm_debug_cells_gc_interval = 0;
  76
  77 /*
  78   Global variable, so you can switch it off at runtime by setting
  79   scm_i_cell_validation_already_running.
  80  */
  81 int scm_i_cell_validation_already_running ;
  82
  83 #if (SCM_DEBUG_CELL_ACCESSES == 1)
  84
  85
  86 /*
  87
  88   Assert that the given object is a valid reference to a valid cell.  This
  89   test involves to determine whether the object is a cell pointer, whether
  90   this pointer actually points into a heap segment and whether the cell
  91   pointed to is not a free cell.  Further, additional garbage collections may
  92   get executed after a user defined number of cell accesses.  This helps to
  93   find places in the C code where references are dropped for extremely short
  94   periods.
  95
  96 */
  97 void
  98 scm_i_expensive_validation_check (SCM cell)
  99 {
 100   if (!scm_in_heap_p (cell))
 101     {
 102       fprintf (stderr, "scm_assert_cell_valid: this object does not live in the heap: %lux\n",
 103                (unsigned long) SCM_UNPACK (cell));
 104       abort ();
 105     }
 106
 107   /* If desired, perform additional garbage collections after a user
 108    * defined number of cell accesses.
 109    */
 110   if (scm_debug_cells_gc_interval)
 111     {
 112       static unsigned int counter = 0;
 113
 114       if (counter != 0)
 115         {
 116           --counter;
 117         }
 118       else
 119         {
 120           counter = scm_debug_cells_gc_interval;
 121           scm_gc ();
 122         }
 123     }
 124 }
 125
 126 void
 127 scm_assert_cell_valid (SCM cell)
 128 {
 129   if (!scm_i_cell_validation_already_running && scm_debug_cell_accesses_p)
 130     {
 131       scm_i_cell_validation_already_running = 1;  /* set to avoid recursion */
 132
 133       /*
 134         During GC, no user-code should be run, and the guile core
 135         should use non-protected accessors.
 136       */
 137       if (scm_gc_running_p)
 138         return;
 139
 140       /*
 141         Only scm_in_heap_p and rescanning the heap is wildly
 142         expensive.
 143       */
 144       if (scm_expensive_debug_cell_accesses_p)
 145         scm_i_expensive_validation_check (cell);
 146 #if (SCM_DEBUG_MARKING_API == 0)
 147       if (!SCM_GC_MARK_P (cell))
 148         {
 149           fprintf (stderr,
 150                    "scm_assert_cell_valid: this object is unmarked. \n"
 151                    "It has been garbage-collected in the last GC run: "
 152                    "%lux\n",
 153                    (unsigned long) SCM_UNPACK (cell));
 154           abort ();
 155         }
 156 #endif /* SCM_DEBUG_MARKING_API */
 157
 158       scm_i_cell_validation_already_running = 0;  /* re-enable */
 159     }
 160 }
 161
 162
 163
 164 SCM_DEFINE (scm_set_debug_cell_accesses_x, "set-debug-cell-accesses!", 1, 0, 0,
 165             (SCM flag),
 166             "If @var{flag} is @code{#f}, cell access checking is disabled.\n"
 167             "If @var{flag} is @code{#t}, cheap cell access checking is enabled,\n"
 168             "but no additional calls to garbage collection are issued.\n"
 169             "If @var{flag} is a number, strict cell access checking is enabled,\n"
 170             "with an additional garbage collection after the given\n"
 171             "number of cell accesses.\n"
 172             "This procedure only exists when the compile-time flag\n"
 173             "@code{SCM_DEBUG_CELL_ACCESSES} was set to 1.")
 174 #define FUNC_NAME s_scm_set_debug_cell_accesses_x
 175 {
 176   if (scm_is_false (flag))
 177     {
 178       scm_debug_cell_accesses_p = 0;
 179     }
 180   else if (scm_is_eq (flag, SCM_BOOL_T))
 181     {
 182       scm_debug_cells_gc_interval = 0;
 183       scm_debug_cell_accesses_p = 1;
 184       scm_expensive_debug_cell_accesses_p = 0;
 185     }
 186   else
 187     {
 188       scm_debug_cells_gc_interval = scm_to_signed_integer (flag, 0, INT_MAX);
 189       scm_debug_cell_accesses_p = 1;
 190       scm_expensive_debug_cell_accesses_p = 1;
 191     }
 192   return SCM_UNSPECIFIED;
 193 }
 194 #undef FUNC_NAME
 195
 196
 197 #endif  /* SCM_DEBUG_CELL_ACCESSES == 1 */
 198
 199 \f
 200
 201
 202 /* scm_mtrigger
 203  * is the number of bytes of malloc allocation needed to trigger gc.
 204  */
 205 unsigned long scm_mtrigger;
 206
 207 /* GC Statistics Keeping
 208  */
 209 unsigned long scm_cells_allocated = 0;
 210 unsigned long scm_last_cells_allocated = 0;
 211 unsigned long scm_mallocated = 0;
 212 long int scm_i_find_heap_calls = 0;
 213 /* Global GC sweep statistics since the last full GC.  */
 214 scm_t_sweep_statistics scm_i_gc_sweep_stats = { 0, 0 };
 215
 216 /* Total count of cells marked/swept.  */
 217 static double scm_gc_cells_marked_acc = 0.;
 218 static double scm_gc_cells_marked_conservatively_acc = 0.;
 219 static double scm_gc_cells_swept_acc = 0.;
 220 static double scm_gc_cells_allocated_acc = 0.;
 221
 222 static unsigned long scm_gc_time_taken = 0;
 223 static unsigned long scm_gc_mark_time_taken = 0;
 224
 225 static unsigned long scm_gc_times = 0;
 226
 227 static int scm_gc_cell_yield_percentage = 0;
 228 static unsigned long protected_obj_count = 0;
 229
 230 /* The following are accessed from `gc-malloc.c' and `gc-card.c'.  */
 231 int scm_gc_malloc_yield_percentage = 0;
 232 unsigned long scm_gc_malloc_collected = 0;
 233
 234
 235 SCM_SYMBOL (sym_cells_allocated, "cells-allocated");
 236 SCM_SYMBOL (sym_heap_size, "cell-heap-size");
 237 SCM_SYMBOL (sym_mallocated, "bytes-malloced");
 238 SCM_SYMBOL (sym_mtrigger, "gc-malloc-threshold");
 239 SCM_SYMBOL (sym_heap_segments, "cell-heap-segments");
 240 SCM_SYMBOL (sym_gc_time_taken, "gc-time-taken");
 241 SCM_SYMBOL (sym_gc_mark_time_taken, "gc-mark-time-taken");
 242 SCM_SYMBOL (sym_times, "gc-times");
 243 SCM_SYMBOL (sym_cells_marked, "cells-marked");
 244 SCM_SYMBOL (sym_cells_marked_conservatively, "cells-marked-conservatively");
 245 SCM_SYMBOL (sym_cells_swept, "cells-swept");
 246 SCM_SYMBOL (sym_malloc_yield, "malloc-yield");
 247 SCM_SYMBOL (sym_cell_yield, "cell-yield");
 248 SCM_SYMBOL (sym_protected_objects, "protected-objects");
 249 SCM_SYMBOL (sym_total_cells_allocated, "total-cells-allocated");
 250
 251
 252 /* Number of calls to SCM_NEWCELL since startup.  */
 253 unsigned scm_newcell_count;
 254 unsigned scm_newcell2_count;
 255
 256
 257 /* {Scheme Interface to GC}
 258  */
 259 static SCM
 260 tag_table_to_type_alist (void *closure, SCM key, SCM val, SCM acc)
 261 {
 262   if (scm_is_integer (key))
 263     {
 264       int c_tag = scm_to_int (key);
 265
 266       char const * name = scm_i_tag_name (c_tag);
 267       if (name != NULL)
 268         {
 269           key = scm_from_locale_string (name);
 270         }
 271       else
 272         {
 273           char s[100];
 274           sprintf (s, "tag %d", c_tag);
 275           key = scm_from_locale_string (s);
 276         }
 277     }
 278
 279   return scm_cons (scm_cons (key, val), acc);
 280 }
 281
 282 SCM_DEFINE (scm_gc_live_object_stats, "gc-live-object-stats", 0, 0, 0,
 283             (),
 284             "Return an alist of statistics of the current live objects. ")
 285 #define FUNC_NAME s_scm_gc_live_object_stats
 286 {
 287   SCM tab = scm_make_hash_table (scm_from_int (57));
 288   SCM alist;
 289
 290   scm_i_all_segments_statistics (tab);
 291
 292   alist
 293     = scm_internal_hash_fold (&tag_table_to_type_alist, NULL, SCM_EOL, tab);
 294
 295   return alist;
 296 }
 297 #undef FUNC_NAME
 298
 299 extern int scm_gc_malloc_yield_percentage;
 300 SCM_DEFINE (scm_gc_stats, "gc-stats", 0, 0, 0,
 301             (),
 302             "Return an association list of statistics about Guile's current\n"
 303             "use of storage.\n")
 304 #define FUNC_NAME s_scm_gc_stats
 305 {
 306   long i = 0;
 307   SCM heap_segs = SCM_EOL ;
 308   unsigned long int local_scm_mtrigger;
 309   unsigned long int local_scm_mallocated;
 310   unsigned long int local_scm_heap_size;
 311   int local_scm_gc_cell_yield_percentage;
 312   int local_scm_gc_malloc_yield_percentage;
 313   unsigned long int local_scm_cells_allocated;
 314   unsigned long int local_scm_gc_time_taken;
 315   unsigned long int local_scm_gc_times;
 316   unsigned long int local_scm_gc_mark_time_taken;
 317   unsigned long int local_protected_obj_count;
 318   double local_scm_gc_cells_swept;
 319   double local_scm_gc_cells_marked;
 320   double local_scm_gc_cells_marked_conservatively;
 321   double local_scm_total_cells_allocated;
 322   SCM answer;
 323   unsigned long *bounds = 0;
 324   int table_size = 0;
 325   SCM_CRITICAL_SECTION_START;
 326
 327   bounds = scm_i_segment_table_info (&table_size);
 328
 329   /* Below, we cons to produce the resulting list.  We want a snapshot of
 330    * the heap situation before consing.
 331    */
 332   local_scm_mtrigger = scm_mtrigger;
 333   local_scm_mallocated = scm_mallocated;
 334   local_scm_heap_size =
 335     (scm_i_master_freelist.heap_total_cells + scm_i_master_freelist2.heap_total_cells);
 336
 337   local_scm_cells_allocated =
 338     scm_cells_allocated + scm_i_gc_sweep_stats.collected;
 339
 340   local_scm_gc_time_taken = scm_gc_time_taken;
 341   local_scm_gc_mark_time_taken = scm_gc_mark_time_taken;
 342   local_scm_gc_times = scm_gc_times;
 343   local_scm_gc_malloc_yield_percentage = scm_gc_malloc_yield_percentage;
 344   local_scm_gc_cell_yield_percentage = scm_gc_cell_yield_percentage;
 345   local_protected_obj_count = protected_obj_count;
 346   local_scm_gc_cells_swept =
 347     (double) scm_gc_cells_swept_acc
 348     + (double) scm_i_gc_sweep_stats.swept;
 349   local_scm_gc_cells_marked = scm_gc_cells_marked_acc
 350     + (double) scm_i_gc_sweep_stats.swept
 351     - (double) scm_i_gc_sweep_stats.collected;
 352   local_scm_gc_cells_marked_conservatively
 353     = scm_gc_cells_marked_conservatively_acc;
 354
 355   local_scm_total_cells_allocated = scm_gc_cells_allocated_acc
 356     + (double) scm_i_gc_sweep_stats.collected;
 357
 358   for (i = table_size; i--;)
 359     {
 360       heap_segs = scm_cons (scm_cons (scm_from_ulong (bounds[2*i]),
 361                                       scm_from_ulong (bounds[2*i+1])),
 362                             heap_segs);
 363     }
 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_total_cells_allocated,
 373                           scm_from_double (local_scm_total_cells_allocated)),
 374                 scm_cons (sym_heap_size,
 375                           scm_from_ulong (local_scm_heap_size)),
 376                 scm_cons (sym_cells_marked_conservatively,
 377                           scm_from_ulong (local_scm_gc_cells_marked_conservatively)),
 378                 scm_cons (sym_mallocated,
 379                           scm_from_ulong (local_scm_mallocated)),
 380                 scm_cons (sym_mtrigger,
 381                           scm_from_ulong (local_scm_mtrigger)),
 382                 scm_cons (sym_times,
 383                           scm_from_ulong (local_scm_gc_times)),
 384                 scm_cons (sym_gc_mark_time_taken,
 385                           scm_from_ulong (local_scm_gc_mark_time_taken)),
 386                 scm_cons (sym_cells_marked,
 387                           scm_from_double (local_scm_gc_cells_marked)),
 388                 scm_cons (sym_cells_swept,
 389                           scm_from_double (local_scm_gc_cells_swept)),
 390                 scm_cons (sym_malloc_yield,
 391                           scm_from_long (local_scm_gc_malloc_yield_percentage)),
 392                 scm_cons (sym_cell_yield,
 393                           scm_from_long (local_scm_gc_cell_yield_percentage)),
 394                 scm_cons (sym_protected_objects,
 395                           scm_from_ulong (local_protected_obj_count)),
 396                 scm_cons (sym_heap_segments, heap_segs),
 397                 SCM_UNDEFINED);
 398   SCM_CRITICAL_SECTION_END;
 399
 400   free (bounds);
 401   return answer;
 402 }
 403 #undef FUNC_NAME
 404
 405 /*
 406   Update nice-to-know-statistics.
 407  */
 408 static void
 409 gc_end_stats ()
 410 {
 411   /* CELLS SWEPT is another word for the number of cells that were examined
 412      during GC. YIELD is the number that we cleaned out. MARKED is the number
 413      that weren't cleaned.  */
 414   scm_gc_cell_yield_percentage = (scm_i_gc_sweep_stats.collected * 100) /
 415     (scm_i_master_freelist.heap_total_cells + scm_i_master_freelist2.heap_total_cells);
 416
 417   scm_gc_cells_allocated_acc +=
 418     (double) scm_i_gc_sweep_stats.collected;
 419   scm_gc_cells_marked_acc += (double) scm_i_last_marked_cell_count;
 420   scm_gc_cells_marked_conservatively_acc += (double) scm_i_find_heap_calls;
 421   scm_gc_cells_swept_acc += (double) scm_i_gc_sweep_stats.swept;
 422
 423   ++scm_gc_times;
 424 }
 425
 426 SCM_DEFINE (scm_object_address, "object-address", 1, 0, 0,
 427             (SCM obj),
 428             "Return an integer that for the lifetime of @var{obj} is uniquely\n"
 429             "returned by this function for @var{obj}")
 430 #define FUNC_NAME s_scm_object_address
 431 {
 432   return scm_from_ulong (SCM_UNPACK (obj));
 433 }
 434 #undef FUNC_NAME
 435
 436
 437 SCM_DEFINE (scm_gc, "gc", 0, 0, 0,
 438            (),
 439             "Scans all of SCM objects and reclaims for further use those that are\n"
 440             "no longer accessible.")
 441 #define FUNC_NAME s_scm_gc
 442 {
 443   scm_i_scm_pthread_mutex_lock (&scm_i_sweep_mutex);
 444   scm_gc_running_p = 1;
 445   scm_i_gc ("call");
 446   /* njrev: It looks as though other places, e.g. scm_realloc,
 447      can call scm_i_gc without acquiring the sweep mutex.  Does this
 448      matter?  Also scm_i_gc (or its descendants) touch the
 449      scm_sys_protects, which are protected in some cases
 450      (e.g. scm_permobjs above in scm_gc_stats) by a critical section,
 451      not by the sweep mutex.  Shouldn't all the GC-relevant objects be
 452      protected in the same way? */
 453   scm_gc_running_p = 0;
 454   scm_i_pthread_mutex_unlock (&scm_i_sweep_mutex);
 455   scm_c_hook_run (&scm_after_gc_c_hook, 0);
 456   return SCM_UNSPECIFIED;
 457 }
 458 #undef FUNC_NAME
 459
 460
 461 \f
 462
 463 /* The master is global and common while the freelist will be
 464  * individual for each thread.
 465  */
 466
 467 SCM
 468 scm_gc_for_newcell (scm_t_cell_type_statistics *freelist, SCM *free_cells)
 469 {
 470   SCM cell;
 471   int did_gc = 0;
 472
 473   scm_i_scm_pthread_mutex_lock (&scm_i_sweep_mutex);
 474   scm_gc_running_p = 1;
 475
 476   *free_cells = scm_i_sweep_for_freelist (freelist);
 477   if (*free_cells == SCM_EOL)
 478     {
 479       float delta = scm_i_gc_heap_size_delta (freelist);
 480       if (delta > 0.0)
 481         {
 482           size_t bytes = ((unsigned long) delta) * sizeof (scm_t_cell);
 483           freelist->heap_segment_idx =
 484             scm_i_get_new_heap_segment (freelist, bytes, abort_on_error);
 485
 486           *free_cells = scm_i_sweep_for_freelist (freelist);
 487         }
 488     }
 489
 490   if (*free_cells == SCM_EOL)
 491     {
 492       /*
 493         out of fresh cells. Try to get some new ones.
 494        */
 495       char reason[] = "0-cells";
 496       reason[0] += freelist->span;
 497
 498       did_gc = 1;
 499       scm_i_gc (reason);
 500
 501       *free_cells = scm_i_sweep_for_freelist (freelist);
 502     }
 503
 504   if (*free_cells == SCM_EOL)
 505     {
 506       /*
 507         failed getting new cells. Get new juice or die.
 508       */
 509       float delta = scm_i_gc_heap_size_delta (freelist);
 510       assert (delta > 0.0);
 511       size_t bytes = ((unsigned long) delta) * sizeof (scm_t_cell);
 512       freelist->heap_segment_idx =
 513         scm_i_get_new_heap_segment (freelist, bytes, abort_on_error);
 514
 515       *free_cells = scm_i_sweep_for_freelist (freelist);
 516     }
 517
 518   if (*free_cells == SCM_EOL)
 519     abort ();
 520
 521   cell = *free_cells;
 522
 523   *free_cells = SCM_FREE_CELL_CDR (cell);
 524
 525   scm_gc_running_p = 0;
 526   scm_i_pthread_mutex_unlock (&scm_i_sweep_mutex);
 527
 528   if (did_gc)
 529     scm_c_hook_run (&scm_after_gc_c_hook, 0);
 530
 531   return cell;
 532 }
 533
 534
 535 scm_t_c_hook scm_before_gc_c_hook;
 536 scm_t_c_hook scm_before_mark_c_hook;
 537 scm_t_c_hook scm_before_sweep_c_hook;
 538 scm_t_c_hook scm_after_sweep_c_hook;
 539 scm_t_c_hook scm_after_gc_c_hook;
 540
 541 static void
 542 scm_check_deprecated_memory_return ()
 543 {
 544   if (scm_mallocated < scm_i_deprecated_memory_return)
 545     {
 546       /* The byte count of allocated objects has underflowed.  This is
 547          probably because you forgot to report the sizes of objects you
 548          have allocated, by calling scm_done_malloc or some such.  When
 549          the GC freed them, it subtracted their size from
 550          scm_mallocated, which underflowed.  */
 551       fprintf (stderr,
 552                "scm_gc_sweep: Byte count of allocated objects has underflowed.\n"
 553                "This is probably because the GC hasn't been correctly informed\n"
 554                "about object sizes\n");
 555       abort ();
 556     }
 557   scm_mallocated -= scm_i_deprecated_memory_return;
 558   scm_i_deprecated_memory_return = 0;
 559 }
 560
 561 long int scm_i_last_marked_cell_count;
 562
 563 /* Must be called while holding scm_i_sweep_mutex.
 564
 565    This function is fairly long, but it touches various global
 566    variables. To not obscure the side effects on global variables,
 567    this function has not been split up.
 568  */
 569 void
 570 scm_i_gc (const char *what)
 571 {
 572   unsigned long t_before_gc = 0;
 573
 574   scm_i_thread_put_to_sleep ();
 575
 576   scm_c_hook_run (&scm_before_gc_c_hook, 0);
 577
 578 #ifdef DEBUGINFO
 579   fprintf (stderr,"gc reason %s\n", what);
 580   fprintf (stderr,
 581            scm_is_null (*SCM_FREELIST_LOC (scm_i_freelist))
 582            ? "*"
 583            : (scm_is_null (*SCM_FREELIST_LOC (scm_i_freelist2)) ? "o" : "m"));
 584 #endif
 585
 586   t_before_gc = scm_c_get_internal_run_time ();
 587   scm_gc_malloc_collected = 0;
 588
 589   /*
 590     Set freelists to NULL so scm_cons () always triggers gc, causing
 591     the assertion above to fail.
 592   */
 593   *SCM_FREELIST_LOC (scm_i_freelist) = SCM_EOL;
 594   *SCM_FREELIST_LOC (scm_i_freelist2) = SCM_EOL;
 595
 596   /*
 597     Let's finish the sweep. The conservative GC might point into the
 598     garbage, and marking that would create a mess.
 599    */
 600   scm_i_sweep_all_segments ("GC", &scm_i_gc_sweep_stats);
 601   scm_check_deprecated_memory_return ();
 602
 603 #if (SCM_DEBUG_CELL_ACCESSES == 0 && SCM_SIZEOF_UNSIGNED_LONG == 4)
 604   /* Sanity check our numbers. */
 605   /* TODO(hanwen): figure out why the stats are off on x64_64. */
 606   /* If this was not true, someone touched mark bits outside of the
 607      mark phase. */
 608   if (scm_i_last_marked_cell_count != scm_i_marked_count ())
 609     {
 610       static char msg[] =
 611         "The number of marked objects changed since the last GC: %d vs %d.";
 612       /* At some point, we should probably use a deprecation warning. */
 613       fprintf(stderr, msg, scm_i_last_marked_cell_count, scm_i_marked_count ());
 614     }
 615   assert (scm_i_gc_sweep_stats.swept
 616           == (scm_i_master_freelist.heap_total_cells
 617               + scm_i_master_freelist2.heap_total_cells));
 618   assert (scm_i_gc_sweep_stats.collected + scm_i_last_marked_cell_count
 619           == scm_i_gc_sweep_stats.swept);
 620 #endif /* SCM_DEBUG_CELL_ACCESSES */
 621
 622   /* Mark */
 623   scm_c_hook_run (&scm_before_mark_c_hook, 0);
 624
 625   scm_mark_all ();
 626   scm_gc_mark_time_taken += (scm_c_get_internal_run_time () - t_before_gc);
 627
 628   scm_i_last_marked_cell_count = scm_cells_allocated = scm_i_marked_count ();
 629
 630   /* Sweep
 631
 632     TODO: the after_sweep hook should probably be moved to just before
 633     the mark, since that's where the sweep is finished in lazy
 634     sweeping.
 635
 636     MDJ 030219 <djurfeldt@nada.kth.se>: No, probably not.  The
 637     original meaning implied at least two things: that it would be
 638     called when
 639
 640       1. the freelist is re-initialized (no evaluation possible, though)
 641
 642     and
 643
 644       2. the heap is "fresh"
 645          (it is well-defined what data is used and what is not)
 646
 647     Neither of these conditions would hold just before the mark phase.
 648
 649     Of course, the lazy sweeping has muddled the distinction between
 650     scm_before_sweep_c_hook and scm_after_sweep_c_hook, but even if
 651     there were no difference, it would still be useful to have two
 652     distinct classes of hook functions since this can prevent some
 653     bad interference when several modules adds gc hooks.
 654    */
 655   scm_c_hook_run (&scm_before_sweep_c_hook, 0);
 656
 657   /*
 658     Nothing here: lazy sweeping.
 659    */
 660   scm_i_reset_segments ();
 661
 662   *SCM_FREELIST_LOC (scm_i_freelist) = SCM_EOL;
 663   *SCM_FREELIST_LOC (scm_i_freelist2) = SCM_EOL;
 664
 665   /* Invalidate the freelists of other threads. */
 666   scm_i_thread_invalidate_freelists ();
 667
 668   scm_c_hook_run (&scm_after_sweep_c_hook, 0);
 669
 670   gc_end_stats ();
 671
 672   scm_i_gc_sweep_stats.collected = scm_i_gc_sweep_stats.swept = 0;
 673   scm_i_gc_sweep_freelist_reset (&scm_i_master_freelist);
 674   scm_i_gc_sweep_freelist_reset (&scm_i_master_freelist2);
 675
 676   /* Arguably, this statistic is fairly useless: marking will dominate
 677      the time taken.
 678   */
 679   scm_gc_time_taken += (scm_c_get_internal_run_time () - t_before_gc);
 680
 681   scm_i_thread_wake_up ();
 682   /*
 683     For debugging purposes, you could do
 684     scm_i_sweep_all_segments ("debug"), but then the remains of the
 685     cell aren't left to analyse.
 686    */
 687 }
 688
 689
 690 \f
 691 /* {GC Protection Helper Functions}
 692  */
 693
 694
 695 /*
 696  * If within a function you need to protect one or more scheme objects from
 697  * garbage collection, pass them as parameters to one of the
 698  * scm_remember_upto_here* functions below.  These functions don't do
 699  * anything, but since the compiler does not know that they are actually
 700  * no-ops, it will generate code that calls these functions with the given
 701  * parameters.  Therefore, you can be sure that the compiler will keep those
 702  * scheme values alive (on the stack or in a register) up to the point where
 703  * scm_remember_upto_here* is called.  In other words, place the call to
 704  * scm_remember_upto_here* _behind_ the last code in your function, that
 705  * depends on the scheme object to exist.
 706  *
 707  * Example: We want to make sure that the string object str does not get
 708  * garbage collected during the execution of 'some_function' in the code
 709  * below, because otherwise the characters belonging to str would be freed and
 710  * 'some_function' might access freed memory.  To make sure that the compiler
 711  * keeps str alive on the stack or in a register such that it is visible to
 712  * the conservative gc we add the call to scm_remember_upto_here_1 _after_ the
 713  * call to 'some_function'.  Note that this would not be necessary if str was
 714  * used anyway after the call to 'some_function'.
 715  *   char *chars = scm_i_string_chars (str);
 716  *   some_function (chars);
 717  *   scm_remember_upto_here_1 (str);  // str will be alive up to this point.
 718  */
 719
 720 /* Remove any macro versions of these while defining the functions.
 721    Functions are always included in the library, for upward binary
 722    compatibility and in case combinations of GCC and non-GCC are used.  */
 723 #undef scm_remember_upto_here_1
 724 #undef scm_remember_upto_here_2
 725
 726 void
 727 scm_remember_upto_here_1 (SCM obj SCM_UNUSED)
 728 {
 729   /* Empty.  Protects a single object from garbage collection. */
 730 }
 731
 732 void
 733 scm_remember_upto_here_2 (SCM obj1 SCM_UNUSED, SCM obj2 SCM_UNUSED)
 734 {
 735   /* Empty.  Protects two objects from garbage collection. */
 736 }
 737
 738 void
 739 scm_remember_upto_here (SCM obj SCM_UNUSED, ...)
 740 {
 741   /* Empty.  Protects any number of objects from garbage collection. */
 742 }
 743
 744 /*
 745   These crazy functions prevent garbage collection
 746   of arguments after the first argument by
 747   ensuring they remain live throughout the
 748   function because they are used in the last
 749   line of the code block.
 750   It'd be better to have a nice compiler hint to
 751   aid the conservative stack-scanning GC. --03/09/00 gjb */
 752 SCM
 753 scm_return_first (SCM elt, ...)
 754 {
 755   return elt;
 756 }
 757
 758 int
 759 scm_return_first_int (int i, ...)
 760 {
 761   return i;
 762 }
 763
 764
 765 SCM
 766 scm_permanent_object (SCM obj)
 767 {
 768   SCM cell = scm_cons (obj, SCM_EOL);
 769   SCM_CRITICAL_SECTION_START;
 770   SCM_SETCDR (cell, scm_permobjs);
 771   scm_permobjs = cell;
 772   SCM_CRITICAL_SECTION_END;
 773   return obj;
 774 }
 775
 776
 777 /* Protect OBJ from the garbage collector.  OBJ will not be freed, even if all
 778    other references are dropped, until the object is unprotected by calling
 779    scm_gc_unprotect_object (OBJ).  Calls to scm_gc_protect/unprotect_object nest,
 780    i. e. it is possible to protect the same object several times, but it is
 781    necessary to unprotect the object the same number of times to actually get
 782    the object unprotected.  It is an error to unprotect an object more often
 783    than it has been protected before.  The function scm_protect_object returns
 784    OBJ.
 785 */
 786
 787 /* Implementation note:  For every object X, there is a counter which
 788    scm_gc_protect_object (X) increments and scm_gc_unprotect_object (X) decrements.
 789 */
 790
 791
 792
 793 SCM
 794 scm_gc_protect_object (SCM obj)
 795 {
 796   SCM handle;
 797
 798   /* This critical section barrier will be replaced by a mutex. */
 799   /* njrev: Indeed; if my comment above is correct, there is the same
 800      critsec/mutex inconsistency here. */
 801   SCM_CRITICAL_SECTION_START;
 802
 803   handle = scm_hashq_create_handle_x (scm_protects, obj, scm_from_int (0));
 804   SCM_SETCDR (handle, scm_sum (SCM_CDR (handle), scm_from_int (1)));
 805
 806   protected_obj_count ++;
 807
 808   SCM_CRITICAL_SECTION_END;
 809
 810   return obj;
 811 }
 812
 813
 814 /* Remove any protection for OBJ established by a prior call to
 815    scm_protect_object.  This function returns OBJ.
 816
 817    See scm_protect_object for more information.  */
 818 SCM
 819 scm_gc_unprotect_object (SCM obj)
 820 {
 821   SCM handle;
 822
 823   /* This critical section barrier will be replaced by a mutex. */
 824   /* njrev: and again. */
 825   SCM_CRITICAL_SECTION_START;
 826
 827   if (scm_gc_running_p)
 828     {
 829       fprintf (stderr, "scm_unprotect_object called during GC.\n");
 830       abort ();
 831     }
 832
 833   handle = scm_hashq_get_handle (scm_protects, obj);
 834
 835   if (scm_is_false (handle))
 836     {
 837       fprintf (stderr, "scm_unprotect_object called on unprotected object\n");
 838       abort ();
 839     }
 840   else
 841     {
 842       SCM count = scm_difference (SCM_CDR (handle), scm_from_int (1));
 843       if (scm_is_eq (count, scm_from_int (0)))
 844         scm_hashq_remove_x (scm_protects, obj);
 845       else
 846         SCM_SETCDR (handle, count);
 847     }
 848   protected_obj_count --;
 849
 850   SCM_CRITICAL_SECTION_END;
 851
 852   return obj;
 853 }
 854
 855 void
 856 scm_gc_register_root (SCM *p)
 857 {
 858   SCM handle;
 859   SCM key = scm_from_ulong ((unsigned long) p);
 860
 861   /* This critical section barrier will be replaced by a mutex. */
 862   /* njrev: and again. */
 863   SCM_CRITICAL_SECTION_START;
 864
 865   handle = scm_hashv_create_handle_x (scm_gc_registered_roots, key,
 866                                       scm_from_int (0));
 867   /* njrev: note also that the above can probably signal an error */
 868   SCM_SETCDR (handle, scm_sum (SCM_CDR (handle), scm_from_int (1)));
 869
 870   SCM_CRITICAL_SECTION_END;
 871 }
 872
 873 void
 874 scm_gc_unregister_root (SCM *p)
 875 {
 876   SCM handle;
 877   SCM key = scm_from_ulong ((unsigned long) p);
 878
 879   /* This critical section barrier will be replaced by a mutex. */
 880   /* njrev: and again. */
 881   SCM_CRITICAL_SECTION_START;
 882
 883   handle = scm_hashv_get_handle (scm_gc_registered_roots, key);
 884
 885   if (scm_is_false (handle))
 886     {
 887       fprintf (stderr, "scm_gc_unregister_root called on unregistered root\n");
 888       abort ();
 889     }
 890   else
 891     {
 892       SCM count = scm_difference (SCM_CDR (handle), scm_from_int (1));
 893       if (scm_is_eq (count, scm_from_int (0)))
 894         scm_hashv_remove_x (scm_gc_registered_roots, key);
 895       else
 896         SCM_SETCDR (handle, count);
 897     }
 898
 899   SCM_CRITICAL_SECTION_END;
 900 }
 901
 902 void
 903 scm_gc_register_roots (SCM *b, unsigned long n)
 904 {
 905   SCM *p = b;
 906   for (; p < b + n; ++p)
 907     scm_gc_register_root (p);
 908 }
 909
 910 void
 911 scm_gc_unregister_roots (SCM *b, unsigned long n)
 912 {
 913   SCM *p = b;
 914   for (; p < b + n; ++p)
 915     scm_gc_unregister_root (p);
 916 }
 917
 918 int scm_i_terminating;
 919
 920 \f
 921
 922
 923 /*
 924   MOVE THIS FUNCTION. IT DOES NOT HAVE ANYTHING TODO WITH GC.
 925  */
 926
 927 /* Get an integer from an environment variable.  */
 928 int
 929 scm_getenv_int (const char *var, int def)
 930 {
 931   char *end = 0;
 932   char *val = getenv (var);
 933   long res = def;
 934   if (!val)
 935     return def;
 936   res = strtol (val, &end, 10);
 937   if (end == val)
 938     return def;
 939   return res;
 940 }
 941
 942 void
 943 scm_storage_prehistory ()
 944 {
 945   scm_c_hook_init (&scm_before_gc_c_hook, 0, SCM_C_HOOK_NORMAL);
 946   scm_c_hook_init (&scm_before_mark_c_hook, 0, SCM_C_HOOK_NORMAL);
 947   scm_c_hook_init (&scm_before_sweep_c_hook, 0, SCM_C_HOOK_NORMAL);
 948   scm_c_hook_init (&scm_after_sweep_c_hook, 0, SCM_C_HOOK_NORMAL);
 949   scm_c_hook_init (&scm_after_gc_c_hook, 0, SCM_C_HOOK_NORMAL);
 950 }
 951
 952 scm_i_pthread_mutex_t scm_i_gc_admin_mutex = SCM_I_PTHREAD_MUTEX_INITIALIZER;
 953
 954 int
 955 scm_init_storage ()
 956 {
 957   size_t j;
 958
 959   j = SCM_NUM_PROTECTS;
 960   while (j)
 961     scm_sys_protects[--j] = SCM_BOOL_F;
 962
 963   scm_gc_init_freelist ();
 964   scm_gc_init_malloc ();
 965
 966 #if 0
 967   /* We can't have a cleanup handler since we have no thread to run it
 968      in. */
 969
 970 #ifdef HAVE_ATEXIT
 971   atexit (cleanup);
 972 #else
 973 #ifdef HAVE_ON_EXIT
 974   on_exit (cleanup, 0);
 975 #endif
 976 #endif
 977
 978 #endif
 979
 980   scm_stand_in_procs = scm_make_weak_key_hash_table (scm_from_int (257));
 981   scm_permobjs = SCM_EOL;
 982   scm_protects = scm_c_make_hash_table (31);
 983   scm_gc_registered_roots = scm_c_make_hash_table (31);
 984
 985   return 0;
 986 }
 987
 988 \f
 989
 990 SCM scm_after_gc_hook;
 991
 992 static SCM gc_async;
 993
 994 /* The function gc_async_thunk causes the execution of the after-gc-hook.  It
 995  * is run after the gc, as soon as the asynchronous events are handled by the
 996  * evaluator.
 997  */
 998 static SCM
 999 gc_async_thunk (void)
1000 {
1001   scm_c_run_hook (scm_after_gc_hook, SCM_EOL);
1002   return SCM_UNSPECIFIED;
1003 }
1004
1005
1006 /* The function mark_gc_async is run by the scm_after_gc_c_hook at the end of
1007  * the garbage collection.  The only purpose of this function is to mark the
1008  * gc_async (which will eventually lead to the execution of the
1009  * gc_async_thunk).
1010  */
1011 static void *
1012 mark_gc_async (void * hook_data SCM_UNUSED,
1013                void *fn_data SCM_UNUSED,
1014                void *data SCM_UNUSED)
1015 {
1016   /* If cell access debugging is enabled, the user may choose to perform
1017    * additional garbage collections after an arbitrary number of cell
1018    * accesses.  We don't want the scheme level after-gc-hook to be performed
1019    * for each of these garbage collections for the following reason: The
1020    * execution of the after-gc-hook causes cell accesses itself.  Thus, if the
1021    * after-gc-hook was performed with every gc, and if the gc was performed
1022    * after a very small number of cell accesses, then the number of cell
1023    * accesses during the execution of the after-gc-hook will suffice to cause
1024    * the execution of the next gc.  Then, guile would keep executing the
1025    * after-gc-hook over and over again, and would never come to do other
1026    * things.
1027    *
1028    * To overcome this problem, if cell access debugging with additional
1029    * garbage collections is enabled, the after-gc-hook is never run by the
1030    * garbage collecter.  When running guile with cell access debugging and the
1031    * execution of the after-gc-hook is desired, then it is necessary to run
1032    * the hook explicitly from the user code.  This has the effect, that from
1033    * the scheme level point of view it seems that garbage collection is
1034    * performed with a much lower frequency than it actually is.  Obviously,
1035    * this will not work for code that depends on a fixed one to one
1036    * relationship between the execution counts of the C level garbage
1037    * collection hooks and the execution count of the scheme level
1038    * after-gc-hook.
1039    */
1040
1041 #if (SCM_DEBUG_CELL_ACCESSES == 1)
1042   if (scm_debug_cells_gc_interval == 0)
1043     scm_system_async_mark (gc_async);
1044 #else
1045   scm_system_async_mark (gc_async);
1046 #endif
1047
1048   return NULL;
1049 }
1050
1051 void
1052 scm_init_gc ()
1053 {
1054   scm_gc_init_mark ();
1055
1056   scm_after_gc_hook = scm_permanent_object (scm_make_hook (SCM_INUM0));
1057   scm_c_define ("after-gc-hook", scm_after_gc_hook);
1058
1059   gc_async = scm_c_make_subr ("%gc-thunk", scm_tc7_subr_0,
1060                               gc_async_thunk);
1061
1062   scm_c_hook_add (&scm_after_gc_c_hook, mark_gc_async, NULL, 0);
1063
1064 #include "libguile/gc.x"
1065 }
1066
1067 #ifdef __ia64__
1068 # ifdef __hpux
1069 #  include <sys/param.h>
1070 #  include <sys/pstat.h>
1071 void *
1072 scm_ia64_register_backing_store_base (void)
1073 {
1074   struct pst_vm_status vm_status;
1075   int i = 0;
1076   while (pstat_getprocvm (&vm_status, sizeof (vm_status), 0, i++) == 1)
1077     if (vm_status.pst_type == PS_RSESTACK)
1078       return (void *) vm_status.pst_vaddr;
1079   abort ();
1080 }
1081 void *
1082 scm_ia64_ar_bsp (const void *ctx)
1083 {
1084   uint64_t bsp;
1085   __uc_get_ar_bsp (ctx, &bsp);
1086   return (void *) bsp;
1087 }
1088 # endif /* hpux */
1089 # ifdef linux
1090 #  include <ucontext.h>
1091 void *
1092 scm_ia64_register_backing_store_base (void)
1093 {
1094   extern void *__libc_ia64_register_backing_store_base;
1095   return __libc_ia64_register_backing_store_base;
1096 }
1097 void *
1098 scm_ia64_ar_bsp (const void *opaque)
1099 {
1100   const ucontext_t *ctx = opaque;
1101   return (void *) ctx->uc_mcontext.sc_ar_bsp;
1102 }
1103 # endif /* linux */
1104 #endif /* __ia64__ */
1105
1106 void
1107 scm_gc_sweep (void)
1108 #define FUNC_NAME "scm_gc_sweep"
1109 {
1110 }
1111
1112 #undef FUNC_NAME
1113
1114
1115
1116 /*
1117   Local Variables:
1118   c-file-style: "gnu"
1119   End:
1120 */