boehm-gc/alloc.c

   1 /*
   2  * Copyright 1988, 1989 Hans-J. Boehm, Alan J. Demers
   3  * Copyright (c) 1991-1996 by Xerox Corporation.  All rights reserved.
   4  * Copyright (c) 1998 by Silicon Graphics.  All rights reserved.
   5  * Copyright (c) 1999 by Hewlett-Packard Company. All rights reserved.
   6  *
   7  * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
   8  * OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
   9  *
  10  * Permission is hereby granted to use or copy this program
  11  * for any purpose,  provided the above notices are retained on all copies.
  12  * Permission to modify the code and to distribute modified code is granted,
  13  * provided the above notices are retained, and a notice that the code was
  14  * modified is included with the above copyright notice.
  15  *
  16  */
  17
  18
  19 # include "private/gc_priv.h"
  20
  21 # include <stdio.h>
  22 # if !defined(MACOS) && !defined(MSWINCE)
  23 #   include <signal.h>
  24 #   include <sys/types.h>
  25 # endif
  26
  27 /*
  28  * Separate free lists are maintained for different sized objects
  29  * up to MAXOBJSZ.
  30  * The call GC_allocobj(i,k) ensures that the freelist for
  31  * kind k objects of size i points to a non-empty
  32  * free list. It returns a pointer to the first entry on the free list.
  33  * In a single-threaded world, GC_allocobj may be called to allocate
  34  * an object of (small) size i as follows:
  35  *
  36  *            opp = &(GC_objfreelist[i]);
  37  *            if (*opp == 0) GC_allocobj(i, NORMAL);
  38  *            ptr = *opp;
  39  *            *opp = obj_link(ptr);
  40  *
  41  * Note that this is very fast if the free list is non-empty; it should
  42  * only involve the execution of 4 or 5 simple instructions.
  43  * All composite objects on freelists are cleared, except for
  44  * their first word.
  45  */
  46
  47 /*
  48  *  The allocator uses GC_allochblk to allocate large chunks of objects.
  49  * These chunks all start on addresses which are multiples of
  50  * HBLKSZ.   Each allocated chunk has an associated header,
  51  * which can be located quickly based on the address of the chunk.
  52  * (See headers.c for details.)
  53  * This makes it possible to check quickly whether an
  54  * arbitrary address corresponds to an object administered by the
  55  * allocator.
  56  */
  57
  58 word GC_non_gc_bytes = 0;  /* Number of bytes not intended to be collected */
  59
  60 word GC_gc_no = 0;
  61
  62 #ifndef SMALL_CONFIG
  63   int GC_incremental = 0;  /* By default, stop the world.       */
  64 #endif
  65
  66 int GC_parallel = FALSE;   /* By default, parallel GC is off.   */
  67
  68 int GC_full_freq = 19;     /* Every 20th collection is a full   */
  69                            /* collection, whether we need it    */
  70                            /* or not.                           */
  71
  72 GC_bool GC_need_full_gc = FALSE;
  73                            /* Need full GC do to heap growth.   */
  74
  75 #ifdef THREADS
  76   GC_bool GC_world_stopped = FALSE;
  77 # define IF_THREADS(x) x
  78 #else
  79 # define IF_THREADS(x)
  80 #endif
  81
  82 word GC_used_heap_size_after_full = 0;
  83
  84 char * GC_copyright[] =
  85 {"Copyright 1988,1989 Hans-J. Boehm and Alan J. Demers ",
  86 "Copyright (c) 1991-1995 by Xerox Corporation.  All rights reserved. ",
  87 "Copyright (c) 1996-1998 by Silicon Graphics.  All rights reserved. ",
  88 "Copyright (c) 1999-2001 by Hewlett-Packard Company.  All rights reserved. ",
  89 "THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY",
  90 " EXPRESSED OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.",
  91 "See source code for details." };
  92
  93 # include "version.h"
  94
  95 #if defined(SAVE_CALL_CHAIN) && \
  96         !(defined(REDIRECT_MALLOC) && defined(GC_HAVE_BUILTIN_BACKTRACE))
  97 #   define SAVE_CALL_CHAIN_IN_GC
  98     /* This is only safe if the call chain save mechanism won't end up  */
  99     /* calling GC_malloc.  The GNU C library documentation suggests     */
 100     /* that backtrace doesn't use malloc, but at least the initial      */
 101     /* call in some versions does seem to invoke the dynamic linker,    */
 102     /* which uses malloc.                                               */
 103 #endif
 104
 105 /* some more variables */
 106
 107 extern signed_word GC_mem_found;  /* Number of reclaimed longwords      */
 108                                   /* after garbage collection           */
 109
 110 GC_bool GC_dont_expand = 0;
 111
 112 word GC_free_space_divisor = 3;
 113
 114 extern GC_bool GC_collection_in_progress();
 115                 /* Collection is in progress, or was abandoned. */
 116
 117 int GC_never_stop_func GC_PROTO((void)) { return(0); }
 118
 119 unsigned long GC_time_limit = TIME_LIMIT;
 120
 121 CLOCK_TYPE GC_start_time;       /* Time at which we stopped world.      */
 122                                 /* used only in GC_timeout_stop_func.   */
 123
 124 int GC_n_attempts = 0;          /* Number of attempts at finishing      */
 125                                 /* collection within GC_time_limit.     */
 126
 127 #if defined(SMALL_CONFIG) || defined(NO_CLOCK)
 128 #   define GC_timeout_stop_func GC_never_stop_func
 129 #else
 130   int GC_timeout_stop_func GC_PROTO((void))
 131   {
 132     CLOCK_TYPE current_time;
 133     static unsigned count = 0;
 134     unsigned long time_diff;
 135
 136     if ((count++ & 3) != 0) return(0);
 137     GET_TIME(current_time);
 138     time_diff = MS_TIME_DIFF(current_time,GC_start_time);
 139     if (time_diff >= GC_time_limit) {
 140 #       ifdef CONDPRINT
 141           if (GC_print_stats) {
 142             GC_printf0("Abandoning stopped marking after ");
 143             GC_printf1("%lu msecs", (unsigned long)time_diff);
 144             GC_printf1("(attempt %ld)\n", (unsigned long) GC_n_attempts);
 145           }
 146 #       endif
 147         return(1);
 148     }
 149     return(0);
 150   }
 151 #endif /* !SMALL_CONFIG */
 152
 153 /* Return the minimum number of words that must be allocated between    */
 154 /* collections to amortize the collection cost.                         */
 155 static word min_words_allocd()
 156 {
 157 #   ifdef THREADS
 158         /* We punt, for now. */
 159         register signed_word stack_size = 10000;
 160 #   else
 161         int dummy;
 162         register signed_word stack_size = (ptr_t)(&dummy) - GC_stackbottom;
 163 #   endif
 164     word total_root_size;           /* includes double stack size,      */
 165                                     /* since the stack is expensive     */
 166                                     /* to scan.                         */
 167     word scan_size;             /* Estimate of memory to be scanned     */
 168                                 /* during normal GC.                    */
 169
 170     if (stack_size < 0) stack_size = -stack_size;
 171     total_root_size = 2 * stack_size + GC_root_size;
 172     scan_size = BYTES_TO_WORDS(GC_heapsize - GC_large_free_bytes
 173                                + (GC_large_free_bytes >> 2)
 174                                    /* use a bit more of large empty heap */
 175                                + total_root_size);
 176     if (TRUE_INCREMENTAL) {
 177         return scan_size / (2 * GC_free_space_divisor);
 178     } else {
 179         return scan_size / GC_free_space_divisor;
 180     }
 181 }
 182
 183 /* Return the number of words allocated, adjusted for explicit storage  */
 184 /* management, etc..  This number is used in deciding when to trigger   */
 185 /* collections.                                                         */
 186 word GC_adj_words_allocd()
 187 {
 188     register signed_word result;
 189     register signed_word expl_managed =
 190                 BYTES_TO_WORDS((long)GC_non_gc_bytes
 191                                 - (long)GC_non_gc_bytes_at_gc);
 192
 193     /* Don't count what was explicitly freed, or newly allocated for    */
 194     /* explicit management.  Note that deallocating an explicitly       */
 195     /* managed object should not alter result, assuming the client      */
 196     /* is playing by the rules.                                         */
 197     result = (signed_word)GC_words_allocd
 198              - (signed_word)GC_mem_freed
 199              + (signed_word)GC_finalizer_mem_freed - expl_managed;
 200     if (result > (signed_word)GC_words_allocd) {
 201         result = GC_words_allocd;
 202         /* probably client bug or unfortunate scheduling */
 203     }
 204     result += GC_words_finalized;
 205         /* We count objects enqueued for finalization as though they    */
 206         /* had been reallocated this round. Finalization is user        */
 207         /* visible progress.  And if we don't count this, we have       */
 208         /* stability problems for programs that finalize all objects.   */
 209     if ((GC_words_wasted >> 3) < result)
 210         result += GC_words_wasted;
 211         /* This doesn't reflect useful work.  But if there is lots of   */
 212         /* new fragmentation, the same is probably true of the heap,    */
 213         /* and the collection will be correspondingly cheaper.          */
 214     if (result < (signed_word)(GC_words_allocd >> 3)) {
 215         /* Always count at least 1/8 of the allocations.  We don't want */
 216         /* to collect too infrequently, since that would inhibit        */
 217         /* coalescing of free storage blocks.                           */
 218         /* This also makes us partially robust against client bugs.     */
 219         return(GC_words_allocd >> 3);
 220     } else {
 221         return(result);
 222     }
 223 }
 224
 225
 226 /* Clear up a few frames worth of garbage left at the top of the stack. */
 227 /* This is used to prevent us from accidentally treating garbade left   */
 228 /* on the stack by other parts of the collector as roots.  This         */
 229 /* differs from the code in misc.c, which actually tries to keep the    */
 230 /* stack clear of long-lived, client-generated garbage.                 */
 231 void GC_clear_a_few_frames()
 232 {
 233 #   define NWORDS 64
 234     word frames[NWORDS];
 235     /* Some compilers will warn that frames was set but never used.     */
 236     /* That's the whole idea ...                                        */
 237     register int i;
 238
 239     for (i = 0; i < NWORDS; i++) frames[i] = 0;
 240 }
 241
 242 /* Heap size at which we need a collection to avoid expanding past      */
 243 /* limits used by blacklisting.                                         */
 244 static word GC_collect_at_heapsize = (word)(-1);
 245
 246 /* Have we allocated enough to amortize a collection? */
 247 GC_bool GC_should_collect()
 248 {
 249     return(GC_adj_words_allocd() >= min_words_allocd()
 250            || GC_heapsize >= GC_collect_at_heapsize);
 251 }
 252
 253
 254 void GC_notify_full_gc()
 255 {
 256     if (GC_start_call_back != (void (*) GC_PROTO((void)))0) {
 257         (*GC_start_call_back)();
 258     }
 259 }
 260
 261 GC_bool GC_is_full_gc = FALSE;
 262
 263 /*
 264  * Initiate a garbage collection if appropriate.
 265  * Choose judiciously
 266  * between partial, full, and stop-world collections.
 267  * Assumes lock held, signals disabled.
 268  */
 269 void GC_maybe_gc()
 270 {
 271     static int n_partial_gcs = 0;
 272
 273     if (GC_should_collect()) {
 274         if (!GC_incremental) {
 275             GC_gcollect_inner();
 276             n_partial_gcs = 0;
 277             return;
 278         } else {
 279 #         ifdef PARALLEL_MARK
 280             GC_wait_for_reclaim();
 281 #         endif
 282           if (GC_need_full_gc || n_partial_gcs >= GC_full_freq) {
 283 #           ifdef CONDPRINT
 284               if (GC_print_stats) {
 285                 GC_printf2(
 286                   "***>Full mark for collection %lu after %ld allocd bytes\n",
 287                   (unsigned long) GC_gc_no+1,
 288                   (long)WORDS_TO_BYTES(GC_words_allocd));
 289               }
 290 #           endif
 291             GC_promote_black_lists();
 292             (void)GC_reclaim_all((GC_stop_func)0, TRUE);
 293             GC_clear_marks();
 294             n_partial_gcs = 0;
 295             GC_notify_full_gc();
 296             GC_is_full_gc = TRUE;
 297           } else {
 298             n_partial_gcs++;
 299           }
 300         }
 301         /* We try to mark with the world stopped.       */
 302         /* If we run out of time, this turns into       */
 303         /* incremental marking.                 */
 304 #       ifndef NO_CLOCK
 305           if (GC_time_limit != GC_TIME_UNLIMITED) { GET_TIME(GC_start_time); }
 306 #       endif
 307         if (GC_stopped_mark(GC_time_limit == GC_TIME_UNLIMITED?
 308                             GC_never_stop_func : GC_timeout_stop_func)) {
 309 #           ifdef SAVE_CALL_CHAIN_IN_GC
 310                 GC_save_callers(GC_last_stack);
 311 #           endif
 312             GC_finish_collection();
 313         } else {
 314             if (!GC_is_full_gc) {
 315                 /* Count this as the first attempt */
 316                 GC_n_attempts++;
 317             }
 318         }
 319     }
 320 }
 321
 322
 323 /*
 324  * Stop the world garbage collection.  Assumes lock held, signals disabled.
 325  * If stop_func is not GC_never_stop_func, then abort if stop_func returns TRUE.
 326  * Return TRUE if we successfully completed the collection.
 327  */
 328 GC_bool GC_try_to_collect_inner(stop_func)
 329 GC_stop_func stop_func;
 330 {
 331 #   ifdef CONDPRINT
 332         CLOCK_TYPE start_time, current_time;
 333 #   endif
 334     if (GC_dont_gc) return FALSE;
 335     if (GC_incremental && GC_collection_in_progress()) {
 336 #   ifdef CONDPRINT
 337       if (GC_print_stats) {
 338         GC_printf0(
 339             "GC_try_to_collect_inner: finishing collection in progress\n");
 340       }
 341 #   endif /* CONDPRINT */
 342       /* Just finish collection already in progress.    */
 343         while(GC_collection_in_progress()) {
 344             if (stop_func()) return(FALSE);
 345             GC_collect_a_little_inner(1);
 346         }
 347     }
 348     if (stop_func == GC_never_stop_func) GC_notify_full_gc();
 349 #   ifdef CONDPRINT
 350       if (GC_print_stats) {
 351         if (GC_print_stats) GET_TIME(start_time);
 352         GC_printf2(
 353            "Initiating full world-stop collection %lu after %ld allocd bytes\n",
 354            (unsigned long) GC_gc_no+1,
 355            (long)WORDS_TO_BYTES(GC_words_allocd));
 356       }
 357 #   endif
 358     GC_promote_black_lists();
 359     /* Make sure all blocks have been reclaimed, so sweep routines      */
 360     /* don't see cleared mark bits.                                     */
 361     /* If we're guaranteed to finish, then this is unnecessary.         */
 362     /* In the find_leak case, we have to finish to guarantee that       */
 363     /* previously unmarked objects are not reported as leaks.           */
 364 #       ifdef PARALLEL_MARK
 365             GC_wait_for_reclaim();
 366 #       endif
 367         if ((GC_find_leak || stop_func != GC_never_stop_func)
 368             && !GC_reclaim_all(stop_func, FALSE)) {
 369             /* Aborted.  So far everything is still consistent. */
 370             return(FALSE);
 371         }
 372     GC_invalidate_mark_state();  /* Flush mark stack.   */
 373     GC_clear_marks();
 374 #   ifdef SAVE_CALL_CHAIN_IN_GC
 375         GC_save_callers(GC_last_stack);
 376 #   endif
 377     GC_is_full_gc = TRUE;
 378     if (!GC_stopped_mark(stop_func)) {
 379       if (!GC_incremental) {
 380         /* We're partially done and have no way to complete or use      */
 381         /* current work.  Reestablish invariants as cheaply as          */
 382         /* possible.                                                    */
 383         GC_invalidate_mark_state();
 384         GC_unpromote_black_lists();
 385       } /* else we claim the world is already still consistent.  We'll  */
 386         /* finish incrementally.                                        */
 387       return(FALSE);
 388     }
 389     GC_finish_collection();
 390 #   if defined(CONDPRINT)
 391       if (GC_print_stats) {
 392         GET_TIME(current_time);
 393         GC_printf1("Complete collection took %lu msecs\n",
 394                    MS_TIME_DIFF(current_time,start_time));
 395       }
 396 #   endif
 397     return(TRUE);
 398 }
 399
 400
 401
 402 /*
 403  * Perform n units of garbage collection work.  A unit is intended to touch
 404  * roughly GC_RATE pages.  Every once in a while, we do more than that.
 405  * This needa to be a fairly large number with our current incremental
 406  * GC strategy, since otherwise we allocate too much during GC, and the
 407  * cleanup gets expensive.
 408  */
 409 # define GC_RATE 10
 410 # define MAX_PRIOR_ATTEMPTS 1
 411         /* Maximum number of prior attempts at world stop marking       */
 412         /* A value of 1 means that we finish the second time, no matter */
 413         /* how long it takes.  Doesn't count the initial root scan      */
 414         /* for a full GC.                                               */
 415
 416 int GC_deficit = 0;     /* The number of extra calls to GC_mark_some    */
 417                         /* that we have made.                           */
 418
 419 void GC_collect_a_little_inner(n)
 420 int n;
 421 {
 422     register int i;
 423
 424     if (GC_dont_gc) return;
 425     if (GC_incremental && GC_collection_in_progress()) {
 426         for (i = GC_deficit; i < GC_RATE*n; i++) {
 427             if (GC_mark_some((ptr_t)0)) {
 428                 /* Need to finish a collection */
 429 #               ifdef SAVE_CALL_CHAIN_IN_GC
 430                     GC_save_callers(GC_last_stack);
 431 #               endif
 432 #               ifdef PARALLEL_MARK
 433                     GC_wait_for_reclaim();
 434 #               endif
 435                 if (GC_n_attempts < MAX_PRIOR_ATTEMPTS
 436                     && GC_time_limit != GC_TIME_UNLIMITED) {
 437                   GET_TIME(GC_start_time);
 438                   if (!GC_stopped_mark(GC_timeout_stop_func)) {
 439                     GC_n_attempts++;
 440                     break;
 441                   }
 442                 } else {
 443                   (void)GC_stopped_mark(GC_never_stop_func);
 444                 }
 445                 GC_finish_collection();
 446                 break;
 447             }
 448         }
 449         if (GC_deficit > 0) GC_deficit -= GC_RATE*n;
 450         if (GC_deficit < 0) GC_deficit = 0;
 451     } else {
 452         GC_maybe_gc();
 453     }
 454 }
 455
 456 int GC_collect_a_little GC_PROTO(())
 457 {
 458     int result;
 459     DCL_LOCK_STATE;
 460
 461     DISABLE_SIGNALS();
 462     LOCK();
 463     GC_collect_a_little_inner(1);
 464     result = (int)GC_collection_in_progress();
 465     UNLOCK();
 466     ENABLE_SIGNALS();
 467     if (!result && GC_debugging_started) GC_print_all_smashed();
 468     return(result);
 469 }
 470
 471 /*
 472  * Assumes lock is held, signals are disabled.
 473  * We stop the world.
 474  * If stop_func() ever returns TRUE, we may fail and return FALSE.
 475  * Increment GC_gc_no if we succeed.
 476  */
 477 GC_bool GC_stopped_mark(stop_func)
 478 GC_stop_func stop_func;
 479 {
 480     register int i;
 481     int dummy;
 482 #   if defined(PRINTTIMES) || defined(CONDPRINT)
 483         CLOCK_TYPE start_time, current_time;
 484 #   endif
 485
 486 #   ifdef PRINTTIMES
 487         GET_TIME(start_time);
 488 #   endif
 489 #   if defined(CONDPRINT) && !defined(PRINTTIMES)
 490         if (GC_print_stats) GET_TIME(start_time);
 491 #   endif
 492 #   if defined(REGISTER_LIBRARIES_EARLY)
 493         GC_cond_register_dynamic_libraries();
 494 #   endif
 495     STOP_WORLD();
 496     IF_THREADS(GC_world_stopped = TRUE);
 497 #   ifdef CONDPRINT
 498       if (GC_print_stats) {
 499         GC_printf1("--> Marking for collection %lu ",
 500                    (unsigned long) GC_gc_no + 1);
 501         GC_printf2("after %lu allocd bytes + %lu wasted bytes\n",
 502                    (unsigned long) WORDS_TO_BYTES(GC_words_allocd),
 503                    (unsigned long) WORDS_TO_BYTES(GC_words_wasted));
 504       }
 505 #   endif
 506 #   ifdef MAKE_BACK_GRAPH
 507       if (GC_print_back_height) {
 508         GC_build_back_graph();
 509       }
 510 #   endif
 511
 512     /* Mark from all roots.  */
 513         /* Minimize junk left in my registers and on the stack */
 514             GC_clear_a_few_frames();
 515             GC_noop(0,0,0,0,0,0);
 516         GC_initiate_gc();
 517         for(i = 0;;i++) {
 518             if ((*stop_func)()) {
 519 #                   ifdef CONDPRINT
 520                       if (GC_print_stats) {
 521                         GC_printf0("Abandoned stopped marking after ");
 522                         GC_printf1("%lu iterations\n",
 523                                    (unsigned long)i);
 524                       }
 525 #                   endif
 526                     GC_deficit = i; /* Give the mutator a chance. */
 527                     IF_THREADS(GC_world_stopped = FALSE);
 528                     START_WORLD();
 529                     return(FALSE);
 530             }
 531             if (GC_mark_some((ptr_t)(&dummy))) break;
 532         }
 533
 534     GC_gc_no++;
 535 #   ifdef PRINTSTATS
 536       GC_printf2("Collection %lu reclaimed %ld bytes",
 537                   (unsigned long) GC_gc_no - 1,
 538                   (long)WORDS_TO_BYTES(GC_mem_found));
 539 #   else
 540 #     ifdef CONDPRINT
 541         if (GC_print_stats) {
 542           GC_printf1("Collection %lu finished", (unsigned long) GC_gc_no - 1);
 543         }
 544 #     endif
 545 #   endif /* !PRINTSTATS */
 546 #   ifdef CONDPRINT
 547       if (GC_print_stats) {
 548         GC_printf1(" ---> heapsize = %lu bytes\n",
 549                    (unsigned long) GC_heapsize);
 550         /* Printf arguments may be pushed in funny places.  Clear the   */
 551         /* space.                                                       */
 552         GC_printf0("");
 553       }
 554 #   endif  /* CONDPRINT  */
 555
 556     /* Check all debugged objects for consistency */
 557         if (GC_debugging_started) {
 558             (*GC_check_heap)();
 559         }
 560
 561     IF_THREADS(GC_world_stopped = FALSE);
 562     START_WORLD();
 563 #   ifdef PRINTTIMES
 564         GET_TIME(current_time);
 565         GC_printf1("World-stopped marking took %lu msecs\n",
 566                    MS_TIME_DIFF(current_time,start_time));
 567 #   else
 568 #     ifdef CONDPRINT
 569         if (GC_print_stats) {
 570           GET_TIME(current_time);
 571           GC_printf1("World-stopped marking took %lu msecs\n",
 572                      MS_TIME_DIFF(current_time,start_time));
 573         }
 574 #     endif
 575 #   endif
 576     return(TRUE);
 577 }
 578
 579 /* Set all mark bits for the free list whose first entry is q   */
 580 #ifdef __STDC__
 581   void GC_set_fl_marks(ptr_t q)
 582 #else
 583   void GC_set_fl_marks(q)
 584   ptr_t q;
 585 #endif
 586 {
 587    ptr_t p;
 588    struct hblk * h, * last_h = 0;
 589    hdr *hhdr;
 590    int word_no;
 591
 592    for (p = q; p != 0; p = obj_link(p)){
 593         h = HBLKPTR(p);
 594         if (h != last_h) {
 595           last_h = h;
 596           hhdr = HDR(h);
 597         }
 598         word_no = (((word *)p) - ((word *)h));
 599         set_mark_bit_from_hdr(hhdr, word_no);
 600    }
 601 }
 602
 603 /* Clear all mark bits for the free list whose first entry is q */
 604 /* Decrement GC_mem_found by number of words on free list.      */
 605 #ifdef __STDC__
 606   void GC_clear_fl_marks(ptr_t q)
 607 #else
 608   void GC_clear_fl_marks(q)
 609   ptr_t q;
 610 #endif
 611 {
 612    ptr_t p;
 613    struct hblk * h, * last_h = 0;
 614    hdr *hhdr;
 615    int word_no;
 616
 617    for (p = q; p != 0; p = obj_link(p)){
 618         h = HBLKPTR(p);
 619         if (h != last_h) {
 620           last_h = h;
 621           hhdr = HDR(h);
 622         }
 623         word_no = (((word *)p) - ((word *)h));
 624         clear_mark_bit_from_hdr(hhdr, word_no);
 625 #       ifdef GATHERSTATS
 626             GC_mem_found -= hhdr -> hb_sz;
 627 #       endif
 628    }
 629 }
 630
 631 /* Finish up a collection.  Assumes lock is held, signals are disabled, */
 632 /* but the world is otherwise running.                                  */
 633 void GC_finish_collection()
 634 {
 635 #   ifdef PRINTTIMES
 636         CLOCK_TYPE start_time;
 637         CLOCK_TYPE finalize_time;
 638         CLOCK_TYPE done_time;
 639
 640         GET_TIME(start_time);
 641         finalize_time = start_time;
 642 #   endif
 643
 644 #   ifdef GATHERSTATS
 645         GC_mem_found = 0;
 646 #   endif
 647 #   if defined(LINUX) && defined(__ELF__) && !defined(SMALL_CONFIG)
 648         if (getenv("GC_PRINT_ADDRESS_MAP") != 0) {
 649           GC_print_address_map();
 650         }
 651 #   endif
 652     COND_DUMP;
 653     if (GC_find_leak) {
 654       /* Mark all objects on the free list.  All objects should be */
 655       /* marked when we're done.                                   */
 656         {
 657           register word size;           /* current object size          */
 658           int kind;
 659           ptr_t q;
 660
 661           for (kind = 0; kind < GC_n_kinds; kind++) {
 662             for (size = 1; size <= MAXOBJSZ; size++) {
 663               q = GC_obj_kinds[kind].ok_freelist[size];
 664               if (q != 0) GC_set_fl_marks(q);
 665             }
 666           }
 667         }
 668         GC_start_reclaim(TRUE);
 669           /* The above just checks; it doesn't really reclaim anything. */
 670     }
 671
 672     GC_finalize();
 673 #   ifdef STUBBORN_ALLOC
 674       GC_clean_changing_list();
 675 #   endif
 676
 677 #   ifdef PRINTTIMES
 678       GET_TIME(finalize_time);
 679 #   endif
 680
 681     if (GC_print_back_height) {
 682 #     ifdef MAKE_BACK_GRAPH
 683         GC_traverse_back_graph();
 684 #     else
 685 #       ifndef SMALL_CONFIG
 686           GC_err_printf0("Back height not available: "
 687                          "Rebuild collector with -DMAKE_BACK_GRAPH\n");
 688 #       endif
 689 #     endif
 690     }
 691
 692     /* Clear free list mark bits, in case they got accidentally marked   */
 693     /* (or GC_find_leak is set and they were intentionally marked).      */
 694     /* Also subtract memory remaining from GC_mem_found count.           */
 695     /* Note that composite objects on free list are cleared.             */
 696     /* Thus accidentally marking a free list is not a problem;  only     */
 697     /* objects on the list itself will be marked, and that's fixed here. */
 698       {
 699         register word size;             /* current object size          */
 700         register ptr_t q;       /* pointer to current object    */
 701         int kind;
 702
 703         for (kind = 0; kind < GC_n_kinds; kind++) {
 704           for (size = 1; size <= MAXOBJSZ; size++) {
 705             q = GC_obj_kinds[kind].ok_freelist[size];
 706             if (q != 0) GC_clear_fl_marks(q);
 707           }
 708         }
 709       }
 710
 711
 712 #   ifdef PRINTSTATS
 713         GC_printf1("Bytes recovered before sweep - f.l. count = %ld\n",
 714                   (long)WORDS_TO_BYTES(GC_mem_found));
 715 #   endif
 716     /* Reconstruct free lists to contain everything not marked */
 717         GC_start_reclaim(FALSE);
 718         if (GC_is_full_gc)  {
 719             GC_used_heap_size_after_full = USED_HEAP_SIZE;
 720             GC_need_full_gc = FALSE;
 721         } else {
 722             GC_need_full_gc =
 723                  BYTES_TO_WORDS(USED_HEAP_SIZE - GC_used_heap_size_after_full)
 724                  > min_words_allocd();
 725         }
 726
 727 #   ifdef PRINTSTATS
 728         GC_printf2(
 729                   "Immediately reclaimed %ld bytes in heap of size %lu bytes",
 730                   (long)WORDS_TO_BYTES(GC_mem_found),
 731                   (unsigned long)GC_heapsize);
 732 #       ifdef USE_MUNMAP
 733           GC_printf1("(%lu unmapped)", GC_unmapped_bytes);
 734 #       endif
 735         GC_printf2(
 736                 "\n%lu (atomic) + %lu (composite) collectable bytes in use\n",
 737                 (unsigned long)WORDS_TO_BYTES(GC_atomic_in_use),
 738                 (unsigned long)WORDS_TO_BYTES(GC_composite_in_use));
 739 #   endif
 740
 741       GC_n_attempts = 0;
 742       GC_is_full_gc = FALSE;
 743     /* Reset or increment counters for next cycle */
 744       GC_words_allocd_before_gc += GC_words_allocd;
 745       GC_non_gc_bytes_at_gc = GC_non_gc_bytes;
 746       GC_words_allocd = 0;
 747       GC_words_wasted = 0;
 748       GC_mem_freed = 0;
 749       GC_finalizer_mem_freed = 0;
 750
 751 #   ifdef USE_MUNMAP
 752       GC_unmap_old();
 753 #   endif
 754 #   ifdef PRINTTIMES
 755         GET_TIME(done_time);
 756         GC_printf2("Finalize + initiate sweep took %lu + %lu msecs\n",
 757                    MS_TIME_DIFF(finalize_time,start_time),
 758                    MS_TIME_DIFF(done_time,finalize_time));
 759 #   endif
 760 }
 761
 762 /* Externally callable routine to invoke full, stop-world collection */
 763 # if defined(__STDC__) || defined(__cplusplus)
 764     int GC_try_to_collect(GC_stop_func stop_func)
 765 # else
 766     int GC_try_to_collect(stop_func)
 767     GC_stop_func stop_func;
 768 # endif
 769 {
 770     int result;
 771     DCL_LOCK_STATE;
 772
 773     if (GC_debugging_started) GC_print_all_smashed();
 774     GC_INVOKE_FINALIZERS();
 775     DISABLE_SIGNALS();
 776     LOCK();
 777     ENTER_GC();
 778     if (!GC_is_initialized) GC_init_inner();
 779     /* Minimize junk left in my registers */
 780       GC_noop(0,0,0,0,0,0);
 781     result = (int)GC_try_to_collect_inner(stop_func);
 782     EXIT_GC();
 783     UNLOCK();
 784     ENABLE_SIGNALS();
 785     if(result) {
 786         if (GC_debugging_started) GC_print_all_smashed();
 787         GC_INVOKE_FINALIZERS();
 788     }
 789     return(result);
 790 }
 791
 792 void GC_gcollect GC_PROTO(())
 793 {
 794     (void)GC_try_to_collect(GC_never_stop_func);
 795     if (GC_have_errors) GC_print_all_errors();
 796 }
 797
 798 word GC_n_heap_sects = 0;       /* Number of sections currently in heap. */
 799
 800 /*
 801  * Use the chunk of memory starting at p of size bytes as part of the heap.
 802  * Assumes p is HBLKSIZE aligned, and bytes is a multiple of HBLKSIZE.
 803  */
 804 void GC_add_to_heap(p, bytes)
 805 struct hblk *p;
 806 word bytes;
 807 {
 808     word words;
 809     hdr * phdr;
 810
 811     if (GC_n_heap_sects >= MAX_HEAP_SECTS) {
 812         ABORT("Too many heap sections: Increase MAXHINCR or MAX_HEAP_SECTS");
 813     }
 814     phdr = GC_install_header(p);
 815     if (0 == phdr) {
 816         /* This is extremely unlikely. Can't add it.  This will         */
 817         /* almost certainly result in a 0 return from the allocator,    */
 818         /* which is entirely appropriate.                               */
 819         return;
 820     }
 821     GC_heap_sects[GC_n_heap_sects].hs_start = (ptr_t)p;
 822     GC_heap_sects[GC_n_heap_sects].hs_bytes = bytes;
 823     GC_n_heap_sects++;
 824     words = BYTES_TO_WORDS(bytes);
 825     phdr -> hb_sz = words;
 826     phdr -> hb_map = (unsigned char *)1;   /* A value != GC_invalid_map */
 827     phdr -> hb_flags = 0;
 828     GC_freehblk(p);
 829     GC_heapsize += bytes;
 830     if ((ptr_t)p <= (ptr_t)GC_least_plausible_heap_addr
 831         || GC_least_plausible_heap_addr == 0) {
 832         GC_least_plausible_heap_addr = (GC_PTR)((ptr_t)p - sizeof(word));
 833                 /* Making it a little smaller than necessary prevents   */
 834                 /* us from getting a false hit from the variable        */
 835                 /* itself.  There's some unintentional reflection       */
 836                 /* here.                                                */
 837     }
 838     if ((ptr_t)p + bytes >= (ptr_t)GC_greatest_plausible_heap_addr) {
 839         GC_greatest_plausible_heap_addr = (GC_PTR)((ptr_t)p + bytes);
 840     }
 841 }
 842
 843 # if !defined(NO_DEBUGGING)
 844 void GC_print_heap_sects()
 845 {
 846     register unsigned i;
 847
 848     GC_printf1("Total heap size: %lu\n", (unsigned long) GC_heapsize);
 849     for (i = 0; i < GC_n_heap_sects; i++) {
 850         unsigned long start = (unsigned long) GC_heap_sects[i].hs_start;
 851         unsigned long len = (unsigned long) GC_heap_sects[i].hs_bytes;
 852         struct hblk *h;
 853         unsigned nbl = 0;
 854
 855         GC_printf3("Section %ld from 0x%lx to 0x%lx ", (unsigned long)i,
 856                    start, (unsigned long)(start + len));
 857         for (h = (struct hblk *)start; h < (struct hblk *)(start + len); h++) {
 858             if (GC_is_black_listed(h, HBLKSIZE)) nbl++;
 859         }
 860         GC_printf2("%lu/%lu blacklisted\n", (unsigned long)nbl,
 861                    (unsigned long)(len/HBLKSIZE));
 862     }
 863 }
 864 # endif
 865
 866 GC_PTR GC_least_plausible_heap_addr = (GC_PTR)ONES;
 867 GC_PTR GC_greatest_plausible_heap_addr = 0;
 868
 869 ptr_t GC_max(x,y)
 870 ptr_t x, y;
 871 {
 872     return(x > y? x : y);
 873 }
 874
 875 ptr_t GC_min(x,y)
 876 ptr_t x, y;
 877 {
 878     return(x < y? x : y);
 879 }
 880
 881 # if defined(__STDC__) || defined(__cplusplus)
 882     void GC_set_max_heap_size(GC_word n)
 883 # else
 884     void GC_set_max_heap_size(n)
 885     GC_word n;
 886 # endif
 887 {
 888     GC_max_heapsize = n;
 889 }
 890
 891 GC_word GC_max_retries = 0;
 892
 893 /*
 894  * this explicitly increases the size of the heap.  It is used
 895  * internally, but may also be invoked from GC_expand_hp by the user.
 896  * The argument is in units of HBLKSIZE.
 897  * Tiny values of n are rounded up.
 898  * Returns FALSE on failure.
 899  */
 900 GC_bool GC_expand_hp_inner(n)
 901 word n;
 902 {
 903     word bytes;
 904     struct hblk * space;
 905     word expansion_slop;        /* Number of bytes by which we expect the */
 906                                 /* heap to expand soon.                   */
 907
 908     if (n < MINHINCR) n = MINHINCR;
 909     bytes = n * HBLKSIZE;
 910     /* Make sure bytes is a multiple of GC_page_size */
 911       {
 912         word mask = GC_page_size - 1;
 913         bytes += mask;
 914         bytes &= ~mask;
 915       }
 916
 917     if (GC_max_heapsize != 0 && GC_heapsize + bytes > GC_max_heapsize) {
 918         /* Exceeded self-imposed limit */
 919         return(FALSE);
 920     }
 921     space = GET_MEM(bytes);
 922     if( space == 0 ) {
 923 #       ifdef CONDPRINT
 924           if (GC_print_stats) {
 925             GC_printf1("Failed to expand heap by %ld bytes\n",
 926                        (unsigned long)bytes);
 927           }
 928 #       endif
 929         return(FALSE);
 930     }
 931 #   ifdef CONDPRINT
 932       if (GC_print_stats) {
 933         GC_printf2("Increasing heap size by %lu after %lu allocated bytes\n",
 934                    (unsigned long)bytes,
 935                    (unsigned long)WORDS_TO_BYTES(GC_words_allocd));
 936 #       ifdef UNDEFINED
 937           GC_printf1("Root size = %lu\n", GC_root_size);
 938           GC_print_block_list(); GC_print_hblkfreelist();
 939           GC_printf0("\n");
 940 #       endif
 941       }
 942 #   endif
 943     expansion_slop = WORDS_TO_BYTES(min_words_allocd()) + 4*MAXHINCR*HBLKSIZE;
 944     if (GC_last_heap_addr == 0 && !((word)space & SIGNB)
 945         || (GC_last_heap_addr != 0 && GC_last_heap_addr < (ptr_t)space)) {
 946         /* Assume the heap is growing up */
 947         GC_greatest_plausible_heap_addr =
 948             (GC_PTR)GC_max((ptr_t)GC_greatest_plausible_heap_addr,
 949                            (ptr_t)space + bytes + expansion_slop);
 950     } else {
 951         /* Heap is growing down */
 952         GC_least_plausible_heap_addr =
 953             (GC_PTR)GC_min((ptr_t)GC_least_plausible_heap_addr,
 954                            (ptr_t)space - expansion_slop);
 955     }
 956 #   if defined(LARGE_CONFIG)
 957       if (((ptr_t)GC_greatest_plausible_heap_addr <= (ptr_t)space + bytes
 958            || (ptr_t)GC_least_plausible_heap_addr >= (ptr_t)space)
 959           && GC_heapsize > 0) {
 960         /* GC_add_to_heap will fix this, but ... */
 961         WARN("Too close to address space limit: blacklisting ineffective\n", 0);
 962       }
 963 #   endif
 964     GC_prev_heap_addr = GC_last_heap_addr;
 965     GC_last_heap_addr = (ptr_t)space;
 966     GC_add_to_heap(space, bytes);
 967     /* Force GC before we are likely to allocate past expansion_slop */
 968       GC_collect_at_heapsize =
 969           GC_heapsize + expansion_slop - 2*MAXHINCR*HBLKSIZE;
 970 #     if defined(LARGE_CONFIG)
 971         if (GC_collect_at_heapsize < GC_heapsize /* wrapped */)
 972           GC_collect_at_heapsize = (word)(-1);
 973 #     endif
 974     return(TRUE);
 975 }
 976
 977 /* Really returns a bool, but it's externally visible, so that's clumsy. */
 978 /* Arguments is in bytes.                                               */
 979 # if defined(__STDC__) || defined(__cplusplus)
 980   int GC_expand_hp(size_t bytes)
 981 # else
 982   int GC_expand_hp(bytes)
 983   size_t bytes;
 984 # endif
 985 {
 986     int result;
 987     DCL_LOCK_STATE;
 988
 989     DISABLE_SIGNALS();
 990     LOCK();
 991     if (!GC_is_initialized) GC_init_inner();
 992     result = (int)GC_expand_hp_inner(divHBLKSZ((word)bytes));
 993     if (result) GC_requested_heapsize += bytes;
 994     UNLOCK();
 995     ENABLE_SIGNALS();
 996     return(result);
 997 }
 998
 999 unsigned GC_fail_count = 0;
1000                         /* How many consecutive GC/expansion failures?  */
1001                         /* Reset by GC_allochblk.                       */
1002
1003 GC_bool GC_collect_or_expand(needed_blocks, ignore_off_page)
1004 word needed_blocks;
1005 GC_bool ignore_off_page;
1006 {
1007     if (!GC_incremental && !GC_dont_gc &&
1008         ((GC_dont_expand && GC_words_allocd > 0) || GC_should_collect())) {
1009       GC_gcollect_inner();
1010     } else {
1011       word blocks_to_get = GC_heapsize/(HBLKSIZE*GC_free_space_divisor)
1012                            + needed_blocks;
1013
1014       if (blocks_to_get > MAXHINCR) {
1015           word slop;
1016
1017           /* Get the minimum required to make it likely that we         */
1018           /* can satisfy the current request in the presence of black-  */
1019           /* listing.  This will probably be more than MAXHINCR.        */
1020           if (ignore_off_page) {
1021               slop = 4;
1022           } else {
1023               slop = 2*divHBLKSZ(BL_LIMIT);
1024               if (slop > needed_blocks) slop = needed_blocks;
1025           }
1026           if (needed_blocks + slop > MAXHINCR) {
1027               blocks_to_get = needed_blocks + slop;
1028           } else {
1029               blocks_to_get = MAXHINCR;
1030           }
1031       }
1032       if (!GC_expand_hp_inner(blocks_to_get)
1033         && !GC_expand_hp_inner(needed_blocks)) {
1034         if (GC_fail_count++ < GC_max_retries) {
1035             WARN("Out of Memory!  Trying to continue ...\n", 0);
1036             GC_gcollect_inner();
1037         } else {
1038 #           if !defined(AMIGA) || !defined(GC_AMIGA_FASTALLOC)
1039               WARN("Out of Memory!  Returning NIL!\n", 0);
1040 #           endif
1041             return(FALSE);
1042         }
1043       } else {
1044 #         ifdef CONDPRINT
1045             if (GC_fail_count && GC_print_stats) {
1046               GC_printf0("Memory available again ...\n");
1047             }
1048 #         endif
1049       }
1050     }
1051     return(TRUE);
1052 }
1053
1054 /*
1055  * Make sure the object free list for sz is not empty.
1056  * Return a pointer to the first object on the free list.
1057  * The object MUST BE REMOVED FROM THE FREE LIST BY THE CALLER.
1058  * Assumes we hold the allocator lock and signals are disabled.
1059  *
1060  */
1061 ptr_t GC_allocobj(sz, kind)
1062 word sz;
1063 int kind;
1064 {
1065     ptr_t * flh = &(GC_obj_kinds[kind].ok_freelist[sz]);
1066     GC_bool tried_minor = FALSE;
1067
1068     if (sz == 0) return(0);
1069
1070     while (*flh == 0) {
1071       ENTER_GC();
1072       /* Do our share of marking work */
1073         if(TRUE_INCREMENTAL) GC_collect_a_little_inner(1);
1074       /* Sweep blocks for objects of this size */
1075         GC_continue_reclaim(sz, kind);
1076       EXIT_GC();
1077       if (*flh == 0) {
1078         GC_new_hblk(sz, kind);
1079       }
1080       if (*flh == 0) {
1081         ENTER_GC();
1082         if (GC_incremental && GC_time_limit == GC_TIME_UNLIMITED
1083             && ! tried_minor ) {
1084             GC_collect_a_little_inner(1);
1085             tried_minor = TRUE;
1086         } else {
1087           if (!GC_collect_or_expand((word)1,FALSE)) {
1088             EXIT_GC();
1089             return(0);
1090           }
1091         }
1092         EXIT_GC();
1093       }
1094     }
1095     /* Successful allocation; reset failure count.      */
1096     GC_fail_count = 0;
1097
1098     return(*flh);
1099 }