boehm-gc/alloc.c

   1 /*
   2  * Copyright 1988, 1989 Hans-J. Boehm, Alan J. Demers
   3  * Copyright (c) 1991-1994 by Xerox Corporation.  All rights reserved.
   4  *
   5  * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
   6  * OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
   7  *
   8  * Permission is hereby granted to use or copy this program
   9  * for any purpose,  provided the above notices are retained on all copies.
  10  * Permission to modify the code and to distribute modified code is granted,
  11  * provided the above notices are retained, and a notice that the code was
  12  * modified is included with the above copyright notice.
  13  *
  14  */
  15 /* Boehm, February 16, 1996 2:26 pm PST */
  16
  17
  18 # include "gc_priv.h"
  19
  20 # include <stdio.h>
  21 # ifndef MACOS
  22 #   include <signal.h>
  23 #   include <sys/types.h>
  24 # endif
  25
  26 /*
  27  * Separate free lists are maintained for different sized objects
  28  * up to MAXOBJSZ.
  29  * The call GC_allocobj(i,k) ensures that the freelist for
  30  * kind k objects of size i points to a non-empty
  31  * free list. It returns a pointer to the first entry on the free list.
  32  * In a single-threaded world, GC_allocobj may be called to allocate
  33  * an object of (small) size i as follows:
  34  *
  35  *            opp = &(GC_objfreelist[i]);
  36  *            if (*opp == 0) GC_allocobj(i, NORMAL);
  37  *            ptr = *opp;
  38  *            *opp = obj_link(ptr);
  39  *
  40  * Note that this is very fast if the free list is non-empty; it should
  41  * only involve the execution of 4 or 5 simple instructions.
  42  * All composite objects on freelists are cleared, except for
  43  * their first word.
  44  */
  45
  46 /*
  47  *  The allocator uses GC_allochblk to allocate large chunks of objects.
  48  * These chunks all start on addresses which are multiples of
  49  * HBLKSZ.   Each allocated chunk has an associated header,
  50  * which can be located quickly based on the address of the chunk.
  51  * (See headers.c for details.)
  52  * This makes it possible to check quickly whether an
  53  * arbitrary address corresponds to an object administered by the
  54  * allocator.
  55  */
  56
  57 word GC_non_gc_bytes = 0;  /* Number of bytes not intended to be collected */
  58
  59 word GC_gc_no = 0;
  60
  61 int GC_incremental = 0;    /* By default, stop the world.       */
  62
  63 int GC_full_freq = 4;      /* Every 5th collection is a full    */
  64                            /* collection.                       */
  65
  66 char * GC_copyright[] =
  67 {"Copyright 1988,1989 Hans-J. Boehm and Alan J. Demers ",
  68 "Copyright (c) 1991-1995 by Xerox Corporation.  All rights reserved. ",
  69 "Copyright (c) 1996-1997 by Silicon Graphics.  All rights reserved. ",
  70 "THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY",
  71 " EXPRESSED OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.",
  72 "See source code for details." };
  73
  74 # include "version.h"
  75
  76 /* some more variables */
  77
  78 extern signed_word GC_mem_found;  /* Number of reclaimed longwords      */
  79                                   /* after garbage collection           */
  80
  81 GC_bool GC_dont_expand = 0;
  82
  83 word GC_free_space_divisor = 4;
  84
  85 extern GC_bool GC_collection_in_progress();
  86
  87 int GC_never_stop_func GC_PROTO((void)) { return(0); }
  88
  89 CLOCK_TYPE GC_start_time;
  90
  91 int GC_timeout_stop_func GC_PROTO((void))
  92 {
  93     CLOCK_TYPE current_time;
  94     static unsigned count = 0;
  95     unsigned long time_diff;
  96
  97     if ((count++ & 3) != 0) return(0);
  98 #ifndef NO_CLOCK
  99     GET_TIME(current_time);
 100     time_diff = MS_TIME_DIFF(current_time,GC_start_time);
 101     if (time_diff >= TIME_LIMIT) {
 102 #       ifdef PRINTSTATS
 103             GC_printf0("Abandoning stopped marking after ");
 104             GC_printf1("%lu msecs\n", (unsigned long)time_diff);
 105 #       endif
 106         return(1);
 107     }
 108 #endif
 109     return(0);
 110 }
 111
 112 /* Return the minimum number of words that must be allocated between    */
 113 /* collections to amortize the collection cost.                         */
 114 static word min_words_allocd()
 115 {
 116 #   ifdef THREADS
 117         /* We punt, for now. */
 118         register signed_word stack_size = 10000;
 119 #   else
 120         int dummy;
 121         register signed_word stack_size = (ptr_t)(&dummy) - GC_stackbottom;
 122 #   endif
 123     register word total_root_size;  /* includes double stack size,      */
 124                                     /* since the stack is expensive     */
 125                                     /* to scan.                         */
 126
 127     if (stack_size < 0) stack_size = -stack_size;
 128     total_root_size = 2 * stack_size + GC_root_size;
 129     if (GC_incremental) {
 130         return(BYTES_TO_WORDS(GC_heapsize + total_root_size)
 131                / (2 * GC_free_space_divisor));
 132     } else {
 133         return(BYTES_TO_WORDS(GC_heapsize + total_root_size)
 134                / GC_free_space_divisor);
 135     }
 136 }
 137
 138 /* Return the number of words allocated, adjusted for explicit storage  */
 139 /* management, etc..  This number is used in deciding when to trigger   */
 140 /* collections.                                                         */
 141 word GC_adj_words_allocd()
 142 {
 143     register signed_word result;
 144     register signed_word expl_managed =
 145                 BYTES_TO_WORDS((long)GC_non_gc_bytes
 146                                 - (long)GC_non_gc_bytes_at_gc);
 147
 148     /* Don't count what was explicitly freed, or newly allocated for    */
 149     /* explicit management.  Note that deallocating an explicitly       */
 150     /* managed object should not alter result, assuming the client      */
 151     /* is playing by the rules.                                         */
 152     result = (signed_word)GC_words_allocd
 153              - (signed_word)GC_mem_freed - expl_managed;
 154     if (result > (signed_word)GC_words_allocd) {
 155         result = GC_words_allocd;
 156         /* probably client bug or unfortunate scheduling */
 157     }
 158     result += GC_words_finalized;
 159         /* We count objects enqueued for finalization as though they    */
 160         /* had been reallocated this round. Finalization is user        */
 161         /* visible progress.  And if we don't count this, we have       */
 162         /* stability problems for programs that finalize all objects.   */
 163     result += GC_words_wasted;
 164         /* This doesn't reflect useful work.  But if there is lots of   */
 165         /* new fragmentation, the same is probably true of the heap,    */
 166         /* and the collection will be correspondingly cheaper.          */
 167     if (result < (signed_word)(GC_words_allocd >> 3)) {
 168         /* Always count at least 1/8 of the allocations.  We don't want */
 169         /* to collect too infrequently, since that would inhibit        */
 170         /* coalescing of free storage blocks.                           */
 171         /* This also makes us partially robust against client bugs.     */
 172         return(GC_words_allocd >> 3);
 173     } else {
 174         return(result);
 175     }
 176 }
 177
 178
 179 /* Clear up a few frames worth of garbage left at the top of the stack. */
 180 /* This is used to prevent us from accidentally treating garbade left   */
 181 /* on the stack by other parts of the collector as roots.  This         */
 182 /* differs from the code in misc.c, which actually tries to keep the    */
 183 /* stack clear of long-lived, client-generated garbage.                 */
 184 void GC_clear_a_few_frames()
 185 {
 186 #   define NWORDS 64
 187     word frames[NWORDS];
 188     register int i;
 189
 190     for (i = 0; i < NWORDS; i++) frames[i] = 0;
 191 }
 192
 193 /* Have we allocated enough to amortize a collection? */
 194 GC_bool GC_should_collect()
 195 {
 196     return(GC_adj_words_allocd() >= min_words_allocd());
 197 }
 198
 199 void GC_notify_full_gc()
 200 {
 201     if (GC_start_call_back != (void (*)())0) {
 202         (*GC_start_call_back)();
 203     }
 204 }
 205
 206 /*
 207  * Initiate a garbage collection if appropriate.
 208  * Choose judiciously
 209  * between partial, full, and stop-world collections.
 210  * Assumes lock held, signals disabled.
 211  */
 212 void GC_maybe_gc()
 213 {
 214     static int n_partial_gcs = 0;
 215     if (GC_should_collect()) {
 216         if (!GC_incremental) {
 217             GC_notify_full_gc();
 218             GC_gcollect_inner();
 219             n_partial_gcs = 0;
 220             return;
 221         } else if (n_partial_gcs >= GC_full_freq) {
 222 #           ifdef PRINTSTATS
 223               GC_printf2(
 224                 "***>Full mark for collection %lu after %ld allocd bytes\n",
 225                 (unsigned long) GC_gc_no+1,
 226                 (long)WORDS_TO_BYTES(GC_words_allocd));
 227 #           endif
 228             GC_promote_black_lists();
 229             (void)GC_reclaim_all((GC_stop_func)0, TRUE);
 230             GC_clear_marks();
 231             n_partial_gcs = 0;
 232             GC_notify_full_gc();
 233         } else {
 234             n_partial_gcs++;
 235         }
 236         /* We try to mark with the world stopped.       */
 237         /* If we run out of time, this turns into       */
 238         /* incremental marking.                 */
 239 #ifndef NO_CLOCK
 240         GET_TIME(GC_start_time);
 241 #endif
 242         if (GC_stopped_mark(GC_timeout_stop_func)) {
 243 #           ifdef SAVE_CALL_CHAIN
 244                 GC_save_callers(GC_last_stack);
 245 #           endif
 246             GC_finish_collection();
 247         }
 248     }
 249 }
 250
 251
 252 /*
 253  * Stop the world garbage collection.  Assumes lock held, signals disabled.
 254  * If stop_func is not GC_never_stop_func, then abort if stop_func returns TRUE.
 255  */
 256 GC_bool GC_try_to_collect_inner(stop_func)
 257 GC_stop_func stop_func;
 258 {
 259     if (GC_collection_in_progress()) {
 260 #   ifdef PRINTSTATS
 261         GC_printf0(
 262             "GC_try_to_collect_inner: finishing collection in progress\n");
 263 #    endif /* PRINTSTATS */
 264       /* Just finish collection already in progress.    */
 265         while(GC_collection_in_progress()) {
 266             if (stop_func()) return(FALSE);
 267             GC_collect_a_little_inner(1);
 268         }
 269     }
 270 #   ifdef PRINTSTATS
 271         GC_printf2(
 272            "Initiating full world-stop collection %lu after %ld allocd bytes\n",
 273            (unsigned long) GC_gc_no+1,
 274            (long)WORDS_TO_BYTES(GC_words_allocd));
 275 #   endif
 276     GC_promote_black_lists();
 277     /* Make sure all blocks have been reclaimed, so sweep routines      */
 278     /* don't see cleared mark bits.                                     */
 279     /* If we're guaranteed to finish, then this is unnecessary.         */
 280         if (stop_func != GC_never_stop_func
 281             && !GC_reclaim_all(stop_func, FALSE)) {
 282             /* Aborted.  So far everything is still consistent. */
 283             return(FALSE);
 284         }
 285     GC_invalidate_mark_state();  /* Flush mark stack.   */
 286     GC_clear_marks();
 287 #   ifdef SAVE_CALL_CHAIN
 288         GC_save_callers(GC_last_stack);
 289 #   endif
 290     if (!GC_stopped_mark(stop_func)) {
 291       if (!GC_incremental) {
 292         /* We're partially done and have no way to complete or use      */
 293         /* current work.  Reestablish invariants as cheaply as          */
 294         /* possible.                                                    */
 295         GC_invalidate_mark_state();
 296         GC_unpromote_black_lists();
 297       } /* else we claim the world is already still consistent.  We'll  */
 298         /* finish incrementally.                                        */
 299       return(FALSE);
 300     }
 301     GC_finish_collection();
 302     return(TRUE);
 303 }
 304
 305
 306
 307 /*
 308  * Perform n units of garbage collection work.  A unit is intended to touch
 309  * roughly a GC_RATE pages.  Every once in a while, we do more than that.
 310  */
 311 # define GC_RATE 8
 312
 313 int GC_deficit = 0;     /* The number of extra calls to GC_mark_some    */
 314                         /* that we have made.                           */
 315                         /* Negative values are equivalent to 0.         */
 316
 317 void GC_collect_a_little_inner(n)
 318 int n;
 319 {
 320     register int i;
 321
 322     if (GC_collection_in_progress()) {
 323         for (i = GC_deficit; i < GC_RATE*n; i++) {
 324             if (GC_mark_some()) {
 325                 /* Need to finish a collection */
 326 #               ifdef SAVE_CALL_CHAIN
 327                     GC_save_callers(GC_last_stack);
 328 #               endif
 329                 (void) GC_stopped_mark(GC_never_stop_func);
 330                 GC_finish_collection();
 331                 break;
 332             }
 333         }
 334         if (GC_deficit > 0) GC_deficit -= GC_RATE*n;
 335     } else {
 336         GC_maybe_gc();
 337     }
 338 }
 339
 340 int GC_collect_a_little GC_PROTO(())
 341 {
 342     int result;
 343     DCL_LOCK_STATE;
 344
 345     DISABLE_SIGNALS();
 346     LOCK();
 347     GC_collect_a_little_inner(1);
 348     result = (int)GC_collection_in_progress();
 349     UNLOCK();
 350     ENABLE_SIGNALS();
 351     return(result);
 352 }
 353
 354 /*
 355  * Assumes lock is held, signals are disabled.
 356  * We stop the world.
 357  * If final is TRUE, then we finish the collection, no matter how long
 358  * it takes.
 359  * Otherwise we may fail and return FALSE if this takes too long.
 360  * Increment GC_gc_no if we succeed.
 361  */
 362 GC_bool GC_stopped_mark(stop_func)
 363 GC_stop_func stop_func;
 364 {
 365     register int i;
 366 #   ifdef PRINTSTATS
 367         CLOCK_TYPE start_time, current_time;
 368 #   endif
 369
 370     STOP_WORLD();
 371 #   ifdef PRINTSTATS
 372         GET_TIME(start_time);
 373         GC_printf1("--> Marking for collection %lu ",
 374                    (unsigned long) GC_gc_no + 1);
 375         GC_printf2("after %lu allocd bytes + %lu wasted bytes\n",
 376                    (unsigned long) WORDS_TO_BYTES(GC_words_allocd),
 377                    (unsigned long) WORDS_TO_BYTES(GC_words_wasted));
 378 #   endif
 379
 380     /* Mark from all roots.  */
 381         /* Minimize junk left in my registers and on the stack */
 382             GC_clear_a_few_frames();
 383             GC_noop(0,0,0,0,0,0);
 384         GC_initiate_gc();
 385         for(i = 0;;i++) {
 386             if ((*stop_func)()) {
 387 #                   ifdef PRINTSTATS
 388                         GC_printf0("Abandoned stopped marking after ");
 389                         GC_printf1("%lu iterations\n",
 390                                    (unsigned long)i);
 391 #                   endif
 392                     GC_deficit = i; /* Give the mutator a chance. */
 393                     START_WORLD();
 394                     return(FALSE);
 395             }
 396             if (GC_mark_some()) break;
 397         }
 398
 399     GC_gc_no++;
 400 #   ifdef PRINTSTATS
 401       GC_printf2("Collection %lu reclaimed %ld bytes",
 402                   (unsigned long) GC_gc_no - 1,
 403                   (long)WORDS_TO_BYTES(GC_mem_found));
 404       GC_printf1(" ---> heapsize = %lu bytes\n",
 405                 (unsigned long) GC_heapsize);
 406       /* Printf arguments may be pushed in funny places.  Clear the     */
 407       /* space.                                                         */
 408       GC_printf0("");
 409 #   endif
 410
 411     /* Check all debugged objects for consistency */
 412         if (GC_debugging_started) {
 413             (*GC_check_heap)();
 414         }
 415
 416 #   ifdef PRINTTIMES
 417         GET_TIME(current_time);
 418         GC_printf1("World-stopped marking took %lu msecs\n",
 419                    MS_TIME_DIFF(current_time,start_time));
 420 #   endif
 421     START_WORLD();
 422     return(TRUE);
 423 }
 424
 425
 426 /* Finish up a collection.  Assumes lock is held, signals are disabled, */
 427 /* but the world is otherwise running.                                  */
 428 void GC_finish_collection()
 429 {
 430 #   ifdef PRINTTIMES
 431         CLOCK_TYPE start_time;
 432         CLOCK_TYPE finalize_time;
 433         CLOCK_TYPE done_time;
 434
 435         GET_TIME(start_time);
 436         finalize_time = start_time;
 437 #   endif
 438
 439 #   ifdef GATHERSTATS
 440         GC_mem_found = 0;
 441 #   endif
 442 #   ifdef FIND_LEAK
 443       /* Mark all objects on the free list.  All objects should be */
 444       /* marked when we're done.                                   */
 445         {
 446           register word size;           /* current object size          */
 447           register ptr_t p;     /* pointer to current object    */
 448           register struct hblk * h;     /* pointer to block containing *p */
 449           register hdr * hhdr;
 450           register int word_no;           /* "index" of *p in *q          */
 451           int kind;
 452
 453           for (kind = 0; kind < GC_n_kinds; kind++) {
 454             for (size = 1; size <= MAXOBJSZ; size++) {
 455               for (p= GC_obj_kinds[kind].ok_freelist[size];
 456                    p != 0; p=obj_link(p)){
 457                 h = HBLKPTR(p);
 458                 hhdr = HDR(h);
 459                 word_no = (((word *)p) - ((word *)h));
 460                 set_mark_bit_from_hdr(hhdr, word_no);
 461               }
 462             }
 463           }
 464         }
 465       /* Check that everything is marked */
 466         GC_start_reclaim(TRUE);
 467 #   else
 468
 469       GC_finalize();
 470 #     ifdef STUBBORN_ALLOC
 471         GC_clean_changing_list();
 472 #     endif
 473
 474 #     ifdef PRINTTIMES
 475         GET_TIME(finalize_time);
 476 #     endif
 477
 478       /* Clear free list mark bits, in case they got accidentally marked   */
 479       /* Note: HBLKPTR(p) == pointer to head of block containing *p        */
 480       /* Also subtract memory remaining from GC_mem_found count.           */
 481       /* Note that composite objects on free list are cleared.             */
 482       /* Thus accidentally marking a free list is not a problem;  only     */
 483       /* objects on the list itself will be marked, and that's fixed here. */
 484       {
 485         register word size;             /* current object size          */
 486         register ptr_t p;       /* pointer to current object    */
 487         register struct hblk * h;       /* pointer to block containing *p */
 488         register hdr * hhdr;
 489         register int word_no;           /* "index" of *p in *q          */
 490         int kind;
 491
 492         for (kind = 0; kind < GC_n_kinds; kind++) {
 493           for (size = 1; size <= MAXOBJSZ; size++) {
 494             for (p= GC_obj_kinds[kind].ok_freelist[size];
 495                  p != 0; p=obj_link(p)){
 496                 h = HBLKPTR(p);
 497                 hhdr = HDR(h);
 498                 word_no = (((word *)p) - ((word *)h));
 499                 clear_mark_bit_from_hdr(hhdr, word_no);
 500 #               ifdef GATHERSTATS
 501                     GC_mem_found -= size;
 502 #               endif
 503             }
 504           }
 505         }
 506       }
 507
 508
 509 #     ifdef PRINTSTATS
 510         GC_printf1("Bytes recovered before sweep - f.l. count = %ld\n",
 511                   (long)WORDS_TO_BYTES(GC_mem_found));
 512 #     endif
 513
 514     /* Reconstruct free lists to contain everything not marked */
 515       GC_start_reclaim(FALSE);
 516
 517 #   endif /* !FIND_LEAK */
 518
 519 #   ifdef PRINTSTATS
 520         GC_printf2(
 521                   "Immediately reclaimed %ld bytes in heap of size %lu bytes\n",
 522                   (long)WORDS_TO_BYTES(GC_mem_found),
 523                   (unsigned long)GC_heapsize);
 524         GC_printf2("%lu (atomic) + %lu (composite) collectable bytes in use\n",
 525                    (unsigned long)WORDS_TO_BYTES(GC_atomic_in_use),
 526                    (unsigned long)WORDS_TO_BYTES(GC_composite_in_use));
 527 #   endif
 528
 529     /* Reset or increment counters for next cycle */
 530       GC_words_allocd_before_gc += GC_words_allocd;
 531       GC_non_gc_bytes_at_gc = GC_non_gc_bytes;
 532       GC_words_allocd = 0;
 533       GC_words_wasted = 0;
 534       GC_mem_freed = 0;
 535
 536 #   ifdef PRINTTIMES
 537         GET_TIME(done_time);
 538         GC_printf2("Finalize + initiate sweep took %lu + %lu msecs\n",
 539                    MS_TIME_DIFF(finalize_time,start_time),
 540                    MS_TIME_DIFF(done_time,finalize_time));
 541 #   endif
 542 }
 543
 544 /* Externally callable routine to invoke full, stop-world collection */
 545 # if defined(__STDC__) || defined(__cplusplus)
 546     int GC_try_to_collect(GC_stop_func stop_func)
 547 # else
 548     int GC_try_to_collect(stop_func)
 549     GC_stop_func stop_func;
 550 # endif
 551 {
 552     int result;
 553     DCL_LOCK_STATE;
 554
 555     GC_INVOKE_FINALIZERS();
 556     DISABLE_SIGNALS();
 557     LOCK();
 558     ENTER_GC();
 559     if (!GC_is_initialized) GC_init_inner();
 560     /* Minimize junk left in my registers */
 561       GC_noop(0,0,0,0,0,0);
 562     result = (int)GC_try_to_collect_inner(stop_func);
 563     EXIT_GC();
 564     UNLOCK();
 565     ENABLE_SIGNALS();
 566     if(result) GC_INVOKE_FINALIZERS();
 567     return(result);
 568 }
 569
 570 void GC_gcollect GC_PROTO(())
 571 {
 572     GC_notify_full_gc();
 573     (void)GC_try_to_collect(GC_never_stop_func);
 574 }
 575
 576 word GC_n_heap_sects = 0;       /* Number of sections currently in heap. */
 577
 578 /*
 579  * Use the chunk of memory starting at p of syze bytes as part of the heap.
 580  * Assumes p is HBLKSIZE aligned, and bytes is a multiple of HBLKSIZE.
 581  */
 582 void GC_add_to_heap(p, bytes)
 583 struct hblk *p;
 584 word bytes;
 585 {
 586     word words;
 587
 588     if (GC_n_heap_sects >= MAX_HEAP_SECTS) {
 589         ABORT("Too many heap sections: Increase MAXHINCR or MAX_HEAP_SECTS");
 590     }
 591     if (!GC_install_header(p)) {
 592         /* This is extremely unlikely. Can't add it.  This will         */
 593         /* almost certainly result in a 0 return from the allocator,    */
 594         /* which is entirely appropriate.                               */
 595         return;
 596     }
 597     GC_heap_sects[GC_n_heap_sects].hs_start = (ptr_t)p;
 598     GC_heap_sects[GC_n_heap_sects].hs_bytes = bytes;
 599     GC_n_heap_sects++;
 600     words = BYTES_TO_WORDS(bytes - HDR_BYTES);
 601     HDR(p) -> hb_sz = words;
 602     GC_freehblk(p);
 603     GC_heapsize += bytes;
 604     if ((ptr_t)p <= GC_least_plausible_heap_addr
 605         || GC_least_plausible_heap_addr == 0) {
 606         GC_least_plausible_heap_addr = (ptr_t)p - sizeof(word);
 607                 /* Making it a little smaller than necessary prevents   */
 608                 /* us from getting a false hit from the variable        */
 609                 /* itself.  There's some unintentional reflection       */
 610                 /* here.                                                */
 611     }
 612     if ((ptr_t)p + bytes >= GC_greatest_plausible_heap_addr) {
 613         GC_greatest_plausible_heap_addr = (ptr_t)p + bytes;
 614     }
 615 }
 616
 617 #ifdef PRESERVE_LAST
 618 GC_bool GC_in_last_heap_sect(p)
 619 ptr_t p;
 620 {
 621     struct HeapSect * last_heap_sect = &(GC_heap_sects[GC_n_heap_sects-1]);
 622     ptr_t start = last_heap_sect -> hs_start;
 623     ptr_t end;
 624
 625     if (p < start) return FALSE;
 626     end = start + last_heap_sect -> hs_bytes;
 627     if (p >= end) return FALSE;
 628     return TRUE;
 629 }
 630 #endif
 631
 632 # if !defined(NO_DEBUGGING)
 633 void GC_print_heap_sects()
 634 {
 635     register unsigned i;
 636
 637     GC_printf1("Total heap size: %lu\n", (unsigned long) GC_heapsize);
 638     for (i = 0; i < GC_n_heap_sects; i++) {
 639         unsigned long start = (unsigned long) GC_heap_sects[i].hs_start;
 640         unsigned long len = (unsigned long) GC_heap_sects[i].hs_bytes;
 641         struct hblk *h;
 642         unsigned nbl = 0;
 643
 644         GC_printf3("Section %ld from 0x%lx to 0x%lx ", (unsigned long)i,
 645                    start, (unsigned long)(start + len));
 646         for (h = (struct hblk *)start; h < (struct hblk *)(start + len); h++) {
 647             if (GC_is_black_listed(h, HBLKSIZE)) nbl++;
 648         }
 649         GC_printf2("%lu/%lu blacklisted\n", (unsigned long)nbl,
 650                    (unsigned long)(len/HBLKSIZE));
 651     }
 652 }
 653 # endif
 654
 655 ptr_t GC_least_plausible_heap_addr = (ptr_t)ONES;
 656 ptr_t GC_greatest_plausible_heap_addr = 0;
 657
 658 ptr_t GC_max(x,y)
 659 ptr_t x, y;
 660 {
 661     return(x > y? x : y);
 662 }
 663
 664 ptr_t GC_min(x,y)
 665 ptr_t x, y;
 666 {
 667     return(x < y? x : y);
 668 }
 669
 670 # if defined(__STDC__) || defined(__cplusplus)
 671     void GC_set_max_heap_size(GC_word n)
 672 # else
 673     void GC_set_max_heap_size(n)
 674     GC_word n;
 675 # endif
 676 {
 677     GC_max_heapsize = n;
 678 }
 679
 680 GC_word GC_max_retries = 0;
 681
 682 /*
 683  * this explicitly increases the size of the heap.  It is used
 684  * internally, but may also be invoked from GC_expand_hp by the user.
 685  * The argument is in units of HBLKSIZE.
 686  * Tiny values of n are rounded up.
 687  * Returns FALSE on failure.
 688  */
 689 GC_bool GC_expand_hp_inner(n)
 690 word n;
 691 {
 692     word bytes;
 693     struct hblk * space;
 694     word expansion_slop;        /* Number of bytes by which we expect the */
 695                                 /* heap to expand soon.                   */
 696
 697     if (n < MINHINCR) n = MINHINCR;
 698     bytes = n * HBLKSIZE;
 699     /* Make sure bytes is a multiple of GC_page_size */
 700       {
 701         word mask = GC_page_size - 1;
 702         bytes += mask;
 703         bytes &= ~mask;
 704       }
 705
 706     if (GC_max_heapsize != 0 && GC_heapsize + bytes > GC_max_heapsize) {
 707         /* Exceeded self-imposed limit */
 708         return(FALSE);
 709     }
 710     space = GET_MEM(bytes);
 711     if( space == 0 ) {
 712         return(FALSE);
 713     }
 714 #   ifdef PRINTSTATS
 715         GC_printf2("Increasing heap size by %lu after %lu allocated bytes\n",
 716                    (unsigned long)bytes,
 717                    (unsigned long)WORDS_TO_BYTES(GC_words_allocd));
 718 #       ifdef UNDEFINED
 719           GC_printf1("Root size = %lu\n", GC_root_size);
 720           GC_print_block_list(); GC_print_hblkfreelist();
 721           GC_printf0("\n");
 722 #       endif
 723 #   endif
 724     expansion_slop = 8 * WORDS_TO_BYTES(min_words_allocd());
 725     if (5 * HBLKSIZE * MAXHINCR > expansion_slop) {
 726         expansion_slop = 5 * HBLKSIZE * MAXHINCR;
 727     }
 728     if (GC_last_heap_addr == 0 && !((word)space & SIGNB)
 729         || GC_last_heap_addr != 0 && GC_last_heap_addr < (ptr_t)space) {
 730         /* Assume the heap is growing up */
 731         GC_greatest_plausible_heap_addr =
 732             GC_max(GC_greatest_plausible_heap_addr,
 733                    (ptr_t)space + bytes + expansion_slop);
 734     } else {
 735         /* Heap is growing down */
 736         GC_least_plausible_heap_addr =
 737             GC_min(GC_least_plausible_heap_addr,
 738                    (ptr_t)space - expansion_slop);
 739     }
 740     GC_prev_heap_addr = GC_last_heap_addr;
 741     GC_last_heap_addr = (ptr_t)space;
 742     GC_add_to_heap(space, bytes);
 743     return(TRUE);
 744 }
 745
 746 /* Really returns a bool, but it's externally visible, so that's clumsy. */
 747 /* Arguments is in bytes.                                               */
 748 # if defined(__STDC__) || defined(__cplusplus)
 749   int GC_expand_hp(size_t bytes)
 750 # else
 751   int GC_expand_hp(bytes)
 752   size_t bytes;
 753 # endif
 754 {
 755     int result;
 756     DCL_LOCK_STATE;
 757
 758     DISABLE_SIGNALS();
 759     LOCK();
 760     if (!GC_is_initialized) GC_init_inner();
 761     result = (int)GC_expand_hp_inner(divHBLKSZ((word)bytes));
 762     UNLOCK();
 763     ENABLE_SIGNALS();
 764     return(result);
 765 }
 766
 767 unsigned GC_fail_count = 0;
 768                         /* How many consecutive GC/expansion failures?  */
 769                         /* Reset by GC_allochblk.                       */
 770
 771 GC_bool GC_collect_or_expand(needed_blocks, ignore_off_page)
 772 word needed_blocks;
 773 GC_bool ignore_off_page;
 774 {
 775
 776     if (!GC_incremental && !GC_dont_gc && GC_should_collect()) {
 777       GC_notify_full_gc();
 778       GC_gcollect_inner();
 779     } else {
 780       word blocks_to_get = GC_heapsize/(HBLKSIZE*GC_free_space_divisor)
 781                            + needed_blocks;
 782
 783       if (blocks_to_get > MAXHINCR) {
 784           word slop;
 785
 786           if (ignore_off_page) {
 787               slop = 4;
 788           } else {
 789               slop = 2*divHBLKSZ(BL_LIMIT);
 790               if (slop > needed_blocks) slop = needed_blocks;
 791           }
 792           if (needed_blocks + slop > MAXHINCR) {
 793               blocks_to_get = needed_blocks + slop;
 794           } else {
 795               blocks_to_get = MAXHINCR;
 796           }
 797       }
 798       if (!GC_expand_hp_inner(blocks_to_get)
 799         && !GC_expand_hp_inner(needed_blocks)) {
 800         if (GC_fail_count++ < GC_max_retries) {
 801             WARN("Out of Memory!  Trying to continue ...\n", 0);
 802             GC_notify_full_gc();
 803             GC_gcollect_inner();
 804         } else {
 805             WARN("Out of Memory!  Returning NIL!\n", 0);
 806             return(FALSE);
 807         }
 808       } else if (GC_fail_count) {
 809 #         ifdef PRINTSTATS
 810             GC_printf0("Memory available again ...\n");
 811 #         endif
 812       }
 813     }
 814     return(TRUE);
 815 }
 816
 817 /*
 818  * Make sure the object free list for sz is not empty.
 819  * Return a pointer to the first object on the free list.
 820  * The object MUST BE REMOVED FROM THE FREE LIST BY THE CALLER.
 821  * Assumes we hold the allocator lock and signals are disabled.
 822  *
 823  */
 824 ptr_t GC_allocobj(sz, kind)
 825 word sz;
 826 int kind;
 827 {
 828     register ptr_t * flh = &(GC_obj_kinds[kind].ok_freelist[sz]);
 829
 830     if (sz == 0) return(0);
 831
 832     while (*flh == 0) {
 833       ENTER_GC();
 834       /* Do our share of marking work */
 835         if(GC_incremental && !GC_dont_gc) GC_collect_a_little_inner(1);
 836       /* Sweep blocks for objects of this size */
 837           GC_continue_reclaim(sz, kind);
 838       EXIT_GC();
 839       if (*flh == 0) {
 840         GC_new_hblk(sz, kind);
 841       }
 842       if (*flh == 0) {
 843         ENTER_GC();
 844         if (!GC_collect_or_expand((word)1,FALSE)) {
 845             EXIT_GC();
 846             return(0);
 847         }
 848         EXIT_GC();
 849       }
 850     }
 851
 852     return(*flh);
 853 }