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alloc.c

/*
 * Copyright 1988, 1989 Hans-J. Boehm, Alan J. Demers
 * Copyright (c) 1991-1996 by Xerox Corporation.  All rights reserved.
 * Copyright (c) 1998 by Silicon Graphics.  All rights reserved.
 * Copyright (c) 1999 by Hewlett-Packard Company. All rights reserved.
 *
 * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
 * OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.
 *
 * Permission is hereby granted to use or copy this program
 * for any purpose,  provided the above notices are retained on all copies.
 * Permission to modify the code and to distribute modified code is granted,
 * provided the above notices are retained, and a notice that the code was
 * modified is included with the above copyright notice.
 *
 */


# include "private/gc_priv.h"

# include <stdio.h>
# if !defined(MACOS) && !defined(MSWINCE)
#   include <signal.h>
#   include <sys/types.h>
# endif

/*
 * Separate free lists are maintained for different sized objects
 * up to MAXOBJSZ.
 * The call GC_allocobj(i,k) ensures that the freelist for
 * kind k objects of size i points to a non-empty
 * free list. It returns a pointer to the first entry on the free list.
 * In a single-threaded world, GC_allocobj may be called to allocate
 * an object of (small) size i as follows:
 *
 *            opp = &(GC_objfreelist[i]);
 *            if (*opp == 0) GC_allocobj(i, NORMAL);
 *            ptr = *opp;
 *            *opp = obj_link(ptr);
 *
 * Note that this is very fast if the free list is non-empty; it should
 * only involve the execution of 4 or 5 simple instructions.
 * All composite objects on freelists are cleared, except for
 * their first word.
 */

/*
 *  The allocator uses GC_allochblk to allocate large chunks of objects.
 * These chunks all start on addresses which are multiples of
 * HBLKSZ.   Each allocated chunk has an associated header,
 * which can be located quickly based on the address of the chunk.
 * (See headers.c for details.) 
 * This makes it possible to check quickly whether an
 * arbitrary address corresponds to an object administered by the
 * allocator.
 */

word GC_non_gc_bytes = 0;  /* Number of bytes not intended to be collected */

word GC_gc_no = 0;

#ifndef SMALL_CONFIG
  int GC_incremental = 0;  /* By default, stop the world.   */
#endif

int GC_parallel = FALSE;   /* By default, parallel GC is off.     */

int GC_full_freq = 19;     /* Every 20th collection is a full     */
                     /* collection, whether we need it      */
                     /* or not.                         */

GC_bool GC_need_full_gc = FALSE;
                     /* Need full GC do to heap growth.     */

#ifdef THREADS
  GC_bool GC_world_stopped = FALSE;
# define IF_THREADS(x) x
#else
# define IF_THREADS(x)
#endif

word GC_used_heap_size_after_full = 0;

char * GC_copyright[] =
{"Copyright 1988,1989 Hans-J. Boehm and Alan J. Demers ",
"Copyright (c) 1991-1995 by Xerox Corporation.  All rights reserved. ",
"Copyright (c) 1996-1998 by Silicon Graphics.  All rights reserved. ",
"Copyright (c) 1999-2001 by Hewlett-Packard Company.  All rights reserved. ",
"THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY",
" EXPRESSED OR IMPLIED.  ANY USE IS AT YOUR OWN RISK.",
"See source code for details." };

# include "version.h"

#if defined(SAVE_CALL_CHAIN) && \
      !(defined(REDIRECT_MALLOC) && defined(GC_HAVE_BUILTIN_BACKTRACE))
#   define SAVE_CALL_CHAIN_IN_GC
    /* This is only safe if the call chain save mechanism won't end up  */
    /* calling GC_malloc.  The GNU C library documentation suggests     */
    /* that backtrace doesn't use malloc, but at least the initial      */
    /* call in some versions does seem to invoke the dynamic linker,    */
    /* which uses malloc.                                   */
#endif

/* some more variables */

extern signed_word GC_mem_found;  /* Number of reclaimed longwords      */
                          /* after garbage collection       */

GC_bool GC_dont_expand = 0;

word GC_free_space_divisor = 3;

extern GC_bool GC_collection_in_progress();
            /* Collection is in progress, or was abandoned. */

int GC_never_stop_func GC_PROTO((void)) { return(0); }

unsigned long GC_time_limit = TIME_LIMIT;

CLOCK_TYPE GC_start_time;     /* Time at which we stopped world.  */
                        /* used only in GC_timeout_stop_func.     */

int GC_n_attempts = 0;        /* Number of attempts at finishing  */
                        /* collection within GC_time_limit. */

#if defined(SMALL_CONFIG) || defined(NO_CLOCK)
#   define GC_timeout_stop_func GC_never_stop_func
#else
  int GC_timeout_stop_func GC_PROTO((void))
  {
    CLOCK_TYPE current_time;
    static unsigned count = 0;
    unsigned long time_diff;
    
    if ((count++ & 3) != 0) return(0);
    GET_TIME(current_time);
    time_diff = MS_TIME_DIFF(current_time,GC_start_time);
    if (time_diff >= GC_time_limit) {
#     ifdef CONDPRINT
        if (GC_print_stats) {
          GC_printf0("Abandoning stopped marking after ");
          GC_printf1("%lu msecs", (unsigned long)time_diff);
          GC_printf1("(attempt %ld)\n", (unsigned long) GC_n_attempts);
        }
#     endif
      return(1);
    }
    return(0);
  }
#endif /* !SMALL_CONFIG */

/* Return the minimum number of words that must be allocated between    */
/* collections to amortize the collection cost.                   */
static word min_words_allocd()
{
#   ifdef THREADS
      /* We punt, for now. */
      register signed_word stack_size = 10000;
#   else
        int dummy;
        register signed_word stack_size = (ptr_t)(&dummy) - GC_stackbottom;
#   endif
    word total_root_size;         /* includes double stack size,  */
                            /* since the stack is expensive */
                            /* to scan.                     */
    word scan_size;           /* Estimate of memory to be scanned       */
                        /* during normal GC.                */
    
    if (stack_size < 0) stack_size = -stack_size;
    total_root_size = 2 * stack_size + GC_root_size;
    scan_size = BYTES_TO_WORDS(GC_heapsize - GC_large_free_bytes
                         + (GC_large_free_bytes >> 2)
                           /* use a bit more of large empty heap */
                         + total_root_size);
    if (TRUE_INCREMENTAL) {
        return scan_size / (2 * GC_free_space_divisor);
    } else {
        return scan_size / GC_free_space_divisor;
    }
}

/* Return the number of words allocated, adjusted for explicit storage  */
/* management, etc..  This number is used in deciding when to trigger   */
/* collections.                                             */
word GC_adj_words_allocd()
{
    register signed_word result;
    register signed_word expl_managed =
            BYTES_TO_WORDS((long)GC_non_gc_bytes
                        - (long)GC_non_gc_bytes_at_gc);
    
    /* Don't count what was explicitly freed, or newly allocated for    */
    /* explicit management.  Note that deallocating an explicitly */
    /* managed object should not alter result, assuming the client      */
    /* is playing by the rules.                                   */
    result = (signed_word)GC_words_allocd
           - (signed_word)GC_mem_freed 
           + (signed_word)GC_finalizer_mem_freed - expl_managed;
    if (result > (signed_word)GC_words_allocd) {
        result = GC_words_allocd;
      /* probably client bug or unfortunate scheduling */
    }
    result += GC_words_finalized;
      /* We count objects enqueued for finalization as though they      */
      /* had been reallocated this round. Finalization is user    */
      /* visible progress.  And if we don't count this, we have   */
      /* stability problems for programs that finalize all objects.     */
    if ((signed_word)(GC_words_wasted >> 3) < result)
        result += GC_words_wasted;
      /* This doesn't reflect useful work.  But if there is lots of     */
      /* new fragmentation, the same is probably true of the heap,      */
      /* and the collection will be correspondingly cheaper.            */
    if (result < (signed_word)(GC_words_allocd >> 3)) {
      /* Always count at least 1/8 of the allocations.  We don't want   */
      /* to collect too infrequently, since that would inhibit    */
      /* coalescing of free storage blocks.                       */
      /* This also makes us partially robust against client bugs. */
        return(GC_words_allocd >> 3);
    } else {
        return(result);
    }
}


/* Clear up a few frames worth of garbage left at the top of the stack. */
/* This is used to prevent us from accidentally treating garbade left   */
/* on the stack by other parts of the collector as roots.  This   */
/* differs from the code in misc.c, which actually tries to keep the    */
/* stack clear of long-lived, client-generated garbage.                 */
void GC_clear_a_few_frames()
{
#   define NWORDS 64
    word frames[NWORDS];
    /* Some compilers will warn that frames was set but never used.     */
    /* That's the whole idea ...                            */
    register int i;
    
    for (i = 0; i < NWORDS; i++) frames[i] = 0;
}

/* Heap size at which we need a collection to avoid expanding past      */
/* limits used by blacklisting.                                   */
static word GC_collect_at_heapsize = (word)(-1);

/* Have we allocated enough to amortize a collection? */
GC_bool GC_should_collect()
{
    return(GC_adj_words_allocd() >= min_words_allocd()
         || GC_heapsize >= GC_collect_at_heapsize);
}


void GC_notify_full_gc()
{
    if (GC_start_call_back != (void (*) GC_PROTO((void)))0) {
      (*GC_start_call_back)();
    }
}

GC_bool GC_is_full_gc = FALSE;

/* 
 * Initiate a garbage collection if appropriate.
 * Choose judiciously
 * between partial, full, and stop-world collections.
 * Assumes lock held, signals disabled.
 */
void GC_maybe_gc()
{
    static int n_partial_gcs = 0;

    if (GC_should_collect()) {
        if (!GC_incremental) {
            GC_gcollect_inner();
            n_partial_gcs = 0;
            return;
        } else {
#       ifdef PARALLEL_MARK
          GC_wait_for_reclaim();
#       endif
        if (GC_need_full_gc || n_partial_gcs >= GC_full_freq) {
#         ifdef CONDPRINT
            if (GC_print_stats) {
              GC_printf2(
                "***>Full mark for collection %lu after %ld allocd bytes\n",
              (unsigned long) GC_gc_no+1,
              (long)WORDS_TO_BYTES(GC_words_allocd));
            }
#           endif
          GC_promote_black_lists();
          (void)GC_reclaim_all((GC_stop_func)0, TRUE);
          GC_clear_marks();
            n_partial_gcs = 0;
          GC_notify_full_gc();
          GC_is_full_gc = TRUE;
          } else {
            n_partial_gcs++;
          }
      }
        /* We try to mark with the world stopped.     */
        /* If we run out of time, this turns into     */
        /* incremental marking.                 */
#     ifndef NO_CLOCK
          if (GC_time_limit != GC_TIME_UNLIMITED) { GET_TIME(GC_start_time); }
#     endif
        if (GC_stopped_mark(GC_time_limit == GC_TIME_UNLIMITED? 
                      GC_never_stop_func : GC_timeout_stop_func)) {
#           ifdef SAVE_CALL_CHAIN_IN_GC
                GC_save_callers(GC_last_stack);
#           endif
            GC_finish_collection();
        } else {
          if (!GC_is_full_gc) {
            /* Count this as the first attempt */
              GC_n_attempts++;
          }
      }
    }
}


/*
 * Stop the world garbage collection.  Assumes lock held, signals disabled.
 * If stop_func is not GC_never_stop_func, then abort if stop_func returns TRUE.
 * Return TRUE if we successfully completed the collection.
 */
GC_bool GC_try_to_collect_inner(stop_func)
GC_stop_func stop_func;
{
#   ifdef CONDPRINT
        CLOCK_TYPE start_time, current_time;
#   endif
    if (GC_dont_gc) return FALSE;
    if (GC_incremental && GC_collection_in_progress()) {
#   ifdef CONDPRINT
      if (GC_print_stats) {
      GC_printf0(
          "GC_try_to_collect_inner: finishing collection in progress\n");
      }
#   endif /* CONDPRINT */
      /* Just finish collection already in progress.  */
      while(GC_collection_in_progress()) {
          if (stop_func()) return(FALSE);
          GC_collect_a_little_inner(1);
      }
    }
    if (stop_func == GC_never_stop_func) GC_notify_full_gc();
#   ifdef CONDPRINT
      if (GC_print_stats) {
        if (GC_print_stats) GET_TIME(start_time);
      GC_printf2(
         "Initiating full world-stop collection %lu after %ld allocd bytes\n",
         (unsigned long) GC_gc_no+1,
         (long)WORDS_TO_BYTES(GC_words_allocd));
      }
#   endif
    GC_promote_black_lists();
    /* Make sure all blocks have been reclaimed, so sweep routines      */
    /* don't see cleared mark bits.                         */
    /* If we're guaranteed to finish, then this is unnecessary.         */
    /* In the find_leak case, we have to finish to guarantee that       */
    /* previously unmarked objects are not reported as leaks.           */
#       ifdef PARALLEL_MARK
          GC_wait_for_reclaim();
#       endif
      if ((GC_find_leak || stop_func != GC_never_stop_func)
          && !GC_reclaim_all(stop_func, FALSE)) {
          /* Aborted.  So far everything is still consistent.     */
          return(FALSE);
      }
    GC_invalidate_mark_state();  /* Flush mark stack. */
    GC_clear_marks();
#   ifdef SAVE_CALL_CHAIN_IN_GC
        GC_save_callers(GC_last_stack);
#   endif
    GC_is_full_gc = TRUE;
    if (!GC_stopped_mark(stop_func)) {
      if (!GC_incremental) {
      /* We're partially done and have no way to complete or use  */
      /* current work.  Reestablish invariants as cheaply as            */
      /* possible.                                          */
      GC_invalidate_mark_state();
      GC_unpromote_black_lists();
      } /* else we claim the world is already still consistent.  We'll  */
        /* finish incrementally.                            */
      return(FALSE);
    }
    GC_finish_collection();
#   if defined(CONDPRINT)
      if (GC_print_stats) {
        GET_TIME(current_time);
        GC_printf1("Complete collection took %lu msecs\n",
                   MS_TIME_DIFF(current_time,start_time));
      }
#   endif
    return(TRUE);
}



/*
 * Perform n units of garbage collection work.  A unit is intended to touch
 * roughly GC_RATE pages.  Every once in a while, we do more than that.
 * This needs to be a fairly large number with our current incremental
 * GC strategy, since otherwise we allocate too much during GC, and the
 * cleanup gets expensive.
 */
# define GC_RATE 10 
# define MAX_PRIOR_ATTEMPTS 1
      /* Maximum number of prior attempts at world stop marking   */
      /* A value of 1 means that we finish the second time, no matter */
      /* how long it takes.  Doesn't count the initial root scan  */
      /* for a full GC.                               */

int GC_deficit = 0;     /* The number of extra calls to GC_mark_some    */
                  /* that we have made.                     */

void GC_collect_a_little_inner(n)
int n;
{
    register int i;
    
    if (GC_dont_gc) return;
    if (GC_incremental && GC_collection_in_progress()) {
      for (i = GC_deficit; i < GC_RATE*n; i++) {
          if (GC_mark_some((ptr_t)0)) {
              /* Need to finish a collection */
#                 ifdef SAVE_CALL_CHAIN_IN_GC
                GC_save_callers(GC_last_stack);
#                 endif
#           ifdef PARALLEL_MARK
                GC_wait_for_reclaim();
#           endif
            if (GC_n_attempts < MAX_PRIOR_ATTEMPTS
                && GC_time_limit != GC_TIME_UNLIMITED) {
              GET_TIME(GC_start_time);
              if (!GC_stopped_mark(GC_timeout_stop_func)) {
                GC_n_attempts++;
                break;
              }
            } else {
              (void)GC_stopped_mark(GC_never_stop_func);
            }
              GC_finish_collection();
              break;
          }
      }
      if (GC_deficit > 0) GC_deficit -= GC_RATE*n;
      if (GC_deficit < 0) GC_deficit = 0;
    } else {
        GC_maybe_gc();
    }
}

int GC_collect_a_little GC_PROTO(())
{
    int result;
    DCL_LOCK_STATE;

    DISABLE_SIGNALS();
    LOCK();
    GC_collect_a_little_inner(1);
    result = (int)GC_collection_in_progress();
    UNLOCK();
    ENABLE_SIGNALS();
    if (!result && GC_debugging_started) GC_print_all_smashed();
    return(result);
}

/*
 * Assumes lock is held, signals are disabled.
 * We stop the world.
 * If stop_func() ever returns TRUE, we may fail and return FALSE.
 * Increment GC_gc_no if we succeed.
 */
GC_bool GC_stopped_mark(stop_func)
GC_stop_func stop_func;
{
    register int i;
    int dummy;
#   if defined(PRINTTIMES) || defined(CONDPRINT)
      CLOCK_TYPE start_time, current_time;
#   endif
      
#   ifdef PRINTTIMES
      GET_TIME(start_time);
#   endif
#   if defined(CONDPRINT) && !defined(PRINTTIMES)
      if (GC_print_stats) GET_TIME(start_time);
#   endif
#   if defined(REGISTER_LIBRARIES_EARLY)
        GC_cond_register_dynamic_libraries();
#   endif
    STOP_WORLD();
    IF_THREADS(GC_world_stopped = TRUE);
#   ifdef CONDPRINT
      if (GC_print_stats) {
      GC_printf1("--> Marking for collection %lu ",
                 (unsigned long) GC_gc_no + 1);
      GC_printf2("after %lu allocd bytes + %lu wasted bytes\n",
               (unsigned long) WORDS_TO_BYTES(GC_words_allocd),
               (unsigned long) WORDS_TO_BYTES(GC_words_wasted));
      }
#   endif
#   ifdef MAKE_BACK_GRAPH
      if (GC_print_back_height) {
        GC_build_back_graph();
      }
#   endif

    /* Mark from all roots.  */
        /* Minimize junk left in my registers and on the stack */
            GC_clear_a_few_frames();
            GC_noop(0,0,0,0,0,0);
      GC_initiate_gc();
      for(i = 0;;i++) {
          if ((*stop_func)()) {
#               ifdef CONDPRINT
                  if (GC_print_stats) {
                  GC_printf0("Abandoned stopped marking after ");
                  GC_printf1("%lu iterations\n",
                           (unsigned long)i);
                  }
#               endif
                GC_deficit = i; /* Give the mutator a chance. */
                    IF_THREADS(GC_world_stopped = FALSE);
                  START_WORLD();
                  return(FALSE);
          }
          if (GC_mark_some((ptr_t)(&dummy))) break;
      }
      
    GC_gc_no++;
#   ifdef PRINTSTATS
      GC_printf2("Collection %lu reclaimed %ld bytes",
              (unsigned long) GC_gc_no - 1,
              (long)WORDS_TO_BYTES(GC_mem_found));
#   else
#     ifdef CONDPRINT
        if (GC_print_stats) {
        GC_printf1("Collection %lu finished", (unsigned long) GC_gc_no - 1);
      }
#     endif
#   endif /* !PRINTSTATS */
#   ifdef CONDPRINT
      if (GC_print_stats) {
        GC_printf1(" ---> heapsize = %lu bytes\n",
                       (unsigned long) GC_heapsize);
        /* Printf arguments may be pushed in funny places.  Clear the   */
        /* space.                                     */
        GC_printf0("");
      }
#   endif  /* CONDPRINT  */

    /* Check all debugged objects for consistency */
        if (GC_debugging_started) {
            (*GC_check_heap)();
        }
    
    IF_THREADS(GC_world_stopped = FALSE);
    START_WORLD();
#   ifdef PRINTTIMES
      GET_TIME(current_time);
      GC_printf1("World-stopped marking took %lu msecs\n",
                 MS_TIME_DIFF(current_time,start_time));
#   else
#     ifdef CONDPRINT
      if (GC_print_stats) {
        GET_TIME(current_time);
        GC_printf1("World-stopped marking took %lu msecs\n",
                   MS_TIME_DIFF(current_time,start_time));
      }
#     endif
#   endif
    return(TRUE);
}

/* Set all mark bits for the free list whose first entry is q     */
#ifdef __STDC__
  void GC_set_fl_marks(ptr_t q)
#else
  void GC_set_fl_marks(q)
  ptr_t q;
#endif
{
   ptr_t p;
   struct hblk * h, * last_h = 0;
   hdr *hhdr;
   int word_no;

   for (p = q; p != 0; p = obj_link(p)){
      h = HBLKPTR(p);
      if (h != last_h) {
        last_h = h; 
        hhdr = HDR(h);
      }
      word_no = (((word *)p) - ((word *)h));
      set_mark_bit_from_hdr(hhdr, word_no);
   }
}

/* Clear all mark bits for the free list whose first entry is q   */
/* Decrement GC_mem_found by number of words on free list.  */
#ifdef __STDC__
  void GC_clear_fl_marks(ptr_t q)
#else
  void GC_clear_fl_marks(q)
  ptr_t q;
#endif
{
   ptr_t p;
   struct hblk * h, * last_h = 0;
   hdr *hhdr;
   int word_no;

   for (p = q; p != 0; p = obj_link(p)){
      h = HBLKPTR(p);
      if (h != last_h) {
        last_h = h; 
        hhdr = HDR(h);
      }
      word_no = (((word *)p) - ((word *)h));
      clear_mark_bit_from_hdr(hhdr, word_no);
#     ifdef GATHERSTATS
          GC_mem_found -= hhdr -> hb_sz;
#     endif
   }
}

/* Finish up a collection.  Assumes lock is held, signals are disabled, */
/* but the world is otherwise running.                            */
void GC_finish_collection()
{
#   ifdef PRINTTIMES
      CLOCK_TYPE start_time;
      CLOCK_TYPE finalize_time;
      CLOCK_TYPE done_time;
      
      GET_TIME(start_time);
      finalize_time = start_time;
#   endif

#   ifdef GATHERSTATS
        GC_mem_found = 0;
#   endif
#   if defined(LINUX) && defined(__ELF__) && !defined(SMALL_CONFIG)
      if (getenv("GC_PRINT_ADDRESS_MAP") != 0) {
        GC_print_address_map();
      }
#   endif
    COND_DUMP;
    if (GC_find_leak) {
      /* Mark all objects on the free list.  All objects should be */
      /* marked when we're done.                         */
      {
        register word size;         /* current object size        */
        int kind;
        ptr_t q;

        for (kind = 0; kind < GC_n_kinds; kind++) {
          for (size = 1; size <= MAXOBJSZ; size++) {
            q = GC_obj_kinds[kind].ok_freelist[size];
            if (q != 0) GC_set_fl_marks(q);
          }
        }
      }
      GC_start_reclaim(TRUE);
        /* The above just checks; it doesn't really reclaim anything. */
    }

    GC_finalize();
#   ifdef STUBBORN_ALLOC
      GC_clean_changing_list();
#   endif

#   ifdef PRINTTIMES
      GET_TIME(finalize_time);
#   endif

    if (GC_print_back_height) {
#     ifdef MAKE_BACK_GRAPH
      GC_traverse_back_graph();
#     else
#     ifndef SMALL_CONFIG
        GC_err_printf0("Back height not available: "
                     "Rebuild collector with -DMAKE_BACK_GRAPH\n");
#     endif
#     endif
    }

    /* Clear free list mark bits, in case they got accidentally marked   */
    /* (or GC_find_leak is set and they were intentionally marked).      */
    /* Also subtract memory remaining from GC_mem_found count.           */
    /* Note that composite objects on free list are cleared.             */
    /* Thus accidentally marking a free list is not a problem;  only     */
    /* objects on the list itself will be marked, and that's fixed here. */
      {
      register word size;           /* current object size        */
      register ptr_t q; /* pointer to current object  */
      int kind;

      for (kind = 0; kind < GC_n_kinds; kind++) {
        for (size = 1; size <= MAXOBJSZ; size++) {
          q = GC_obj_kinds[kind].ok_freelist[size];
          if (q != 0) GC_clear_fl_marks(q);
        }
      }
      }


#   ifdef PRINTSTATS
      GC_printf1("Bytes recovered before sweep - f.l. count = %ld\n",
                (long)WORDS_TO_BYTES(GC_mem_found));
#   endif
    /* Reconstruct free lists to contain everything not marked */
        GC_start_reclaim(FALSE);
        if (GC_is_full_gc)  {
          GC_used_heap_size_after_full = USED_HEAP_SIZE;
          GC_need_full_gc = FALSE;
      } else {
          GC_need_full_gc =
             BYTES_TO_WORDS(USED_HEAP_SIZE - GC_used_heap_size_after_full)
             > min_words_allocd();
      }

#   ifdef PRINTSTATS
      GC_printf2(
              "Immediately reclaimed %ld bytes in heap of size %lu bytes",
                (long)WORDS_TO_BYTES(GC_mem_found),
                (unsigned long)GC_heapsize);
#     ifdef USE_MUNMAP
        GC_printf1("(%lu unmapped)", GC_unmapped_bytes);
#     endif
      GC_printf2(
            "\n%lu (atomic) + %lu (composite) collectable bytes in use\n",
              (unsigned long)WORDS_TO_BYTES(GC_atomic_in_use),
              (unsigned long)WORDS_TO_BYTES(GC_composite_in_use));
#   endif

      GC_n_attempts = 0;
      GC_is_full_gc = FALSE;
    /* Reset or increment counters for next cycle */
      GC_words_allocd_before_gc += GC_words_allocd;
      GC_non_gc_bytes_at_gc = GC_non_gc_bytes;
      GC_words_allocd = 0;
      GC_words_wasted = 0;
      GC_mem_freed = 0;
      GC_finalizer_mem_freed = 0;
      
#   ifdef USE_MUNMAP
      GC_unmap_old();
#   endif
#   ifdef PRINTTIMES
      GET_TIME(done_time);
      GC_printf2("Finalize + initiate sweep took %lu + %lu msecs\n",
                 MS_TIME_DIFF(finalize_time,start_time),
                 MS_TIME_DIFF(done_time,finalize_time));
#   endif
}

/* Externally callable routine to invoke full, stop-world collection */
# if defined(__STDC__) || defined(__cplusplus)
    int GC_try_to_collect(GC_stop_func stop_func)
# else
    int GC_try_to_collect(stop_func)
    GC_stop_func stop_func;
# endif
{
    int result;
    DCL_LOCK_STATE;
    
    if (GC_debugging_started) GC_print_all_smashed();
    GC_INVOKE_FINALIZERS();
    DISABLE_SIGNALS();
    LOCK();
    ENTER_GC();
    if (!GC_is_initialized) GC_init_inner();
    /* Minimize junk left in my registers */
      GC_noop(0,0,0,0,0,0);
    result = (int)GC_try_to_collect_inner(stop_func);
    EXIT_GC();
    UNLOCK();
    ENABLE_SIGNALS();
    if(result) {
        if (GC_debugging_started) GC_print_all_smashed();
        GC_INVOKE_FINALIZERS();
    }
    return(result);
}

void GC_gcollect GC_PROTO(())
{
    (void)GC_try_to_collect(GC_never_stop_func);
    if (GC_have_errors) GC_print_all_errors();
}

word GC_n_heap_sects = 0;     /* Number of sections currently in heap. */

/*
 * Use the chunk of memory starting at p of size bytes as part of the heap.
 * Assumes p is HBLKSIZE aligned, and bytes is a multiple of HBLKSIZE.
 */
void GC_add_to_heap(p, bytes)
struct hblk *p;
word bytes;
{
    word words;
    hdr * phdr;
    
    if (GC_n_heap_sects >= MAX_HEAP_SECTS) {
      ABORT("Too many heap sections: Increase MAXHINCR or MAX_HEAP_SECTS");
    }
    phdr = GC_install_header(p);
    if (0 == phdr) {
      /* This is extremely unlikely. Can't add it.  This will           */
      /* almost certainly result in a     0 return from the allocator,  */
      /* which is entirely appropriate.                     */
      return;
    }
    GC_heap_sects[GC_n_heap_sects].hs_start = (ptr_t)p;
    GC_heap_sects[GC_n_heap_sects].hs_bytes = bytes;
    GC_n_heap_sects++;
    words = BYTES_TO_WORDS(bytes);
    phdr -> hb_sz = words;
    phdr -> hb_map = (unsigned char *)1;   /* A value != GC_invalid_map */
    phdr -> hb_flags = 0;
    GC_freehblk(p);
    GC_heapsize += bytes;
    if ((ptr_t)p <= (ptr_t)GC_least_plausible_heap_addr
        || GC_least_plausible_heap_addr == 0) {
        GC_least_plausible_heap_addr = (GC_PTR)((ptr_t)p - sizeof(word));
            /* Making it a little smaller than necessary prevents */
            /* us from getting a false hit from the variable      */
            /* itself.  There's some unintentional reflection     */
            /* here.                                  */
    }
    if ((ptr_t)p + bytes >= (ptr_t)GC_greatest_plausible_heap_addr) {
        GC_greatest_plausible_heap_addr = (GC_PTR)((ptr_t)p + bytes);
    }
}

# if !defined(NO_DEBUGGING)
void GC_print_heap_sects()
{
    register unsigned i;
    
    GC_printf1("Total heap size: %lu\n", (unsigned long) GC_heapsize);
    for (i = 0; i < GC_n_heap_sects; i++) {
        unsigned long start = (unsigned long) GC_heap_sects[i].hs_start;
        unsigned long len = (unsigned long) GC_heap_sects[i].hs_bytes;
        struct hblk *h;
        unsigned nbl = 0;
        
      GC_printf3("Section %ld from 0x%lx to 0x%lx ", (unsigned long)i,
               start, (unsigned long)(start + len));
      for (h = (struct hblk *)start; h < (struct hblk *)(start + len); h++) {
          if (GC_is_black_listed(h, HBLKSIZE)) nbl++;
      }
      GC_printf2("%lu/%lu blacklisted\n", (unsigned long)nbl,
               (unsigned long)(len/HBLKSIZE));
    }
}
# endif

GC_PTR GC_least_plausible_heap_addr = (GC_PTR)ONES;
GC_PTR GC_greatest_plausible_heap_addr = 0;

ptr_t GC_max(x,y)
ptr_t x, y;
{
    return(x > y? x : y);
}

ptr_t GC_min(x,y)
ptr_t x, y;
{
    return(x < y? x : y);
}

# if defined(__STDC__) || defined(__cplusplus)
    void GC_set_max_heap_size(GC_word n)
# else
    void GC_set_max_heap_size(n)
    GC_word n;
# endif
{
    GC_max_heapsize = n;
}

GC_word GC_max_retries = 0;

/*
 * this explicitly increases the size of the heap.  It is used
 * internally, but may also be invoked from GC_expand_hp by the user.
 * The argument is in units of HBLKSIZE.
 * Tiny values of n are rounded up.
 * Returns FALSE on failure.
 */
GC_bool GC_expand_hp_inner(n)
word n;
{
    word bytes;
    struct hblk * space;
    word expansion_slop;      /* Number of bytes by which we expect the */
                        /* heap to expand soon.               */

    if (n < MINHINCR) n = MINHINCR;
    bytes = n * HBLKSIZE;
    /* Make sure bytes is a multiple of GC_page_size */
      {
      word mask = GC_page_size - 1;
      bytes += mask;
      bytes &= ~mask;
      }
    
    if (GC_max_heapsize != 0 && GC_heapsize + bytes > GC_max_heapsize) {
        /* Exceeded self-imposed limit */
        return(FALSE);
    }
    space = GET_MEM(bytes);
    if( space == 0 ) {
#     ifdef CONDPRINT
        if (GC_print_stats) {
          GC_printf1("Failed to expand heap by %ld bytes\n",
                   (unsigned long)bytes);
        }
#       endif
      return(FALSE);
    }
#   ifdef CONDPRINT
      if (GC_print_stats) {
      GC_printf2("Increasing heap size by %lu after %lu allocated bytes\n",
                 (unsigned long)bytes,
                 (unsigned long)WORDS_TO_BYTES(GC_words_allocd));
#     ifdef UNDEFINED
        GC_printf1("Root size = %lu\n", GC_root_size);
        GC_print_block_list(); GC_print_hblkfreelist();
        GC_printf0("\n");
#     endif
      }
#   endif
    expansion_slop = WORDS_TO_BYTES(min_words_allocd()) + 4*MAXHINCR*HBLKSIZE;
    if (GC_last_heap_addr == 0 && !((word)space & SIGNB)
        || (GC_last_heap_addr != 0 && GC_last_heap_addr < (ptr_t)space)) {
        /* Assume the heap is growing up */
        GC_greatest_plausible_heap_addr =
            (GC_PTR)GC_max((ptr_t)GC_greatest_plausible_heap_addr,
                           (ptr_t)space + bytes + expansion_slop);
    } else {
        /* Heap is growing down */
        GC_least_plausible_heap_addr =
            (GC_PTR)GC_min((ptr_t)GC_least_plausible_heap_addr,
                           (ptr_t)space - expansion_slop);
    }
#   if defined(LARGE_CONFIG)
      if (((ptr_t)GC_greatest_plausible_heap_addr <= (ptr_t)space + bytes
           || (ptr_t)GC_least_plausible_heap_addr >= (ptr_t)space)
        && GC_heapsize > 0) {
      /* GC_add_to_heap will fix this, but ... */
      WARN("Too close to address space limit: blacklisting ineffective\n", 0);
      }
#   endif
    GC_prev_heap_addr = GC_last_heap_addr;
    GC_last_heap_addr = (ptr_t)space;
    GC_add_to_heap(space, bytes);
    /* Force GC before we are likely to allocate past expansion_slop */
      GC_collect_at_heapsize =
        GC_heapsize + expansion_slop - 2*MAXHINCR*HBLKSIZE;
#     if defined(LARGE_CONFIG)
        if (GC_collect_at_heapsize < GC_heapsize /* wrapped */)
        GC_collect_at_heapsize = (word)(-1);
#     endif
    return(TRUE);
}

/* Really returns a bool, but it's externally visible, so that's clumsy. */
/* Arguments is in bytes.                                   */
# if defined(__STDC__) || defined(__cplusplus)
  int GC_expand_hp(size_t bytes)
# else
  int GC_expand_hp(bytes)
  size_t bytes;
# endif
{
    int result;
    DCL_LOCK_STATE;
    
    DISABLE_SIGNALS();
    LOCK();
    if (!GC_is_initialized) GC_init_inner();
    result = (int)GC_expand_hp_inner(divHBLKSZ((word)bytes));
    if (result) GC_requested_heapsize += bytes;
    UNLOCK();
    ENABLE_SIGNALS();
    return(result);
}

unsigned GC_fail_count = 0;  
                  /* How many consecutive GC/expansion failures?  */
                  /* Reset by GC_allochblk.                 */

GC_bool GC_collect_or_expand(needed_blocks, ignore_off_page)
word needed_blocks;
GC_bool ignore_off_page;
{
    if (!GC_incremental && !GC_dont_gc &&
      ((GC_dont_expand && GC_words_allocd > 0) || GC_should_collect())) {
      GC_gcollect_inner();
    } else {
      word blocks_to_get = GC_heapsize/(HBLKSIZE*GC_free_space_divisor)
                           + needed_blocks;
      
      if (blocks_to_get > MAXHINCR) {
          word slop;
          
        /* Get the minimum required to make it likely that we           */
        /* can satisfy the current request in the presence of black-    */
        /* listing.  This will probably be more than MAXHINCR.    */
          if (ignore_off_page) {
              slop = 4;
          } else {
            slop = 2*divHBLKSZ(BL_LIMIT);
            if (slop > needed_blocks) slop = needed_blocks;
        }
          if (needed_blocks + slop > MAXHINCR) {
              blocks_to_get = needed_blocks + slop;
          } else {
              blocks_to_get = MAXHINCR;
          }
      }
      if (!GC_expand_hp_inner(blocks_to_get)
        && !GC_expand_hp_inner(needed_blocks)) {
            if (GC_fail_count++ < GC_max_retries) {
                WARN("Out of Memory!  Trying to continue ...\n", 0);
          GC_gcollect_inner();
      } else {
#         if !defined(AMIGA) || !defined(GC_AMIGA_FASTALLOC)
            WARN("Out of Memory!  Returning NIL!\n", 0);
#         endif
          return(FALSE);
      }
      } else {
#       ifdef CONDPRINT
            if (GC_fail_count && GC_print_stats) {
            GC_printf0("Memory available again ...\n");
          }
#       endif
      }
    }
    return(TRUE);
}

/*
 * Make sure the object free list for sz is not empty.
 * Return a pointer to the first object on the free list.
 * The object MUST BE REMOVED FROM THE FREE LIST BY THE CALLER.
 * Assumes we hold the allocator lock and signals are disabled.
 *
 */
ptr_t GC_allocobj(sz, kind)
word sz;
int kind;
{
    ptr_t * flh = &(GC_obj_kinds[kind].ok_freelist[sz]);
    GC_bool tried_minor = FALSE;
    
    if (sz == 0) return(0);

    while (*flh == 0) {
      ENTER_GC();
      /* Do our share of marking work */
        if(TRUE_INCREMENTAL) GC_collect_a_little_inner(1);
      /* Sweep blocks for objects of this size */
        GC_continue_reclaim(sz, kind);
      EXIT_GC();
      if (*flh == 0) {
        GC_new_hblk(sz, kind);
      }
      if (*flh == 0) {
        ENTER_GC();
      if (GC_incremental && GC_time_limit == GC_TIME_UNLIMITED
          && ! tried_minor ) {
          GC_collect_a_little_inner(1);
          tried_minor = TRUE;
      } else {
          if (!GC_collect_or_expand((word)1,FALSE)) {
          EXIT_GC();
          return(0);
        }
      }
      EXIT_GC();
      }
    }
    /* Successful allocation; reset failure count.    */
    GC_fail_count = 0;
    
    return(*flh);
}

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