1487

Committed 25 Apr 2023 06:55AM UTC coverage: 76.661% (+0.05%) from 76.615%

Build # 1487

Build Type

push

travis-ci-com

Committed by

ivmai

Commit Message

Do incremental mark some in GC_collect_a_little even if GC is disabled

Previous behavior was not documented but this API function did nothing
in this case.  That might cause a deadlock in the client code if the
incremental collection was ongoing and the client called
GC_collect_a_little() repeatedly (while the result is true).

The new behavior, for the cause of disabled garbage collection, is to
perform some amount of marking if the incremental collection is
ongoing (but not stopping the world and, thus, not causing the memory
reclaim to start), returning true if there is something more to mark.

* alloc.c (GC_try_to_collect_inner): Change a loop to do-while one.
* alloc.c (GC_collect_a_little): Do not check GC_dont_gc (i.e. call
GC_collect_a_little_inner() unconditionally); add comment.
* include/gc/gc.h (GC_collect_a_little): Update comment (describe the
case when GC is disabled).
* tests/gctest.c (check_heap_stats): Do not call GC_is_disabled(); add
comment.

Run Details

5 of 5 new or added lines in 2 files covered. (100.0%)

7788 of 10159 relevant lines covered (76.66%)

8863351.24 hits per line

Source File
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77.47

/alloc.c

/*
 * Copyright (c) 1988-1989 Hans-J. Boehm, Alan J. Demers
 * Copyright (c) 1991-1996 by Xerox Corporation.  All rights reserved.
 * Copyright (c) 1996-1999 by Silicon Graphics.  All rights reserved.
 * Copyright (c) 1999-2011 Hewlett-Packard Development Company, L.P.
 * Copyright (c) 2008-2022 Ivan Maidanski
 *
 * 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"

#if !defined(MACOS) && !defined(MSWINCE)
# include <signal.h>
# if !defined(GC_NO_TYPES) && !defined(SN_TARGET_PSP2) \
     && !defined(__CC_ARM)
#   include <sys/types.h>
# endif
#endif

/*
 * Separate free lists are maintained for different sized objects
 * up to MAXOBJBYTES.
 * 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 lb (and NORMAL kind) as follows
 * (GC_generic_malloc_inner is a wrapper over GC_allocobj which also
 * fills in GC_size_map if needed):
 *
 *   lg = GC_size_map[lb];
 *   op = GC_objfreelist[lg];
 *   if (NULL == op) {
 *     op = GC_generic_malloc_inner(lb, NORMAL, 0);
 *   } else {
 *     GC_objfreelist[lg] = obj_link(op);
 *     GC_bytes_allocd += GRANULES_TO_BYTES((word)lg);
 *   }
 *
 * 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 NO_CLOCK
  static unsigned long full_gc_total_time = 0; /* in ms, may wrap */
  static unsigned full_gc_total_ns_frac = 0; /* fraction of 1 ms */
  static GC_bool measure_performance = FALSE;
                /* Do performance measurements if set to true (e.g.,    */
                /* accumulation of the total time of full collections). */

  GC_API void GC_CALL GC_start_performance_measurement(void)
  {
    measure_performance = TRUE;
  }

  GC_API unsigned long GC_CALL GC_get_full_gc_total_time(void)
  {
    return full_gc_total_time;
  }
#endif /* !NO_CLOCK */

#ifndef GC_DISABLE_INCREMENTAL
  GC_INNER GC_bool GC_incremental = FALSE; /* By default, stop the world. */
  STATIC GC_bool GC_should_start_incremental_collection = FALSE;
#endif

GC_API int GC_CALL GC_is_incremental_mode(void)
{
  return (int)GC_incremental;
}

#ifdef THREADS
  int GC_parallel = FALSE;      /* By default, parallel GC is off.      */
#endif

#if defined(GC_FULL_FREQ) && !defined(CPPCHECK)
  int GC_full_freq = GC_FULL_FREQ;
#else
  int GC_full_freq = 19;   /* Every 20th collection is a full   */
                           /* collection, whether we need it    */
                           /* or not.                           */
#endif

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

#ifdef THREAD_LOCAL_ALLOC
  GC_INNER GC_bool GC_world_stopped = FALSE;
#endif

STATIC GC_bool GC_disable_automatic_collection = FALSE;

GC_API void GC_CALL GC_set_disable_automatic_collection(int value)
{
  LOCK();
  GC_disable_automatic_collection = (GC_bool)value;
  UNLOCK();
}

GC_API int GC_CALL GC_get_disable_automatic_collection(void)
{
  int value;

  LOCK();
  value = (int)GC_disable_automatic_collection;
  UNLOCK();
  return value;
}

STATIC word GC_used_heap_size_after_full = 0;

/* Version macros are now defined in gc_version.h, which is included by */
/* gc.h, which is included by gc_priv.h.                                */
#ifndef GC_NO_VERSION_VAR
  EXTERN_C_BEGIN
  extern const unsigned GC_version;
  EXTERN_C_END
  const unsigned GC_version = ((GC_VERSION_MAJOR << 16) |
                        (GC_VERSION_MINOR << 8) | GC_VERSION_MICRO);
#endif

GC_API unsigned GC_CALL GC_get_version(void)
{
  return (GC_VERSION_MAJOR << 16) | (GC_VERSION_MINOR << 8) |
          GC_VERSION_MICRO;
}

/* some more variables */

#ifdef GC_DONT_EXPAND
  int GC_dont_expand = TRUE;
#else
  int GC_dont_expand = FALSE;
#endif

#if defined(GC_FREE_SPACE_DIVISOR) && !defined(CPPCHECK)
  word GC_free_space_divisor = GC_FREE_SPACE_DIVISOR; /* must be > 0 */
#else
  word GC_free_space_divisor = 3;
#endif

GC_INNER int GC_CALLBACK GC_never_stop_func(void)
{
  return FALSE;
}

#if defined(GC_TIME_LIMIT) && !defined(CPPCHECK)
  unsigned long GC_time_limit = GC_TIME_LIMIT;
                           /* We try to keep pause times from exceeding  */
                           /* this by much. In milliseconds.             */
#elif defined(PARALLEL_MARK)
  unsigned long GC_time_limit = GC_TIME_UNLIMITED;
                        /* The parallel marker cannot be interrupted for */
                        /* now, so the time limit is absent by default.  */
#else
  unsigned long GC_time_limit = 15;
#endif

#ifndef NO_CLOCK
  STATIC unsigned long GC_time_lim_nsec = 0;
                        /* The nanoseconds add-on to GC_time_limit      */
                        /* value.  Not updated by GC_set_time_limit().  */
                        /* Ignored if the value of GC_time_limit is     */
                        /* GC_TIME_UNLIMITED.                           */

# define TV_NSEC_LIMIT (1000UL * 1000) /* amount of nanoseconds in 1 ms */

  GC_API void GC_CALL GC_set_time_limit_tv(struct GC_timeval_s tv)
  {
    GC_ASSERT(tv.tv_ms <= GC_TIME_UNLIMITED);
    GC_ASSERT(tv.tv_nsec < TV_NSEC_LIMIT);
    GC_time_limit = tv.tv_ms;
    GC_time_lim_nsec = tv.tv_nsec;
  }

  GC_API struct GC_timeval_s GC_CALL GC_get_time_limit_tv(void)
  {
    struct GC_timeval_s tv;

    tv.tv_ms = GC_time_limit;
    tv.tv_nsec = GC_time_lim_nsec;
    return tv;
  }

  STATIC CLOCK_TYPE GC_start_time = CLOCK_TYPE_INITIALIZER;
                                /* Time at which we stopped world.      */
                                /* used only in GC_timeout_stop_func.   */
#endif /* !NO_CLOCK */

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

STATIC GC_stop_func GC_default_stop_func = GC_never_stop_func;
                                /* Accessed holding the allocator lock. */

GC_API void GC_CALL GC_set_stop_func(GC_stop_func stop_func)
{
  GC_ASSERT(NONNULL_ARG_NOT_NULL(stop_func));
  LOCK();
  GC_default_stop_func = stop_func;
  UNLOCK();
}

GC_API GC_stop_func GC_CALL GC_get_stop_func(void)
{
  GC_stop_func stop_func;

  LOCK();
  stop_func = GC_default_stop_func;
  UNLOCK();
  return stop_func;
}

#if defined(GC_DISABLE_INCREMENTAL) || defined(NO_CLOCK)
# define GC_timeout_stop_func GC_default_stop_func
#else
  STATIC int GC_CALLBACK GC_timeout_stop_func(void)
  {
    CLOCK_TYPE current_time;
    static unsigned count = 0;
    unsigned long time_diff, nsec_diff;

    if (GC_default_stop_func())
      return TRUE;

    if (GC_time_limit == GC_TIME_UNLIMITED || (count++ & 3) != 0)
      return FALSE;

    GET_TIME(current_time);
    time_diff = MS_TIME_DIFF(current_time,GC_start_time);
    nsec_diff = NS_FRAC_TIME_DIFF(current_time, GC_start_time);
#   if defined(CPPCHECK)
      GC_noop1((word)&nsec_diff);
#   endif
    if (time_diff >= GC_time_limit
        && (time_diff > GC_time_limit || nsec_diff >= GC_time_lim_nsec)) {
      GC_COND_LOG_PRINTF("Abandoning stopped marking after %lu ms %lu ns"
                         " (attempt %d)\n",
                         time_diff, nsec_diff, GC_n_attempts);
      return TRUE;
    }

    return FALSE;
  }
#endif /* !GC_DISABLE_INCREMENTAL */

#ifdef THREADS
  GC_INNER word GC_total_stacksize = 0; /* updated on every push_all_stacks */
#endif

static size_t min_bytes_allocd_minimum = 1;
                        /* The lowest value returned by min_bytes_allocd(). */

GC_API void GC_CALL GC_set_min_bytes_allocd(size_t value)
{
    GC_ASSERT(value > 0);
    min_bytes_allocd_minimum = value;
}

GC_API size_t GC_CALL GC_get_min_bytes_allocd(void)
{
    return min_bytes_allocd_minimum;
}

/* Return the minimum number of bytes that must be allocated between    */
/* collections to amortize the collection cost.  Should be non-zero.    */
static word min_bytes_allocd(void)
{
    word result;
    word stack_size;
    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.                    */

#   ifdef THREADS
      if (GC_need_to_lock) {
        /* We are multi-threaded... */
        stack_size = GC_total_stacksize;
        /* For now, we just use the value computed during the latest GC. */
#       ifdef DEBUG_THREADS
          GC_log_printf("Total stacks size: %lu\n",
                        (unsigned long)stack_size);
#       endif
      } else
#   endif
    /* else*/ {
#     ifdef STACK_NOT_SCANNED
        stack_size = 0;
#     elif defined(STACK_GROWS_UP)
        stack_size = GC_approx_sp() - GC_stackbottom;
#     else
        stack_size = GC_stackbottom - GC_approx_sp();
#     endif
    }

    total_root_size = 2 * stack_size + GC_root_size;
    scan_size = 2 * GC_composite_in_use + GC_atomic_in_use / 4
                + total_root_size;
    result = scan_size / GC_free_space_divisor;
    if (GC_incremental) {
      result /= 2;
    }
    return result > min_bytes_allocd_minimum
            ? result : min_bytes_allocd_minimum;
}

STATIC word GC_non_gc_bytes_at_gc = 0;
                /* Number of explicitly managed bytes of storage        */
                /* at last collection.                                  */

/* Return the number of bytes allocated, adjusted for explicit storage  */
/* management, etc..  This number is used in deciding when to trigger   */
/* collections.                                                         */
STATIC word GC_adj_bytes_allocd(void)
{
    signed_word result;
    signed_word expl_managed = (signed_word)GC_non_gc_bytes
                                - (signed_word)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_bytes_allocd
             + (signed_word)GC_bytes_dropped
             - (signed_word)GC_bytes_freed
             + (signed_word)GC_finalizer_bytes_freed
             - expl_managed;
    if (result > (signed_word)GC_bytes_allocd) {
        result = GC_bytes_allocd;
        /* probably client bug or unfortunate scheduling */
    }
    result += GC_bytes_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 (result < (signed_word)(GC_bytes_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.     */
        result = (signed_word)(GC_bytes_allocd >> 3);
    }
    return (word)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 garbage 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.                 */
STATIC void GC_clear_a_few_frames(void)
{
#   ifndef CLEAR_NWORDS
#     define CLEAR_NWORDS 64
#   endif
    volatile word frames[CLEAR_NWORDS];
    BZERO((word *)frames, CLEAR_NWORDS * sizeof(word));
}

GC_API void GC_CALL GC_start_incremental_collection(void)
{
# ifndef GC_DISABLE_INCREMENTAL
    if (!GC_incremental) return;

    LOCK();
    GC_should_start_incremental_collection = TRUE;
    if (!GC_dont_gc) {
      ENTER_GC();
      GC_collect_a_little_inner(1);
      EXIT_GC();
    }
    UNLOCK();
# endif
}

/* Have we allocated enough to amortize a collection? */
GC_INNER GC_bool GC_should_collect(void)
{
    static word last_min_bytes_allocd;
    static word last_gc_no;

    GC_ASSERT(I_HOLD_LOCK());
    if (last_gc_no != GC_gc_no) {
      last_min_bytes_allocd = min_bytes_allocd();
      last_gc_no = GC_gc_no;
    }
# ifndef GC_DISABLE_INCREMENTAL
    if (GC_should_start_incremental_collection) {
      GC_should_start_incremental_collection = FALSE;
      return TRUE;
    }
# endif
    if (GC_disable_automatic_collection) return FALSE;

    if (GC_last_heap_growth_gc_no == GC_gc_no)
      return TRUE; /* avoid expanding past limits used by blacklisting  */

    return GC_adj_bytes_allocd() >= last_min_bytes_allocd;
}

/* STATIC */ GC_start_callback_proc GC_start_call_back = 0;
                        /* Called at start of full collections.         */
                        /* Not called if 0.  Called with the allocation */
                        /* lock held.  Not used by GC itself.           */

GC_API void GC_CALL GC_set_start_callback(GC_start_callback_proc fn)
{
    LOCK();
    GC_start_call_back = fn;
    UNLOCK();
}

GC_API GC_start_callback_proc GC_CALL GC_get_start_callback(void)
{
    GC_start_callback_proc fn;

    LOCK();
    fn = GC_start_call_back;
    UNLOCK();
    return fn;
}

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

STATIC GC_bool GC_is_full_gc = FALSE;

STATIC GC_bool GC_stopped_mark(GC_stop_func stop_func);
STATIC void GC_finish_collection(void);

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

  GC_ASSERT(I_HOLD_LOCK());
  ASSERT_CANCEL_DISABLED();
  if (!GC_should_collect()) return;

  if (!GC_incremental) {
    GC_gcollect_inner();
    return;
  }

  GC_ASSERT(!GC_collection_in_progress());
# ifdef PARALLEL_MARK
    if (GC_parallel)
      GC_wait_for_reclaim();
# endif
  if (GC_need_full_gc || n_partial_gcs >= GC_full_freq) {
    GC_COND_LOG_PRINTF(
                "***>Full mark for collection #%lu after %lu allocd bytes\n",
                (unsigned long)GC_gc_no + 1, (unsigned long)GC_bytes_allocd);
    GC_promote_black_lists();
    (void)GC_reclaim_all((GC_stop_func)0, TRUE);
    GC_notify_full_gc();
    GC_clear_marks();
    n_partial_gcs = 0;
    GC_is_full_gc = TRUE;
  } else {
    n_partial_gcs++;
  }

  /* Try to mark with the world stopped.  If we run out of      */
  /* time, this turns into an incremental marking.              */
# ifndef NO_CLOCK
    if (GC_time_limit != GC_TIME_UNLIMITED) GET_TIME(GC_start_time);
# endif
  if (GC_stopped_mark(GC_timeout_stop_func)) {
#   ifdef SAVE_CALL_CHAIN
      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++;
  }
}

STATIC GC_on_collection_event_proc GC_on_collection_event = 0;

GC_API void GC_CALL GC_set_on_collection_event(GC_on_collection_event_proc fn)
{
    /* fn may be 0 (means no event notifier). */
    LOCK();
    GC_on_collection_event = fn;
    UNLOCK();
}

GC_API GC_on_collection_event_proc GC_CALL GC_get_on_collection_event(void)
{
    GC_on_collection_event_proc fn;

    LOCK();
    fn = GC_on_collection_event;
    UNLOCK();
    return fn;
}

/* Stop the world garbage collection.  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_INNER GC_bool GC_try_to_collect_inner(GC_stop_func stop_func)
{
#   ifndef NO_CLOCK
      CLOCK_TYPE start_time = CLOCK_TYPE_INITIALIZER;
      GC_bool start_time_valid;
#   endif

    ASSERT_CANCEL_DISABLED();
    GC_ASSERT(I_HOLD_LOCK());
    GC_ASSERT(GC_is_initialized);
    if (GC_dont_gc || (*stop_func)()) return FALSE;
    if (GC_on_collection_event)
      GC_on_collection_event(GC_EVENT_START);
    if (GC_incremental && GC_collection_in_progress()) {
      GC_COND_LOG_PRINTF(
            "GC_try_to_collect_inner: finishing collection in progress\n");
      /* Just finish collection already in progress.    */
        do {
            if ((*stop_func)()) {
              /* TODO: Notify GC_EVENT_ABANDON */
              return FALSE;
            }
            ENTER_GC();
            GC_collect_a_little_inner(1);
            EXIT_GC();
        } while (GC_collection_in_progress());
    }
    GC_notify_full_gc();
#   ifndef NO_CLOCK
      start_time_valid = FALSE;
      if ((GC_print_stats | (int)measure_performance) != 0) {
        if (GC_print_stats)
          GC_log_printf("Initiating full world-stop collection!\n");
        start_time_valid = TRUE;
        GET_TIME(start_time);
      }
#   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
          if (GC_parallel)
            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. */
            /* TODO: Notify GC_EVENT_ABANDON */
            return FALSE;
        }
    GC_invalidate_mark_state();  /* Flush mark stack.   */
    GC_clear_marks();
#   ifdef SAVE_CALL_CHAIN
        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.                                        */
      /* TODO: Notify GC_EVENT_ABANDON */
      return FALSE;
    }
    GC_finish_collection();
#   ifndef NO_CLOCK
      if (start_time_valid) {
        CLOCK_TYPE current_time;
        unsigned long time_diff, ns_frac_diff;

        GET_TIME(current_time);
        time_diff = MS_TIME_DIFF(current_time, start_time);
        ns_frac_diff = NS_FRAC_TIME_DIFF(current_time, start_time);
        if (measure_performance) {
          full_gc_total_time += time_diff; /* may wrap */
          full_gc_total_ns_frac += (unsigned)ns_frac_diff;
          if (full_gc_total_ns_frac >= 1000000U) {
            /* Overflow of the nanoseconds part. */
            full_gc_total_ns_frac -= 1000000U;
            full_gc_total_time++;
          }
        }
        if (GC_print_stats)
          GC_log_printf("Complete collection took %lu ms %lu ns\n",
                        time_diff, ns_frac_diff);
      }
#   endif
    if (GC_on_collection_event)
      GC_on_collection_event(GC_EVENT_END);
    return TRUE;
}

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

/* The default value of GC_rate.        */
#ifndef GC_RATE
# define GC_RATE 10
#endif

/* When GC_collect_a_little_inner() performs n units of GC work, a unit */
/* is intended to touch roughly GC_rate pages.  (But, 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.         */
STATIC int GC_rate = GC_RATE;

GC_API void GC_CALL GC_set_rate(int value)
{
    GC_ASSERT(value > 0);
    GC_rate = value;
}

GC_API int GC_CALL GC_get_rate(void)
{
    return GC_rate;
}

/* The default maximum number of prior attempts at world stop marking.  */
#ifndef MAX_PRIOR_ATTEMPTS
# define MAX_PRIOR_ATTEMPTS 3
#endif

/* The 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.  Does not count the initial root scan for a full GC.  */
static int max_prior_attempts = MAX_PRIOR_ATTEMPTS;

GC_API void GC_CALL GC_set_max_prior_attempts(int value)
{
    GC_ASSERT(value >= 0);
    max_prior_attempts = value;
}

GC_API int GC_CALL GC_get_max_prior_attempts(void)
{
    return max_prior_attempts;
}

GC_INNER void GC_collect_a_little_inner(int n)
{
    IF_CANCEL(int cancel_state;)

    GC_ASSERT(I_HOLD_LOCK());
    GC_ASSERT(GC_is_initialized);
    DISABLE_CANCEL(cancel_state);
    if (GC_incremental && GC_collection_in_progress()) {
        int i;
        int max_deficit = GC_rate * n;

#       ifdef PARALLEL_MARK
            if (GC_time_limit != GC_TIME_UNLIMITED)
                GC_parallel_mark_disabled = TRUE;
#       endif
        for (i = GC_deficit; i < max_deficit; i++) {
            if (GC_mark_some(NULL))
                break;
        }
#       ifdef PARALLEL_MARK
            GC_parallel_mark_disabled = FALSE;
#       endif

        if (i < max_deficit && !GC_dont_gc) {
            GC_ASSERT(!GC_collection_in_progress());
            /* Need to follow up with a full collection.        */
#           ifdef SAVE_CALL_CHAIN
                GC_save_callers(GC_last_stack);
#           endif
#           ifdef PARALLEL_MARK
                if (GC_parallel)
                    GC_wait_for_reclaim();
#           endif
#           ifndef NO_CLOCK
                if (GC_time_limit != GC_TIME_UNLIMITED
                        && GC_n_attempts < max_prior_attempts)
                    GET_TIME(GC_start_time);
#           endif
            if (GC_stopped_mark(GC_n_attempts < max_prior_attempts ?
                                GC_timeout_stop_func : GC_never_stop_func)) {
                GC_finish_collection();
            } else {
                GC_n_attempts++;
            }
        }
        if (GC_deficit > 0) {
            GC_deficit -= max_deficit;
            if (GC_deficit < 0)
                GC_deficit = 0;
        }
    } else if (!GC_dont_gc) {
        GC_maybe_gc();
    }
    RESTORE_CANCEL(cancel_state);
}

GC_INNER void (*GC_check_heap)(void) = 0;
GC_INNER void (*GC_print_all_smashed)(void) = 0;

GC_API int GC_CALL GC_collect_a_little(void)
{
    int result;

    if (!EXPECT(GC_is_initialized, TRUE)) GC_init();
    LOCK();
    ENTER_GC();
    /* Note: if the collection is in progress, this may do marking (not */
    /* stopping the world) even in case of disabled GC.                 */
    GC_collect_a_little_inner(1);
    EXIT_GC();
    result = (int)GC_collection_in_progress();
    UNLOCK();
    if (!result && GC_debugging_started) GC_print_all_smashed();
    return result;
}

#ifndef NO_CLOCK
  /* Variables for world-stop average delay time statistic computation. */
  /* "divisor" is incremented every world-stop and halved when reached  */
  /* its maximum (or upon "total_time" overflow).                       */
  static unsigned world_stopped_total_time = 0;
  static unsigned world_stopped_total_divisor = 0;
# ifndef MAX_TOTAL_TIME_DIVISOR
    /* We shall not use big values here (so "outdated" delay time       */
    /* values would have less impact on "average" delay time value than */
    /* newer ones).                                                     */
#   define MAX_TOTAL_TIME_DIVISOR 1000
# endif
#endif /* !NO_CLOCK */

#ifdef USE_MUNMAP
# ifndef MUNMAP_THRESHOLD
#   define MUNMAP_THRESHOLD 7
# endif
  GC_INNER unsigned GC_unmap_threshold = MUNMAP_THRESHOLD;

# define IF_USE_MUNMAP(x) x
# define COMMA_IF_USE_MUNMAP(x) /* comma */, x
#else
# define IF_USE_MUNMAP(x) /* empty */
# define COMMA_IF_USE_MUNMAP(x) /* empty */
#endif

/* We stop the world and mark from all roots.  If stop_func() ever      */
/* returns TRUE, we may fail and return FALSE.  Increment GC_gc_no if   */
/* we succeed.                                                          */
STATIC GC_bool GC_stopped_mark(GC_stop_func stop_func)
{
    int i;
    ptr_t cold_gc_frame = GC_approx_sp();
#   ifndef NO_CLOCK
      CLOCK_TYPE start_time = CLOCK_TYPE_INITIALIZER;
#   endif

    GC_ASSERT(I_HOLD_LOCK());
    GC_ASSERT(GC_is_initialized);
#   if !defined(REDIRECT_MALLOC) && defined(USE_WINALLOC)
        GC_add_current_malloc_heap();
#   endif
#   if defined(REGISTER_LIBRARIES_EARLY)
        GC_cond_register_dynamic_libraries();
#   endif

#   ifndef NO_CLOCK
      if (GC_PRINT_STATS_FLAG)
        GET_TIME(start_time);
#   endif

#   if !defined(GC_NO_FINALIZATION) && !defined(GC_TOGGLE_REFS_NOT_NEEDED)
      GC_process_togglerefs();
#   endif
#   ifdef THREADS
      if (GC_on_collection_event)
        GC_on_collection_event(GC_EVENT_PRE_STOP_WORLD);
#   endif
    STOP_WORLD();
#   ifdef THREADS
      if (GC_on_collection_event)
        GC_on_collection_event(GC_EVENT_POST_STOP_WORLD);
#   endif

#   ifdef THREAD_LOCAL_ALLOC
      GC_world_stopped = TRUE;
#   endif
        /* Output blank line for convenience here */
    GC_COND_LOG_PRINTF(
              "\n--> Marking for collection #%lu after %lu allocated bytes\n",
              (unsigned long)GC_gc_no + 1, (unsigned long) GC_bytes_allocd);
#   ifdef MAKE_BACK_GRAPH
      if (GC_print_back_height) {
        GC_build_back_graph();
      }
#   endif

    /* Mark from all roots.  */
        if (GC_on_collection_event)
          GC_on_collection_event(GC_EVENT_MARK_START);

        /* Minimize junk left in my registers and on the stack */
            GC_clear_a_few_frames();
            GC_noop6(0,0,0,0,0,0);

        GC_initiate_gc();
#       ifdef PARALLEL_MARK
          if (stop_func != GC_never_stop_func)
            GC_parallel_mark_disabled = TRUE;
#       endif
        for (i = 0; !(*stop_func)(); i++) {
          if (GC_mark_some(cold_gc_frame)) {
#           ifdef PARALLEL_MARK
              if (GC_parallel && GC_parallel_mark_disabled) {
                GC_COND_LOG_PRINTF("Stopped marking done after %d iterations"
                                   " with disabled parallel marker\n", i);
              }
#           endif
            i = -1;
            break;
          }
        }
#       ifdef PARALLEL_MARK
          GC_parallel_mark_disabled = FALSE;
#       endif

        if (i >= 0) {
          GC_COND_LOG_PRINTF("Abandoned stopped marking after"
                             " %d iterations\n", i);
          GC_deficit = i;       /* Give the mutator a chance.   */
#         ifdef THREAD_LOCAL_ALLOC
            GC_world_stopped = FALSE;
#         endif

#         ifdef THREADS
            if (GC_on_collection_event)
              GC_on_collection_event(GC_EVENT_PRE_START_WORLD);
#         endif

          START_WORLD();

#         ifdef THREADS
            if (GC_on_collection_event)
              GC_on_collection_event(GC_EVENT_POST_START_WORLD);
#         endif

          /* TODO: Notify GC_EVENT_MARK_ABANDON */
          return FALSE;
        }

    GC_gc_no++;
    /* Check all debugged objects for consistency */
    if (GC_debugging_started) {
      (*GC_check_heap)();
    }
    if (GC_on_collection_event) {
      GC_on_collection_event(GC_EVENT_MARK_END);
#     ifdef THREADS
        GC_on_collection_event(GC_EVENT_PRE_START_WORLD);
#     endif
    }
#   ifdef THREAD_LOCAL_ALLOC
      GC_world_stopped = FALSE;
#   endif

    START_WORLD();

#   ifdef THREADS
      if (GC_on_collection_event)
        GC_on_collection_event(GC_EVENT_POST_START_WORLD);
#   endif

#   ifndef NO_CLOCK
      if (GC_PRINT_STATS_FLAG) {
        unsigned long time_diff;
        unsigned total_time, divisor;
        CLOCK_TYPE current_time;

        GET_TIME(current_time);
        time_diff = MS_TIME_DIFF(current_time,start_time);

        /* Compute new world-stop delay total time */
        total_time = world_stopped_total_time;
        divisor = world_stopped_total_divisor;
        if (total_time > (((unsigned)-1) >> 1)
            || divisor >= MAX_TOTAL_TIME_DIVISOR) {
          /* Halve values if overflow occurs */
          total_time >>= 1;
          divisor >>= 1;
        }
        total_time += time_diff < (((unsigned)-1) >> 1) ?
                        (unsigned)time_diff : ((unsigned)-1) >> 1;
        /* Update old world_stopped_total_time and its divisor */
        world_stopped_total_time = total_time;
        world_stopped_total_divisor = ++divisor;

        GC_ASSERT(divisor != 0);
        GC_log_printf("World-stopped marking took %lu ms %lu ns"
                      " (%u ms in average)\n",
                      time_diff, NS_FRAC_TIME_DIFF(current_time, start_time),
                      total_time / divisor);
      }
#   endif
    return TRUE;
}

/* Set all mark bits for the free list whose first entry is q   */
GC_INNER void GC_set_fl_marks(ptr_t q)
{
    if (q /* != NULL */) { /* CPPCHECK */
      struct hblk *h = HBLKPTR(q);
      struct hblk *last_h = h;
      hdr *hhdr = HDR(h);
      IF_PER_OBJ(word sz = hhdr->hb_sz;)

      for (;;) {
        word bit_no = MARK_BIT_NO((ptr_t)q - (ptr_t)h, sz);

        if (!mark_bit_from_hdr(hhdr, bit_no)) {
          set_mark_bit_from_hdr(hhdr, bit_no);
          ++hhdr -> hb_n_marks;
        }

        q = (ptr_t)obj_link(q);
        if (q == NULL)
          break;

        h = HBLKPTR(q);
        if (h != last_h) {
          last_h = h;
          hhdr = HDR(h);
          IF_PER_OBJ(sz = hhdr->hb_sz;)
        }
      }
    }
}

#if defined(GC_ASSERTIONS) && defined(THREAD_LOCAL_ALLOC)
  /* Check that all mark bits for the free list whose first entry is    */
  /* (*pfreelist) are set.  Check skipped if points to a special value. */
  void GC_check_fl_marks(void **pfreelist)
  {
    /* TODO: There is a data race with GC_FAST_MALLOC_GRANS (which does */
    /* not do atomic updates to the free-list).  The race seems to be   */
    /* harmless, and for now we just skip this check in case of TSan.   */
#   if defined(AO_HAVE_load_acquire_read) && !defined(THREAD_SANITIZER)
      AO_t *list = (AO_t *)AO_load_acquire_read((AO_t *)pfreelist);
                /* Atomic operations are used because the world is running. */
      AO_t *prev;
      AO_t *p;

      if ((word)list <= HBLKSIZE) return;

      prev = (AO_t *)pfreelist;
      for (p = list; p != NULL;) {
        AO_t *next;

        if (!GC_is_marked(p)) {
          ABORT_ARG2("Unmarked local free list entry",
                     ": object %p on list %p", (void *)p, (void *)list);
        }

        /* While traversing the free-list, it re-reads the pointer to   */
        /* the current node before accepting its next pointer and       */
        /* bails out if the latter has changed.  That way, it won't     */
        /* try to follow the pointer which might be been modified       */
        /* after the object was returned to the client.  It might       */
        /* perform the mark-check on the just allocated object but      */
        /* that should be harmless.                                     */
        next = (AO_t *)AO_load_acquire_read(p);
        if (AO_load(prev) != (AO_t)p)
          break;
        prev = p;
        p = next;
      }
#   else
      /* FIXME: Not implemented (just skipped). */
      (void)pfreelist;
#   endif
  }
#endif /* GC_ASSERTIONS && THREAD_LOCAL_ALLOC */

/* Clear all mark bits for the free list whose first entry is q */
/* Decrement GC_bytes_found by number of bytes on free list.    */
STATIC void GC_clear_fl_marks(ptr_t q)
{
      struct hblk *h = HBLKPTR(q);
      struct hblk *last_h = h;
      hdr *hhdr = HDR(h);
      word sz = hhdr->hb_sz; /* Normally set only once. */

      for (;;) {
        word bit_no = MARK_BIT_NO((ptr_t)q - (ptr_t)h, sz);

        if (mark_bit_from_hdr(hhdr, bit_no)) {
          size_t n_marks = hhdr -> hb_n_marks;

          GC_ASSERT(n_marks != 0);
          clear_mark_bit_from_hdr(hhdr, bit_no);
          n_marks--;
#         ifdef PARALLEL_MARK
            /* Appr. count, don't decrement to zero! */
            if (0 != n_marks || !GC_parallel) {
              hhdr -> hb_n_marks = n_marks;
            }
#         else
            hhdr -> hb_n_marks = n_marks;
#         endif
        }
        GC_bytes_found -= sz;

        q = (ptr_t)obj_link(q);
        if (q == NULL)
          break;

        h = HBLKPTR(q);
        if (h != last_h) {
          last_h = h;
          hhdr = HDR(h);
          sz = hhdr->hb_sz;
        }
      }
}

#if defined(GC_ASSERTIONS) && defined(THREAD_LOCAL_ALLOC)
  void GC_check_tls(void);
#endif

GC_on_heap_resize_proc GC_on_heap_resize = 0;

/* Used for logging only. */
GC_INLINE int GC_compute_heap_usage_percent(void)
{
  word used = GC_composite_in_use + GC_atomic_in_use + GC_bytes_allocd;
  word heap_sz = GC_heapsize - GC_unmapped_bytes;
# if defined(CPPCHECK)
    word limit = (GC_WORD_MAX >> 1) / 50; /* to avoid a false positive */
# else
    const word limit = GC_WORD_MAX / 100;
# endif

  return used >= heap_sz ? 0 : used < limit ?
                (int)((used * 100) / heap_sz) : (int)(used / (heap_sz / 100));
}

#define GC_DBGLOG_PRINT_HEAP_IN_USE() \
  GC_DBGLOG_PRINTF("In-use heap: %d%% (%lu KiB pointers + %lu KiB other)\n", \
                   GC_compute_heap_usage_percent(), \
                   TO_KiB_UL(GC_composite_in_use), \
                   TO_KiB_UL(GC_atomic_in_use + GC_bytes_allocd))

/* Finish up a collection.  Assumes mark bits are consistent, but the   */
/* world is otherwise running.                                          */
STATIC void GC_finish_collection(void)
{
#   ifndef NO_CLOCK
      CLOCK_TYPE start_time = CLOCK_TYPE_INITIALIZER;
      CLOCK_TYPE finalize_time = CLOCK_TYPE_INITIALIZER;
#   endif

    GC_ASSERT(I_HOLD_LOCK());
#   if defined(GC_ASSERTIONS) \
       && defined(THREAD_LOCAL_ALLOC) && !defined(DBG_HDRS_ALL)
        /* Check that we marked some of our own data.           */
        /* TODO: Add more checks. */
        GC_check_tls();
#   endif

#   ifndef NO_CLOCK
      if (GC_print_stats)
        GET_TIME(start_time);
#   endif
    if (GC_on_collection_event)
      GC_on_collection_event(GC_EVENT_RECLAIM_START);

#   ifndef GC_GET_HEAP_USAGE_NOT_NEEDED
      if (GC_bytes_found > 0)
        GC_reclaimed_bytes_before_gc += (word)GC_bytes_found;
#   endif
    GC_bytes_found = 0;
#   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.                                        */
      word size;        /* current object size  */
      unsigned kind;
      ptr_t q;

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

#   ifndef GC_NO_FINALIZATION
      GC_finalize();
#   endif
#   ifndef NO_CLOCK
      if (GC_print_stats)
        GET_TIME(finalize_time);
#   endif

    if (GC_print_back_height) {
#     ifdef MAKE_BACK_GRAPH
        GC_traverse_back_graph();
#     elif !defined(SMALL_CONFIG)
        GC_err_printf("Back height not available: "
                      "Rebuild collector with -DMAKE_BACK_GRAPH\n");
#     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_bytes_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. */
    {
      word size;        /* current object size          */
      ptr_t q;          /* pointer to current object    */
      unsigned kind;

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

    GC_VERBOSE_LOG_PRINTF("Bytes recovered before sweep - f.l. count = %ld\n",
                          (long)GC_bytes_found);

    /* Reconstruct free lists to contain everything not marked */
    GC_start_reclaim(FALSE);

#   ifdef USE_MUNMAP
      if (GC_unmap_threshold > 0 /* unmapping enabled? */
          && EXPECT(GC_gc_no != 1, TRUE)) /* do not unmap during GC init */
        GC_unmap_old(GC_unmap_threshold);

      GC_ASSERT(GC_heapsize >= GC_unmapped_bytes);
#   endif
    GC_ASSERT(GC_our_mem_bytes >= GC_heapsize);
    GC_DBGLOG_PRINTF("GC #%lu freed %ld bytes, heap %lu KiB ("
                     IF_USE_MUNMAP("+ %lu KiB unmapped ")
                     "+ %lu KiB internal)\n",
                     (unsigned long)GC_gc_no, (long)GC_bytes_found,
                     TO_KiB_UL(GC_heapsize - GC_unmapped_bytes) /*, */
                     COMMA_IF_USE_MUNMAP(TO_KiB_UL(GC_unmapped_bytes)),
                     TO_KiB_UL(GC_our_mem_bytes - GC_heapsize
                               + sizeof(GC_arrays)));
    GC_DBGLOG_PRINT_HEAP_IN_USE();
    if (GC_is_full_gc) {
        GC_used_heap_size_after_full = GC_heapsize - GC_large_free_bytes;
        GC_need_full_gc = FALSE;
    } else {
        GC_need_full_gc = GC_heapsize - GC_used_heap_size_after_full
                          > min_bytes_allocd() + GC_large_free_bytes;
    }

    /* Reset or increment counters for next cycle */
    GC_n_attempts = 0;
    GC_is_full_gc = FALSE;
    GC_bytes_allocd_before_gc += GC_bytes_allocd;
    GC_non_gc_bytes_at_gc = GC_non_gc_bytes;
    GC_bytes_allocd = 0;
    GC_bytes_dropped = 0;
    GC_bytes_freed = 0;
    GC_finalizer_bytes_freed = 0;

    if (GC_on_collection_event)
      GC_on_collection_event(GC_EVENT_RECLAIM_END);
#   ifndef NO_CLOCK
      if (GC_print_stats) {
        CLOCK_TYPE done_time;

        GET_TIME(done_time);
#       if !defined(SMALL_CONFIG) && !defined(GC_NO_FINALIZATION)
          /* A convenient place to output finalization statistics.      */
          GC_print_finalization_stats();
#       endif
        GC_log_printf("Finalize and initiate sweep took %lu ms %lu ns"
                      " + %lu ms %lu ns\n",
                      MS_TIME_DIFF(finalize_time, start_time),
                      NS_FRAC_TIME_DIFF(finalize_time, start_time),
                      MS_TIME_DIFF(done_time, finalize_time),
                      NS_FRAC_TIME_DIFF(done_time, finalize_time));
      }
#   elif !defined(SMALL_CONFIG) && !defined(GC_NO_FINALIZATION)
      if (GC_print_stats)
        GC_print_finalization_stats();
#   endif
}

STATIC word GC_heapsize_at_forced_unmap = 0;
                                /* accessed with the allocation lock held */

/* If stop_func == 0 then GC_default_stop_func is used instead.         */
STATIC GC_bool GC_try_to_collect_general(GC_stop_func stop_func,
                                         GC_bool force_unmap)
{
    GC_bool result;
    IF_USE_MUNMAP(int old_unmap_threshold;)
    IF_CANCEL(int cancel_state;)

    if (!EXPECT(GC_is_initialized, TRUE)) GC_init();
    if (GC_debugging_started) GC_print_all_smashed();
    GC_INVOKE_FINALIZERS();
    LOCK();
    if (force_unmap) {
      /* Record current heap size to make heap growth more conservative */
      /* afterwards (as if the heap is growing from zero size again).   */
      GC_heapsize_at_forced_unmap = GC_heapsize;
    }
    DISABLE_CANCEL(cancel_state);
#   ifdef USE_MUNMAP
      old_unmap_threshold = GC_unmap_threshold;
      if (force_unmap ||
          (GC_force_unmap_on_gcollect && old_unmap_threshold > 0))
        GC_unmap_threshold = 1; /* unmap as much as possible */
#   endif
    ENTER_GC();
    /* Minimize junk left in my registers */
      GC_noop6(0,0,0,0,0,0);
    result = GC_try_to_collect_inner(stop_func != 0 ? stop_func :
                                     GC_default_stop_func);
    EXIT_GC();
    IF_USE_MUNMAP(GC_unmap_threshold = old_unmap_threshold); /* restore */
    RESTORE_CANCEL(cancel_state);
    UNLOCK();
    if (result) {
        if (GC_debugging_started) GC_print_all_smashed();
        GC_INVOKE_FINALIZERS();
    }
    return result;
}

/* Externally callable routines to invoke full, stop-the-world collection. */

GC_API int GC_CALL GC_try_to_collect(GC_stop_func stop_func)
{
    GC_ASSERT(NONNULL_ARG_NOT_NULL(stop_func));
    return (int)GC_try_to_collect_general(stop_func, FALSE);
}

GC_API void GC_CALL GC_gcollect(void)
{
    /* 0 is passed as stop_func to get GC_default_stop_func value       */
    /* while holding the allocation lock (to prevent data races).       */
    (void)GC_try_to_collect_general(0, FALSE);
    if (get_have_errors())
      GC_print_all_errors();
}

GC_API void GC_CALL GC_gcollect_and_unmap(void)
{
    /* Collect and force memory unmapping to OS. */
    (void)GC_try_to_collect_general(GC_never_stop_func, TRUE);
}

#ifdef USE_PROC_FOR_LIBRARIES
  /* Add HBLKSIZE aligned, GET_MEM-generated block to GC_our_memory. */
  GC_INNER void GC_add_to_our_memory(ptr_t p, size_t bytes)
  {
    GC_ASSERT(I_HOLD_LOCK());
    GC_ASSERT(p != NULL);
    if (GC_n_memory >= MAX_HEAP_SECTS)
      ABORT("Too many GC-allocated memory sections: Increase MAX_HEAP_SECTS");
    GC_our_memory[GC_n_memory].hs_start = p;
    GC_our_memory[GC_n_memory].hs_bytes = bytes;
    GC_n_memory++;
    GC_our_mem_bytes += bytes;
  }
#endif

/* Use the chunk of memory starting at p of size bytes as part of the heap. */
/* Assumes p is HBLKSIZE aligned, bytes argument is a multiple of HBLKSIZE. */
STATIC void GC_add_to_heap(struct hblk *p, size_t bytes)
{
    hdr * phdr;
    word endp;
    size_t old_capacity = 0;
    void *old_heap_sects = NULL;
#   ifdef GC_ASSERTIONS
      unsigned i;
#   endif

    GC_ASSERT(I_HOLD_LOCK());
    GC_ASSERT((word)p % HBLKSIZE == 0);
    GC_ASSERT(bytes % HBLKSIZE == 0);
    GC_ASSERT(bytes > 0);
    GC_ASSERT(GC_all_nils != NULL);

    if (EXPECT(GC_n_heap_sects == GC_capacity_heap_sects, FALSE)) {
      /* Allocate new GC_heap_sects with sufficient capacity.   */
#     ifndef INITIAL_HEAP_SECTS
#       define INITIAL_HEAP_SECTS 32
#     endif
      size_t new_capacity = GC_n_heap_sects > 0 ?
                (size_t)GC_n_heap_sects * 2 : INITIAL_HEAP_SECTS;
      void *new_heap_sects =
                GC_scratch_alloc(new_capacity * sizeof(struct HeapSect));

      if (NULL == new_heap_sects) {
        /* Retry with smaller yet sufficient capacity.  */
        new_capacity = (size_t)GC_n_heap_sects + INITIAL_HEAP_SECTS;
        new_heap_sects =
                GC_scratch_alloc(new_capacity * sizeof(struct HeapSect));
        if (NULL == new_heap_sects)
          ABORT("Insufficient memory for heap sections");
      }
      old_capacity = GC_capacity_heap_sects;
      old_heap_sects = GC_heap_sects;
      /* Transfer GC_heap_sects contents to the newly allocated array.  */
      if (GC_n_heap_sects > 0)
        BCOPY(old_heap_sects, new_heap_sects,
              GC_n_heap_sects * sizeof(struct HeapSect));
      GC_capacity_heap_sects = new_capacity;
      GC_heap_sects = (struct HeapSect *)new_heap_sects;
      GC_COND_LOG_PRINTF("Grew heap sections array to %lu elements\n",
                         (unsigned long)new_capacity);
    }

    while (EXPECT((word)p <= HBLKSIZE, FALSE)) {
        /* Can't handle memory near address zero. */
        ++p;
        bytes -= HBLKSIZE;
        if (0 == bytes) return;
    }
    endp = (word)p + bytes;
    if (EXPECT(endp <= (word)p, FALSE)) {
        /* Address wrapped. */
        bytes -= HBLKSIZE;
        if (0 == bytes) return;
        endp -= HBLKSIZE;
    }
    phdr = GC_install_header(p);
    if (EXPECT(NULL == phdr, FALSE)) {
        /* 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_ASSERT(endp > (word)p && endp == (word)p + bytes);
#   ifdef GC_ASSERTIONS
      /* Ensure no intersection between sections.       */
      for (i = 0; i < GC_n_heap_sects; i++) {
        word hs_start = (word)GC_heap_sects[i].hs_start;
        word hs_end = hs_start + GC_heap_sects[i].hs_bytes;

        GC_ASSERT(!((hs_start <= (word)p && (word)p < hs_end)
                    || (hs_start < endp && endp <= hs_end)
                    || ((word)p < hs_start && hs_end < endp)));
      }
#   endif
    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++;
    phdr -> hb_sz = bytes;
    phdr -> hb_flags = 0;
    GC_freehblk(p);
    GC_heapsize += bytes;

    if ((word)p <= (word)GC_least_plausible_heap_addr
        || EXPECT(NULL == GC_least_plausible_heap_addr, FALSE)) {
        GC_least_plausible_heap_addr = (void *)((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 (endp > (word)GC_greatest_plausible_heap_addr) {
        GC_greatest_plausible_heap_addr = (void *)endp;
    }

    if (EXPECT(old_capacity > 0, FALSE)) {
#     ifndef GWW_VDB
        /* Recycling may call GC_add_to_heap() again but should not     */
        /* cause resizing of GC_heap_sects.                             */
        GC_scratch_recycle_no_gww(old_heap_sects,
                                  old_capacity * sizeof(struct HeapSect));
#     else
        /* TODO: implement GWW-aware recycling as in alloc_mark_stack */
        GC_noop1((word)old_heap_sects);
#     endif
    }
}

#if !defined(NO_DEBUGGING)
  void GC_print_heap_sects(void)
  {
    unsigned i;

    GC_printf("Total heap size: %lu" IF_USE_MUNMAP(" (%lu unmapped)") "\n",
              (unsigned long)GC_heapsize /*, */
              COMMA_IF_USE_MUNMAP((unsigned long)GC_unmapped_bytes));

    for (i = 0; i < GC_n_heap_sects; i++) {
      ptr_t start = GC_heap_sects[i].hs_start;
      size_t len = GC_heap_sects[i].hs_bytes;
      struct hblk *h;
      unsigned nbl = 0;

      for (h = (struct hblk *)start; (word)h < (word)(start + len); h++) {
        if (GC_is_black_listed(h, HBLKSIZE)) nbl++;
      }
      GC_printf("Section %d from %p to %p %u/%lu blacklisted\n",
                i, (void *)start, (void *)&start[len],
                nbl, (unsigned long)divHBLKSZ(len));
    }
  }
#endif

void * GC_least_plausible_heap_addr = (void *)GC_WORD_MAX;
void * GC_greatest_plausible_heap_addr = 0;

STATIC word GC_max_heapsize = 0;

GC_API void GC_CALL GC_set_max_heap_size(GC_word n)
{
    GC_max_heapsize = n;
}

word GC_max_retries = 0;

GC_INNER void GC_scratch_recycle_inner(void *ptr, size_t bytes)
{
  size_t page_offset;
  size_t displ = 0;
  size_t recycled_bytes;

  GC_ASSERT(I_HOLD_LOCK());
  if (NULL == ptr) return;

  GC_ASSERT(bytes != 0);
  GC_ASSERT(GC_page_size != 0);
  /* TODO: Assert correct memory flags if GWW_VDB */
  page_offset = (word)ptr & (GC_page_size - 1);
  if (page_offset != 0)
    displ = GC_page_size - page_offset;
  recycled_bytes = bytes > displ ? (bytes - displ) & ~(GC_page_size - 1) : 0;
  GC_COND_LOG_PRINTF("Recycle %lu/%lu scratch-allocated bytes at %p\n",
                (unsigned long)recycled_bytes, (unsigned long)bytes, ptr);
  if (recycled_bytes > 0)
    GC_add_to_heap((struct hblk *)((word)ptr + displ), recycled_bytes);
}

/* 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 (zero is treated as 1).         */
/* Returns FALSE on failure.                                            */
GC_INNER GC_bool GC_expand_hp_inner(word n)
{
    size_t bytes;
    struct hblk * space;
    word expansion_slop;        /* Number of bytes by which we expect   */
                                /* the heap to expand soon.             */

    GC_ASSERT(I_HOLD_LOCK());
    GC_ASSERT(GC_page_size != 0);
    if (0 == n) n = 1;
    bytes = ROUNDUP_PAGESIZE((size_t)n * HBLKSIZE);
    GC_DBGLOG_PRINT_HEAP_IN_USE();
    if (GC_max_heapsize != 0
        && (GC_max_heapsize < (word)bytes
            || GC_heapsize > GC_max_heapsize - (word)bytes)) {
        /* Exceeded self-imposed limit */
        return FALSE;
    }
    space = GET_MEM(bytes);
    if (EXPECT(NULL == space, FALSE)) {
        WARN("Failed to expand heap by %" WARN_PRIuPTR " KiB\n", bytes >> 10);
        return FALSE;
    }
    GC_add_to_our_memory((ptr_t)space, bytes);
    GC_last_heap_growth_gc_no = GC_gc_no;
    GC_INFOLOG_PRINTF("Grow heap to %lu KiB after %lu bytes allocated\n",
                      TO_KiB_UL(GC_heapsize + bytes),
                      (unsigned long)GC_bytes_allocd);

    /* Adjust heap limits generously for blacklisting to work better.   */
    /* GC_add_to_heap performs minimal adjustment needed for            */
    /* correctness.                                                     */
    expansion_slop = min_bytes_allocd() + 4 * MAXHINCR * HBLKSIZE;
    if ((GC_last_heap_addr == 0 && !((word)space & SIGNB))
        || (GC_last_heap_addr != 0
            && (word)GC_last_heap_addr < (word)space)) {
        /* Assume the heap is growing up. */
        word new_limit = (word)space + (word)bytes + expansion_slop;
        if (new_limit > (word)space
            && (word)GC_greatest_plausible_heap_addr < new_limit)
          GC_greatest_plausible_heap_addr = (void *)new_limit;
    } else {
        /* Heap is growing down. */
        word new_limit = (word)space - expansion_slop;
        if (new_limit < (word)space
            && (word)GC_least_plausible_heap_addr > new_limit)
          GC_least_plausible_heap_addr = (void *)new_limit;
    }
    GC_last_heap_addr = (ptr_t)space;

    GC_add_to_heap(space, bytes);
    if (GC_on_heap_resize)
        (*GC_on_heap_resize)(GC_heapsize);

    return TRUE;
}

/* Really returns a bool, but it's externally visible, so that's clumsy. */
GC_API int GC_CALL GC_expand_hp(size_t bytes)
{
    word n_blocks = OBJ_SZ_TO_BLOCKS_CHECKED(bytes);
    word old_heapsize;
    GC_bool result;

    if (!EXPECT(GC_is_initialized, TRUE)) GC_init();
    LOCK();
    old_heapsize = GC_heapsize;
    result = GC_expand_hp_inner(n_blocks);
    if (result) {
      GC_requested_heapsize += bytes;
      if (GC_dont_gc) {
        /* Do not call WARN if the heap growth is intentional.  */
        GC_ASSERT(GC_heapsize >= old_heapsize);
        GC_heapsize_on_gc_disable += GC_heapsize - old_heapsize;
      }
    }
    UNLOCK();
    return (int)result;
}

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

/* The minimum value of the ratio of allocated bytes since the latest   */
/* GC to the amount of finalizers created since that GC which triggers  */
/* the collection instead heap expansion.  Has no effect in the         */
/* incremental mode.                                                    */
#if defined(GC_ALLOCD_BYTES_PER_FINALIZER) && !defined(CPPCHECK)
  STATIC word GC_allocd_bytes_per_finalizer = GC_ALLOCD_BYTES_PER_FINALIZER;
#else
  STATIC word GC_allocd_bytes_per_finalizer = 10000;
#endif

GC_API void GC_CALL GC_set_allocd_bytes_per_finalizer(GC_word value)
{
  GC_allocd_bytes_per_finalizer = value;
}

GC_API GC_word GC_CALL GC_get_allocd_bytes_per_finalizer(void)
{
  return GC_allocd_bytes_per_finalizer;
}

static word last_fo_entries = 0;
static word last_bytes_finalized = 0;

/* Collect or expand heap in an attempt make the indicated number of    */
/* free blocks available.  Should be called until the blocks are        */
/* available (setting retry value to TRUE unless this is the first call */
/* in a loop) or until it fails by returning FALSE.  The flags argument */
/* should be IGNORE_OFF_PAGE or 0.                                      */
GC_INNER GC_bool GC_collect_or_expand(word needed_blocks,
                                      unsigned flags,
                                      GC_bool retry)
{
    GC_bool gc_not_stopped = TRUE;
    word blocks_to_get;
    IF_CANCEL(int cancel_state;)

    GC_ASSERT(I_HOLD_LOCK());
    GC_ASSERT(GC_is_initialized);
    DISABLE_CANCEL(cancel_state);
    if (!GC_incremental && !GC_dont_gc &&
        ((GC_dont_expand && GC_bytes_allocd > 0)
         || (GC_fo_entries > last_fo_entries
             && (last_bytes_finalized | GC_bytes_finalized) != 0
             && (GC_fo_entries - last_fo_entries)
                * GC_allocd_bytes_per_finalizer > GC_bytes_allocd)
         || GC_should_collect())) {
      /* Try to do a full collection using 'default' stop_func (unless  */
      /* nothing has been allocated since the latest collection or heap */
      /* expansion is disabled).                                        */
      gc_not_stopped = GC_try_to_collect_inner(
                        GC_bytes_allocd > 0 && (!GC_dont_expand || !retry) ?
                        GC_default_stop_func : GC_never_stop_func);
      if (gc_not_stopped == TRUE || !retry) {
        /* Either the collection hasn't been aborted or this is the     */
        /* first attempt (in a loop).                                   */
        last_fo_entries = GC_fo_entries;
        last_bytes_finalized = GC_bytes_finalized;
        RESTORE_CANCEL(cancel_state);
        return TRUE;
      }
    }

    blocks_to_get = (GC_heapsize - GC_heapsize_at_forced_unmap)
                        / (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 ((flags & IGNORE_OFF_PAGE) != 0) {
        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 (blocks_to_get > divHBLKSZ(GC_WORD_MAX))
        blocks_to_get = divHBLKSZ(GC_WORD_MAX);
    } else if (blocks_to_get < MINHINCR) {
      blocks_to_get = MINHINCR;
    }

    if (GC_max_heapsize > GC_heapsize) {
      word max_get_blocks = divHBLKSZ(GC_max_heapsize - GC_heapsize);
      if (blocks_to_get > max_get_blocks)
        blocks_to_get = max_get_blocks > needed_blocks
                        ? max_get_blocks : needed_blocks;
    }

#   ifdef USE_MUNMAP
      if (GC_unmap_threshold > 1) {
        /* Return as much memory to the OS as possible before   */
        /* trying to get memory from it.                        */
        GC_unmap_old(0);
      }
#   endif
    if (!GC_expand_hp_inner(blocks_to_get)
        && (blocks_to_get == needed_blocks
            || !GC_expand_hp_inner(needed_blocks))) {
      if (gc_not_stopped == FALSE) {
        /* Don't increment GC_fail_count here (and no warning).     */
        GC_gcollect_inner();
        GC_ASSERT(GC_bytes_allocd == 0);
      } else 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)
#         ifdef USE_MUNMAP
            GC_ASSERT(GC_heapsize >= GC_unmapped_bytes);
#         endif
          WARN("Out of Memory! Heap size: %" WARN_PRIuPTR " MiB."
               " Returning NULL!\n", (GC_heapsize - GC_unmapped_bytes) >> 20);
#       endif
        RESTORE_CANCEL(cancel_state);
        return FALSE;
      }
    } else if (GC_fail_count) {
      GC_COND_LOG_PRINTF("Memory available again...\n");
    }
    RESTORE_CANCEL(cancel_state);
    return TRUE;
}

/*
 * Make sure the object free list for size gran (in granules) 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.
 */
GC_INNER ptr_t GC_allocobj(size_t gran, int kind)
{
    void ** flh = &GC_obj_kinds[kind].ok_freelist[gran];
    GC_bool tried_minor = FALSE;
    GC_bool retry = FALSE;

    GC_ASSERT(I_HOLD_LOCK());
    GC_ASSERT(GC_is_initialized);
    if (0 == gran) return NULL;

    while (NULL == *flh) {
      ENTER_GC();
#     ifndef GC_DISABLE_INCREMENTAL
        if (GC_incremental && GC_time_limit != GC_TIME_UNLIMITED
            && !GC_dont_gc) {
          /* True incremental mode, not just generational.      */
          /* Do our share of marking work.                      */
          GC_collect_a_little_inner(1);
        }
#     endif
      /* Sweep blocks for objects of this size */
        GC_ASSERT(!GC_is_full_gc
                  || NULL == GC_obj_kinds[kind].ok_reclaim_list
                  || NULL == GC_obj_kinds[kind].ok_reclaim_list[gran]);
        GC_continue_reclaim(gran, kind);
      EXIT_GC();
#     if defined(CPPCHECK)
        GC_noop1((word)&flh);
#     endif
      if (NULL == *flh) {
        GC_new_hblk(gran, kind);
#       if defined(CPPCHECK)
          GC_noop1((word)&flh);
#       endif
        if (NULL == *flh) {
          ENTER_GC();
          if (GC_incremental && GC_time_limit == GC_TIME_UNLIMITED
              && !tried_minor && !GC_dont_gc) {
            GC_collect_a_little_inner(1);
            tried_minor = TRUE;
          } else {
            if (!GC_collect_or_expand(1, 0 /* flags */, retry)) {
              EXIT_GC();
              return NULL;
            }
            retry = TRUE;
          }
          EXIT_GC();
        }
      }
    }
    /* Successful allocation; reset failure count.      */
    GC_fail_count = 0;

    return (ptr_t)(*flh);
}

ivmai / bdwgc / 1487

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