/*

 * Copyright 1988, 1989 Hans-J. Boehm, Alan J. Demers

 * Copyright (c) 1991-1994 by Xerox Corporation.  All rights reserved.

 * Copyright (c) 1998-1999 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>

#ifdef GC_USE_ENTIRE_HEAP

  int GC_use_entire_heap = TRUE;

#else

  int GC_use_entire_heap = FALSE;

#endif

/*

 * Free heap blocks are kept on one of several free lists,

 * depending on the size of the block.  Each free list is doubly linked.

 * Adjacent free blocks are coalesced.

 */

# define MAX_BLACK_LIST_ALLOC (2*HBLKSIZE)

                /* largest block we will allocate starting on a black   */

                /* listed block.  Must be >= HBLKSIZE.                  */

# define UNIQUE_THRESHOLD 32

        /* Sizes up to this many HBLKs each have their own free list    */

# define HUGE_THRESHOLD 256

        /* Sizes of at least this many heap blocks are mapped to a      */

        /* single free list.                                            */

# define FL_COMPRESSION 8

        /* In between sizes map this many distinct sizes to a single    */

        /* bin.                                                         */

# define N_HBLK_FLS ((HUGE_THRESHOLD - UNIQUE_THRESHOLD) / FL_COMPRESSION \

                     + UNIQUE_THRESHOLD)

#ifndef GC_GCJ_SUPPORT

  STATIC

#endif

  struct hblk * GC_hblkfreelist[N_HBLK_FLS+1] = { 0 };

                                /* List of completely empty heap blocks */

                                /* Linked through hb_next field of      */

                                /* header structure associated with     */

                                /* block.  Remains externally visible   */

                                /* as used by GNU GCJ currently.        */

#ifndef GC_GCJ_SUPPORT

  STATIC

#endif

  word GC_free_bytes[N_HBLK_FLS+1] = { 0 };

        /* Number of free bytes on each list.  Remains visible to GCJ.  */

/* Return the largest n such that the number of free bytes on lists     */

/* n .. N_HBLK_FLS is greater or equal to GC_max_large_allocd_bytes     */

/* minus GC_large_allocd_bytes.  If there is no such n, return 0.       */

GC_INLINE int GC_enough_large_bytes_left(void)

{

    int n;

    word bytes = GC_large_allocd_bytes;

    GC_ASSERT(GC_max_large_allocd_bytes <= GC_heapsize);

    for (n = N_HBLK_FLS; n >= 0; --n) {

        bytes += GC_free_bytes[n];

        if (bytes >= GC_max_large_allocd_bytes) return n;

    }

    return 0;

}

/* Map a number of blocks to the appropriate large block free list index. */

STATIC int GC_hblk_fl_from_blocks(word blocks_needed)

{

    if (blocks_needed <= UNIQUE_THRESHOLD) return (int)blocks_needed;

    if (blocks_needed >= HUGE_THRESHOLD) return N_HBLK_FLS;

    return (int)(blocks_needed - UNIQUE_THRESHOLD)/FL_COMPRESSION

                                        + UNIQUE_THRESHOLD;

}

# define PHDR(hhdr) HDR((hhdr) -> hb_prev)

# define NHDR(hhdr) HDR((hhdr) -> hb_next)

# ifdef USE_MUNMAP

#   define IS_MAPPED(hhdr) (((hhdr) -> hb_flags & WAS_UNMAPPED) == 0)

# else

#   define IS_MAPPED(hhdr) TRUE

# endif /* !USE_MUNMAP */

#if !defined(NO_DEBUGGING) || defined(GC_ASSERTIONS)

  /* Should return the same value as GC_large_free_bytes.       */

  GC_INNER word GC_compute_large_free_bytes(void)

  {

      word total_free = 0;

      unsigned i;

      for (i = 0; i <= N_HBLK_FLS; ++i) {

        struct hblk * h;

        hdr * hhdr;

        for (h = GC_hblkfreelist[i]; h != 0; h = hhdr->hb_next) {

          hhdr = HDR(h);

          total_free += hhdr->hb_sz;

        }

      }

      return total_free;

  }

#endif /* !NO_DEBUGGING || GC_ASSERTIONS */

# if !defined(NO_DEBUGGING)

void GC_print_hblkfreelist(void)

{

    unsigned i;

    word total;

    for (i = 0; i <= N_HBLK_FLS; ++i) {

      struct hblk * h = GC_hblkfreelist[i];

      if (0 != h) GC_printf("Free list %u (total size %lu):\n",

                            i, (unsigned long)GC_free_bytes[i]);

      while (h != 0) {

        hdr * hhdr = HDR(h);

        GC_printf("\t%p size %lu %s black listed\n",

                (void *)h, (unsigned long) hhdr -> hb_sz,

                GC_is_black_listed(h, HBLKSIZE) != 0 ? "start" :

                GC_is_black_listed(h, hhdr -> hb_sz) != 0 ? "partially" :

                                                        "not");

        h = hhdr -> hb_next;

      }

    }

    GC_printf("GC_large_free_bytes: %lu\n",

              (unsigned long)GC_large_free_bytes);

    if ((total = GC_compute_large_free_bytes()) != GC_large_free_bytes)

          GC_err_printf("GC_large_free_bytes INCONSISTENT!! Should be: %lu\n",

                        (unsigned long)total);

}

/* Return the free list index on which the block described by the header */

/* appears, or -1 if it appears nowhere.                                 */

static int free_list_index_of(hdr *wanted)

{

    int i;

    for (i = 0; i <= N_HBLK_FLS; ++i) {

      struct hblk * h;

      hdr * hhdr;

      for (h = GC_hblkfreelist[i]; h != 0; h = hhdr -> hb_next) {

        hhdr = HDR(h);

        if (hhdr == wanted) return i;

      }

    }

    return -1;

}

GC_API void GC_CALL GC_dump_regions(void)

{

    unsigned i;

    for (i = 0; i < GC_n_heap_sects; ++i) {

        ptr_t start = GC_heap_sects[i].hs_start;

        size_t bytes = GC_heap_sects[i].hs_bytes;

        ptr_t end = start + bytes;

        ptr_t p;

        /* Merge in contiguous sections.        */

          while (i+1 < GC_n_heap_sects && GC_heap_sects[i+1].hs_start == end) {

            ++i;

            end = GC_heap_sects[i].hs_start + GC_heap_sects[i].hs_bytes;

          }

        GC_printf("***Section from %p to %p\n", (void *)start, (void *)end);

        for (p = start; (word)p < (word)end; ) {

            hdr *hhdr = HDR(p);

            if (IS_FORWARDING_ADDR_OR_NIL(hhdr)) {

                GC_printf("\t%p Missing header!!(%p)\n",

                          (void *)p, (void *)hhdr);

                p += HBLKSIZE;

                continue;

            }

            if (HBLK_IS_FREE(hhdr)) {

                int correct_index = GC_hblk_fl_from_blocks(

                                        divHBLKSZ(hhdr -> hb_sz));

                int actual_index;

                GC_printf("\t%p\tfree block of size 0x%lx bytes%s\n",

                          (void *)p, (unsigned long)(hhdr -> hb_sz),

                          IS_MAPPED(hhdr) ? "" : " (unmapped)");

                actual_index = free_list_index_of(hhdr);

                if (-1 == actual_index) {

                    GC_printf("\t\tBlock not on free list %d!!\n",

                              correct_index);

                } else if (correct_index != actual_index) {

                    GC_printf("\t\tBlock on list %d, should be on %d!!\n",

                              actual_index, correct_index);

                }

                p += hhdr -> hb_sz;

            } else {

                GC_printf("\t%p\tused for blocks of size 0x%lx bytes\n",

                          (void *)p, (unsigned long)(hhdr -> hb_sz));

                p += HBLKSIZE * OBJ_SZ_TO_BLOCKS(hhdr -> hb_sz);

            }

        }

    }

}

# endif /* NO_DEBUGGING */

/* Initialize hdr for a block containing the indicated size and         */

/* kind of objects.                                                     */

/* Return FALSE on failure.                                             */

static GC_bool setup_header(hdr * hhdr, struct hblk *block, size_t byte_sz,

                            int kind, unsigned flags)

{

    word descr;

#   ifdef MARK_BIT_PER_GRANULE

      if (byte_sz > MAXOBJBYTES)

        flags |= LARGE_BLOCK;

#   endif

#   ifdef ENABLE_DISCLAIM

      if (GC_obj_kinds[kind].ok_disclaim_proc)

        flags |= HAS_DISCLAIM;

      if (GC_obj_kinds[kind].ok_mark_unconditionally)

        flags |= MARK_UNCONDITIONALLY;

#   endif

    /* Set size, kind and mark proc fields */

      hhdr -> hb_sz = byte_sz;

      hhdr -> hb_obj_kind = (unsigned char)kind;

      hhdr -> hb_flags = (unsigned char)flags;

      hhdr -> hb_block = block;

      descr = GC_obj_kinds[kind].ok_descriptor;

      if (GC_obj_kinds[kind].ok_relocate_descr) descr += byte_sz;

      hhdr -> hb_descr = descr;

#   ifdef MARK_BIT_PER_OBJ

     /* Set hb_inv_sz as portably as possible.                          */

     /* We set it to the smallest value such that sz * inv_sz > 2**32    */

     /* This may be more precision than necessary.                      */

      if (byte_sz > MAXOBJBYTES) {

         hhdr -> hb_inv_sz = LARGE_INV_SZ;

      } else {

        word inv_sz;

#       if CPP_WORDSZ == 64

          inv_sz = ((word)1 << 32)/byte_sz;

          if (((inv_sz*byte_sz) >> 32) == 0) ++inv_sz;

#       else  /* 32 bit words */

          GC_ASSERT(byte_sz >= 4);

          inv_sz = ((unsigned)1 << 31)/byte_sz;

          inv_sz *= 2;

          while (inv_sz*byte_sz > byte_sz) ++inv_sz;

#       endif

        hhdr -> hb_inv_sz = inv_sz;

      }

#   else /* MARK_BIT_PER_GRANULE */

    {

      size_t granules = BYTES_TO_GRANULES(byte_sz);

      if (EXPECT(!GC_add_map_entry(granules), FALSE)) {

        /* Make it look like a valid block. */

        hhdr -> hb_sz = HBLKSIZE;

        hhdr -> hb_descr = 0;

        hhdr -> hb_flags |= LARGE_BLOCK;

        hhdr -> hb_map = 0;

        return FALSE;

      }

      hhdr -> hb_map = GC_obj_map[(hhdr -> hb_flags & LARGE_BLOCK) != 0 ?

                                    0 : granules];

    }

#   endif /* MARK_BIT_PER_GRANULE */

    /* Clear mark bits */

    GC_clear_hdr_marks(hhdr);

    hhdr -> hb_last_reclaimed = (unsigned short)GC_gc_no;

    return(TRUE);

}

/* Remove hhdr from the free list (it is assumed to specified by index). */

STATIC void GC_remove_from_fl_at(hdr *hhdr, int index)

{

    GC_ASSERT(((hhdr -> hb_sz) & (HBLKSIZE-1)) == 0);

    if (hhdr -> hb_prev == 0) {

        GC_ASSERT(HDR(GC_hblkfreelist[index]) == hhdr);

        GC_hblkfreelist[index] = hhdr -> hb_next;

    } else {

        hdr *phdr;

        GET_HDR(hhdr -> hb_prev, phdr);

        phdr -> hb_next = hhdr -> hb_next;

    }

    /* We always need index to maintain free counts.    */

    GC_ASSERT(GC_free_bytes[index] >= hhdr -> hb_sz);

    GC_free_bytes[index] -= hhdr -> hb_sz;

    if (0 != hhdr -> hb_next) {

        hdr * nhdr;

        GC_ASSERT(!IS_FORWARDING_ADDR_OR_NIL(NHDR(hhdr)));

        GET_HDR(hhdr -> hb_next, nhdr);

        nhdr -> hb_prev = hhdr -> hb_prev;

    }

}

/* Remove hhdr from the appropriate free list (we assume it is on the   */

/* size-appropriate free list).                                         */

GC_INLINE void GC_remove_from_fl(hdr *hhdr)

{

  GC_remove_from_fl_at(hhdr, GC_hblk_fl_from_blocks(divHBLKSZ(hhdr->hb_sz)));

}

/* Return a pointer to the free block ending just before h, if any.     */

STATIC struct hblk * GC_free_block_ending_at(struct hblk *h)

{

    struct hblk * p = h - 1;

    hdr * phdr;

    GET_HDR(p, phdr);

    while (0 != phdr && IS_FORWARDING_ADDR_OR_NIL(phdr)) {

        p = FORWARDED_ADDR(p,phdr);

        phdr = HDR(p);

    }

    if (0 != phdr) {

        if(HBLK_IS_FREE(phdr)) {

            return p;

        } else {

            return 0;

        }

    }

    p = GC_prev_block(h - 1);

    if (0 != p) {

      phdr = HDR(p);

      if (HBLK_IS_FREE(phdr) && (ptr_t)p + phdr -> hb_sz == (ptr_t)h) {

        return p;

      }

    }

    return 0;

}

/* Add hhdr to the appropriate free list.               */

/* We maintain individual free lists sorted by address. */

STATIC void GC_add_to_fl(struct hblk *h, hdr *hhdr)

{

    int index = GC_hblk_fl_from_blocks(divHBLKSZ(hhdr -> hb_sz));

    struct hblk *second = GC_hblkfreelist[index];

#   if defined(GC_ASSERTIONS) && !defined(USE_MUNMAP)

      struct hblk *next = (struct hblk *)((word)h + hhdr -> hb_sz);

      hdr * nexthdr = HDR(next);

      struct hblk *prev = GC_free_block_ending_at(h);

      hdr * prevhdr = HDR(prev);

      GC_ASSERT(nexthdr == 0 || !HBLK_IS_FREE(nexthdr)

                || (GC_heapsize & SIGNB) != 0);

                /* In the last case, blocks may be too large to merge. */

      GC_ASSERT(prev == 0 || !HBLK_IS_FREE(prevhdr)

                || (GC_heapsize & SIGNB) != 0);

#   endif

    GC_ASSERT(((hhdr -> hb_sz) & (HBLKSIZE-1)) == 0);

    GC_hblkfreelist[index] = h;

    GC_free_bytes[index] += hhdr -> hb_sz;

    GC_ASSERT(GC_free_bytes[index] <= GC_large_free_bytes);

    hhdr -> hb_next = second;

    hhdr -> hb_prev = 0;

    if (0 != second) {

      hdr * second_hdr;

      GET_HDR(second, second_hdr);

      second_hdr -> hb_prev = h;

    }

    hhdr -> hb_flags |= FREE_BLK;

}

#ifdef USE_MUNMAP

#   ifndef MUNMAP_THRESHOLD

#     define MUNMAP_THRESHOLD 6

#   endif

GC_INNER int GC_unmap_threshold = MUNMAP_THRESHOLD;

/* Unmap blocks that haven't been recently touched.  This is the only way */

/* way blocks are ever unmapped.                                          */

GC_INNER void GC_unmap_old(void)

{

    int i;

    if (GC_unmap_threshold == 0)

      return; /* unmapping disabled */

    for (i = 0; i <= N_HBLK_FLS; ++i) {

      struct hblk * h;

      hdr * hhdr;

      for (h = GC_hblkfreelist[i]; 0 != h; h = hhdr -> hb_next) {

        hhdr = HDR(h);

        if (!IS_MAPPED(hhdr)) continue;

        /* Check that the interval is larger than the threshold (the    */

        /* truncated counter value wrapping is handled correctly).      */

        if ((unsigned short)(GC_gc_no - hhdr->hb_last_reclaimed) >

                (unsigned short)GC_unmap_threshold) {

          GC_unmap((ptr_t)h, hhdr -> hb_sz);

          hhdr -> hb_flags |= WAS_UNMAPPED;

        }

      }

    }

}

/* Merge all unmapped blocks that are adjacent to other free            */

/* blocks.  This may involve remapping, since all blocks are either     */

/* fully mapped or fully unmapped.                                      */

GC_INNER void GC_merge_unmapped(void)

{

    int i;

    for (i = 0; i <= N_HBLK_FLS; ++i) {

      struct hblk *h = GC_hblkfreelist[i];

      while (h != 0) {

        struct hblk *next;

        hdr *hhdr, *nexthdr;

        word size, nextsize;

        GET_HDR(h, hhdr);

        size = hhdr->hb_sz;

        next = (struct hblk *)((word)h + size);

        GET_HDR(next, nexthdr);

        /* Coalesce with successor, if possible */

          if (0 != nexthdr && HBLK_IS_FREE(nexthdr)

              && (signed_word) (size + (nextsize = nexthdr->hb_sz)) > 0

                 /* no pot. overflow */) {

            /* Note that we usually try to avoid adjacent free blocks   */

            /* that are either both mapped or both unmapped.  But that  */

            /* isn't guaranteed to hold since we remap blocks when we   */

            /* split them, and don't merge at that point.  It may also  */

            /* not hold if the merged block would be too big.           */

            if (IS_MAPPED(hhdr) && !IS_MAPPED(nexthdr)) {

              /* make both consistent, so that we can merge */

                if (size > nextsize) {

                  GC_remap((ptr_t)next, nextsize);

                } else {

                  GC_unmap((ptr_t)h, size);

                  GC_unmap_gap((ptr_t)h, size, (ptr_t)next, nextsize);

                  hhdr -> hb_flags |= WAS_UNMAPPED;

                }

            } else if (IS_MAPPED(nexthdr) && !IS_MAPPED(hhdr)) {

              if (size > nextsize) {

                GC_unmap((ptr_t)next, nextsize);

                GC_unmap_gap((ptr_t)h, size, (ptr_t)next, nextsize);

              } else {

                GC_remap((ptr_t)h, size);

                hhdr -> hb_flags &= ~WAS_UNMAPPED;

                hhdr -> hb_last_reclaimed = nexthdr -> hb_last_reclaimed;

              }

            } else if (!IS_MAPPED(hhdr) && !IS_MAPPED(nexthdr)) {

              /* Unmap any gap in the middle */

                GC_unmap_gap((ptr_t)h, size, (ptr_t)next, nextsize);

            }

            /* If they are both unmapped, we merge, but leave unmapped. */

            GC_remove_from_fl_at(hhdr, i);

            GC_remove_from_fl(nexthdr);

            hhdr -> hb_sz += nexthdr -> hb_sz;

            GC_remove_header(next);

            GC_add_to_fl(h, hhdr);

            /* Start over at beginning of list */

            h = GC_hblkfreelist[i];

          } else /* not mergable with successor */ {

            h = hhdr -> hb_next;

          }

      } /* while (h != 0) ... */

    } /* for ... */

}

#endif /* USE_MUNMAP */

/*

 * Return a pointer to a block starting at h of length bytes.

 * Memory for the block is mapped.

 * Remove the block from its free list, and return the remainder (if any)

 * to its appropriate free list.

 * May fail by returning 0.

 * The header for the returned block must be set up by the caller.

 * If the return value is not 0, then hhdr is the header for it.

 */

STATIC struct hblk * GC_get_first_part(struct hblk *h, hdr *hhdr,

                                       size_t bytes, int index)

{

    word total_size = hhdr -> hb_sz;

    struct hblk * rest;

    hdr * rest_hdr;

    GC_ASSERT((total_size & (HBLKSIZE-1)) == 0);

    GC_remove_from_fl_at(hhdr, index);

    if (total_size == bytes) return h;

    rest = (struct hblk *)((word)h + bytes);

    rest_hdr = GC_install_header(rest);

    if (0 == rest_hdr) {

        /* FIXME: This is likely to be very bad news ... */

        WARN("Header allocation failed: dropping block\n", 0);

        return(0);

    }

    rest_hdr -> hb_sz = total_size - bytes;

    rest_hdr -> hb_flags = 0;

#   ifdef GC_ASSERTIONS

      /* Mark h not free, to avoid assertion about adjacent free blocks. */

        hhdr -> hb_flags &= ~FREE_BLK;

#   endif

    GC_add_to_fl(rest, rest_hdr);

    return h;

}

/*

 * H is a free block.  N points at an address inside it.

 * A new header for n has already been set up.  Fix up h's header

 * to reflect the fact that it is being split, move it to the

 * appropriate free list.

 * N replaces h in the original free list.

 *

 * Nhdr is not completely filled in, since it is about to allocated.

 * It may in fact end up on the wrong free list for its size.

 * That's not a disaster, since n is about to be allocated

 * by our caller.

 * (Hence adding it to a free list is silly.  But this path is hopefully

 * rare enough that it doesn't matter.  The code is cleaner this way.)

 */

STATIC void GC_split_block(struct hblk *h, hdr *hhdr, struct hblk *n,

                           hdr *nhdr, int index /* Index of free list */)

{

    word total_size = hhdr -> hb_sz;

    word h_size = (word)n - (word)h;

    struct hblk *prev = hhdr -> hb_prev;

    struct hblk *next = hhdr -> hb_next;

    /* Replace h with n on its freelist */

      nhdr -> hb_prev = prev;

      nhdr -> hb_next = next;

      nhdr -> hb_sz = total_size - h_size;

      nhdr -> hb_flags = 0;

      if (0 != prev) {

        HDR(prev) -> hb_next = n;

      } else {

        GC_hblkfreelist[index] = n;

      }

      if (0 != next) {

        HDR(next) -> hb_prev = n;

      }

      GC_ASSERT(GC_free_bytes[index] > h_size);

      GC_free_bytes[index] -= h_size;

#   ifdef USE_MUNMAP

      hhdr -> hb_last_reclaimed = (unsigned short)GC_gc_no;

#   endif

    hhdr -> hb_sz = h_size;

    GC_add_to_fl(h, hhdr);

    nhdr -> hb_flags |= FREE_BLK;

}

STATIC struct hblk *

GC_allochblk_nth(size_t sz /* bytes */, int kind, unsigned flags, int n,

                 int may_split);

#define AVOID_SPLIT_REMAPPED 2

/*

 * Allocate (and return pointer to) a heap block

 *   for objects of size sz bytes, searching the nth free list.

 *

 * NOTE: We set obj_map field in header correctly.

 *       Caller is responsible for building an object freelist in block.

 *

 * The client is responsible for clearing the block, if necessary.

 */

GC_INNER struct hblk *

GC_allochblk(size_t sz, int kind, unsigned flags/* IGNORE_OFF_PAGE or 0 */)

{

    word blocks;

    int start_list;

    struct hblk *result;

    int may_split;

    int split_limit; /* Highest index of free list whose blocks we      */

                     /* split.                                          */

    GC_ASSERT((sz & (GRANULE_BYTES - 1)) == 0);

    blocks = OBJ_SZ_TO_BLOCKS_CHECKED(sz);

    if ((signed_word)(blocks * HBLKSIZE) < 0) {

      return 0;

    }

    start_list = GC_hblk_fl_from_blocks(blocks);

    /* Try for an exact match first. */

    result = GC_allochblk_nth(sz, kind, flags, start_list, FALSE);

    if (0 != result) return result;

    may_split = TRUE;

    if (GC_use_entire_heap || GC_dont_gc

        || USED_HEAP_SIZE < GC_requested_heapsize

        || GC_incremental || !GC_should_collect()) {

        /* Should use more of the heap, even if it requires splitting. */

        split_limit = N_HBLK_FLS;

    } else if (GC_finalizer_bytes_freed > (GC_heapsize >> 4)) {

          /* If we are deallocating lots of memory from         */

          /* finalizers, fail and collect sooner rather         */

          /* than later.                                        */

          split_limit = 0;

    } else {

          /* If we have enough large blocks left to cover any   */

          /* previous request for large blocks, we go ahead     */

          /* and split.  Assuming a steady state, that should   */

          /* be safe.  It means that we can use the full        */

          /* heap if we allocate only small objects.            */

          split_limit = GC_enough_large_bytes_left();

#         ifdef USE_MUNMAP

            if (split_limit > 0)

              may_split = AVOID_SPLIT_REMAPPED;

#         endif

    }

    if (start_list < UNIQUE_THRESHOLD) {

      /* No reason to try start_list again, since all blocks are exact  */

      /* matches.                                                       */

      ++start_list;

    }

    for (; start_list <= split_limit; ++start_list) {

        result = GC_allochblk_nth(sz, kind, flags, start_list, may_split);

        if (0 != result)

            break;

    }

    return result;

}

STATIC long GC_large_alloc_warn_suppressed = 0;

                        /* Number of warnings suppressed so far.        */

/* The same, but with search restricted to nth free list.  Flags is     */

/* IGNORE_OFF_PAGE or zero.  sz is in bytes.  The may_split flag        */

/* indicates whether it is OK to split larger blocks (if set to         */

/* AVOID_SPLIT_REMAPPED then memory remapping followed by splitting     */

/* should be generally avoided).                                        */

STATIC struct hblk *

GC_allochblk_nth(size_t sz, int kind, unsigned flags, int n, int may_split)

{

    struct hblk *hbp;

    hdr * hhdr;                 /* Header corr. to hbp */

    struct hblk *thishbp;

    hdr * thishdr;              /* Header corr. to thishbp */

    signed_word size_needed = HBLKSIZE * OBJ_SZ_TO_BLOCKS_CHECKED(sz);

                                /* number of bytes in requested objects */

    /* search for a big enough block in free list */

        for (hbp = GC_hblkfreelist[n];; hbp = hhdr -> hb_next) {

            signed_word size_avail; /* bytes available in this block */

            if (NULL == hbp) return NULL;

            GET_HDR(hbp, hhdr); /* set hhdr value */

            size_avail = hhdr->hb_sz;

            if (size_avail < size_needed) continue;

            if (size_avail != size_needed) {

              if (!may_split) continue;

              /* If the next heap block is obviously better, go on.     */

              /* This prevents us from disassembling a single large     */

              /* block to get tiny blocks.                              */

              thishbp = hhdr -> hb_next;

              if (thishbp != 0) {

                signed_word next_size;

                GET_HDR(thishbp, thishdr);

                next_size = (signed_word)(thishdr -> hb_sz);

                if (next_size < size_avail

                    && next_size >= size_needed

                    && !GC_is_black_listed(thishbp, (word)size_needed)) {

                    continue;

                }

              }

            }

            if (!IS_UNCOLLECTABLE(kind) && (kind != PTRFREE

                        || size_needed > (signed_word)MAX_BLACK_LIST_ALLOC)) {

              struct hblk * lasthbp = hbp;

              ptr_t search_end = (ptr_t)hbp + size_avail - size_needed;

              signed_word orig_avail = size_avail;

              signed_word eff_size_needed = (flags & IGNORE_OFF_PAGE) != 0 ?

                                                (signed_word)HBLKSIZE

                                                : size_needed;

              while ((word)lasthbp <= (word)search_end

                     && (thishbp = GC_is_black_listed(lasthbp,

                                            (word)eff_size_needed)) != 0) {

                lasthbp = thishbp;

              }

              size_avail -= (ptr_t)lasthbp - (ptr_t)hbp;

              thishbp = lasthbp;

              if (size_avail >= size_needed) {

                if (thishbp != hbp) {

#                 ifdef USE_MUNMAP

                    /* Avoid remapping followed by splitting.   */

                    if (may_split == AVOID_SPLIT_REMAPPED && !IS_MAPPED(hhdr))

                      continue;

#                 endif

                  thishdr = GC_install_header(thishbp);

                  if (0 != thishdr) {

                  /* Make sure it's mapped before we mangle it. */

#                   ifdef USE_MUNMAP

                      if (!IS_MAPPED(hhdr)) {

                        GC_remap((ptr_t)hbp, hhdr -> hb_sz);

                        hhdr -> hb_flags &= ~WAS_UNMAPPED;

                      }

#                   endif

                  /* Split the block at thishbp */

                      GC_split_block(hbp, hhdr, thishbp, thishdr, n);

                  /* Advance to thishbp */

                      hbp = thishbp;

                      hhdr = thishdr;

                      /* We must now allocate thishbp, since it may     */

                      /* be on the wrong free list.                     */

                  }

                }

              } else if (size_needed > (signed_word)BL_LIMIT

                         && orig_avail - size_needed

                            > (signed_word)BL_LIMIT) {

                /* Punt, since anything else risks unreasonable heap growth. */

                if (++GC_large_alloc_warn_suppressed

                    >= GC_large_alloc_warn_interval) {

                  WARN("Repeated allocation of very large block "

                       "(appr. size %" WARN_PRIdPTR "):\n"

                       "\tMay lead to memory leak and poor performance\n",

                       size_needed);

                  GC_large_alloc_warn_suppressed = 0;

                }

                size_avail = orig_avail;

              } else if (size_avail == 0 && size_needed == HBLKSIZE

                         && IS_MAPPED(hhdr)) {

                if (!GC_find_leak) {

                  static unsigned count = 0;

                  /* The block is completely blacklisted.  We need      */

                  /* to drop some such blocks, since otherwise we spend */

                  /* all our time traversing them if pointer-free       */

                  /* blocks are unpopular.                              */

                  /* A dropped block will be reconsidered at next GC.   */

                  if ((++count & 3) == 0) {

                    /* Allocate and drop the block in small chunks, to  */

                    /* maximize the chance that we will recover some    */

                    /* later.                                           */

                      word total_size = hhdr -> hb_sz;

                      struct hblk * limit = hbp + divHBLKSZ(total_size);

                      struct hblk * h;

                      struct hblk * prev = hhdr -> hb_prev;

                      GC_large_free_bytes -= total_size;

                      GC_bytes_dropped += total_size;

                      GC_remove_from_fl_at(hhdr, n);

                      for (h = hbp; (word)h < (word)limit; h++) {

                        if (h != hbp) {

                          hhdr = GC_install_header(h);

                        }

                        if (NULL != hhdr) {

                          (void)setup_header(hhdr, h, HBLKSIZE, PTRFREE, 0);

                                                    /* Can't fail. */

                          if (GC_debugging_started) {

                            BZERO(h, HBLKSIZE);

                          }

                        }

                      }

                    /* Restore hbp to point at free block */

                      hbp = prev;

                      if (0 == hbp) {

                        return GC_allochblk_nth(sz, kind, flags, n, may_split);

                      }

                      hhdr = HDR(hbp);

                  }

                }

              }

            }

            if( size_avail >= size_needed ) {

#               ifdef USE_MUNMAP

                  if (!IS_MAPPED(hhdr)) {

                    GC_remap((ptr_t)hbp, hhdr -> hb_sz);

                    hhdr -> hb_flags &= ~WAS_UNMAPPED;

                    /* Note: This may leave adjacent, mapped free blocks. */

                  }

#               endif

                /* hbp may be on the wrong freelist; the parameter n    */

                /* is important.                                        */

                hbp = GC_get_first_part(hbp, hhdr, size_needed, n);

                break;

            }

        }

    if (0 == hbp) return 0;

    /* Add it to map of valid blocks */

        if (!GC_install_counts(hbp, (word)size_needed)) return(0);

        /* This leaks memory under very rare conditions. */

    /* Set up header */

        if (!setup_header(hhdr, hbp, sz, kind, flags)) {

            GC_remove_counts(hbp, (word)size_needed);

            return(0); /* ditto */

        }

#   ifndef GC_DISABLE_INCREMENTAL

        /* Notify virtual dirty bit implementation that we are about to */

        /* write.  Ensure that pointer-free objects are not protected   */

        /* if it is avoidable.  This also ensures that newly allocated  */

        /* blocks are treated as dirty.  Necessary since we don't       */

        /* protect free blocks.                                         */

        GC_ASSERT((size_needed & (HBLKSIZE-1)) == 0);

        GC_remove_protection(hbp, divHBLKSZ(size_needed),

                             (hhdr -> hb_descr == 0) /* pointer-free */);

#   endif

    /* We just successfully allocated a block.  Restart count of        */

    /* consecutive failures.                                            */

    GC_fail_count = 0;

    GC_large_free_bytes -= size_needed;

    GC_ASSERT(IS_MAPPED(hhdr));

    return( hbp );

}

/*

 * Free a heap block.

 *

 * Coalesce the block with its neighbors if possible.

 *

 * All mark words are assumed to be cleared.

 */

GC_INNER void GC_freehblk(struct hblk *hbp)

{

    struct hblk *next, *prev;

    hdr *hhdr, *prevhdr, *nexthdr;

    word size;

    GET_HDR(hbp, hhdr);

    size = HBLKSIZE * OBJ_SZ_TO_BLOCKS(hhdr->hb_sz);

    if ((signed_word)size <= 0)

      ABORT("Deallocating excessively large block.  Too large an allocation?");

      /* Probably possible if we try to allocate more than half the address */

      /* space at once.  If we don't catch it here, strange things happen   */

      /* later.                                                             */

    GC_remove_counts(hbp, size);

    hhdr->hb_sz = size;

#   ifdef USE_MUNMAP

      hhdr -> hb_last_reclaimed = (unsigned short)GC_gc_no;

#   endif

    /* Check for duplicate deallocation in the easy case */

      if (HBLK_IS_FREE(hhdr)) {

        ABORT_ARG1("Duplicate large block deallocation",

                   " of %p", (void *)hbp);

      }

    GC_ASSERT(IS_MAPPED(hhdr));

    hhdr -> hb_flags |= FREE_BLK;

    next = (struct hblk *)((ptr_t)hbp + size);

    GET_HDR(next, nexthdr);

    prev = GC_free_block_ending_at(hbp);

    /* Coalesce with successor, if possible */

      if(0 != nexthdr && HBLK_IS_FREE(nexthdr) && IS_MAPPED(nexthdr)

         && (signed_word)(hhdr -> hb_sz + nexthdr -> hb_sz) > 0

         /* no overflow */) {

        GC_remove_from_fl(nexthdr);

        hhdr -> hb_sz += nexthdr -> hb_sz;

        GC_remove_header(next);

      }

    /* Coalesce with predecessor, if possible. */

      if (0 != prev) {

        prevhdr = HDR(prev);

        if (IS_MAPPED(prevhdr)

            && (signed_word)(hhdr -> hb_sz + prevhdr -> hb_sz) > 0) {

          GC_remove_from_fl(prevhdr);

          prevhdr -> hb_sz += hhdr -> hb_sz;

#         ifdef USE_MUNMAP

            prevhdr -> hb_last_reclaimed = (unsigned short)GC_gc_no;