text: /* Malloc implementation for multiple threads without lock contention.
     Copyright (C) 2001 Free Software Foundation, Inc.
     This file is part of the GNU C Library.
     Contributed by Wolfram Gloger <wg@malloc.de>, 2001.
  
     The GNU C Library is free software; you can redistribute it and/or
     modify it under the terms of the GNU Library General Public License as
     published by the Free Software Foundation; either version 2 of the
     License, or (at your option) any later version.
  
     The GNU C Library is distributed in the hope that it will be useful,
     but WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     Library General Public License for more details.
  
     You should have received a copy of the GNU Library General Public
     License along with the GNU C Library; see the file COPYING.LIB.  If not,
     write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
     Boston, MA 02111-1307, USA.  */
  
  /* $Id: arena.c,v 1.9 2004/11/05 14:42:23 wg Exp $ */
  
  /* Compile-time constants.  */
  
  #define HEAP_MIN_SIZE (32*1024)
  #ifndef HEAP_MAX_SIZE
  #define HEAP_MAX_SIZE (1024*1024) /* must be a power of two */
  #endif
  
  /* HEAP_MIN_SIZE and HEAP_MAX_SIZE limit the size of mmap()ed heaps
     that are dynamically created for multi-threaded programs.  The
     maximum size must be a power of two, for fast determination of
     which heap belongs to a chunk.  It should be much larger than the
     mmap threshold, so that requests with a size just below that
     threshold can be fulfilled without creating too many heaps.  */
  
  
  #ifndef THREAD_STATS
  #define THREAD_STATS 0
  #endif
  
  /* If THREAD_STATS is non-zero, some statistics on mutex locking are
     computed.  */
  
  /***************************************************************************/
  
  #define top(ar_ptr) ((ar_ptr)->top)
  
  /* A heap is a single contiguous memory region holding (coalesceable)
     malloc_chunks.  It is allocated with mmap() and always starts at an
     address aligned to HEAP_MAX_SIZE.  Not used unless compiling with
     USE_ARENAS. */
  
  typedef struct _heap_info {
    mstate ar_ptr; /* Arena for this heap. */
    struct _heap_info *prev; /* Previous heap. */
    size_t size;   /* Current size in bytes. */
    size_t pad;    /* Make sure the following data is properly aligned. */
  } heap_info;
  
  /* Thread specific data */
  
  static tsd_key_t arena_key;
  static mutex_t list_lock;
  
  #if THREAD_STATS
  static int stat_n_heaps;
  #define THREAD_STAT(x) x
  #else
  #define THREAD_STAT(x) do ; while(0)
  #endif
  
  /* Mapped memory in non-main arenas (reliable only for NO_THREADS). */
  static unsigned long arena_mem;
  
  /* Already initialized? */
  int __malloc_initialized = -1;
  
  /**************************************************************************/
  
  #if USE_ARENAS
  
  /* arena_get() acquires an arena and locks the corresponding mutex.
     First, try the one last locked successfully by this thread.  (This
     is the common case and handled with a macro for speed.)  Then, loop
     once over the circularly linked list of arenas.  If no arena is
     readily available, create a new one.  In this latter case, `size'
     is just a hint as to how much memory will be required immediately
     in the new arena. */
  
  #define arena_get(ptr, size) do { \
    Void_t *vptr = NULL; \
    ptr = (mstate)tsd_getspecific(arena_key, vptr); \
    if(ptr && !mutex_trylock(&ptr->mutex)) { \
      THREAD_STAT(++(ptr->stat_lock_direct)); \
    } else \
      ptr = arena_get2(ptr, (size)); \
  } while(0)
  
  /* find the heap and corresponding arena for a given ptr */
  
  #define heap_for_ptr(ptr) \
   ((heap_info *)((unsigned long)(ptr) & ~(HEAP_MAX_SIZE-1)))
  #define arena_for_chunk(ptr) \
   (chunk_non_main_arena(ptr) ? heap_for_ptr(ptr)->ar_ptr : &main_arena)
  
  #else /* !USE_ARENAS */
  
  /* There is only one arena, main_arena. */
  
  #if THREAD_STATS
  #define arena_get(ar_ptr, sz) do { \
    ar_ptr = &main_arena; \
    if(!mutex_trylock(&ar_ptr->mutex)) \
      ++(ar_ptr->stat_lock_direct); \
    else { \
      (void)mutex_lock(&ar_ptr->mutex); \
      ++(ar_ptr->stat_lock_wait); \
    } \
  } while(0)
  #else
  #define arena_get(ar_ptr, sz) do { \
    ar_ptr = &main_arena; \
    (void)mutex_lock(&ar_ptr->mutex); \
  } while(0)
  #endif
  #define arena_for_chunk(ptr) (&main_arena)
  
  #endif /* USE_ARENAS */
  
  /**************************************************************************/
  
  #ifndef NO_THREADS
  
  /* atfork support.  */
  
  static __malloc_ptr_t (*save_malloc_hook) __MALLOC_P ((size_t __size,
  						       __const __malloc_ptr_t));
  # if !defined _LIBC || !defined USE_TLS || (defined SHARED && !USE___THREAD)
  static __malloc_ptr_t (*save_memalign_hook) __MALLOC_P ((size_t __align,
  							 size_t __size,
  						       __const __malloc_ptr_t));
  # endif
  static void           (*save_free_hook) __MALLOC_P ((__malloc_ptr_t __ptr,
  						     __const __malloc_ptr_t));
  static Void_t*        save_arena;
  
  /* Magic value for the thread-specific arena pointer when
     malloc_atfork() is in use.  */
  
  #define ATFORK_ARENA_PTR ((Void_t*)-1)
  
  /* The following hooks are used while the `atfork' handling mechanism
     is active. */
  
  static Void_t*
  malloc_atfork(size_t sz, const Void_t *caller)
  {
    Void_t *vptr = NULL;
    Void_t *victim;
  
    tsd_getspecific(arena_key, vptr);
    if(vptr == ATFORK_ARENA_PTR) {
      /* We are the only thread that may allocate at all.  */
      if(save_malloc_hook != malloc_check) {
        return _int_malloc(&main_arena, sz);
      } else {
        if(top_check()<0)
          return 0;
        victim = _int_malloc(&main_arena, sz+1);
        return mem2mem_check(victim, sz);
      }
    } else {
      /* Suspend the thread until the `atfork' handlers have completed.
         By that time, the hooks will have been reset as well, so that
         mALLOc() can be used again. */
      (void)mutex_lock(&list_lock);
      (void)mutex_unlock(&list_lock);
      return public_mALLOc(sz);
    }
  }
  
  static void
  free_atfork(Void_t* mem, const Void_t *caller)
  {
    Void_t *vptr = NULL;
    mstate ar_ptr;
    mchunkptr p;                          /* chunk corresponding to mem */
  
    if (mem == 0)                              /* free(0) has no effect */
      return;
  
    p = mem2chunk(mem);         /* do not bother to replicate free_check here */
  
  #if HAVE_MMAP
    if (chunk_is_mmapped(p))                       /* release mmapped memory. */
    {
      munmap_chunk(p);
      return;
    }
  #endif
  
    ar_ptr = arena_for_chunk(p);
    tsd_getspecific(arena_key, vptr);
    if(vptr != ATFORK_ARENA_PTR)
      (void)mutex_lock(&ar_ptr->mutex);
    _int_free(ar_ptr, mem);
    if(vptr != ATFORK_ARENA_PTR)
      (void)mutex_unlock(&ar_ptr->mutex);
  }
  
  /* The following two functions are registered via thread_atfork() to
     make sure that the mutexes remain in a consistent state in the
     fork()ed version of a thread.  Also adapt the malloc and free hooks
     temporarily, because the `atfork' handler mechanism may use
     malloc/free internally (e.g. in LinuxThreads). */
  
  static void
  ptmalloc_lock_all __MALLOC_P((void))
  {
    mstate ar_ptr;
  
    if(__malloc_initialized < 1)
      return;
    (void)mutex_lock(&list_lock);
    for(ar_ptr = &main_arena;;) {
      (void)mutex_lock(&ar_ptr->mutex);
      ar_ptr = ar_ptr->next;
      if(ar_ptr == &main_arena) break;
    }
    save_malloc_hook = __malloc_hook;
    save_free_hook = __free_hook;
    __malloc_hook = malloc_atfork;
    __free_hook = free_atfork;
    /* Only the current thread may perform malloc/free calls now. */
    tsd_getspecific(arena_key, save_arena);
    tsd_setspecific(arena_key, ATFORK_ARENA_PTR);
  }
  
  static void
  ptmalloc_unlock_all __MALLOC_P((void))
  {
    mstate ar_ptr;
  
    if(__malloc_initialized < 1)
      return;
    tsd_setspecific(arena_key, save_arena);
    __malloc_hook = save_malloc_hook;
    __free_hook = save_free_hook;
    for(ar_ptr = &main_arena;;) {
      (void)mutex_unlock(&ar_ptr->mutex);
      ar_ptr = ar_ptr->next;
      if(ar_ptr == &main_arena) break;
    }
    (void)mutex_unlock(&list_lock);
  }
  
  #ifdef __linux__
  
  /* In LinuxThreads, unlocking a mutex in the child process after a
     fork() is currently unsafe, whereas re-initializing it is safe and
     does not leak resources.  Therefore, a special atfork handler is
     installed for the child. */
  
  static void
  ptmalloc_unlock_all2 __MALLOC_P((void))
  {
    mstate ar_ptr;
  
    if(__malloc_initialized < 1)
      return;
  #if defined _LIBC || defined MALLOC_HOOKS
    tsd_setspecific(arena_key, save_arena);
    __malloc_hook = save_malloc_hook;
    __free_hook = save_free_hook;
  #endif
    for(ar_ptr = &main_arena;;) {
      (void)mutex_init(&ar_ptr->mutex);
      ar_ptr = ar_ptr->next;
      if(ar_ptr == &main_arena) break;
    }
    (void)mutex_init(&list_lock);
  }
  
  #else
  
  #define ptmalloc_unlock_all2 ptmalloc_unlock_all
  
  #endif
  
  #endif /* !defined NO_THREADS */
  
  /* Initialization routine. */
  #ifdef _LIBC
  #include <string.h>
  extern char **_environ;
  
  static char *
  internal_function
  next_env_entry (char ***position)
  {
    char **current = *position;
    char *result = NULL;
  
    while (*current != NULL)
      {
        if (__builtin_expect ((*current)[0] == 'M', 0)
  	  && (*current)[1] == 'A'
  	  && (*current)[2] == 'L'
  	  && (*current)[3] == 'L'
  	  && (*current)[4] == 'O'
  	  && (*current)[5] == 'C'
  	  && (*current)[6] == '_')
  	{
  	  result = &(*current)[7];
  
  	  /* Save current position for next visit.  */
  	  *position = ++current;
  
  	  break;
  	}
  
        ++current;
      }
  
    return result;
  }
  #endif /* _LIBC */
  
  /* Set up basic state so that _int_malloc et al can work.  */
  static void
  ptmalloc_init_minimal __MALLOC_P((void))
  {
  #if DEFAULT_TOP_PAD != 0
    mp_.top_pad        = DEFAULT_TOP_PAD;
  #endif
    mp_.n_mmaps_max    = DEFAULT_MMAP_MAX;
    mp_.mmap_threshold = DEFAULT_MMAP_THRESHOLD;
    mp_.trim_threshold = DEFAULT_TRIM_THRESHOLD;
    mp_.pagesize       = malloc_getpagesize;
  }
  
  
  #if !(USE_STARTER & 2)
  static
  #endif
  void
  ptmalloc_init __MALLOC_P((void))
  {
  #if __STD_C
    const char* s;
  #else
    char* s;
  #endif
    int secure = 0;
  
    if(__malloc_initialized >= 0) return;
    __malloc_initialized = 0;
  
    if (mp_.pagesize == 0)
      ptmalloc_init_minimal();
  
  #ifndef NO_THREADS
  # if USE_STARTER & 1
    /* With some threads implementations, creating thread-specific data
       or initializing a mutex may call malloc() itself.  Provide a
       simple starter version (realloc() won't work). */
    save_malloc_hook = __malloc_hook;
    save_memalign_hook = __memalign_hook;
    save_free_hook = __free_hook;
    __malloc_hook = malloc_starter;
    __memalign_hook = memalign_starter;
    __free_hook = free_starter;
  #  ifdef _LIBC
    /* Initialize the pthreads interface. */
    if (__pthread_initialize != NULL)
      __pthread_initialize();
  #  endif /* !defined _LIBC */
  # endif /* USE_STARTER & 1 */
  #endif /* !defined NO_THREADS */
    mutex_init(&main_arena.mutex);
    main_arena.next = &main_arena;
  
    mutex_init(&list_lock);
    tsd_key_create(&arena_key, NULL);
    tsd_setspecific(arena_key, (Void_t *)&main_arena);
    thread_atfork(ptmalloc_lock_all, ptmalloc_unlock_all, ptmalloc_unlock_all2);
  #ifndef NO_THREADS
  # if USE_STARTER & 1
    __malloc_hook = save_malloc_hook;
    __memalign_hook = save_memalign_hook;
    __free_hook = save_free_hook;
  # endif
  # if USE_STARTER & 2
    __malloc_hook = 0;
    __memalign_hook = 0;
    __free_hook = 0;
  # endif
  #endif
  #ifdef _LIBC
    secure = __libc_enable_secure;
    s = NULL;
    if (__builtin_expect (_environ != NULL, 1))
      {
        char **runp = _environ;
        char *envline;
  
        while (__builtin_expect ((envline = next_env_entry (&runp)) != NULL,
  			       0))
  	{
  	  size_t len = strcspn (envline, "=");
  
  	  if (envline[len] != '=')
  	    /* This is a "MALLOC_" variable at the end of the string
  	       without a '=' character.  Ignore it since otherwise we
  	       will access invalid memory below.  */
  	    continue;
  
  	  switch (len)
  	    {
  	    case 6:
  	      if (memcmp (envline, "CHECK_", 6) == 0)
  		s = &envline[7];
  	      break;
  	    case 8:
  	      if (! secure && memcmp (envline, "TOP_PAD_", 8) == 0)
  		mALLOPt(M_TOP_PAD, atoi(&envline[9]));
  	      break;
  	    case 9:
  	      if (! secure && memcmp (envline, "MMAP_MAX_", 9) == 0)
  		mALLOPt(M_MMAP_MAX, atoi(&envline[10]));
  	      break;
  	    case 15:
  	      if (! secure)
  		{
  		  if (memcmp (envline, "TRIM_THRESHOLD_", 15) == 0)
  		    mALLOPt(M_TRIM_THRESHOLD, atoi(&envline[16]));
  		  else if (memcmp (envline, "MMAP_THRESHOLD_", 15) == 0)
  		    mALLOPt(M_MMAP_THRESHOLD, atoi(&envline[16]));
  		}
  	      break;
  	    default:
  	      break;
  	    }
  	}
      }
  #else
    if (! secure)
      {
        if((s = getenv("MALLOC_TRIM_THRESHOLD_")))
  	mALLOPt(M_TRIM_THRESHOLD, atoi(s));
        if((s = getenv("MALLOC_TOP_PAD_")))
  	mALLOPt(M_TOP_PAD, atoi(s));
        if((s = getenv("MALLOC_MMAP_THRESHOLD_")))
  	mALLOPt(M_MMAP_THRESHOLD, atoi(s));
        if((s = getenv("MALLOC_MMAP_MAX_")))
  	mALLOPt(M_MMAP_MAX, atoi(s));
      }
    s = getenv("MALLOC_CHECK_");
  #endif
    if(s) {
      if(s[0]) mALLOPt(M_CHECK_ACTION, (int)(s[0] - '0'));
      __malloc_check_init();
    }
    if(__malloc_initialize_hook != NULL)
      (*__malloc_initialize_hook)();
    __malloc_initialized = 1;
  }
  
  /* There are platforms (e.g. Hurd) with a link-time hook mechanism. */
  #ifdef thread_atfork_static
  thread_atfork_static(ptmalloc_lock_all, ptmalloc_unlock_all, \
                       ptmalloc_unlock_all2)
  #endif
  
  
  
  /* Managing heaps and arenas (for concurrent threads) */
  
  #if USE_ARENAS
  
  #if MALLOC_DEBUG > 1
  
  /* Print the complete contents of a single heap to stderr. */
  
  static void
  #if __STD_C
  dump_heap(heap_info *heap)
  #else
  dump_heap(heap) heap_info *heap;
  #endif
  {
    char *ptr;
    mchunkptr p;
  
    fprintf(stderr, "Heap %p, size %10lx:\n", heap, (long)heap->size);
    ptr = (heap->ar_ptr != (mstate)(heap+1)) ?
      (char*)(heap + 1) : (char*)(heap + 1) + sizeof(struct malloc_state);
    p = (mchunkptr)(((unsigned long)ptr + MALLOC_ALIGN_MASK) &
                    ~MALLOC_ALIGN_MASK);
    for(;;) {
      fprintf(stderr, "chunk %p size %10lx", p, (long)p->size);
      if(p == top(heap->ar_ptr)) {
        fprintf(stderr, " (top)\n");
        break;
      } else if(p->size == (0|PREV_INUSE)) {
        fprintf(stderr, " (fence)\n");
        break;
      }
      fprintf(stderr, "\n");
      p = next_chunk(p);
    }
  }
  
  #endif /* MALLOC_DEBUG > 1 */
  
  /* Create a new heap.  size is automatically rounded up to a multiple
     of the page size. */
  
  static heap_info *
  internal_function
  #if __STD_C
  new_heap(size_t size, size_t top_pad)
  #else
  new_heap(size, top_pad) size_t size, top_pad;
  #endif
  {
    size_t page_mask = malloc_getpagesize - 1;
    char *p1, *p2;
    unsigned long ul;
    heap_info *h;
  
    if(size+top_pad < HEAP_MIN_SIZE)
      size = HEAP_MIN_SIZE;
    else if(size+top_pad <= HEAP_MAX_SIZE)
      size += top_pad;
    else if(size > HEAP_MAX_SIZE)
      return 0;
    else
      size = HEAP_MAX_SIZE;
    size = (size + page_mask) & ~page_mask;
  
    /* A memory region aligned to a multiple of HEAP_MAX_SIZE is needed.
       No swap space needs to be reserved for the following large
       mapping (on Linux, this is the case for all non-writable mappings
       anyway). */
    p1 = (char *)MMAP(0, HEAP_MAX_SIZE<<1, PROT_NONE, MAP_PRIVATE|MAP_NORESERVE);
    if(p1 != MAP_FAILED) {
      p2 = (char *)(((unsigned long)p1 + (HEAP_MAX_SIZE-1)) & ~(HEAP_MAX_SIZE-1));
      ul = p2 - p1;
      munmap(p1, ul);
      munmap(p2 + HEAP_MAX_SIZE, HEAP_MAX_SIZE - ul);
    } else {
      /* Try to take the chance that an allocation of only HEAP_MAX_SIZE
         is already aligned. */
      p2 = (char *)MMAP(0, HEAP_MAX_SIZE, PROT_NONE, MAP_PRIVATE|MAP_NORESERVE);
      if(p2 == MAP_FAILED)
        return 0;
      if((unsigned long)p2 & (HEAP_MAX_SIZE-1)) {
        munmap(p2, HEAP_MAX_SIZE);
        return 0;
      }
    }
    if(mprotect(p2, size, PROT_READ|PROT_WRITE) != 0) {
      munmap(p2, HEAP_MAX_SIZE);
      return 0;
    }
    h = (heap_info *)p2;
    h->size = size;
    THREAD_STAT(stat_n_heaps++);
    return h;
  }
  
  /* Grow or shrink a heap.  size is automatically rounded up to a
     multiple of the page size if it is positive. */
  
  static int
  #if __STD_C
  grow_heap(heap_info *h, long diff)
  #else
  grow_heap(h, diff) heap_info *h; long diff;
  #endif
  {
    size_t page_mask = malloc_getpagesize - 1;
    long new_size;
  
    if(diff >= 0) {
      diff = (diff + page_mask) & ~page_mask;
      new_size = (long)h->size + diff;
      if(new_size > HEAP_MAX_SIZE)
        return -1;
      if(mprotect((char *)h + h->size, diff, PROT_READ|PROT_WRITE) != 0)
        return -2;
    } else {
      new_size = (long)h->size + diff;
      if(new_size < (long)sizeof(*h))
        return -1;
      /* Try to re-map the extra heap space freshly to save memory, and
         make it inaccessible. */
      if((char *)MMAP((char *)h + new_size, -diff, PROT_NONE,
                      MAP_PRIVATE|MAP_FIXED) == (char *) MAP_FAILED)
        return -2;
      /*fprintf(stderr, "shrink %p %08lx\n", h, new_size);*/
    }
    h->size = new_size;
    return 0;
  }
  
  /* Delete a heap. */
  
  #define delete_heap(heap) munmap((char*)(heap), HEAP_MAX_SIZE)
  
  static int
  internal_function
  #if __STD_C
  heap_trim(heap_info *heap, size_t pad)
  #else
  heap_trim(heap, pad) heap_info *heap; size_t pad;
  #endif
  {
    mstate ar_ptr = heap->ar_ptr;
    unsigned long pagesz = mp_.pagesize;
    mchunkptr top_chunk = top(ar_ptr), p, bck, fwd;
    heap_info *prev_heap;
    long new_size, top_size, extra;
  
    /* Can this heap go away completely? */
    while(top_chunk == chunk_at_offset(heap, sizeof(*heap))) {
      prev_heap = heap->prev;
      p = chunk_at_offset(prev_heap, prev_heap->size - (MINSIZE-2*SIZE_SZ));
      assert(p->size == (0|PREV_INUSE)); /* must be fencepost */
      p = prev_chunk(p);
      new_size = chunksize(p) + (MINSIZE-2*SIZE_SZ);
      assert(new_size>0 && new_size<(long)(2*MINSIZE));
      if(!prev_inuse(p))
        new_size += p->prev_size;
      assert(new_size>0 && new_size<HEAP_MAX_SIZE);
      if(new_size + (HEAP_MAX_SIZE - prev_heap->size) < pad + MINSIZE + pagesz)
        break;
      ar_ptr->system_mem -= heap->size;
      arena_mem -= heap->size;
      delete_heap(heap);
      heap = prev_heap;
      if(!prev_inuse(p)) { /* consolidate backward */
        p = prev_chunk(p);
        unlink(p, bck, fwd);
      }
      assert(((unsigned long)((char*)p + new_size) & (pagesz-1)) == 0);
      assert( ((char*)p + new_size) == ((char*)heap + heap->size) );
      top(ar_ptr) = top_chunk = p;
      set_head(top_chunk, new_size | PREV_INUSE);
      /*check_chunk(ar_ptr, top_chunk);*/
    }
    top_size = chunksize(top_chunk);
    extra = ((top_size - pad - MINSIZE + (pagesz-1))/pagesz - 1) * pagesz;
    if(extra < (long)pagesz)
      return 0;
    /* Try to shrink. */
    if(grow_heap(heap, -extra) != 0)
      return 0;
    ar_ptr->system_mem -= extra;
    arena_mem -= extra;
  
    /* Success. Adjust top accordingly. */
    set_head(top_chunk, (top_size - extra) | PREV_INUSE);
    /*check_chunk(ar_ptr, top_chunk);*/
    return 1;
  }
  
  static mstate
  internal_function
  #if __STD_C
  arena_get2(mstate a_tsd, size_t size)
  #else
  arena_get2(a_tsd, size) mstate a_tsd; size_t size;
  #endif
  {
    mstate a;
    int err;
  
    if(!a_tsd)
      a = a_tsd = &main_arena;
    else {
      a = a_tsd->next;
      if(!a) {
        /* This can only happen while initializing the new arena. */
        (void)mutex_lock(&main_arena.mutex);
        THREAD_STAT(++(main_arena.stat_lock_wait));
        return &main_arena;
      }
    }
  
    /* Check the global, circularly linked list for available arenas. */
   repeat:
    do {
      if(!mutex_trylock(&a->mutex)) {
        THREAD_STAT(++(a->stat_lock_loop));
        tsd_setspecific(arena_key, (Void_t *)a);
        return a;
      }
      a = a->next;
    } while(a != a_tsd);
  
    /* If not even the list_lock can be obtained, try again.  This can
       happen during `atfork', or for example on systems where thread
       creation makes it temporarily impossible to obtain _any_
       locks. */
    if(mutex_trylock(&list_lock)) {
      a = a_tsd;
      goto repeat;
    }
    (void)mutex_unlock(&list_lock);
  
    /* Nothing immediately available, so generate a new arena.  */
    a = _int_new_arena(size);
    if(!a)
      return 0;
  
    tsd_setspecific(arena_key, (Void_t *)a);
    mutex_init(&a->mutex);
    err = mutex_lock(&a->mutex); /* remember result */
  
    /* Add the new arena to the global list.  */
    (void)mutex_lock(&list_lock);
    a->next = main_arena.next;
    atomic_write_barrier ();
    main_arena.next = a;
    (void)mutex_unlock(&list_lock);
  
    if(err) /* locking failed; keep arena for further attempts later */
      return 0;
  
    THREAD_STAT(++(a->stat_lock_loop));
    return a;
  }
  
  /* Create a new arena with initial size "size".  */
  
  mstate
  _int_new_arena(size_t size)
  {
    mstate a;
    heap_info *h;
    char *ptr;
    unsigned long misalign;
  
    h = new_heap(size + (sizeof(*h) + sizeof(*a) + MALLOC_ALIGNMENT),
  	       mp_.top_pad);
    if(!h) {
      /* Maybe size is too large to fit in a single heap.  So, just try
         to create a minimally-sized arena and let _int_malloc() attempt
         to deal with the large request via mmap_chunk().  */
      h = new_heap(sizeof(*h) + sizeof(*a) + MALLOC_ALIGNMENT, mp_.top_pad);
      if(!h)
        return 0;
    }
    a = h->ar_ptr = (mstate)(h+1);
    malloc_init_state(a);
    /*a->next = NULL;*/
    a->system_mem = a->max_system_mem = h->size;
    arena_mem += h->size;
  #ifdef NO_THREADS
    if((unsigned long)(mp_.mmapped_mem + arena_mem + main_arena.system_mem) >
       mp_.max_total_mem)
      mp_.max_total_mem = mp_.mmapped_mem + arena_mem + main_arena.system_mem;
  #endif
  
    /* Set up the top chunk, with proper alignment. */
    ptr = (char *)(a + 1);
    misalign = (unsigned long)chunk2mem(ptr) & MALLOC_ALIGN_MASK;
    if (misalign > 0)
      ptr += MALLOC_ALIGNMENT - misalign;
    top(a) = (mchunkptr)ptr;
    set_head(top(a), (((char*)h + h->size) - ptr) | PREV_INUSE);
  
    return a;
  }
  
  /* Obtain the arena number n.  Needed in malloc_stats.  */
  
  mstate
  _int_get_arena (int n)
  {
    mstate a = &main_arena;
  
    while (n-- != 0) {
      a = a->next;
      if (a == &main_arena)
        return 0;
    }
    return a;
  }
  
  #endif /* USE_ARENAS */
  
  /*
   * Local variables:
   * c-basic-offset: 2
   * End:
   */
  