ptmalloc.c

这是一个内存分配管理的程序

 IAV(80),  IAV(81),  IAV(82),  IAV(83),  IAV(84),  IAV(85),  IAV(86),  IAV(87),
 IAV(88),  IAV(89),  IAV(90),  IAV(91),  IAV(92),  IAV(93),  IAV(94),  IAV(95),
 IAV(96),  IAV(97),  IAV(98),  IAV(99),  IAV(100), IAV(101), IAV(102), IAV(103),
 IAV(104), IAV(105), IAV(106), IAV(107), IAV(108), IAV(109), IAV(110), IAV(111),
 IAV(112), IAV(113), IAV(114), IAV(115), IAV(116), IAV(117), IAV(118), IAV(119),
 IAV(120), IAV(121), IAV(122), IAV(123), IAV(124), IAV(125), IAV(126), IAV(127)
    },
    &main_arena, /* next */
    0, /* size */
#if THREAD_STATS
    0, 0, 0, /* stat_lock_direct, stat_lock_loop, stat_lock_wait */
#endif
    MUTEX_INITIALIZER /* mutex */
};

#undef IAV

/* Thread specific data */

static tsd_key_t arena_key;
static mutex_t list_lock = MUTEX_INITIALIZER;

#if THREAD_STATS
static int stat_n_heaps = 0;
#define THREAD_STAT(x) x
#else
#define THREAD_STAT(x) do ; while(0)
#endif

/* variables holding tunable values */

static unsigned long trim_threshold   = DEFAULT_TRIM_THRESHOLD;
static unsigned long top_pad          = DEFAULT_TOP_PAD;
static unsigned int  n_mmaps_max      = DEFAULT_MMAP_MAX;
static unsigned long mmap_threshold   = DEFAULT_MMAP_THRESHOLD;
static int           check_action     = DEFAULT_CHECK_ACTION;

/* The first value returned from sbrk */
static char* sbrk_base = (char*)(-1);

/* The maximum memory obtained from system via sbrk */
static unsigned long max_sbrked_mem = 0;

/* The maximum via either sbrk or mmap (too difficult to track with threads) */
#ifdef NO_THREADS
static unsigned long max_total_mem = 0;
#endif

/* The total memory obtained from system via sbrk */
#define sbrked_mem (main_arena.size)

/* Tracking mmaps */

static unsigned int n_mmaps = 0;
static unsigned int max_n_mmaps = 0;
static unsigned long mmapped_mem = 0;
static unsigned long max_mmapped_mem = 0;

/* Mapped memory in non-main arenas (reliable only for NO_THREADS). */
static unsigned long arena_mem = 0;



#ifndef _LIBC
#define weak_variable
#else
/* In GNU libc we want the hook variables to be weak definitions to
   avoid a problem with Emacs.  */
#define weak_variable weak_function
#endif

/* Already initialized? */
int __malloc_initialized = -1;


#ifndef NO_THREADS

/* 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). */

#if defined _LIBC || defined MALLOC_HOOKS
static __malloc_ptr_t (*save_malloc_hook) __MALLOC_P ((size_t __size));
static void           (*save_free_hook) __MALLOC_P ((__malloc_ptr_t __ptr));
static Void_t*        save_arena;
#endif

static void
ptmalloc_lock_all __MALLOC_P((void))
{
  arena *ar_ptr;

  (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;
  }
#if defined _LIBC || defined MALLOC_HOOKS
  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, (Void_t*)0);
#endif
}

static void
ptmalloc_unlock_all __MALLOC_P((void))
{
  arena *ar_ptr;

#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_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))
{
  arena *ar_ptr;

#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. */
#if defined(_LIBC)
#if 0
static void ptmalloc_init __MALLOC_P ((void)) __attribute__ ((constructor));
#endif

static void
ptmalloc_init __MALLOC_P((void))
#else
void
ptmalloc_init __MALLOC_P((void))
#endif
{
#if defined _LIBC || defined MALLOC_HOOKS
# if __STD_C
  const char* s;
# else
  char* s;
# endif
#endif

  if(__malloc_initialized >= 0) return;
  __malloc_initialized = 0;
#ifdef _LIBC
  __libc_pagesize = __getpagesize();
#endif
#ifndef NO_THREADS
#if defined _LIBC || defined MALLOC_HOOKS
  /* 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_free_hook = __free_hook;
  __malloc_hook = malloc_starter;
  __free_hook = free_starter;
#endif
#ifdef _LIBC
  /* Initialize the pthreads interface. */
  if (__pthread_initialize != NULL)
    __pthread_initialize();
#endif
#endif /* !defined NO_THREADS */
  mutex_init(&main_arena.mutex);
  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);
#if defined _LIBC || defined MALLOC_HOOKS
  if((s = __secure_getenv("MALLOC_TRIM_THRESHOLD_")))
    mALLOPt(M_TRIM_THRESHOLD, atoi(s));
  if((s = __secure_getenv("MALLOC_TOP_PAD_")))
    mALLOPt(M_TOP_PAD, atoi(s));
  if((s = __secure_getenv("MALLOC_MMAP_THRESHOLD_")))
    mALLOPt(M_MMAP_THRESHOLD, atoi(s));
  if((s = __secure_getenv("MALLOC_MMAP_MAX_")))
    mALLOPt(M_MMAP_MAX, atoi(s));
  s = getenv("MALLOC_CHECK_");
#ifndef NO_THREADS
  __malloc_hook = save_malloc_hook;
  __free_hook = save_free_hook;
#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)();
#endif
  __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

#if defined _LIBC || defined MALLOC_HOOKS

/* Hooks for debugging versions.  The initial hooks just call the
   initialization routine, then do the normal work. */

static Void_t*
#if __STD_C
malloc_hook_ini(size_t sz)
#else
malloc_hook_ini(sz) size_t sz;
#endif
{
  __malloc_hook = NULL;
  ptmalloc_init();
  return mALLOc(sz);
}

static Void_t*
#if __STD_C
realloc_hook_ini(Void_t* ptr, size_t sz)
#else
realloc_hook_ini(ptr, sz) Void_t* ptr; size_t sz;
#endif
{
  __malloc_hook = NULL;
  __realloc_hook = NULL;
  ptmalloc_init();
  return rEALLOc(ptr, sz);
}

static Void_t*
#if __STD_C
memalign_hook_ini(size_t sz, size_t alignment)
#else
memalign_hook_ini(sz, alignment) size_t sz; size_t alignment;
#endif
{
  __memalign_hook = NULL;
  ptmalloc_init();
  return mEMALIGn(sz, alignment);
}

void weak_variable (*__malloc_initialize_hook) __MALLOC_P ((void)) = NULL;
void weak_variable (*__free_hook) __MALLOC_P ((__malloc_ptr_t __ptr)) = NULL;
__malloc_ptr_t weak_variable (*__malloc_hook)
 __MALLOC_P ((size_t __size)) = malloc_hook_ini;
__malloc_ptr_t weak_variable (*__realloc_hook)
 __MALLOC_P ((__malloc_ptr_t __ptr, size_t __size)) = realloc_hook_ini;
__malloc_ptr_t weak_variable (*__memalign_hook)
 __MALLOC_P ((size_t __size, size_t __alignment)) = memalign_hook_ini;
void weak_variable (*__after_morecore_hook) __MALLOC_P ((void)) = NULL;

/* Whether we are using malloc checking.  */
static int using_malloc_checking;

/* A flag that is set by malloc_set_state, to signal that malloc checking
   must not be enabled on the request from the user (via the MALLOC_CHECK_
   environment variable).  It is reset by __malloc_check_init to tell
   malloc_set_state that the user has requested malloc checking.

   The purpose of this flag is to make sure that malloc checking is not
   enabled when the heap to be restored was constructed without malloc
   checking, and thus does not contain the required magic bytes.
   Otherwise the heap would be corrupted by calls to free and realloc.  If
   it turns out that the heap was created with malloc checking and the
   user has requested it malloc_set_state just calls __malloc_check_init
   again to enable it.  On the other hand, reusing such a heap without
   further malloc checking is safe.  */
static int disallow_malloc_check;

/* Activate a standard set of debugging hooks. */
void
__malloc_check_init()
{
  if (disallow_malloc_check) {
    disallow_malloc_check = 0;
    return;
  }
  using_malloc_checking = 1;
  __malloc_hook = malloc_check;
  __free_hook = free_check;
  __realloc_hook = realloc_check;
  __memalign_hook = memalign_check;
  if(check_action & 1)
    fprintf(stderr, "malloc: using debugging hooks\n");
}

#endif





/* Routines dealing with mmap(). */

#if HAVE_MMAP

#ifndef MAP_ANONYMOUS

static int dev_zero_fd = -1; /* Cached file descriptor for /dev/zero. */

#define MMAP(addr, size, prot, flags) ((dev_zero_fd < 0) ? \
 (dev_zero_fd = open("/dev/zero", O_RDWR), \
  mmap((addr), (size), (prot), (flags), dev_zero_fd, 0)) : \
   mmap((addr), (size), (prot), (flags), dev_zero_fd, 0))

#else

#define MMAP(addr, size, prot, flags) \
 (mmap((addr), (size), (prot), (flags)|MAP_ANONYMOUS, -1, 0))

#endif

#if defined __GNUC__ && __GNUC__ >= 2
/* This function is only called from one place, inline it.  */
__inline__
#endif
static mchunkptr
internal_function
#if __STD_C
mmap_chunk(size_t size)
#else
mmap_chunk(size) size_t size;
#endif
{
  size_t page_mask = malloc_getpagesize - 1;
  mchunkptr p;

  if(n_mmaps >= n_mmaps_max) return 0; /* too many regions */

  /* For mmapped chunks, the overhead is one SIZE_SZ unit larger, because
   * there is no following chunk whose prev_size field could be used.
   */
  size = (size + SIZE_SZ + page_mask) & ~page_mask;

  p = (mc