int
__gethostbyname_r (const char *name, struct hostent **resbuf, char *buffer,
			size_t buflen, struct hostent **result, int *h_errnop)
{
...
  enum nss_status status = NSS_STATUS_UNAVAIL;
...
#ifdef HANDLE_DIGITS_DOTS
  switch (__nss_hostname_digits_dots (name, resbuf, &buffer, NULL,
				      buflen, result, &status, AF_INET,
				      h_errnop))
...
}



int
__nss_hostname_digits_dots (const char *name, struct hostent *resbuf,
			    char **buffer, size_t *buffer_size,
			    size_t buflen, struct hostent **result,
			    enum nss_status *status, int af, int *h_errnop)

//defined in include/malloc.h
struct malloc_state;
typedef struct malloc_state *mstate;
...

//defined in malloc/malloc.c. 
//Ln 1051.
struct malloc_chunk;
typedef struct malloc_chunk* mchunkptr;

//Ln 1125.
struct malloc_chunk {

  INTERNAL_SIZE_T      prev_size;  /* Size of previous chunk (if free).  */
  INTERNAL_SIZE_T      size;       /* Size in bytes, including overhead. */

  struct malloc_chunk* fd;         /* double links -- used only if free. */
  struct malloc_chunk* bk;

  /* Only used for large blocks: pointer to next larger size.  */
  struct malloc_chunk* fd_nextsize; /* double links -- used only if free. */
  struct malloc_chunk* bk_nextsize;
};

//Ln 1413.
typedef struct malloc_chunk* mbinptr;

//Ln 1608.
typedef struct malloc_chunk* mfastbinptr;

//Ln 1688.
struct malloc_state {
  /* Serialize access.  */
  mutex_t mutex;

  /* Flags (formerly in max_fast).  */
  int flags;

#if THREAD_STATS
  /* Statistics for locking.  Only used if THREAD_STATS is defined.  */
  long stat_lock_direct, stat_lock_loop, stat_lock_wait;
#endif

  /* Fastbins */
  mfastbinptr      fastbinsY[NFASTBINS];

  /* Base of the topmost chunk -- not otherwise kept in a bin */
  mchunkptr        top;

  /* The remainder from the most recent split of a small request */
  mchunkptr        last_remainder;

  /* Normal bins packed as described above */
  mchunkptr        bins[NBINS * 2 - 2];

  /* Bitmap of bins */
  unsigned int     binmap[BINMAPSIZE];

  /* Linked list */
  struct malloc_state *next;

#ifdef PER_THREAD
  /* Linked list for free arenas.  */
  struct malloc_state *next_free;
#endif

  /* Memory allocated from the system in this arena.  */
  INTERNAL_SIZE_T system_mem;
  INTERNAL_SIZE_T max_system_mem;
};