58     struct _Tune  struct
61       enum { _S_align = 8 };
62       enum { _S_max_bytes = 128 };
63       enum { _S_min_bin = 8 };
64       enum { _S_chunk_size = 4096 - 4 * sizeof(void*) };
65       enum { _S_max_threads = 4096 };
66       enum { _S_freelist_headroom = 10 };
71       size_t	_M_align;
78       size_t	_M_max_bytes; 
83       size_t	_M_min_bin;
91       size_t	_M_chunk_size;
99       size_t 	_M_max_threads;
107       size_t 	_M_freelist_headroom;
110       bool 	_M_force_new; 
113       _Tune()  in _Tune()  function
121       _Tune(size_t __align, size_t __maxb, size_t __minbin, size_t __chunk,   in _Tune()  function