ptmalloc 中 BINS 的数量

The bins field of the malloc_state result body of ptmalloc declares 127 bins, of which the first is unsortbin, and the next 62 are normal bins. Then there are 63 large bins. So what does the 127th bin do? In addition, according to the comments, there should be a 64th larger bin to hold all the chunks that exceed the range.