assert(
   (  old_top == (((mbinptr) (((char *) &((av)->bins[((1) - 1) * 2])) – __builtin_offsetof (struct malloc_chunk, fd))))
   && old_size == 0 )

|| (  (unsigned long)(old_size)
          >=
        (unsigned long)(
      (
       (
          (__builtin_offsetof (struct malloc_chunk, fd_nextsize))
            + ((2 * (sizeof(size_t))) – 1)
       )
       & ~((2 * (sizeof(size_t))) – 1)
      )
    )

   && ((old_top)->size & 0×1)
   && ((unsigned long)old_end & pagemask) == 0 )
);