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 )
);