因为它在边界处，它是唯一一个可以任意的扩展（通过Unix的sbrk系统调用）成更大的块（除非因为所有的内存已经被消耗光了导致sbrk失败）。

Because it is at the border, it is the only chunk that can be arbitrarily extended (via sbrk in Unix) to be bigger than it is (unless of course sbrk fails because all memory has been exhausted).

youdao

因为它在边界处，它是唯一一个可以任意的扩展（通过Unix的sbrk系统调用）成更大的块（除非因为所有的内存已经被消耗光了导致sbrk失败）。

Because it is at the border, it is the only chunk that can be arbitrarily extended (via sbrk in Unix) to be bigger than it is (unless of course sbrk fails because all memory has been exhausted).

youdao