引用第一个链接：

… allocation of additional inaccessible memory during memory allocation
operations is a technique for mitigating against exploitation of heap
buffer overflows. These guard pages are unmapped pages placed between
all memory allocations of one page or larger. The guard page causes a
segmentation fault upon any access.

因此在实现对诸如网络接口,虚拟机和解释器等领域的保护方面非常有用.示例用法：pthread_attr_setguardsize,pthread_attr_getguardsize.