In fact, <i>brk</i> and <i>mmap</i> aren&#x27;t even really guaranteed to return zero filled memory. It just happens that kernels often zero everything to avoid the headache of tracking which pages contain data you aren&#x27;t supposed to see.<p>I guess one can rely on such behavior when writing a platform-specific <i>libc</i>. But in portable code? Yuck.