有关nftw（）和ftw（）的线程安全性的问题

Question

I read two man pages( ftw , nftw ) from opengroup.org, so I thought ftw() and nftw() do not guarantee thread-safety.

But I've found another page about these functions from man7.org, which says ftw() is MT-safe and nftw() is MT-safe cwd .

And these functions are in thread-safety exception list, in this page .

For now, I still believe these functions don't guarantee thread-safety. But I wonder why does this say ftw() is MT-safe.

Why does the page from man7.org say ftw() is MT-safe?

Is it based on POSIX standard?

Answer 1

The fact that POSIX says a function is not multithread-safe only means "it is not guaranteed to be multithread-safe", so you cannot expect it to be or rely that it is. However, it does not mean that it is forbidden for implementations to make it multithread-safe. Implementations may always apply stronger guarantees than the standard requires, they just must not apply weaker ones.