MSVC errno thread safety

Question

Is errno on MSVC thread-safe?

According to the answers in this question POSIX requires that errno is thread-safe. But MSVC is probably not

Answer 1

Although MSVC is definitely not POSIX compliant, errno is implemented in the MSVC runtime (at least as of MSVC2008) in a threadsafe manner.

Although the documentation states that it is extern int errno it's actually implemented as a #define to a function which allows thread-safety to be imposed. If you step through this function in the disassembly window, it is clear that thread local storage is used.

Sadly I can't point to any official documentation that confirms this but such is life!