Comment by cryptonector
4 years ago
If you can call _exit() and exec, then you can call other functions too. I do believe that the Open Group has changed the description of vfork() to discourage its use because of an old and incorrect paper from the 80s. Actual implementations of vfork() are not as dangerous as the Open Group text purports them to be.
Moreover, most posix_spawn() implementations use vfork(), and they call more functions than _exit() and exec on the child side.
Let's be reasonable about these things.
An implementation of posix_spawn() is usually owned by the same people who implemented vfork(), so they know what is and isn't safe to call in that particular implementation. But we don't, and we shouldn't assume that the implementation will not change. That's exactly why public APIs and stability guarantees exist.
Not on Linux!
Even if that's true, doing so after vfork() is still much harder than after fork(), not easier.