Function origin::create_thread

pub fn create_thread(
    fn_: Box<dyn FnOnce() -> Option<Box<dyn Any>>>, 
    stack_size: usize, 
    guard_size: usize
) -> Result<*mut Thread>

Creates a new thread.

fn_ is called on the new thread and passed arg.

This is a safe function because it itself doesn’t dereference arg; it calls fn_, which does, and it’s marked unsafe.