std: Re-enable at_exit()

The new semantics of this function are that the callbacks are run when the *main
thread* exits, not when all threads have exited. This implies that other threads
may still be running when the `at_exit` callbacks are invoked and users need to
be prepared for this situation.

Users in the standard library have been audited in accordance to these new rules
as well.

Closes #20012

1 files changed, 1 insertions, 3 deletions

diff --git a/src/libstd/sys/windows/os.rs b/src/libstd/sys/windows/os.rs
index fa08290a888..5a7be63e39f 100644
--- a/src/libstd/sys/windows/os.rs
+++ b/src/libstd/sys/windows/os.rs
@@ -15,14 +15,12 @@
 
 use prelude::*;
 
-use fmt;
 use io::{IoResult, IoError};
-use libc::{c_int, c_char, c_void};
+use libc::{c_int, c_void};
 use libc;
 use os;
 use path::BytesContainer;
 use ptr;
-use sync::atomic::{AtomicInt, INIT_ATOMIC_INT, SeqCst};
 use sys::fs::FileDesc;
 use slice;