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, 6 insertions, 9 deletions

diff --git a/src/libstd/sys/windows/process.rs b/src/libstd/sys/windows/process.rs
index 0c2c76077dd..0c5a0eb6bb9 100644
--- a/src/libstd/sys/windows/process.rs
+++ b/src/libstd/sys/windows/process.rs
@@ -8,25 +8,24 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use libc::{pid_t, c_void, c_int};
+use prelude::*;
+
+use libc::{pid_t, c_void};
 use libc;
 use c_str::CString;
 use io;
 use mem;
 use os;
 use ptr;
-use prelude::*;
-use io::process::{ProcessExit, ExitStatus, ExitSignal};
+use io::process::{ProcessExit, ExitStatus};
 use collections;
 use path::BytesContainer;
 use hash::Hash;
 use io::{IoResult, IoError};
 
-use sys::fs;
-use sys::{mod, retry, c, wouldblock, set_nonblocking, ms_to_timeval, timer};
+use sys::timer;
 use sys::fs::FileDesc;
-use sys_common::helper_thread::Helper;
-use sys_common::{AsInner, mkerr_libc, timeout};
+use sys_common::{AsInner, timeout};
 
 use io::fs::PathExtensions;
 
@@ -121,8 +120,6 @@ impl Process {
         use libc::funcs::extra::msvcrt::get_osfhandle;
 
         use mem;
-        use iter::{Iterator, IteratorExt};
-        use str::StrExt;
 
         if cfg.gid().is_some() || cfg.uid().is_some() {
             return Err(IoError {