Auto merge of #28069 - alexcrichton:rt-atexit, r=brson

This adds a call to `rt::cleanup` on `process::exit` to make sure we clean up
after ourselves on the way out from Rust.

Closes #28065

3 files changed, 8 insertions, 17 deletions

diff --git a/src/libstd/rt/args.rs b/src/libstd/rt/args.rs
index cf8bac31057..8de713aeac8 100644
--- a/src/libstd/rt/args.rs
+++ b/src/libstd/rt/args.rs
@@ -64,7 +64,6 @@ mod imp {
 
     pub unsafe fn cleanup() {
         take();
-        LOCK.destroy();
     }
 
     pub fn take() -> Option<Vec<Vec<u8>>> {
diff --git a/src/libstd/rt/at_exit_imp.rs b/src/libstd/rt/at_exit_imp.rs
index 54e5b499e53..379c86eb2a0 100644
--- a/src/libstd/rt/at_exit_imp.rs
+++ b/src/libstd/rt/at_exit_imp.rs
@@ -12,10 +12,6 @@
 //!
 //! Documentation can be found on the `rt::at_exit` function.
 
-// FIXME: switch this to use atexit. Currently this
-// segfaults (the queue's memory is mysteriously gone), so
-// instead the cleanup is tied to the `std::rt` entry point.
-
 use alloc::boxed::FnBox;
 use boxed::Box;
 use ptr;
diff --git a/src/libstd/rt/mod.rs b/src/libstd/rt/mod.rs
index 5464e7f9d89..2cbf81b2fc7 100644
--- a/src/libstd/rt/mod.rs
+++ b/src/libstd/rt/mod.rs
@@ -23,6 +23,7 @@
 #![allow(missing_docs)]
 
 use prelude::v1::*;
+use sync::Once;
 use sys;
 use thread;
 
@@ -124,16 +125,11 @@ pub fn at_exit<F: FnOnce() + Send + 'static>(f: F) -> Result<(), ()> {
 }
 
 /// One-time runtime cleanup.
-///
-/// This function is unsafe because it performs no checks to ensure that the
-/// runtime has completely ceased running. It is the responsibility of the
-/// caller to ensure that the runtime is entirely shut down and nothing will be
-/// poking around at the internal components.
-///
-/// Invoking cleanup while portions of the runtime are still in use may cause
-/// undefined behavior.
-pub unsafe fn cleanup() {
-    args::cleanup();
-    sys::stack_overflow::cleanup();
-    at_exit_imp::cleanup();
+pub fn cleanup() {
+    static CLEANUP: Once = Once::new();
+    CLEANUP.call_once(|| unsafe {
+        args::cleanup();
+        sys::stack_overflow::cleanup();
+        at_exit_imp::cleanup();
+    });
 }