From 7171fec13f3a3091f702a8e55f495ad1563dc4cd Mon Sep 17 00:00:00 2001
From: Christiaan Dirkx <christiaan@dirkx.email>
Date: Wed, 21 Apr 2021 16:21:10 +0200
Subject: [PATCH] Remove `Once` from `init`

---
 library/std/src/rt.rs            |  5 ++++-
 library/std/src/sys_common/rt.rs | 11 ++++++-----
 2 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/library/std/src/rt.rs b/library/std/src/rt.rs
index ce6e318c9de..1e19aff51f8 100644
--- a/library/std/src/rt.rs
+++ b/library/std/src/rt.rs
@@ -28,8 +28,11 @@ fn lang_start_internal(
     use crate::panic;
     use crate::sys_common;
 
-    sys_common::rt::init(argc, argv);
+    // SAFETY: Only called once during runtime initialization.
+    unsafe { sys_common::rt::init(argc, argv) };
+
     let exit_code = panic::catch_unwind(main);
+
     sys_common::rt::cleanup();
 
     exit_code.unwrap_or(101) as isize
diff --git a/library/std/src/sys_common/rt.rs b/library/std/src/sys_common/rt.rs
index c0c4a63cde9..c70f2ecc04e 100644
--- a/library/std/src/sys_common/rt.rs
+++ b/library/std/src/sys_common/rt.rs
@@ -1,3 +1,5 @@
+#![deny(unsafe_op_in_unsafe_fn)]
+
 use crate::sync::Once;
 use crate::sys;
 use crate::sys_common::thread_info;
@@ -5,12 +7,11 @@ use crate::thread::Thread;
 
 // One-time runtime initialization.
 // Runs before `main`.
+// SAFETY: must be called only once during runtime initialization.
 // NOTE: this is not guaranteed to run, for example when Rust code is called externally.
 #[cfg_attr(test, allow(dead_code))]
-pub fn init(argc: isize, argv: *const *const u8) {
-    static INIT: Once = Once::new();
-    INIT.call_once(|| unsafe {
-        // SAFETY: Only called once during runtime initialization.
+pub unsafe fn init(argc: isize, argv: *const *const u8) {
+    unsafe {
         sys::init(argc, argv);
 
         let main_guard = sys::thread::guard::init();
@@ -20,7 +21,7 @@ pub fn init(argc: isize, argv: *const *const u8) {
         // info about the stack bounds.
         let thread = Thread::new(Some("main".to_owned()));
         thread_info::set(main_guard, thread);
-    });
+    }
 }
 
 // One-time runtime cleanup.