Remove Once from init

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

library/std/src/sys_common/rt.rs

@@ -1,16 +1,17 @@
+#![deny(unsafe_op_in_unsafe_fn)]
+
 use crate::sync::Once;
 use crate::sys;
 use crate::sys_common::thread_info;
 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.