fixup! Get rid of a warning

Author: vorner

signal-hook-registry/src/lib.rs

@@ -304,6 +304,10 @@ static GLOBAL_INIT: Once = ONCE_INIT;
 impl GlobalData {
     fn get() -> &'static Self {
         let data = GLOBAL_DATA.load(Ordering::Acquire);
+        // # Safety
+        //
+        // * The data actually does live forever - created by Box::into_raw.
+        // * It is _never_ modified (apart for interior mutability, but that one is fine).
         unsafe { data.as_ref().expect("We shall be set up already") }
     }
     fn ensure() -> &'static Self {