Calling init multiple times will leak AtomicPtr in slot with thread panicking.

[Shuran Sun]

signal-hook/src/iterator/exfiltrator/raw.rs

Lines 87 to 94 in 7dfed90

 fn init(&self, slot: &Self::Storage, _: c_int) { 
     let new = Box::default(); 
     let old = slot.0.swap(Box::into_raw(new), Ordering::Release); 
     // We leak the pointer on purpose here. This is invalid state anyway and must not happen, 
     // but if it still does, we can't drop that while some other thread might still be having 
     // the raw pointer. 
     assert!(old.is_null(), "Init called multiple times"); 
 } 

Noticed that if init is called multiple times, the code will panic.

Probable fix is like:
Use compare_and_exchange and only store the value when the slot.0 is null.

[Michal 'vorner' Vaner]

Hello

Can you explain why you think this is actually a bug? Calling init multiple times is invalid use and the crate doesn't use it that way. So why spend extra effort on supporting it?

I believe that while it would panic, that it still does not lead to UB or anything.