LocalKey<T>: document that the dtor cannot unwind

Author: ShE3py

Diff for: library/std/src/thread/local.rs

@@ -22,12 +22,17 @@ use crate::fmt;
 ///
 /// Initialization is dynamically performed on the first call to a setter (e.g.
 /// [`with`]) within a thread, and values that implement [`Drop`] get
-/// destructed when a thread exits. Some caveats apply, which are explained below.
+/// destructed when a thread exits. Some platform-specific caveats apply, which
+/// are explained below.
+/// Note that, should the destructor panics, the whole process will be [aborted],
+/// as the TLS destructor cannot unwind.
 ///
 /// A `LocalKey`'s initializer cannot recursively depend on itself. Using a
 /// `LocalKey` in this way may cause panics, aborts or infinite recursion on
 /// the first call to `with`.
 ///
+/// [abort]: crate::process::abort
+///
 /// # Single-thread Synchronization
 ///
 /// Though there is no potential race with other threads, it is still possible to