From a08df28a6fdb5a2c781f01082e630faa2d7ccde9 Mon Sep 17 00:00:00 2001 From: Mark Rousskov Date: Mon, 23 Dec 2019 08:13:12 -0500 Subject: [PATCH] Document that calling Drop, even after it panics, is UB --- src/libcore/ops/drop.rs | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/src/libcore/ops/drop.rs b/src/libcore/ops/drop.rs index eae63ea2390a8..5233b475c4646 100644 --- a/src/libcore/ops/drop.rs +++ b/src/libcore/ops/drop.rs @@ -99,9 +99,15 @@ pub trait Drop { /// Given that a [`panic!`] will call `drop` as it unwinds, any [`panic!`] /// in a `drop` implementation will likely abort. /// + /// Note that even if this panics, the value is considered to be dropped; + /// you must not cause `drop` to be called again. This is normally automatically + /// handled by the compiler, but when using unsafe code, can sometimes occur + /// unintentionally, particularly when using [`std::ptr::drop_in_place`]. + /// /// [E0040]: ../../error-index.html#E0040 /// [`panic!`]: ../macro.panic.html /// [`std::mem::drop`]: ../../std/mem/fn.drop.html + /// [`std::ptr::drop_in_place`]: ../../std/ptr/fn.drop_in_place.html #[stable(feature = "rust1", since = "1.0.0")] fn drop(&mut self); }