diff options
| -rw-r--r-- | library/alloc/src/vec/in_place_collect.rs | 7 | ||||
| -rw-r--r-- | library/alloc/src/vec/into_iter.rs | 7 |
2 files changed, 11 insertions, 3 deletions
diff --git a/library/alloc/src/vec/in_place_collect.rs b/library/alloc/src/vec/in_place_collect.rs index 359f1a9cec2..83ed3d915a2 100644 --- a/library/alloc/src/vec/in_place_collect.rs +++ b/library/alloc/src/vec/in_place_collect.rs @@ -55,6 +55,9 @@ //! This is handled by the [`InPlaceDrop`] guard for sink items (`U`) and by //! [`vec::IntoIter::forget_allocation_drop_remaining()`] for remaining source items (`T`). //! +//! If dropping any remaining source item (`T`) panics then [`InPlaceDstBufDrop`] will handle dropping +//! the already collected sink items (`U`) and freeing the allocation. +//! //! [`vec::IntoIter::forget_allocation_drop_remaining()`]: super::IntoIter::forget_allocation_drop_remaining() //! //! # O(1) collect @@ -194,8 +197,8 @@ where // Drop any remaining values at the tail of the source but prevent drop of the allocation // itself once IntoIter goes out of scope. // If the drop panics then we also try to drop the destination buffer and its elements. - // This is safe because `forget_allocation_drop_remaining` forgets the allocation *before* - // trying to drop the remaining elements. + // This is safe because `forget_allocation_drop_remaining` immediately forgets the allocation + // and won't panic before that. // // Note: This access to the source wouldn't be allowed by the TrustedRandomIteratorNoCoerce // contract (used by SpecInPlaceCollect below). But see the "O(1) collect" section in the diff --git a/library/alloc/src/vec/into_iter.rs b/library/alloc/src/vec/into_iter.rs index 1b483e3fc77..b5a03392a17 100644 --- a/library/alloc/src/vec/into_iter.rs +++ b/library/alloc/src/vec/into_iter.rs @@ -96,13 +96,16 @@ impl<T, A: Allocator> IntoIter<T, A> { } /// Drops remaining elements and relinquishes the backing allocation. + /// This method guarantees it won't panic before relinquishing + /// the backing allocation. /// /// This is roughly equivalent to the following, but more efficient /// /// ``` /// # let mut into_iter = Vec::<u8>::with_capacity(10).into_iter(); + /// let mut into_iter = std::mem::replace(&mut into_iter, Vec::new().into_iter()); /// (&mut into_iter).for_each(core::mem::drop); - /// unsafe { core::ptr::write(&mut into_iter, Vec::new().into_iter()); } + /// std::mem::forget(into_iter); /// ``` /// /// This method is used by in-place iteration, refer to the vec::in_place_collect @@ -119,6 +122,8 @@ impl<T, A: Allocator> IntoIter<T, A> { self.ptr = self.buf.as_ptr(); self.end = self.buf.as_ptr(); + // Dropping the remaining elements can panic, so this needs to be + // done only after updating the other fields. unsafe { ptr::drop_in_place(remaining); } |