diff options
Diffstat (limited to 'library/alloc/src/boxed')
-rw-r--r-- | library/alloc/src/boxed/thin.rs | 47 |
1 files changed, 34 insertions, 13 deletions
diff --git a/library/alloc/src/boxed/thin.rs b/library/alloc/src/boxed/thin.rs index c477c4490..c1a82e452 100644 --- a/library/alloc/src/boxed/thin.rs +++ b/library/alloc/src/boxed/thin.rs @@ -226,24 +226,45 @@ impl<H> WithHeader<H> { // - Assumes that either `value` can be dereferenced, or is the // `NonNull::dangling()` we use when both `T` and `H` are ZSTs. unsafe fn drop<T: ?Sized>(&self, value: *mut T) { + struct DropGuard<H> { + ptr: NonNull<u8>, + value_layout: Layout, + _marker: PhantomData<H>, + } + + impl<H> Drop for DropGuard<H> { + fn drop(&mut self) { + unsafe { + // SAFETY: Layout must have been computable if we're in drop + let (layout, value_offset) = + WithHeader::<H>::alloc_layout(self.value_layout).unwrap_unchecked(); + + // Note: Don't deallocate if the layout size is zero, because the pointer + // didn't come from the allocator. + if layout.size() != 0 { + alloc::dealloc(self.ptr.as_ptr().sub(value_offset), layout); + } else { + debug_assert!( + value_offset == 0 + && mem::size_of::<H>() == 0 + && self.value_layout.size() == 0 + ); + } + } + } + } + unsafe { - let value_layout = Layout::for_value_raw(value); - // SAFETY: Layout must have been computable if we're in drop - let (layout, value_offset) = Self::alloc_layout(value_layout).unwrap_unchecked(); + // `_guard` will deallocate the memory when dropped, even if `drop_in_place` unwinds. + let _guard = DropGuard { + ptr: self.0, + value_layout: Layout::for_value_raw(value), + _marker: PhantomData::<H>, + }; // We only drop the value because the Pointee trait requires that the metadata is copy // aka trivially droppable. ptr::drop_in_place::<T>(value); - - // Note: Don't deallocate if the layout size is zero, because the pointer - // didn't come from the allocator. - if layout.size() != 0 { - alloc::dealloc(self.0.as_ptr().sub(value_offset), layout); - } else { - debug_assert!( - value_offset == 0 && mem::size_of::<H>() == 0 && value_layout.size() == 0 - ); - } } } |