diff options
Diffstat (limited to 'vendor/triomphe/src/offset_arc.rs')
| -rw-r--r-- | vendor/triomphe/src/offset_arc.rs | 20 |
1 files changed, 12 insertions, 8 deletions
diff --git a/vendor/triomphe/src/offset_arc.rs b/vendor/triomphe/src/offset_arc.rs index 9345416d4..4d7707e77 100644 --- a/vendor/triomphe/src/offset_arc.rs +++ b/vendor/triomphe/src/offset_arc.rs @@ -105,16 +105,20 @@ impl<T> OffsetArc<T> { T: Clone, { unsafe { - // extract the OffsetArc as an owned variable + // extract the OffsetArc as an owned variable. This does not modify + // the refcount and we should be careful to not drop `this` let this = ptr::read(self); - // treat it as a real Arc - let mut arc = Arc::from_raw_offset(this); - // obtain the mutable reference. Cast away the lifetime - // This may mutate `arc` - let ret = Arc::make_mut(&mut arc) as *mut _; + // treat it as a real Arc, but wrapped in a ManuallyDrop + // in case `Arc::make_mut()` panics in the clone impl + let mut arc = ManuallyDrop::new(Arc::from_raw_offset(this)); + // obtain the mutable reference. Cast away the lifetime since + // we have the right lifetime bounds in the parameters. + // This may mutate `arc`. + let ret = Arc::make_mut(&mut *arc) as *mut _; // Store the possibly-mutated arc back inside, after converting - // it to a OffsetArc again - ptr::write(self, Arc::into_raw_offset(arc)); + // it to a OffsetArc again. Release the ManuallyDrop. + // This also does not modify the refcount or call drop on self + ptr::write(self, Arc::into_raw_offset(ManuallyDrop::into_inner(arc))); &mut *ret } } |