Add fn into_raw_with_allocator to Rc/Arc/Weak. by zachs18 · Pull Request #125093 · rust-lang/rust (original) (raw)
Split out from #119761
Add fn into_raw_with_allocator for Rc/rc::Weak1/Arc/sync::Weak.
- Pairs with
from_raw_in(which already exists on all 4 types). - Name matches
Box::into_raw_with_allocator. - Associated fns on
Rc/Arc, methods onWeaks. Future PR/ACP
As a follow-on to this PR, I plan to make a PR/ACP later to move into_raw(_parts) from Container<_, A: Allocator> to only Container<_, Global> (where Container = Vec/Box/Rc/rc::Weak/Arc/sync::Weak) so that users of non-Global allocators have to explicitly handle the allocator when using into_raw-like APIs.
The current behaviors of stdlib containers are inconsistent with respect to what happens to the allocator when into_raw is called (which does not return the allocator)
| Type | into_raw currently callable with | behavior of into_raw |
|---|---|---|
| Box | any allocator | allocator is dropped |
| Vec | any allocator | allocator is forgotten |
| Arc/Rc/Weak | any allocator | allocator is forgotten(Arc) (sync::Weak) (Rc) (rc::Weak) |
In my opinion, neither implicitly dropping nor implicitly forgetting the allocator is ideal; dropping it could immediately invalidate the returned pointer, and forgetting it could unintentionally leak memory. My (to-be) proposed solution is to just forbid calling into_raw(_parts) on containers with non-Global allocators, and require calling into_raw_with_allocator(/Vec::into_raw_parts_with_alloc)
Footnotes
- Technically,
rc::Weak::into_raw_with_allocatoris not newly added, as it was modified and renamed fromrc::Weak::into_raw_and_alloc. ↩