mirror of
https://github.com/rust-lang/rust.git
synced 2026-05-30 13:06:28 +03:00
Matthias Krüger
8d52aae968
Reduce `Box::default` stack copies in debug mode The `Box::new(T::default())` implementation of `Box::default` only had two stack copies in debug mode, compared to the current version, which has four. By avoiding creating any `MaybeUninit<T>`'s and just writing `T` directly to the `Box` pointer, the stack usage in debug mode remains the same as the old version. Another option would be to mark `Box::write` as `#[inline(always)]`, and change it's implementation to to avoid calling `MaybeUninit::write` (which creates a `MaybeUninit<T>` on the stack) and to use `ptr::write` instead. Fixes: #136043