bjoernager/rust
bjoernager/rust
1
Fork 0
Code Activity

trim section on managed-box model

Browse source
This commit is contained in:
Gray Olson 2023-10-03 13:17:26 +02:00 • committed by Manish Goregaokar
parent 9997114e14
commit 058fb50ecd
1 changed files with 4 additions and 9 deletions
Download patch file Download diff file Expand all files Collapse all files

13
library/core/src/pin.rs
View file

@ -183,14 +183,8 @@
//! access to that data to ensure no *moves* or other invalidation occurs, and finally //! access to that data to ensure no *moves* or other invalidation occurs, and finally
//! provide a safe interface on top. //! provide a safe interface on top.
//! //!
//! There are a couple of linked disadvantages to using this model. The core issue is a lack //! There are a couple of linked disadvantages to using this model. The most significant is that
//! of generality. This is an issue because it means that each individual type that implements //! each individual object must assume it is *on its own* to ensure
//! such an interface does so on its own. Each developer implementing such a type must themselves
//! think through all the guarantees needed to ensure the API they present is sound. We would
//! rather build a shared understanding of the problem space and encode that understanding into a
//! shared interface to solve it which everyone helps validate.
//!
//! In addition, in this model, each individual object must assume it is *on its own* to ensure
//! that its data does not become *moved* or otherwise invalidated. Since there is no shared //! that its data does not become *moved* or otherwise invalidated. Since there is no shared
//! contract between values of different types, an object cannot assume that others interacting //! contract between values of different types, an object cannot assume that others interacting
//! with it will properly respect the invariants around interacting with its data and must //! with it will properly respect the invariants around interacting with its data and must
@ -198,7 +192,8 @@
//! requires at least a level of pointer indirection each time a new object is added to the mix //! requires at least a level of pointer indirection each time a new object is added to the mix
//! (and, practically, a heap allocation). //! (and, practically, a heap allocation).
//! //!
//! This is the key thing that drove Rust towards a different model. It is particularly a problem //! Although there were other reason as well, this issue of expensive composition is the key thing
//! that drove Rust towards adopting a different model. It is particularly a problem
//! when one considers, for exapmle, the implications of composing together the [`Future`]s which //! when one considers, for exapmle, the implications of composing together the [`Future`]s which
//! will eventaully make up an asynchronous task (including address-sensitive `async fn` state //! will eventaully make up an asynchronous task (including address-sensitive `async fn` state
//! machines). It is plausible that there could be many layers of [`Future`]s composed together, //! machines). It is plausible that there could be many layers of [`Future`]s composed together,