Make PointerLike opt-in instead of built-in
#133226
Merged
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
|
r? @Nadrieril rustbot has assigned @Nadrieril. Use |
rustbot
added
S-waiting-on-review
|
r? lcnr |
lcnr
reviewed
Nov 20, 2024
lcnr
reviewed
Nov 20, 2024
lcnr
reviewed
Nov 20, 2024
|
this seems reasonable to me and r=me on the impl after nits, idk about the lang side here 😁 I agree with the backcompat concerns, I feel like layout cycles are something we can definitely solve in the solver |
compiler-errors
force-pushed
the
opt-in-pointer-like
branch
from
ccfe08a
to
94260bd
Compare
|
I added two FIXMEs. @bors r=lcnr |
bors
added
S-waiting-on-bors
compiler-errors
force-pushed
the
opt-in-pointer-like
branch
from
94260bd
to
228068b
Compare
|
@bors r=lcnr |
matthiaskrgr
added a commit
to matthiaskrgr/rust
that referenced
this pull request
Nov 20, 2024
…e, r=lcnr Make `PointerLike` opt-in instead of built-in The `PointerLike` trait currently is a built-in trait that computes the layout of the type. This is a bit problematic, because types implement this trait automatically. Since this can be broken due to semver-compatible changes to a type's layout, this is undesirable. Also, calling `layout_of` in the trait system also causes cycles. This PR makes the trait implemented via regular impls, and adds additional validation on top to make sure that those impls are valid. This could eventually be `derive()`d for custom smart pointers, and we can trust *that* as a semver promise rather than risking library authors accidentally breaking it. On the other hand, we may never expose `PointerLike`, but at least now the implementation doesn't invoke `layout_of` which could cause ICEs or cause cycles. Right now for a `PointerLike` impl to be valid, it must be an ADT that is `repr(transparent)` and the non-1zst field needs to implement `PointerLike`. There are also some primitive impls for `&T`/ `&mut T`/`*const T`/`*mut T`/`Box<T>`.
This was referenced Nov 20, 2024
bors
added a commit
to rust-lang-ci/rust
that referenced
this pull request
Nov 20, 2024
…iaskrgr Rollup of 6 pull requests Successful merges: - rust-lang#129838 (uefi: process: Add args support) - rust-lang#130800 (Mark `get_mut` and `set_position` in `std::io::Cursor` as const.) - rust-lang#132708 (Point at `const` definition when used instead of a binding in a `let` statement) - rust-lang#133226 (Make `PointerLike` opt-in instead of built-in) - rust-lang#133244 (Account for `wasm32v1-none` when exporting TLS symbols) - rust-lang#133257 (Add `UnordMap::clear` method) r? `@ghost` `@rustbot` modify labels: rollup
rust-timer
added a commit
to rust-lang-ci/rust
that referenced
this pull request
Nov 21, 2024
Rollup merge of rust-lang#133226 - compiler-errors:opt-in-pointer-like, r=lcnr Make `PointerLike` opt-in instead of built-in The `PointerLike` trait currently is a built-in trait that computes the layout of the type. This is a bit problematic, because types implement this trait automatically. Since this can be broken due to semver-compatible changes to a type's layout, this is undesirable. Also, calling `layout_of` in the trait system also causes cycles. This PR makes the trait implemented via regular impls, and adds additional validation on top to make sure that those impls are valid. This could eventually be `derive()`d for custom smart pointers, and we can trust *that* as a semver promise rather than risking library authors accidentally breaking it. On the other hand, we may never expose `PointerLike`, but at least now the implementation doesn't invoke `layout_of` which could cause ICEs or cause cycles. Right now for a `PointerLike` impl to be valid, it must be an ADT that is `repr(transparent)` and the non-1zst field needs to implement `PointerLike`. There are also some primitive impls for `&T`/ `&mut T`/`*const T`/`*mut T`/`Box<T>`.
This was referenced Nov 21, 2024
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
The
PointerLiketrait currently is a built-in trait that computes the layout of the type. This is a bit problematic, because types implement this trait automatically. Since this can be broken due to semver-compatible changes to a type's layout, this is undesirable. Also, callinglayout_ofin the trait system also causes cycles.This PR makes the trait implemented via regular impls, and adds additional validation on top to make sure that those impls are valid. This could eventually be
derive()d for custom smart pointers, and we can trust that as a semver promise rather than risking library authors accidentally breaking it.On the other hand, we may never expose
PointerLike, but at least now the implementation doesn't invokelayout_ofwhich could cause ICEs or cause cycles.Right now for a
PointerLikeimpl to be valid, it must be an ADT that isrepr(transparent)and the non-1zst field needs to implementPointerLike. There are also some primitive impls for&T/&mut T/*const T/*mut T/Box<T>.