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Tracking Issue for const_ptr_as_ref
#91822
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Make `PTR::as_ref` and similar methods `const`. Tracking issue: rust-lang#91822 Feature gate: `#![feature(const_ptr_as_ref)]` ```rust // core::ptr impl<T: ?Sized> *const T { pub const unsafe fn as_ref<'a>(self) -> Option<&'a T>; pub const unsafe fn as_uninit_ref<'a>(self) -> Option<&'a MaybeUninit<T>> where T: Sized; pub const unsafe fn as_uninit_slice<'a>(self) -> Option<&'a [MaybeUninit<T>]>; } impl<T: ?Sized> *mut T { pub const unsafe fn as_ref<'a>(self) -> Option<&'a T>; pub const unsafe fn as_uninit_ref<'a>(self) -> Option<&'a MaybeUninit<T>> where T: Sized; pub const unsafe fn as_mut<'a>(self) -> Option<&'a mut T>; pub const unsafe fn as_uninit_mut<'a>(self) -> Option<&'a mut MaybeUninit<T>> where T: Sized; pub const unsafe fn as_uninit_slice<'a>(self) -> Option<&'a [MaybeUninit<T>]>; pub const unsafe fn as_uninit_slice_mut<'a>(self) -> Option<&'a mut [MaybeUninit<T>]>; } impl<T: Sized> NonNull<T> { pub const unsafe fn as_uninit_ref<'a>(&self) -> &'a MaybeUninit<T>; pub const unsafe fn as_uninit_mut<'a>(&mut self) -> &'a mut MaybeUninit<T>; } impl<T: ?Sized> NonNull<T> { pub const unsafe fn as_ref<'a>(&self) -> &'a T; pub const unsafe fn as_mut<'a>(&mut self) -> &'a mut T; pub const unsafe fn as_uninit_slice<'a>(&self) -> &'a [MaybeUninit<T>]; pub const unsafe fn as_uninit_slice_mut<'a>(&self) -> &'a mut [MaybeUninit<T>]; } ```
`const`-stablilize `NonNull::as_ref` A bunch of pointer to reference methods have been made unstably const some time ago in rust-lang#91823 under the feature gate `const_ptr_as_ref`. Out of these, `NonNull::as_ref` can be implemented as a `const fn` in stable rust today, so i hereby propose to const stabilize this function only. Tracking issue: rust-lang#91822 `@rustbot` label +T-libs-api -T-libs
`const`-stablilize `NonNull::as_ref` A bunch of pointer to reference methods have been made unstably const some time ago in rust-lang#91823 under the feature gate `const_ptr_as_ref`. Out of these, `NonNull::as_ref` can be implemented as a `const fn` in stable rust today, so i hereby propose to const stabilize this function only. Tracking issue: rust-lang#91822 ``@rustbot`` label +T-libs-api -T-libs
… r=workingjubilee Implement ptr_as_ref_unchecked Implementation of rust-lang#122034. Prefixed the feature name with `ptr_` for clarity. Linked const-unstability to rust-lang#91822, so the post there should probably be updated to mentions the 3 new methods when/if this PR is merged.
… r=workingjubilee Implement ptr_as_ref_unchecked Implementation of rust-lang#122034. Prefixed the feature name with `ptr_` for clarity. Linked const-unstability to rust-lang#91822, so the post there should probably be updated to mentions the 3 new methods when/if this PR is merged.
… r=workingjubilee Implement ptr_as_ref_unchecked Implementation of rust-lang#122034. Prefixed the feature name with `ptr_` for clarity. Linked const-unstability to rust-lang#91822, so the post there should probably be updated to mentions the 3 new methods when/if this PR is merged.
Rollup merge of rust-lang#122492 - GrigorenkoPV:ptr_as_ref_unchecked, r=workingjubilee Implement ptr_as_ref_unchecked Implementation of rust-lang#122034. Prefixed the feature name with `ptr_` for clarity. Linked const-unstability to rust-lang#91822, so the post there should probably be updated to mentions the 3 new methods when/if this PR is merged.
Hello! Now that #122492 has been merged, 3 new methods are also const-gated behind this flag
Should they be added to the OP? |
I have added them to the list. |
@rust-lang/libs-api I propose we const-stabilize the subset of the methods above that are stable for non-const calls: // core::ptr
impl<T: ?Sized> *const T {
pub const unsafe fn as_ref<'a>(self) -> Option<&'a T>;
}
impl<T: ?Sized> *mut T {
pub const unsafe fn as_ref<'a>(self) -> Option<&'a T>;
pub const unsafe fn as_mut<'a>(self) -> Option<&'a mut T>;
}
impl<T: ?Sized> NonNull<T> {
pub const unsafe fn as_mut<'a>(&mut self) -> &'a mut T;
} The rest should be moved to the feature gate tracking their general stability, no separate const-feature-gate is needed. (EDIT: that is happening in #130164) |
Ah wait, the So then only one function is left to be stabilized here: |
@rfcbot fcp merge Subsequent to #129195, we are ready to stabilize rust/library/core/src/ptr/non_null.rs Lines 400 to 404 in d7522d8
This function is the rust/library/core/src/ptr/non_null.rs Lines 362 to 367 in d7522d8
|
Team member @dtolnay has proposed to merge this. The next step is review by the rest of the tagged team members: No concerns currently listed. Once a majority of reviewers approve (and at most 2 approvals are outstanding), this will enter its final comment period. If you spot a major issue that hasn't been raised at any point in this process, please speak up! See this document for info about what commands tagged team members can give me. |
move some const fn out of the const_ptr_as_ref feature When a `const fn` is still `#[unstable]`, it should generally use the same feature to track its regular stability and const-stability. Then when that feature moves towards stabilization we can decide whether the const-ness can be stabilized as well, or whether it should be moved into a new feature. Also, functions like `ptr::as_ref` (which returns an `Option<&mut T>`) require `is_null`, which is tricky and blocked on some design concerns (see rust-lang#74939). So move those to the is_null feature gate, as they should be stabilized together with `ptr.is_null()`. Affects rust-lang#91822, rust-lang#122034, rust-lang#75402, rust-lang#74939
move some const fn out of the const_ptr_as_ref feature When a `const fn` is still `#[unstable]`, it should generally use the same feature to track its regular stability and const-stability. Then when that feature moves towards stabilization we can decide whether the const-ness can be stabilized as well, or whether it should be moved into a new feature. Also, functions like `ptr::as_ref` (which returns an `Option<&mut T>`) require `is_null`, which is tricky and blocked on some design concerns (see rust-lang#74939). So move those to the is_null feature gate, as they should be stabilized together with `ptr.is_null()`. Affects rust-lang#91822, rust-lang#122034, rust-lang#75402, rust-lang#74939
Rollup merge of rust-lang#130164 - RalfJung:const_ptr_as_ref, r=dtolnay move some const fn out of the const_ptr_as_ref feature When a `const fn` is still `#[unstable]`, it should generally use the same feature to track its regular stability and const-stability. Then when that feature moves towards stabilization we can decide whether the const-ness can be stabilized as well, or whether it should be moved into a new feature. Also, functions like `ptr::as_ref` (which returns an `Option<&mut T>`) require `is_null`, which is tricky and blocked on some design concerns (see rust-lang#74939). So move those to the is_null feature gate, as they should be stabilized together with `ptr.is_null()`. Affects rust-lang#91822, rust-lang#122034, rust-lang#75402, rust-lang#74939
🔔 This is now entering its final comment period, as per the review above. 🔔 |
The final comment period, with a disposition to merge, as per the review above, is now complete. As the automated representative of the governance process, I would like to thank the author for their work and everyone else who contributed. This will be merged soon. |
…-referees, r=tgross35 Stabilize 5 `const_mut_refs`-dependent API Since `const_mut_refs` and `const_refs_to_cell` have been stabilized, we now may create mutable references inside our library API. Thus we now stabilize the `const fn` version of these public library APIs which required such in their implementation: - const `NonNull::as_mut` rust-lang#91822 (comment) - const `slice::{first,last}_mut`: rust-lang#83570 (comment) - const `str::as_{mut_ptr,bytes_mut}`: rust-lang#130086 (comment) - const `str::from_utf8_unchecked_mut`: rust-lang#91005 (comment) - const `UnsafeCell::get_mut`: rust-lang#88836 (comment)
…-referees, r=tgross35 Stabilize 5 `const_mut_refs`-dependent API Since `const_mut_refs` and `const_refs_to_cell` have been stabilized, we now may create mutable references inside our library API. Thus we now stabilize the `const fn` version of these public library APIs which required such in their implementation: - const `NonNull::as_mut` rust-lang#91822 (comment) - const `slice::{first,last}_mut`: rust-lang#83570 (comment) - const `str::as_{mut_ptr,bytes_mut}`: rust-lang#130086 (comment) - const `str::from_utf8_unchecked_mut`: rust-lang#91005 (comment) - const `UnsafeCell::get_mut`: rust-lang#88836 (comment)
…-referees, r=tgross35 Stabilize 5 `const_mut_refs`-dependent API Since `const_mut_refs` and `const_refs_to_cell` have been stabilized, we now may create mutable references inside our library API. Thus we now stabilize the `const fn` version of these public library APIs which required such in their implementation: - const `NonNull::as_mut` rust-lang#91822 (comment) - const `slice::{first,last}_mut`: rust-lang#83570 (comment) - const `str::as_{mut_ptr,bytes_mut}`: rust-lang#130086 (comment) - const `str::from_utf8_unchecked_mut`: rust-lang#91005 (comment) - const `UnsafeCell::get_mut`: rust-lang#88836 (comment)
Rollup merge of rust-lang#131177 - workingjubilee:stabilize-const-mut-referees, r=tgross35 Stabilize 5 `const_mut_refs`-dependent API Since `const_mut_refs` and `const_refs_to_cell` have been stabilized, we now may create mutable references inside our library API. Thus we now stabilize the `const fn` version of these public library APIs which required such in their implementation: - const `NonNull::as_mut` rust-lang#91822 (comment) - const `slice::{first,last}_mut`: rust-lang#83570 (comment) - const `str::as_{mut_ptr,bytes_mut}`: rust-lang#130086 (comment) - const `str::from_utf8_unchecked_mut`: rust-lang#91005 (comment) - const `UnsafeCell::get_mut`: rust-lang#88836 (comment)
Feature gate:
#![feature(const_ptr_as_ref)]
Public API
Steps / History
PTR::as_ref
and similar methodsconst
. #91823Unresolved Questions
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