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Clarify that ManuallyDrop<T> has same layout as T #88375
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(rust-highfive has picked a reviewer for you, use r? to override) |
Removing waiting-on-review, since this is blocked on the UCG issue. |
@joshtriplett it feels like a PR modifying the std docs here is the way to make progress on a guarantee (in the absence of some documentation for what else should be done). If it isn't, then it doesn't seem appropriate to leave this PR open -- while it's not a huge cost, if we're not expecting a decision for an indeterminate period or discussion, it doesn't seem useful to keep PRs idle for a long time. Perhaps this should be nominated for some team? |
I don't have any objections to just FCPing this here; it just seemed like the consensus thus far was that this was a matter for the UCG. |
What's the best way to move this forward? |
I think this is blatantly correct, and worth documenting. @rfcbot fcp merge |
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. |
🔔 This is now entering its final comment period, as per the review above. 🔔 |
@bors r+ rollup |
📌 Commit 01b9fac has been approved by |
Clarify that ManuallyDrop<T> has same layout as T This PR implements the documentation change under discussion in rust-lang/unsafe-code-guidelines#302. It should not be approved or merged until the discussion there is resolved.
Rollup of 4 pull requests Successful merges: - rust-lang#88375 (Clarify that ManuallyDrop<T> has same layout as T) - rust-lang#93755 (Allow comparing `Vec`s with different allocators using `==`) - rust-lang#95016 (Docs: make Vec::from_raw_parts documentation less strict) - rust-lang#95098 (impl From<&[T; N]> and From<&mut [T; N]> for Vec<T>) Failed merges: r? `@ghost` `@rustbot` modify labels: rollup
Pkgsrc changes: * adapt patches * new checksums Upstream changes: Version 1.61.0 (2022-05-19) ========================== Language -------- - [`const fn` signatures can now include generic trait bounds][93827] - [`const fn` signatures can now use `impl Trait` in argument and return position][93827] - [Function pointers can now be created, cast, and passed around in a `const fn`][93827] - [Recursive calls can now set the value of a function's opaque `impl Trait` return type][94081] Compiler -------- - [Linking modifier syntax in `#[link]` attributes and on the command line, as well as the `whole-archive` modifier specifically, are now supported][93901] - [The `char` type is now described as UTF-32 in debuginfo][89887] - The [`#[target_feature]`][target_feature] attribute [can now be used with aarch64 features][90621] - X86 [`#[target_feature = "adx"]` is now stable][93745] Libraries --------- - [`ManuallyDrop<T>` is now documented to have the same layout as `T`][88375] - [`#[ignore = "#"]` messages are printed when running tests][92714] - [Consistently show absent stdio handles on Windows as NULL handles][93263] - [Make `std::io::stdio::lock()` return `'static` handles.][93965] Previously, the creation of locked handles to stdin/stdout/stderr would borrow the handles being locked, which prevented writing `let out = std::io::stdout().lock();` because `out` would outlive the return value of `stdout()`. Such code now works, eliminating a common pitfall that affected many Rust users. - [`Vec::from_raw_parts` is now less restrictive about its inputs][95016] - [`std::thread::available_parallelism` now takes cgroup quotas into account.][92697] Since `available_parallelism` is often used to create a thread pool for parallel computation, which may be CPU-bound for performance, `available_parallelism` will return a value consistent with the ability to use that many threads continuously, if possible. For instance, in a container with 8 virtual CPUs but quotas only allowing for 50% usage, `available_parallelism` will return 4. Stabilized APIs --------------- - [`Pin::static_mut`] - [`Pin::static_ref`] - [`Vec::retain_mut`] - [`VecDeque::retain_mut`] - [`Write` for `Cursor<[u8; N]>`][cursor-write-array] - [`std::os::unix::net::SocketAddr::from_pathname`] - [`std::process::ExitCode`] and [`std::process::Termination`]. The stabilization of these two API s now makes it possible for programs to return errors from `main` with custom exit codes. - [`std::thread::JoinHandle::is_finished`] These APIs are now usable in const contexts: - [`<*const T>::offset` and `<*mut T>::offset`][ptr-offset] - [`<*const T>::wrapping_offset` and `<*mut T>::wrapping_offset`] [ptr-wrapping_offset] - [`<*const T>::add` and `<*mut T>::add`][ptr-add] - [`<*const T>::sub` and `<*mut T>::sub`][ptr-sub] - [`<*const T>::wrapping_add` and `<*mut T>::wrapping_add`][ptr-wrapping_add] - [`<*const T>::wrapping_sub` and `<*mut T>::wrapping_sub`][ptr-wrapping_sub] - [`<[T]>::as_mut_ptr`][slice-as_mut_ptr] - [`<[T]>::as_ptr_range`][slice-as_ptr_range] - [`<[T]>::as_mut_ptr_range`][slice-as_mut_ptr_range] Cargo ----- No feature changes, but see compatibility notes. Compatibility Notes ------------------- - Previously native static libraries were linked as `whole-archive` in some cases, but now rustc tries not to use `whole-archive` unless explicitly requested. This [change][93901] may result in linking errors in some cases. To fix such errors, native libraries linked from the command line, build scripts, or [`#[link]` attributes][link-attr] need to - (more common) either be reordered to respect dependencies between them (if `a` depends on `b` then `a` should go first and `b` second) - (less common) or be updated to use the [`+whole-archive`] modifier. - [Catching a second unwind from FFI code while cleaning up from a Rust panic now causes the process to abort][92911] - [Proc macros no longer see `ident` matchers wrapped in groups][92472] - [The number of `#` in `r#` raw string literals is now required to be less than 256][95251] - [When checking that a dyn type satisfies a trait bound, supertrait bounds are now enforced][92285] - [`cargo vendor` now only accepts one value for each `--sync` flag] [cargo/10448] - [`cfg` predicates in `all()` and `any()` are always evaluated to detect errors, instead of short-circuiting.][94295] The compatibility considerations here arise in nightly-only code that used the short-circuiting behavior of `all` to write something like `cfg(all(feature = "nightly", syntax-requiring-nightly))`, which will now fail to compile. Instead, use either `cfg_attr(feature = "nightly", ...)` or nested uses of `cfg`. - [bootstrap: static-libstdcpp is now enabled by default, and can now be disabled when llvm-tools is enabled][94832] Internal Changes ---------------- These changes provide no direct user facing benefits, but represent significant improvements to the internals and overall performance of rustc and related tools. - [debuginfo: Refactor debuginfo generation for types][94261] - [Remove the everybody loops pass][93913] [88375]: rust-lang/rust#88375 [89887]: rust-lang/rust#89887 [90621]: rust-lang/rust#90621 [92285]: rust-lang/rust#92285 [92472]: rust-lang/rust#92472 [92697]: rust-lang/rust#92697 [92714]: rust-lang/rust#92714 [92911]: rust-lang/rust#92911 [93263]: rust-lang/rust#93263 [93745]: rust-lang/rust#93745 [93827]: rust-lang/rust#93827 [93901]: rust-lang/rust#93901 [93913]: rust-lang/rust#93913 [93965]: rust-lang/rust#93965 [94081]: rust-lang/rust#94081 [94261]: rust-lang/rust#94261 [94295]: rust-lang/rust#94295 [94832]: rust-lang/rust#94832 [95016]: rust-lang/rust#95016 [95251]: rust-lang/rust#95251 [`+whole-archive`]: https://doc.rust-lang.org/stable/rustc/command-line-arguments.html#linking-modifiers-whole-archive [`Pin::static_mut`]: https://doc.rust-lang.org/stable/std/pin/struct.Pin.html#method.static_mut [`Pin::static_ref`]: https://doc.rust-lang.org/stable/std/pin/struct.Pin.html#method.static_ref [`Vec::retain_mut`]: https://doc.rust-lang.org/stable/std/vec/struct.Vec.html#method.retain_mut [`VecDeque::retain_mut`]: https://doc.rust-lang.org/stable/std/collections/struct.VecDeque.html#method.retain_mut [`std::os::unix::net::SocketAddr::from_pathname`]: https://doc.rust-lang.org/stable/std/os/unix/net/struct.SocketAddr.html#method.from_pathname [`std::process::ExitCode`]: https://doc.rust-lang.org/stable/std/process/struct.ExitCode.html [`std::process::Termination`]: https://doc.rust-lang.org/stable/std/process/trait.Termination.html [`std::thread::JoinHandle::is_finished`]: https://doc.rust-lang.org/stable/std/thread/struct.JoinHandle.html#method.is_finished [cargo/10448]: rust-lang/cargo#10448 [cursor-write-array]: https://doc.rust-lang.org/stable/std/io/struct.Cursor.html#impl-Write-4 [link-attr]: https://doc.rust-lang.org/stable/reference/items/external-blocks.html#the-link-attribute [ptr-add]: https://doc.rust-lang.org/stable/std/primitive.pointer.html#method.add [ptr-offset]: https://doc.rust-lang.org/stable/std/primitive.pointer.html#method.offset [ptr-sub]: https://doc.rust-lang.org/stable/std/primitive.pointer.html#method.sub [ptr-wrapping_add]: https://doc.rust-lang.org/stable/std/primitive.pointer.html#method.wrapping_add [ptr-wrapping_offset]: https://doc.rust-lang.org/stable/std/primitive.pointer.html#method.wrapping_offset [ptr-wrapping_sub]: https://doc.rust-lang.org/stable/std/primitive.pointer.html#method.wrapping_sub [slice-as_mut_ptr]: https://doc.rust-lang.org/stable/std/primitive.slice.html#method.as_mut_ptr [slice-as_mut_ptr_range]: https://doc.rust-lang.org/stable/std/primitive.slice.html#method.as_mut_ptr_range [slice-as_ptr_range]: https://doc.rust-lang.org/stable/std/primitive.slice.html#method.as_ptr_range [target_feature]: https://doc.rust-lang.org/reference/attributes/codegen.html#the-target_feature-attribute
Pkgsrc changes: * Bump required GCC to 7 (same as LLVM) to avoid ABI issues Fixes native i386 and powerpc 8.x build w/pkgsrc LLVM 14 * Bump available bootstraps to 1.61.0. * Also unlimit stacksize * Sync patches over from wip/rust * Adjust line number in patches which had non-zero offsets. * no longer pass -I/usr/pkg/include through via gcc-wrap script when building natively. Attempt at fixing version skew with curl package vs. internal version of curl (may not work...) * The NetBSD bootstraps now use .xz compression. * Use mk/atomic64.mk. Still have conditional for libatomic-links. * Default to using the internal LLVM when cross-building. Upstream changes: Version 1.62.1 (2022-07-19) ========================== Rust 1.62.1 addresses a few recent regressions in the compiler and standard library, and also mitigates a CPU vulnerability on Intel SGX. * [The compiler fixed unsound function coercions involving `impl Trait` return types.][98608] * [The compiler fixed an incremental compilation bug with `async fn` lifetimes.][98890] * [Windows added a fallback for overlapped I/O in synchronous reads and writes.][98950] * [The `x86_64-fortanix-unknown-sgx` target added a mitigation for the MMIO stale data vulnerability][98126], advisory [INTEL-SA-00615]. [98608]: rust-lang/rust#98608 [98890]: rust-lang/rust#98890 [98950]: rust-lang/rust#98950 [98126]: rust-lang/rust#98126 [INTEL-SA-00615]: https://www.intel.com/content/www/us/en/security-center/advisory/intel-sa-00615.html Version 1.62.0 (2022-06-30) ========================== Language -------- - [Stabilize `#[derive(Default)]` on enums with a `#[default]` variant][94457] - [Stop validating some checks in dead code after functions with uninhabited return types][93313] - [Fix constants not getting dropped if part of a diverging expression][94775] - [Support unit struct/enum variant in destructuring assignment][95380] - [Remove mutable_borrow_reservation_conflict lint and allow the code pattern][96268] Compiler -------- - [linker: Stop using whole-archive on dependencies of dylibs][96436] - [Make `unaligned_references` lint deny-by-default][95372] This lint is also a future compatibility lint, and is expected to eventually become a hard error. - [Only add codegen backend to dep info if -Zbinary-dep-depinfo is used][93969] - [Reject `#[thread_local]` attribute on non-static items][95006] - [Add tier 3 `aarch64-pc-windows-gnullvm` and `x86_64-pc-windows-gnullvm` targets\*][94872] - [Implement a lint to warn about unused macro rules][96150] - [Promote `x86_64-unknown-none` target to Tier 2\*][95705] \* Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support. Libraries --------- - [Move `CStr` to libcore, and `CString` to liballoc][94079] - [Windows: Use a pipe relay for chaining pipes][95841] - [Replace Linux Mutex and Condvar with futex based ones.][95035] - [Replace RwLock by a futex based one on Linux][95801] - [std: directly use pthread in UNIX parker implementation][96393] Stabilized APIs --------------- - [`bool::then_some`] - [`f32::total_cmp`] - [`f64::total_cmp`] - [`Stdin::lines`] - [`windows::CommandExt::raw_arg`] - [`impl<T: Default> Default for AssertUnwindSafe<T>`] - [`From<Rc<str>> for Rc<[u8]>`][rc-u8-from-str] - [`From<Arc<str>> for Arc<[u8]>`][arc-u8-from-str] - [`FusedIterator for EncodeWide`] - [RDM intrinsics on aarch64][stdarch/1285] Clippy ------ - [Create clippy lint against unexpectedly late drop for temporaries in match scrutinee expressions][94206] Cargo ----- - Added the `cargo add` command for adding dependencies to `Cargo.toml` from the command-line. [docs](https://doc.rust-lang.org/nightly/cargo/commands/cargo-add.html) - Package ID specs now support `name@version` syntax in addition to the previous `name:version` to align with the behavior in `cargo add` and other tools. `cargo install` and `cargo yank` also now support this syntax so the version does not need to passed as a separate flag. - The `git` and `registry` directories in Cargo's home directory (usually `~/.cargo`) are now marked as cache directories so that they are not included in backups or content indexing (on Windows). - Added automatic `@` argfile support, which will use "response files" if the command-line to `rustc` exceeds the operating system's limit. Compatibility Notes ------------------- - `cargo test` now passes `--target` to `rustdoc` if the specified target is the same as the host target. [#10594](rust-lang/cargo#10594) - [rustdoc: Remove .woff font files][96279] - [Enforce Copy bounds for repeat elements while considering lifetimes][95819] Internal Changes ---------------- - [Unify ReentrantMutex implementations across all platforms][96042] These changes provide no direct user facing benefits, but represent significant improvements to the internals and overall performance of rustc and related tools. [93313]: rust-lang/rust#93313 [93969]: rust-lang/rust#93969 [94079]: rust-lang/rust#94079 [94206]: rust-lang/rust#94206 [94457]: rust-lang/rust#94457 [94775]: rust-lang/rust#94775 [94872]: rust-lang/rust#94872 [95006]: rust-lang/rust#95006 [95035]: rust-lang/rust#95035 [95372]: rust-lang/rust#95372 [95380]: rust-lang/rust#95380 [95431]: rust-lang/rust#95431 [95705]: rust-lang/rust#95705 [95801]: rust-lang/rust#95801 [95819]: rust-lang/rust#95819 [95841]: rust-lang/rust#95841 [96042]: rust-lang/rust#96042 [96150]: rust-lang/rust#96150 [96268]: rust-lang/rust#96268 [96279]: rust-lang/rust#96279 [96393]: rust-lang/rust#96393 [96436]: rust-lang/rust#96436 [96557]: rust-lang/rust#96557 [`bool::then_some`]: https://doc.rust-lang.org/stable/std/primitive.bool.html#method.then_some [`f32::total_cmp`]: https://doc.rust-lang.org/stable/std/primitive.f32.html#method.total_cmp [`f64::total_cmp`]: https://doc.rust-lang.org/stable/std/primitive.f64.html#method.total_cmp [`Stdin::lines`]: https://doc.rust-lang.org/stable/std/io/struct.Stdin.html#method.lines [`impl<T: Default> Default for AssertUnwindSafe<T>`]: https://doc.rust-lang.org/stable/std/panic/struct.AssertUnwindSafe.html#impl-Default [rc-u8-from-str]: https://doc.rust-lang.org/stable/std/rc/struct.Rc.html#impl-From%3CRc%3Cstr%3E%3E [arc-u8-from-str]: https://doc.rust-lang.org/stable/std/sync/struct.Arc.html#impl-From%3CArc%3Cstr%3E%3E [stdarch/1285]: rust-lang/stdarch#1285 [`windows::CommandExt::raw_arg`]: https://doc.rust-lang.org/stable/std/os/windows/process/trait.CommandExt.html#tymethod.raw_arg [`FusedIterator for EncodeWide`]: https://doc.rust-lang.org/stable/std/os/windows/ffi/struct.EncodeWide.html#impl-FusedIterator Version 1.61.0 (2022-05-19) ========================== Language -------- - [`const fn` signatures can now include generic trait bounds][93827] - [`const fn` signatures can now use `impl Trait` in argument and return position][93827] - [Function pointers can now be created, cast, and passed around in a `const fn`][93827] - [Recursive calls can now set the value of a function's opaque `impl Trait` return type][94081] Compiler -------- - [Linking modifier syntax in `#[link]` attributes and on the command line, as well as the `whole-archive` modifier specifically, are now supported][93901] - [The `char` type is now described as UTF-32 in debuginfo][89887] - The [`#[target_feature]`][target_feature] attribute [can now be used with aarch64 features][90621] - X86 [`#[target_feature = "adx"]` is now stable][93745] Libraries --------- - [`ManuallyDrop<T>` is now documented to have the same layout as `T`][88375] - [`#[ignore = "#"]` messages are printed when running tests][92714] - [Consistently show absent stdio handles on Windows as NULL handles][93263] - [Make `std::io::stdio::lock()` return `'static` handles.][93965] Previously, the creation of locked handles to stdin/stdout/stderr would borrow the handles being locked, which prevented writing `let out = std::io::stdout().lock();` because `out` would outlive the return value of `stdout()`. Such code now works, eliminating a common pitfall that affected many Rust users. - [`Vec::from_raw_parts` is now less restrictive about its inputs][95016] - [`std::thread::available_parallelism` now takes cgroup quotas into account.][92697] Since `available_parallelism` is often used to create a thread pool for parallel computation, which may be CPU-bound for performance, `available_parallelism` will return a value consistent with the ability to use that many threads continuously, if possible. For instance, in a container with 8 virtual CPUs but quotas only allowing for 50% usage, `available_parallelism` will return 4. Stabilized APIs --------------- - [`Pin::static_mut`] - [`Pin::static_ref`] - [`Vec::retain_mut`] - [`VecDeque::retain_mut`] - [`Write` for `Cursor<[u8; N]>`][cursor-write-array] - [`std::os::unix::net::SocketAddr::from_pathname`] - [`std::process::ExitCode`] and [`std::process::Termination`]. The stabilization of these two API s now makes it possible for programs to return errors from `main` with custom exit codes. - [`std::thread::JoinHandle::is_finished`] These APIs are now usable in const contexts: - [`<*const T>::offset` and `<*mut T>::offset`][ptr-offset] - [`<*const T>::wrapping_offset` and `<*mut T>::wrapping_offset`] [ptr-wrapping_offset] - [`<*const T>::add` and `<*mut T>::add`][ptr-add] - [`<*const T>::sub` and `<*mut T>::sub`][ptr-sub] - [`<*const T>::wrapping_add` and `<*mut T>::wrapping_add`][ptr-wrapping_add] - [`<*const T>::wrapping_sub` and `<*mut T>::wrapping_sub`][ptr-wrapping_sub] - [`<[T]>::as_mut_ptr`][slice-as_mut_ptr] - [`<[T]>::as_ptr_range`][slice-as_ptr_range] - [`<[T]>::as_mut_ptr_range`][slice-as_mut_ptr_range] Cargo ----- No feature changes, but see compatibility notes. Compatibility Notes ------------------- - Previously native static libraries were linked as `whole-archive` in some cases, but now rustc tries not to use `whole-archive` unless explicitly requested. This [change][93901] may result in linking errors in some cases. To fix such errors, native libraries linked from the command line, build scripts, or [`#[link]` attributes][link-attr] need to - (more common) either be reordered to respect dependencies between them (if `a` depends on `b` then `a` should go first and `b` second) - (less common) or be updated to use the [`+whole-archive`] modifier. - [Catching a second unwind from FFI code while cleaning up from a Rust panic now causes the process to abort][92911] - [Proc macros no longer see `ident` matchers wrapped in groups][92472] - [The number of `#` in `r#` raw string literals is now required to be less than 256][95251] - [When checking that a dyn type satisfies a trait bound, supertrait bounds are now enforced][92285] - [`cargo vendor` now only accepts one value for each `--sync` flag] [cargo/10448] - [`cfg` predicates in `all()` and `any()` are always evaluated to detect errors, instead of short-circuiting.][94295] The compatibility considerations here arise in nightly-only code that used the short-circuiting behavior of `all` to write something like `cfg(all(feature = "nightly", syntax-requiring-nightly))`, which will now fail to compile. Instead, use either `cfg_attr(feature = "nightly", ...)` or nested uses of `cfg`. - [bootstrap: static-libstdcpp is now enabled by default, and can now be disabled when llvm-tools is enabled][94832] Internal Changes ---------------- These changes provide no direct user facing benefits, but represent significant improvements to the internals and overall performance of rustc and related tools. - [debuginfo: Refactor debuginfo generation for types][94261] - [Remove the everybody loops pass][93913] [88375]: rust-lang/rust#88375 [89887]: rust-lang/rust#89887 [90621]: rust-lang/rust#90621 [92285]: rust-lang/rust#92285 [92472]: rust-lang/rust#92472 [92697]: rust-lang/rust#92697 [92714]: rust-lang/rust#92714 [92911]: rust-lang/rust#92911 [93263]: rust-lang/rust#93263 [93745]: rust-lang/rust#93745 [93827]: rust-lang/rust#93827 [93901]: rust-lang/rust#93901 [93913]: rust-lang/rust#93913 [93965]: rust-lang/rust#93965 [94081]: rust-lang/rust#94081 [94261]: rust-lang/rust#94261 [94295]: rust-lang/rust#94295 [94832]: rust-lang/rust#94832 [95016]: rust-lang/rust#95016 [95251]: rust-lang/rust#95251 [`+whole-archive`]: https://doc.rust-lang.org/stable/rustc/command-line-arguments.html#linking-modifiers-whole-archive [`Pin::static_mut`]: https://doc.rust-lang.org/stable/std/pin/struct.Pin.html#method.static_mut [`Pin::static_ref`]: https://doc.rust-lang.org/stable/std/pin/struct.Pin.html#method.static_ref [`Vec::retain_mut`]: https://doc.rust-lang.org/stable/std/vec/struct.Vec.html#method.retain_mut [`VecDeque::retain_mut`]: https://doc.rust-lang.org/stable/std/collections/struct.VecDeque.html#method.retain_mut [`std::os::unix::net::SocketAddr::from_pathname`]: https://doc.rust-lang.org/stable/std/os/unix/net/struct.SocketAddr.html#method.from_pathname [`std::process::ExitCode`]: https://doc.rust-lang.org/stable/std/process/struct.ExitCode.html [`std::process::Termination`]: https://doc.rust-lang.org/stable/std/process/trait.Termination.html [`std::thread::JoinHandle::is_finished`]: https://doc.rust-lang.org/stable/std/thread/struct.JoinHandle.html#method.is_finished [cargo/10448]: rust-lang/cargo#10448 [cursor-write-array]: https://doc.rust-lang.org/stable/std/io/struct.Cursor.html#impl-Write-4 [link-attr]: https://doc.rust-lang.org/stable/reference/items/external-blocks.html#the-link-attribute [ptr-add]: https://doc.rust-lang.org/stable/std/primitive.pointer.html#method.add [ptr-offset]: https://doc.rust-lang.org/stable/std/primitive.pointer.html#method.offset [ptr-sub]: https://doc.rust-lang.org/stable/std/primitive.pointer.html#method.sub [ptr-wrapping_add]: https://doc.rust-lang.org/stable/std/primitive.pointer.html#method.wrapping_add [ptr-wrapping_offset]: https://doc.rust-lang.org/stable/std/primitive.pointer.html#method.wrapping_offset [ptr-wrapping_sub]: https://doc.rust-lang.org/stable/std/primitive.pointer.html#method.wrapping_sub [slice-as_mut_ptr]: https://doc.rust-lang.org/stable/std/primitive.slice.html#method.as_mut_ptr [slice-as_mut_ptr_range]: https://doc.rust-lang.org/stable/std/primitive.slice.html#method.as_mut_ptr_range [slice-as_ptr_range]: https://doc.rust-lang.org/stable/std/primitive.slice.html#method.as_ptr_range [target_feature]: https://doc.rust-lang.org/reference/attributes/codegen.html#the-target_feature-attribute
This PR implements the documentation change under discussion in rust-lang/unsafe-code-guidelines#302. It should not be approved or merged until the discussion there is resolved.