Mark `get_mut` and `set_position` in `std::io::Cursor` as const.
Relevant tracking issue: #130801
The methods `get_mut` and `set_position` can trivially be marked as const due to #57349 being stabilised.
Rollup of 4 pull requests
Successful merges:
- #131081 (Use `ConstArgKind::Path` for all single-segment paths, not just params under `min_generic_const_args`)
- #132577 (Report the `unexpected_cfgs` lint in external macros)
- #133023 (Merge `-Zhir-stats` into `-Zinput-stats`)
- #133200 (ignore an occasionally-failing test in Miri)
r? `@ghost`
`@rustbot` modify labels: rollup
Improve `{BTreeMap,HashMap}::get_key_value` docs.
They are unusual methods. The docs don't really describe the cases when they might be useful (as opposed to just `get`), and the examples don't demonstrate the interesting cases at all.
This commit improves the docs and the examples.
Rwlock downgrade
Tracking Issue: #128203
This PR adds a `downgrade` method for `RwLock` / `RwLockWriteGuard` on all currently supported platforms.
Outstanding questions:
- [x] ~~Does the `futex.rs` change affect performance at all? It doesn't seem like it will but we can't be certain until we bench it...~~
- [x] ~~Should the SOLID platform implementation [be ported over](https://github.com/rust-lang/rust/pull/128219#discussion_r1693470090) to the `queue.rs` implementation to allow it to support downgrades?~~
They are unusual methods. The docs don't really describe the cases when
they might be useful (as opposed to just `get`), and the examples don't
demonstrate the interesting cases at all.
This commit improves the docs and the examples.
This commit fixes a memory ordering bug in the futex implementation
(`Relaxed` -> `Release` on `downgrade`).
This commit also removes a badly written test that deadlocked and
replaces it with a more reasonable test based on an already-tested
`downgrade` test from the parking-lot crate.
This commit adds the `downgrade` method onto the inner `RwLock` queue
implementation.
There are also a few other style patches included in this commit.
Co-authored-by: Jonas Böttiger <jonasboettiger@icloud.com>
This commit only has documentation changes and a few things moved around
the file. The very few code changes are cosmetic: changes like turning a
`match` statement into an `if let` statement or reducing indentation for
long if statements.
This commit also adds several safety comments on top of `unsafe` blocks
that might not be immediately obvious to a first-time reader.
Code "changes" are in:
- `add_backlinks_and_find_tail`
- `lock_contended`
A majority of the changes are just expanding the comments from 80
columns to 100 columns.
[illumos] use pipe2 to create anonymous pipes
pipe2 allows the newly-created pipe to atomically be CLOEXEC.
pipe2 was added to illumos a long time ago:
5dbfd19ad5. I've verified that this change passes all of std's tests on illumos.
Fix compilation error on Solaris due to flock usage
PR 130999 added the file_lock feature, but libc does not define flock() for the Solaris platform leading to a compilation error.
Additionally, I went through all the Tier 2 platforms and read through their documentation to see whether flock was implemented. This turned up 5 more Unix platforms where flock is not supported, even though it may exist in the libc crate.
Fixes https://github.com/rust-lang/rust/issues/132921
Related to #130999
Fix a copy-paste issue in the NuttX raw type definition
This file is copied from the rtems as initial implementation, and forgot to change the OS name in the comment.
This file is copied from the rtems as initial implementation, and
forgot to change the OS name in the comment.
Signed-off-by: Huang Qi <huangqi3@xiaomi.com>
Make `CloneToUninit` dyn-compatible
Make `CloneToUninit` dyn-compatible, by making `clone_to_uninit`'s `dst` parameter `*mut u8` instead of `*mut Self`, so the method does not reference `Self` except in the `self` parameter and is thus dispatchable from a trait object.
This allows, among other things, adding `CloneToUninit` as a supertrait bound for `trait Foo` to allow cloning `dyn Foo` in some containers. Currently, this means that `Rc::make_mut` and `Arc::make_mut` can work with `dyn Foo` where `trait Foo: CloneToUninit`.
<details><summary>Example</summary>
```rs
#![feature(clone_to_uninit)]
use std::clone::CloneToUninit;
use std::rc::Rc;
use std::fmt::Debug;
use std::borrow::BorrowMut;
trait Foo: BorrowMut<u32> + CloneToUninit + Debug {}
impl<T: BorrowMut<u32> + CloneToUninit + Debug> Foo for T {}
fn main() {
let foo: Rc<dyn Foo> = Rc::new(42_u32);
let mut bar = foo.clone();
*Rc::make_mut(&mut bar).borrow_mut() = 37;
dbg!(foo, bar); // 42, 37
}
```
</details>
Eventually, `Box::<T>::clone` is planned to be converted to use `T::clone_to_uninit`, which when combined with this change, will allow cloning `Box<dyn Foo>` where `trait Foo: CloneToUninit` without any additional `unsafe` code for the author of `trait Foo`.[^1]
This PR should have no stable side-effects, as `CloneToUninit` is unstable so cannot be mentioned on stable, and `CloneToUninit` is not used as a supertrait anywhere in the stdlib.
This change removes some length checks that could only fail if library UB was already hit (e.g. calling `<[T]>::clone_to_uninit` with a too-small-length `dst` is library UB and was previously detected[^2]; since `dst` does not have a length anymore, this now cannot be detected[^3]).
r? libs-api
-----
I chose to make the parameter `*mut u8` instead of `*mut ()` because that might make it simpler to pass the result of `alloc` to `clone_to_uninit`, but `*mut ()` would also make sense, and any `*mut ConcreteType` would *work*. The original motivation for [using specifically `*mut ()`](https://github.com/rust-lang/rust/pull/116113#discussion_r1335303908) appears to be `std::ptr::from_raw_parts_mut`, but that now [takes `*mut impl Thin`](https://doc.rust-lang.org/nightly/std/ptr/fn.from_raw_parts.html) instead of `*mut ()`. I have another branch where the parameter is `*mut ()`, if that is preferred.
It *could* also take something like `&mut [MaybeUninit<u8>]` to be dyn-compatible but still allow size-checking and in some cases safe writing, but this is already an `unsafe` API where misuse is UB, so I'm not sure how many guardrails it's worth adding here, and `&mut [MaybeUninit<u8>]` might be overly cumbersome to construct for callers compared to `*mut u8`
[^1]: Note that `impl<T: CloneToUninit + ?Sized> Clone for Box` must be added before or at the same time as when `CloneToUninit` becomes stable, due to `Box` being `#[fundamental]`, as if there is any stable gap between the stabilization of `CloneToUninit` and `impl<T: CloneToUninit + ?Sized> Clone for Box`, then users could implement both `CloneToUninit for dyn LocalTrait` and separately `Clone for Box<dyn LocalTrait>` during that gap, and be broken by the introduction of `impl<T: CloneToUninit + ?Sized> Clone for Box`.
[^2]: Using a `debug_assert_eq` in [`core::clone::uninit::CopySpec::clone_slice`](https://doc.rust-lang.org/nightly/src/core/clone/uninit.rs.html#28).
[^3]: This PR just uses [the metadata (length) from `self`](e0c1c8bc50/library/core/src/clone.rs (L286)) to construct the `*mut [T]` to pass to `CopySpec::clone_slice` in `<[T]>::clone_to_uninit`.
float types: move copysign, abs, signum to libcore
These operations are explicitly specified to act "bitwise", i.e. they just act on the sign bit and do not even quiet signaling NaNs. We also list them as ["non-arithmetic operations"](https://doc.rust-lang.org/nightly/std/primitive.f32.html#nan-bit-patterns), and all the other non-arithmetic operations are in libcore. There's no reason to expect them to require any sort of runtime support, and from [these experiments](https://github.com/rust-lang/rust/issues/50145#issuecomment-997301250) it seems like LLVM indeed compiles them in a way that does not require any sort of runtime support.
Nominating for `@rust-lang/libs-api` since this change takes immediate effect on stable.
Part of https://github.com/rust-lang/rust/issues/50145.
PR 130999 added the file_lock feature, but libc does not define
flock() for the Solaris platform leading to a compilation error.
Additionally, I went through all the Tier 2 platforms and read through
their documentation to see whether flock was implemented. This turned up
5 more Unix platforms where flock is not supported, even though it may
exist in the libc crate.
pipe2 allows the newly-created pipe to atomically be CLOEXEC.
pipe2 was added to illumos a long time ago:
5dbfd19ad5.
I've verified that this change passes all tests.
split up the first paragraph of doc comments for better summaries
used `./x clippy -Aclippy::all '-Wclippy::too_long_first_doc_paragraph' library/core library/alloc` to find these issues.
Implement file_lock feature
This adds lock(), lock_shared(), try_lock(), try_lock_shared(), and unlock() to File gated behind the file_lock feature flag
This is the initial implementation of https://github.com/rust-lang/rust/issues/130994 for Unix and Windows platforms. I will follow it up with an implementation for WASI preview 2
