Also applies to `Vec::into_raw_parts`.
The expectation is that you can round-trip these methods with
`from_raw`, but this is only true when using the global allocator. With
custom allocators you should instead be using
`into_raw_with_allocator` and `from_raw_in`.
The implementation of `Box::leak` is changed to use
`Box::into_raw_with_allocator` and explicitly leak the allocator (which
was already the existing behavior). This is because, for `leak` to be
safe, the allocator must not free its underlying backing store. The
`Allocator` trait only guarantees that allocated memory remains valid
until the allocator is dropped.
It is currently possible to create a dangling `Weak` to a DST by
calling `Weak::new()` for a sized type, then doing an unsized coercion.
Therefore, the comments are wrong.
These comments were added in <https://github.com/rust-lang/rust/pull/73845>.
As far as I can tell, the guarantee in the comment was only previously
used in the `as_ptr` method. However, the current implementation of
`as_ptr` no longer relies on this guarantee.
Create `Atomic<T>` type alias (rebase)
Rebase of #130543.
Additional changes:
- Switch from `allow` to `expect` for `private_bounds` on `AtomicPrimitive`
- Unhide `AtomicPrimitive::AtomicInner` from docs, because rustdoc shows the definition `pub type Atomic<T> = <T as AtomicPrimitive>::AtomicInner;` and generated links for it.
- `NonZero` did not have this issue, because they kept the new alias private before the direction was changed.
- Use `Atomic<_>` in more places, including inside `Once`'s `Futex`. This is possible thanks to https://github.com/rust-lang/rust-clippy/pull/14125
The rest will either get moved back to #130543 or #130543 will be closed in favor of this instead.
---
* ACP: https://github.com/rust-lang/libs-team/issues/443#event-14293381061
* Tracking issue: #130539
Put the alloc unit tests in a separate alloctests package
Same rationale as https://github.com/rust-lang/rust/pull/135937. This PR has some extra complexity though as a decent amount of tests are testing internal implementation details rather than the public api. As such I opted to include the modules containing the types under test using `#[path]` into the alloctests package. This means that those modules still need `#[cfg(test)]`, but the rest of liballoc no longer need it.
Use `std::mem::{size_of, size_of_val, align_of, align_of_val}` from the
prelude instead of importing or qualifying them.
These functions were added to all preludes in Rust 1.80.
Update documentation for Arc::from_raw, Arc::increment_strong_count, and Arc::decrement_strong_count to clarify allocator requirement
### Related Issue:
This update addresses parts of the issue raised in [#134242](https://github.com/rust-lang/rust/issues/134242), where Arc's documentation lacks `Global Allocator` safety descriptions for three APIs. And this was confirmed by ```@workingjubilee``` :
> Wait, nevermind. I apparently forgot the `increment_strong_count` is implicitly A = Global. Ugh. Another reason these things are hard to track, unfortunately.
### PR Description
This PR updates the document for the following APIs:
- `Arc::from_raw`
- `Arc::increment_strong_count`
- `Arc::decrement_strong_count`
These APIs currently lack an important piece of documentation: **the raw pointer must point to a block of memory allocated by the global allocator**. This crucial detail is specified in the source code but is not reflected in the documentation, which could lead to confusion or incorrect usage by users.
### Problem:
The following example demonstrates the potential confusion caused by the lack of documentation:
```rust
#![feature(allocator_api)]
use std::alloc::{Allocator,AllocError, Layout};
use std::ptr::NonNull;
use std::sync::Arc;
struct LocalAllocator {
memory: NonNull<u8>,
size: usize,
}
impl LocalAllocator {
fn new(size: usize) -> Self {
Self {
memory: unsafe { NonNull::new_unchecked(&mut 0u8 as *mut u8) },
size,
}
}
}
unsafe impl Allocator for LocalAllocator {
fn allocate(&self, _layout: Layout) -> Result<NonNull<[u8]>, AllocError> {
Ok(NonNull::slice_from_raw_parts(self.memory, self.size))
}
unsafe fn deallocate(&self, _ptr: NonNull<u8>, _layout: Layout) {
}
}
fn main() {
let allocator = LocalAllocator::new(64);
let arc = Arc::new_in(5, &allocator); // Here, allocator could be any non-global allocator
let ptr = Arc::into_raw(arc);
unsafe {
Arc::increment_strong_count(ptr);
let arc = Arc::from_raw(ptr);
assert_eq!(2, Arc::strong_count(&arc)); // Failed here!
}
}
```
Add `into_array` conversion destructors for `Box`, `Rc`, and `Arc`.
Tracking issue: #133508
This PR adds the `into_array` destructor for `alloc::boxed::Box<[T]>`, `alloc::rc::Rc<[T]>`, and `alloc::sync::Arc<[T]>`.
Note that this PR assumes the initial proposal of these functions returning `Option`. It is still an open question whether this should instead be `Result`. We can, however, easily change this in a follow-up PR with the necessary consensus.
Field init shorthand allows writing initializers like `tcx: tcx` as
`tcx`. The compiler already uses it extensively. Fix the last few places
where it isn't yet used.
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 `From<&mut {slice}>` for `Box/Rc/Arc<{slice}>`
ACP: https://github.com/rust-lang/libs-team/issues/424
New API:
```rust
impl<T: Clone> From<&mut [T]> for Box<[T]>
impl From<&mut str> for Box<str>
impl From<&mut CStr> for Box<CStr>
impl From<&mut OsStr> for Box<OsStr>
impl From<&mut Path> for Box<Path>
impl<T: Clone> From<&mut [T]> for Rc<[T]>
impl From<&mut str> for Rc<str>
impl From<&mut CStr> for Rc<CStr>
impl From<&mut OsStr> for Rc<OsStr>
impl From<&mut Path> for Rc<Path>
impl<T: Clone> From<&mut [T]> for Arc<[T]>
impl From<&mut str> for Arc<str>
impl From<&mut CStr> for Arc<CStr>
impl From<&mut OsStr> for Arc<OsStr>
impl From<&mut Path> for Arc<Path>
```
Since they are trait implementations, I think these are insta-stable.
As mentioned in https://github.com/rust-lang/libs-team/issues/424#issuecomment-2299415749, a crater run might be needed.
Rename Receiver -> LegacyReceiver
As part of the "arbitrary self types v2" project, we are going to replace the current `Receiver` trait with a new mechanism based on a new, different `Receiver` trait.
This PR renames the old trait to get it out the way. Naming is hard. Options considered included:
* HardCodedReceiver (because it should only be used for things in the standard library, and hence is sort-of hard coded)
* LegacyReceiver
* TargetLessReceiver
* OldReceiver
These are all bad names, but fortunately this will be temporary. Assuming the new mechanism proceeds to stabilization as intended, the legacy trait will be removed altogether.
Although we expect this trait to be used only in the standard library, we suspect it may be in use elsehwere, so we're landing this change separately to identify any surprising breakages.
It's known that this trait is used within the Rust for Linux project; a patch is in progress to remove their dependency.
This is a part of the arbitrary self types v2 project,
https://github.com/rust-lang/rfcs/pull/3519https://github.com/rust-lang/rust/issues/44874
r? `@wesleywiser`
As part of the "arbitrary self types v2" project, we are going to
replace the current `Receiver` trait with a new mechanism based on a
new, different `Receiver` trait.
This PR renames the old trait to get it out the way. Naming is hard.
Options considered included:
* HardCodedReceiver (because it should only be used for things in the
standard library, and hence is sort-of hard coded)
* LegacyReceiver
* TargetLessReceiver
* OldReceiver
These are all bad names, but fortunately this will be temporary.
Assuming the new mechanism proceeds to stabilization as intended, the
legacy trait will be removed altogether.
Although we expect this trait to be used only in the standard library,
we suspect it may be in use elsehwere, so we're landing this change
separately to identify any surprising breakages.
It's known that this trait is used within the Rust for Linux project; a
patch is in progress to remove their dependency.
This is a part of the arbitrary self types v2 project,
https://github.com/rust-lang/rfcs/pull/3519https://github.com/rust-lang/rust/issues/44874
r? @wesleywiser
