impl `From<&[T; N]>` for `Cow<[T]>`
Implement `From<&[T; N]>` for `Cow<[T]>` to simplify its usage in the following example.
```rust
fn foo(data: impl Into<Cow<'static, [&'static str]>>) { /* ... */ }
fn main() {
foo(vec!["hello", "world"]);
foo(&["hello", "world"]); // Error: the trait `From<&[&str; 2]>` is not implemented for `Cow<'static, [&'static str]>`
foo(&["hello", "world"] as &[_]); // Explicit convertion into a slice is required
}
```
stabilise array methods
Closes#76118
Stabilises the remaining array methods
FCP is yet to be carried out for this
There wasn't a clear consensus on the naming, but all the other alternatives had some flaws as discussed in the tracking issue and there was a silence on this issue for a year
Remove special-case handling of `vec.split_off(0)`
#76682 added special handling to `Vec::split_off` for the case where `at == 0`. Instead of copying the vector's contents into a freshly-allocated vector and returning it, the special-case code steals the old vector's allocation, and replaces it with a new (empty) buffer with the same capacity.
That eliminates the need to copy the existing elements, but comes at a surprising cost, as seen in #119913. The returned vector's capacity is no longer determined by the size of its contents (as would be expected for a freshly-allocated vector), and instead uses the full capacity of the old vector.
In cases where the capacity is large but the size is small, that results in a much larger capacity than would be expected from reading the documentation of `split_off`. This is especially bad when `split_off` is called in a loop (to recycle a buffer), and the returned vectors have a wide variety of lengths.
I believe it's better to remove the special-case code, and treat `at == 0` just like any other value:
- The current documentation states that `split_off` returns a “newly allocated vector”, which is not actually true in the current implementation when `at == 0`.
- If the value of `at` could be non-zero at runtime, then the caller has already agreed to the cost of a full memcpy of the taken elements in the general case. Avoiding that copy would be nice if it were close to free, but the different handling of capacity means that it is not.
- If the caller specifically wants to avoid copying in the case where `at == 0`, they can easily implement that behaviour themselves using `mem::replace`.
Fixes#119913.
Initial implementation of `str::from_raw_parts[_mut]`
ACP (accepted): rust-lang/libs-team#167
Tracking issue: #119206
Thanks to ``@Kixiron`` for previous work on this (#107207)
``@rustbot`` label +T-libs-api -T-libs
r? ``@thomcc``
Closes#107207.
Use `assert_unchecked` instead of `assume` intrinsic in the standard library
Now that a public wrapper for the `assume` intrinsic exists, we can use it in the standard library.
CC #119131
Fix deallocation with wrong allocator in (A)Rc::from_box_in
Deallocate the `Box` with the original allocator (via `&A`), not `Global`.
Fixes#119749
<details> <summary>Example code with error and Miri output</summary>
(Note that this UB is not observable on stable, because the only usable allocator on stable is `Global` anyway.)
Code ([playground link](https://play.rust-lang.org/?version=nightly&mode=debug&edition=2021&gist=96193c2c6a1912d7f669fbbe39174b09)):
```rs
#![feature(allocator_api)]
use std::alloc::System;
// uncomment one of these
use std::rc::Rc;
//use std::sync::Arc as Rc;
fn main() {
let x: Box<[u32], System> = Box::new_in([1,2,3], System);
let _: Rc<[u32], System> = Rc::from(x);
}
```
Miri output:
```rs
error: Undefined Behavior: deallocating alloc904, which is C heap memory, using Rust heap deallocation operation
--> /playground/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/alloc/src/alloc.rs:117:14
|
117 | unsafe { __rust_dealloc(ptr, layout.size(), layout.align()) }
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ deallocating alloc904, which is C heap memory, using Rust heap deallocation operation
|
= help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
= help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information
= note: BACKTRACE:
= note: inside `std::alloc::dealloc` at /playground/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/alloc/src/alloc.rs:117:14: 117:64
= note: inside `<std::alloc::Global as std::alloc::Allocator>::deallocate` at /playground/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/alloc/src/alloc.rs:254:22: 254:51
= note: inside `<std::boxed::Box<std::mem::ManuallyDrop<[u32]>> as std::ops::Drop>::drop` at /playground/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/alloc/src/boxed.rs:1244:17: 1244:66
= note: inside `std::ptr::drop_in_place::<std::boxed::Box<std::mem::ManuallyDrop<[u32]>>> - shim(Some(std::boxed::Box<std::mem::ManuallyDrop<[u32]>>))` at /playground/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/ptr/mod.rs:507:1: 507:56
= note: inside `std::mem::drop::<std::boxed::Box<std::mem::ManuallyDrop<[u32]>>>` at /playground/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/mem/mod.rs:992:24: 992:25
= note: inside `std::rc::Rc::<[u32], std::alloc::System>::from_box_in` at /playground/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/alloc/src/rc.rs:1928:13: 1928:22
= note: inside `<std::rc::Rc<[u32], std::alloc::System> as std::convert::From<std::boxed::Box<[u32], std::alloc::System>>>::from` at /playground/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/alloc/src/rc.rs:2504:9: 2504:27
note: inside `main`
--> src/main.rs:10:32
|
10 | let _: Rc<[u32], System> = Rc::from(x);
| ^^^^^^^^^^^
note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
error: aborting due to 1 previous error
```
</details>
Document some alternatives to `Vec::split_off`
One of the discussion points that came up in #119917 is that some people use `Vec::split_off` in cases where they probably shouldn't, because the alternatives (like `mem::take`) are hard to discover.
This PR adds some suggestions to the documentation of `split_off` that should point people towards alternatives that might be more appropriate for their use-case.
I've deliberately tried to keep these changes as simple and uncontroversial as possible, so that they don't depend on how the team decides to handle the concerns raised in #119917. That's why I haven't touched the existing documentation for `split_off`, and haven't added links to `split_off` to the documentation of other methods.
fix: Drop guard was deallocating with the incorrect size
InPlaceDstBufDrop holds onto the allocation before the shrinking happens which means it must deallocate the destination elements but the source allocation.
Thanks `@cuviper` for spotting this.
Remove alignment-changing in-place collect
This removes the alignment-changing in-place collect optimization introduced in #110353
Currently stable users can't benefit from the optimization because GlobaAlloc doesn't support alignment-changing realloc and neither do most posix allocators. So in practice it has a negative impact on performance.
Explanation from https://github.com/rust-lang/rust/issues/120091#issuecomment-1899071681:
> > You mention that in case of alignment mismatch -- when the new alignment is less than the old -- the implementation calls `mremap`.
>
> I was trying to note that this isn't really the case in practice, due to the semantics of Rust's allocator APIs. The only use of the allocator within the `in_place_collect` implementation itself is [a call to `Allocator::shrink()`](db7125f008/library/alloc/src/vec/in_place_collect.rs (L299-L303)), which per its documentation [allows decreasing the required alignment](https://doc.rust-lang.org/1.75.0/core/alloc/trait.Allocator.html). However, in stable Rust, the only available `Allocator` is [`Global`](https://doc.rust-lang.org/1.75.0/alloc/alloc/struct.Global.html), which delegates to the registered `GlobalAlloc`. Since `GlobalAlloc::realloc()` [cannot change the required alignment](https://doc.rust-lang.org/1.75.0/core/alloc/trait.GlobalAlloc.html#method.realloc), the implementation of [`<Global as Allocator>::shrink()`](db7125f008/library/alloc/src/alloc.rs (L280-L321)) must fall back to creating a brand-new allocation, `memcpy`ing the data into it, and freeing the old allocation, whenever the alignment doesn't remain exactly the same.
>
> Therefore, the underlying allocator, provided by libc or some other source, has no opportunity to internally `mremap()` the data when the alignment is changed, since it has no way of knowing that the allocation is the same.
This also removes
* impl From<&Context> for ContextBuilder
* Context::try_waker()
The from implementation is removed because now that
wakers are always supported, there are less incentives
to override the current context. Before, the incentive
was to add Waker support to a reactor that didn't have
any.
InPlaceDstBufDrop holds onto the allocation before the shrinking happens
which means it must deallocate the destination elements but the source
allocation.
Update documentation for Vec::into_boxed_slice to be more clear about excess capacity
Currently, the documentation for Vec::into_boxed_slice says that "if the vector has excess capacity, its items will be moved into a newly-allocated buffer with exactly the right capacity." This is misleading, as copies do not necessarily occur, depending on if the allocator supports in-place shrinking. I copied some of the wording from shrink_to_fit, though it could potentially still be worded better than this.
Currently stable users can't benefit from this because GlobaAlloc doesn't support
alignment-changing realloc and neither do most posix allocators.
So in practice it always results in an extra memcpy.
merge core_panic feature into panic_internals
I don't know why those are two separate features, but it does not seem intentional. This merge is useful because with https://github.com/rust-lang/rust/pull/118123, panic_internals is recognized as an internal feature, but core_panic is not -- but core_panic definitely should be internal.
rc: Take *const T in is_dangling
It is not important which one is used since `is_dangling` does not access memory, but `*const` removes the needs of `*const T` -> `*mut T` casts in `from_raw_in`.
Clean up alloc::sync::Weak Clone implementation
Since both return points (tail and early return) return the same expression and the only difference is whether inner is available, the code that does the atomic operations and checks on inner was moved into the if body and the only return is at the tail. Original comments preserved.
It is not important which one is used since `is_dangling` does not access
memory, but `*const` removes the needs of `*const T` -> `*mut T` casts
in `from_raw_in`.
fix minor mistake in comments describing VecDeque resizing
Avoiding confusion where one of the items in the deque seems to disappear in two of the three cases
Since both return points (tail and early return) return the same
expression and the only difference is whether inner is available, the
code that does the atomic operations and checks on inner was moved into
the if body and the only return is at the tail. Original comments
preserved.
add more niches to rawvec
Previously RawVec only had a single niche in its `NonNull` pointer. With this change it now has `isize::MAX` niches since half the value-space of the capacity field is never needed, we can't have a capacity larger than isize::MAX.
remove redundant imports
detects redundant imports that can be eliminated.
for #117772 :
In order to facilitate review and modification, split the checking code and removing redundant imports code into two PR.
r? `@petrochenkov`
Stablize arc_unwrap_or_clone
Fixes: #93610
This likely needs FCP. I created this PR as it's stabilization is trivial and FCP can be just conducted here. Not sure how to ping the libs API team (last attempt didn't work apparently according to GH UI)
detects redundant imports that can be eliminated.
for #117772 :
In order to facilitate review and modification, split the checking code and
removing redundant imports code into two PR.
Split `Vec::dedup_by` into 2 cycles
First cycle runs until we found 2 same elements, second runs after if there any found in the first one. This allows to avoid any memory writes until we found an item which we want to remove.
This leads to significant performance gains if all `Vec` items are kept: -40% on my benchmark with unique integers.
Results of benchmarks before implementation (including new benchmark where nothing needs to be removed):
* vec::bench_dedup_all_100 74.00ns/iter +/- 13.00ns
* vec::bench_dedup_all_1000 572.00ns/iter +/- 272.00ns
* vec::bench_dedup_all_100000 64.42µs/iter +/- 19.47µs
* __vec::bench_dedup_none_100 67.00ns/iter +/- 17.00ns__
* __vec::bench_dedup_none_1000 662.00ns/iter +/- 86.00ns__
* __vec::bench_dedup_none_10000 9.16µs/iter +/- 2.71µs__
* __vec::bench_dedup_none_100000 91.25µs/iter +/- 1.82µs__
* vec::bench_dedup_random_100 105.00ns/iter +/- 11.00ns
* vec::bench_dedup_random_1000 781.00ns/iter +/- 10.00ns
* vec::bench_dedup_random_10000 9.00µs/iter +/- 5.62µs
* vec::bench_dedup_random_100000 449.81µs/iter +/- 74.99µs
* vec::bench_dedup_slice_truncate_100 105.00ns/iter +/- 16.00ns
* vec::bench_dedup_slice_truncate_1000 2.65µs/iter +/- 481.00ns
* vec::bench_dedup_slice_truncate_10000 18.33µs/iter +/- 5.23µs
* vec::bench_dedup_slice_truncate_100000 501.12µs/iter +/- 46.97µs
Results after implementation:
* vec::bench_dedup_all_100 75.00ns/iter +/- 9.00ns
* vec::bench_dedup_all_1000 494.00ns/iter +/- 117.00ns
* vec::bench_dedup_all_100000 58.13µs/iter +/- 8.78µs
* __vec::bench_dedup_none_100 52.00ns/iter +/- 22.00ns__
* __vec::bench_dedup_none_1000 417.00ns/iter +/- 116.00ns__
* __vec::bench_dedup_none_10000 4.11µs/iter +/- 546.00ns__
* __vec::bench_dedup_none_100000 40.47µs/iter +/- 5.36µs__
* vec::bench_dedup_random_100 77.00ns/iter +/- 15.00ns
* vec::bench_dedup_random_1000 681.00ns/iter +/- 86.00ns
* vec::bench_dedup_random_10000 11.66µs/iter +/- 2.22µs
* vec::bench_dedup_random_100000 469.35µs/iter +/- 20.53µs
* vec::bench_dedup_slice_truncate_100 100.00ns/iter +/- 5.00ns
* vec::bench_dedup_slice_truncate_1000 2.55µs/iter +/- 224.00ns
* vec::bench_dedup_slice_truncate_10000 18.95µs/iter +/- 2.59µs
* vec::bench_dedup_slice_truncate_100000 492.85µs/iter +/- 72.84µs
Resolves#77772
P.S. Note that this is same PR as #92104 I just missed review then forgot about it.
Also, I cannot reopen that pull request so I am creating a new one.
I responded to remaining questions directly by adding commentaries to my code.
#79327 added `'static` bounds to the allocator parameter
for various `Box` + `Pin` APIs to ensure soundness.
But it was a bit overzealous, some of the bounds aren't
actually needed.
Expand in-place iteration specialization to Flatten, FlatMap and ArrayChunks
This enables the following cases to collect in-place:
```rust
let v = vec![[0u8; 4]; 1024]
let v: Vec<_> = v.into_iter().flatten().collect();
let v: Vec<Option<NonZeroUsize>> = vec![NonZeroUsize::new(0); 1024];
let v: Vec<_> = v.into_iter().flatten().collect();
let v = vec![u8; 4096];
let v: Vec<_> = v.into_iter().array_chunks::<4>().collect();
```
Especially the nicheful-option-flattening should be useful in real code.
While a better approach would be to implement it for all ZSTs
which are `Copy` and have trivial `Clone`,
the last property cannot be detected for now.
Signed-off-by: Petr Portnov <me@progrm-jarvis.ru>
Add `std:#️⃣:{DefaultHasher, RandomState}` exports (needs FCP)
This implements rust-lang/libs-team#267 to move the libstd hasher types to `std::hash` where they belong, instead of `std::collections::hash_map`.
<details><summary>The below no longer applies, but is kept for clarity.</summary>
This is a small refactor for #27242, which moves the definitions of `RandomState` and `DefaultHasher` into `std::hash`, but in a way that won't be noticed in the public API.
I've opened rust-lang/libs-team#267 as a formal ACP to move these directly into the root of `std::hash`, but for now, they're at least separated out from the collections code in a way that will make moving that around easier.
I decided to simply copy the rustdoc for `std::hash` from `core::hash` since I think it would be ideal for the two to diverge longer-term, especially if the ACP is accepted. However, I would be willing to factor them out into a common markdown document if that's preferred.
</details>
Stabilize `const_maybe_uninit_zeroed` and `const_mem_zeroed`
Make `MaybeUninit::zeroed` and `mem::zeroed` const stable. Newly stable API:
```rust
// core::mem
pub const unsafe fn zeroed<T>() ->;
impl<T> MaybeUninit<T> {
pub const fn zeroed() -> MaybeUninit<T>;
}
```
This relies on features based around `const_mut_refs`. Per `@RalfJung,` this should be OK since we do not leak any `&mut` to the user.
For this to be possible, intrinsics `assert_zero_valid` and `assert_mem_uninitialized_valid` were made const stable.
Tracking issue: #91850
Zulip discussion: https://rust-lang.zulipchat.com/#narrow/stream/146212-t-compiler.2Fconst-eval/topic/.60const_mut_refs.60.20dependents
r? libs-api
`@rustbot` label -T-libs +T-libs-api +A-const-eval
cc `@RalfJung` `@oli-obk` `@rust-lang/wg-const-eval`
Hint optimizer about try-reserved capacity
This is #116568, but limited only to the less-common `try_reserve` functions to reduce bloat in debug binaries from debug info, while still addressing the main use-case #116570
Make `MaybeUninit::zeroed` const stable. Newly stable API:
// core::mem
impl<T> MaybeUninit<T> {
pub const fn zeroed() -> MaybeUninit<T>;
}
Use of `const_mut_refs` should be acceptable since we do not leak the
mutability.
Tracking issue: #91850
Increase the reach of panic_immediate_abort
I wanted to use/abuse this recently as part of another project, and I was surprised how many panic-related things were left in my binaries if I built a large crate with the feature enabled along with LTO. These changes get all the panic-related symbols that I could find out of my set of locally installed Rust utilities.
Add explicit-endian String::from_utf16 variants
This adds the following APIs under `feature(str_from_utf16_endian)`:
```rust
impl String {
pub fn from_utf16le(v: &[u8]) -> Result<String, FromUtf16Error>;
pub fn from_utf16le_lossy(v: &[u8]) -> String;
pub fn from_utf16be(v: &[u8]) -> Result<String, FromUtf16Error>;
pub fn from_utf16be_lossy(v: &[u8]) -> String;
}
```
These are versions of `String::from_utf16` that explicitly take [UTF-16LE and UTF-16BE](https://unicode.org/faq/utf_bom.html#gen7). Notably, we can do better than just the obvious `decode_utf16(v.array_chunks::<2>().copied().map(u16::from_le_bytes)).collect()` in that:
- We handle the case where the byte slice is not an even number of bytes, and
- In the case that the UTF-16 is native endian and the slice is aligned, we can forward to `String::from_utf16`.
If the Unicode Consortium actively defines how to handle character replacement when decoding a UTF-16 bytestream with a trailing odd byte, I was unable to find reference. However, the behavior implemented here is fairly self-evidently correct: replace the single errant byte with the replacement character.
Implement `From<{&,&mut} [T; N]>` for `Vec<T>` where `T: Clone`
Currently, if `T` implements `Clone`, we can create a `Vec<T>` from an `&[T]` or an `&mut [T]`, can we also support creating a `Vec<T>` from an `&[T; N]` or an `&mut [T; N]`? Also, do I need to add `#[inline]` to the implementation?
ACP: rust-lang/libs-team#220. [Accepted]
Closes#100880.
Update doc for `alloc::format!` and `core::concat!`
Closes#115551.
Used comments instead of `assert!`s as [`std::fmt`](https://doc.rust-lang.org/std/fmt/index.html#usage) uses comments.
Should all the str-related macros (`format!`, `format_args!`, `concat!`, `stringify!`, `println!`, `writeln!`, etc.) references each others? For instance, [`concat!`](https://doc.rust-lang.org/core/macro.concat.html) mentions that integers are stringified, but don't link to `stringify!`.
`@rustbot` label +A-docs +A-fmt
Make useless_ptr_null_checks smarter about some std functions
This teaches the `useless_ptr_null_checks` lint that some std functions can't ever return null pointers, because they need to point to valid data, get references as input, etc.
This is achieved by introducing an `#[rustc_never_returns_null_ptr]` attribute and adding it to these std functions (gated behind bootstrap `cfg_attr`).
Later on, the attribute could maybe be used to tell LLVM that the returned pointer is never null. I don't expect much impact of that though, as the functions are pretty shallow and usually the input data is already never null.
Follow-up of PR #113657Fixes#114442
Also stabilizes saturating_int_assign_impl, gh-92354.
And also make pub fns const where the underlying saturating_*
fns became const in the meantime since the Saturating type was
created.
Add note that Vec::as_mut_ptr() does not materialize a reference to the internal buffer
See discussion on https://github.com/thomcc/rust-typed-arena/issues/62 and [t-opsem](https://rust-lang.zulipchat.com/#narrow/stream/136281-t-opsem/topic/is.20this.20typed_arena.20code.20sound.20under.20stacked.2Ftree.20borrows.3F)
This method already does the correct thing here, but it is worth guaranteeing that it does so it can be used more freely in unsafe code without having to worry about potential Stacked/Tree Borrows violations. This moves one more unsafe usage pattern from the "very likely sound but technically not fully defined" box into "definitely sound", and currently our surface area of the latter is woefully small.
I'm not sure how best to word this, opening this PR as a way to start discussion.
Correct and expand documentation of `handle_alloc_error` and `set_alloc_error_hook`.
The primary goal of this change is to remove the false claim that `handle_alloc_error` always aborts; instead, code should be prepared for `handle_alloc_error` to possibly unwind, and be sound under that condition.
I saw other opportunities for improvement, so I have added all the following information:
* `handle_alloc_error` may panic instead of aborting. (Fixes#114898)
* What happens if a hook returns rather than diverging.
* A hook may panic. (This was already demonstrated in an example, but not stated in prose.)
* A hook must be sound to call — it cannot assume that it is only called by the runtime, since its function pointer can be retrieved by safe code.
I've checked these statements against the source code of `alloc` and `std`, but there may be nuances I haven't caught, so a careful review is welcome.
Add `suggestion` for some `#[deprecated]` items
Consider code:
```rust
fn main() {
let _ = ["a", "b"].connect(" ");
}
```
Currently it shows deprecated warning:
```rust
warning: use of deprecated method `std::slice::<impl [T]>::connect`: renamed to join
--> src/main.rs:2:24
|
2 | let _ = ["a", "b"].connect(" ");
| ^^^^^^^
|
= note: `#[warn(deprecated)]` on by default
```
This PR adds `suggestion` for `connect` and some other deprecated items, so the warning will be changed to this:
```rust
warning: use of deprecated method `std::slice::<impl [T]>::connect`: renamed to join
--> src/main.rs:2:24
|
2 | let _ = ["a", "b"].connect(" ");
| ^^^^^^^
|
= note: `#[warn(deprecated)]` on by default
help: replace the use of the deprecated method
|
2 | let _ = ["a", "b"].join(" ");
| ^^^^
```
Add the following facts:
* `handle_alloc_error` may panic instead of aborting.
* What happens if a hook returns rather than diverging.
* A hook may panic. (This was already demonstrated in an example,
but not stated in prose.)
* A hook must be sound to call — it cannot assume that it is only
called by the runtime, since its function pointer can be retrieved by
safe code.
avoid transmuting Box when we can just cast raw pointers instead
Always better to avoid a transmute, in particular when the layout assumptions it is making are not clearly documented. :)
* remove `impl Provider for Error`
* rename `Demand` to `Request`
* update docstrings to focus on the conceptual API provided by `Request`
* move `core::any::{request_ref, request_value}` functions into `core::error`
* move `core::any::tag`, `core::any::Request`, an `core::any::TaggedOption` into `core::error`
* replace `provide_any` feature name w/ `error_generic_member_access`
* move `core::error::request_{ref,value} tests into core::tests::error module
* update unit and doc tests
Fix documentation of impl From<Vec<T>> for Rc<[T]>
The example in the documentation of `impl From<Vec<T>> for <Rc<[T]>` is irrelevant (likely was copied from `impl From<Box<T>> for <Rc<T>`). I suggest taking corresponding example from the documentation of `Arc` and replacing `Arc` with `Rc`.
It lints against features that are inteded to be internal to the
compiler and standard library. Implements MCP #596.
We allow `internal_features` in the standard library and compiler as those
use many features and this _is_ the standard library from the "internal to the compiler and
standard library" after all.
Marking some features as internal wasn't exactly the most scientific approach, I just marked some
mostly obvious features. While there is a categorization in the macro,
it's not very well upheld (should probably be fixed in another PR).
We always pass `-Ainternal_features` in the testsuite
About 400 UI tests and several other tests use internal features.
Instead of throwing the attribute on each one, just always allow them.
There's nothing wrong with testing internal features^^
Stabilize const-weak-new
This is a fairly uncontroversial library stabilization, so I'm going ahead and proposing it to ride the trains to stable.
This stabilizes the following APIs, which are defined to be non-allocating constructors.
```rust
// alloc::rc
impl<T> Weak<T> {
pub const fn new() -> Weak<T>;
}
// alloc::sync
impl<T> Weak<T> {
pub const fn new() -> Weak<T>;
}
```
Closes#95091
``@rustbot`` modify labels: +needs-fcp
Bump its stabilization version several times along
the way to accommodate changes in release processes.
Co-authored-by: Mara Bos <m-ou.se@m-ou.se>
Co-authored-by: Trevor Gross <t.gross35@gmail.com>
Documentation: Fix Stilted Language in Vec->Indexing
Problem
Language in the Vec->Indexing documentation sounds stilted due to incorrect word ordering: "... type allows to access values by index."
Solution
Reorder words in the Vec->Indexing documentation to flow better: "... type allows access to values by index." The phrase "allows access to" also matches other existing documentation.
Clarify behavior of inclusive bounds in BTreeMap::{lower,upper}_bound
It wasn’t quite clear to me how these methods would interpret inclusive bounds so I added examples for those.
Remove redundant example of `BTreeSet::iter`
The usage and that `Values returned by the iterator are returned in ascending order` are already demonstrated by the other example and the description, so I removed the useless one.
Problem
Language in the Vec->Indexing documentation sounds stilted due to
incorrect word ordering: "... type allows to access values by index."
Solution
Reorder words in the Vec->Indexing documentation to flow better:
"... type allows access to values by index." The phrase "allows access to"
also matches other existing documentation.
The status quo is highly confusing, since the overlap is not apparent,
and specialization is not a feature of Rust. This addresses #87545;
I'm not certain if it closes it, since that issue might also be trackign
a *general* solution for hiding specializing impls automatically.
Add support for allocators in `Rc` & `Arc`
Adds the ability for `std::rc:Rc`, `std::rc::Weak`, `std::sync::Arc`, and `std::sync::Weak` to live in custom allocators
Rename VecDeque's `rotate_left` and `rotate_right` parameters
This pull request introduces a modification to the `VecDeque` collection, specifically the `rotate_left` and `rotate_right` functions, by renaming the parameter associated with these functions.
The rationale behind this change is to provide clearer and more consistent naming for the parameter that specifies the number of places to rotate the double-ended queue. By using `n` as the parameter name in both functions, it becomes easier to understand and remember the purpose of the parameter.
Eliminate ZST allocations in `Box` and `Vec`
This PR fixes 2 issues with `Box` and `RawVec` related to ZST allocations. Specifically, the `Allocator` trait requires that:
- If you allocate a zero-sized layout then you must later deallocate it, otherwise the allocator may leak memory.
- You cannot pass a ZST pointer to the allocator that you haven't previously allocated.
These restrictions exist because an allocator implementation is allowed to allocate non-zero amounts of memory for a zero-sized allocation. For example, `malloc` in libc does this.
Currently, ZSTs are handled differently in `Box` and `Vec`:
- `Vec` never allocates when `T` is a ZST or if the vector capacity is 0.
- `Box` just blindly passes everything on to the allocator, including ZSTs.
This causes problems due to the free conversions between `Box<[T]>` and `Vec<T>`, specifically that ZST allocations could get leaked or a dangling pointer could be passed to `deallocate`.
This PR fixes this by changing `Box` to not allocate for zero-sized values and slices. It also fixes a bug in `RawVec::shrink` where shrinking to a size of zero did not actually free the backing memory.
This reverts commit 001b081cc1.
This change was done as the above commit introduces a regression in type
inference. Regression test located at
`tests/ui/type-inference/issue-113283-alllocator-trait-eq.rs`
Allow comparing `Box`es with different allocators
Currently, comparing `Box`es over different allocators is not allowed:
```Rust
error[E0308]: mismatched types
--> library/alloc/tests/boxed.rs:22:20
|
22 | assert_eq!(b1, b2);
| ^^ expected `Box<{integer}, ConstAllocator>`, found `Box<{integer}, AnotherAllocator>`
|
= note: expected struct `Box<{integer}, ConstAllocator>`
found struct `Box<{integer}, AnotherAllocator>`
For more information about this error, try `rustc --explain E0308`.
error: could not compile `alloc` (test "collectionstests") due to previous error
```
This PR lifts this limitation
remove unused field
Followup to #104455. The field is no longer needed since ExtractIf (previously DrainFilter) doesn't keep draining in its drop impl.
Implement PartialOrd for `Vec`s over different allocators
It is already possible to `PartialEq` `Vec`s with different allocators, but that is not the case with `PartialOrd`.
This is an `Rc` that is guaranteed to only have one strong reference.
Because it is uniquely owned, it can safely implement `DerefMut`, which
allows programs to have an initialization phase where structures inside
the `Rc` can be mutated.
The `UniqueRc` can then be converted to a regular `Rc`, allowing sharing
and but read-only access.
During the "initialization phase," weak references can be created, but
attempting to upgrade these will fail until the `UniqueRc` has been
converted to a regular `Rc`. This feature can be useful to create
cyclic data structures.
This API is an implementation based on the feedback provided to the ACP
at https://github.com/rust-lang/libs-team/issues/90.
Remove `box_free` lang item
This PR removes the `box_free` lang item, replacing it with `Box`'s `Drop` impl. Box dropping is still slightly magic because the contained value is still dropped by the compiler.
Stabilize String::leak
Stabilizes the following API:
```Rust
impl String {
pub fn leak(self) -> &'static mut str;
}
```
closes#102929
blocked by having an FCP for stabilization.
Ignore `core`, `alloc` and `test` tests that require unwinding on `-C panic=abort`
Some of the tests for `core` and `alloc` require unwinding through their use of `catch_unwind`. These tests fail when testing using `-C panic=abort` (in my case through a target without unwinding support, and `-Z panic-abort-tests`), while they should be ignored as they don't indicate a failure.
This PR marks all of these tests with this attribute:
```rust
#[cfg_attr(not(panic = "unwind"), ignore = "test requires unwinding support")]
```
I'm not aware of a way to test this on rust-lang/rust's CI, as we don't test any target with `-C panic=abort`, but I tested this locally on a Ferrocene target and it does indeed make the test suite pass.
Support #[global_allocator] without the allocator shim
This makes it possible to use liballoc/libstd in combination with `--emit obj` if you use `#[global_allocator]`. This is what rust-for-linux uses right now and systemd may use in the future. Currently they have to depend on the exact implementation of the allocator shim to create one themself as `--emit obj` doesn't create an allocator shim.
Note that currently the allocator shim also defines the oom error handler, which is normally required too. Once `#![feature(default_alloc_error_handler)]` becomes the only option, this can be avoided. In addition when using only fallible allocator methods and either `--cfg no_global_oom_handling` for liballoc (like rust-for-linux) or `--gc-sections` no references to the oom error handler will exist.
To avoid this feature being insta-stable, you will have to define `__rust_no_alloc_shim_is_unstable` to avoid linker errors.
(Labeling this with both T-compiler and T-lang as it originally involved both an implementation detail and had an insta-stable user facing change. As noted above, the `__rust_no_alloc_shim_is_unstable` symbol requirement should prevent unintended dependence on this unstable feature.)
Mark internal functions and traits unsafe to reflect preconditions
No semantics are changed in this PR; I only mark some functions and and a trait `unsafe` which already had implicit preconditions. Although it seems somewhat redundant for `numfmt::Part::Copy` to contain a `&[u8]` instead of a `&str`, given that all of its current consumers ultimately expect valid UTF-8. Is the type also intended to work for byte-slice formatting in the future?
Fix duplicate `arcinner_layout_for_value_layout` calls when using the uninit `Arc` constructors
What this fixes is the duplicate calls to `arcinner_layout_for_value_layout` seen here: https://godbolt.org/z/jr5Gxozhj
The issue was discovered alongside #111603 but is otherwise unrelated to the duplicate `alloca`s, which remain unsolved. Everything I tried to solve said main issue has failed.
As for the duplicate layout calculations, I also tried slapping `#[inline]` and `#[inline(always)]` on everything in sight but the only thing that worked in the end is to dedup the calls by hand.
Specialize ToString implementation for fmt::Arguments
Generates far fewer instructions by formatting into a String with `fmt::format` directly instead of going through the `fmt::Display` impl. This change is insta-stable.
Change Vec examples to not assert exact capacity except where it is guaranteed
It was [brought up on discord](https://discord.com/channels/273534239310479360/818964227783262209/1107633959329878077) that the `Vec::into_boxed_slice` example contradicted the `Vec::with_capacity` docs in that the returned `Vec` might have _more_ capacity than requested.
So, to reduce confusion change all the `assert_eq!(vec.capacity(), _)` to `assert!(vec.capacity() >= _)`, except in 4 examples that have guaranteed capacities: `Vec::from_raw_parts`, `Vec::from_raw_parts_in`, `Vec::<()>::with_capacity`,`Vec::<(), _>::with_capacity_in`.
You will need to add the following as replacement for the old __rust_*
definitions when not using the alloc shim.
#[no_mangle]
static __rust_no_alloc_shim_is_unstable: u8 = 0;
enable `rust_2018_idioms` lint group for doctests
With this change, `rust_2018_idioms` lint group will be enabled for compiler/libstd doctests.
Resolves#106086Resolves#99144
Signed-off-by: ozkanonur <work@onurozkan.dev>
Make sure that some stdlib method signatures aren't accidental refinements
In the process of implementing https://rust-lang.github.io/rfcs/3245-refined-impls.html, I found a bunch of stdlib implementations that accidentally "refined" their method signatures by dropping (unnecessary) bounds.
This isn't currently a problem, but may become one if/when method signature refining is stabilized in the future. Shouldn't hurt to make these signatures a bit more accurate anyways.
NOTE (just to be clear lol): This does not affect behavior at all, since we don't actually take advantage of refined implementations yet!
Spelling library
Split per https://github.com/rust-lang/rust/pull/110392
I can squash once people are happy w/ the changes. It's really uncommon for large sets of changes to be perfectly acceptable w/o at least some changes.
I probably won't have time to respond until tomorrow or the next day
Updating Wake example to use new 'pin!' macro
Closes: https://github.com/rust-lang/rust/issues/109965
I have already had this reviewed and approved here: https://github.com/rust-lang/rust/pull/110026 . But because I had some git issues and chose the "nuke it" option as my solution it didn't get merged. I nuked it too quickly. I am sorry for trouble of reviewing twice.
Report allocation errors as panics
OOM is now reported as a panic but with a custom payload type (`AllocErrorPanicPayload`) which holds the layout that was passed to `handle_alloc_error`.
This should be review one commit at a time:
- The first commit adds `AllocErrorPanicPayload` and changes allocation errors to always be reported as panics.
- The second commit removes `#[alloc_error_handler]` and the `alloc_error_hook` API.
ACP: https://github.com/rust-lang/libs-team/issues/192Closes#51540Closes#51245
More `IS_ZST` in `library`
I noticed that `post_inc_start` and `pre_dec_end` were doing this check in different ways
d19b64fb54/library/core/src/slice/iter/macros.rs (L76-L93)
so started making this PR, then added a few more I found since I was already making changes anyway.
I noticed that `post_inc_start` and `pre_dec_end` were doing this check in different ways
d19b64fb54/library/core/src/slice/iter/macros.rs (L76-L93)
so started making this PR, then added a few more I found since I was already making changes anyway.
