btree: add `{Entry,VacantEntry}::insert_entry`
This matches the recently-stabilized methods on `HashMap` entries. I've
reused tracking issue #65225 for now, but we may want to split it.
btree: don't leak value if destructor of key panics
This PR fixes a regression from https://github.com/rust-lang/rust/pull/84904.
The `BTreeMap` already attempts to handle panicking destructors of the key-value pairs by continuing to execute the remaining destructors after one destructor panicked. However, after #84904 the destructor of a value in a key-value pair gets skipped if the destructor of the key panics, only continuing with the next key-value pair. This PR reverts to the behavior before #84904 to also drop the corresponding value if the destructor of a key panics.
This avoids potential memory leaks and can fix the soundness of programs that rely on the destructors being executed (even though this should not be relied upon, because the std collections currently do not guarantee that the remaining elements are dropped after a panic in a destructor).
cc `@Amanieu` because you had opinions on panicking destructors
Use attributes for `dangling_pointers_from_temporaries` lint
Checking for dangling pointers by function name isn't ideal, and leaves out certain pointer-returning methods that don't follow the `as_ptr` naming convention. Using an attribute for this lint cleans things up and allows more thorough coverage of other methods, such as `UnsafeCell::get()`.
Add vec_deque::Iter::as_slices and friends
Add the following methods, that work similarly to VecDeque::as_slices:
- alloc::collections::vec_deque::Iter::as_slices
- alloc::collections::vec_deque::IterMut::into_slices
- alloc::collections::vec_deque::IterMut::as_slices
- alloc::collections::vec_deque::IterMut::as_mut_slices
Obtaining slices from a VecDeque iterator was not previously possible.
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.
btree: simplify the backdoor between set and map
The internal `btree::Recover` trait acted as a private API between
`BTreeSet` and `BTreeMap`, but we can use `pub(_)` restrictions these
days, and some of the methods don't need special handling anymore.
* `BTreeSet::get` can use `BTreeMap::get_key_value`
* `BTreeSet::take` can use `BTreeMap::remove_entry`
* `BTreeSet::replace` does need help, but this now uses a `pub(super)`
method on `BTreeMap` instead of the trait.
* `btree::Recover` is now removed.
The internal `btree::Recover` trait acted as a private API between
`BTreeSet` and `BTreeMap`, but we can use `pub(_)` restrictions these
days, and some of the methods don't need special handling anymore.
* `BTreeSet::get` can use `BTreeMap::get_key_value`
* `BTreeSet::take` can use `BTreeMap::remove_entry`
* `BTreeSet::replace` does need help, but this now uses a `pub(super)`
method on `BTreeMap` instead of the trait.
* `btree::Recover` is now removed.
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.
This updates to a new version of builtins that includes [1], which was
the last blocker to us enabling `f128` tests on all platforms 🎉.
With this update, also change to pinning the version with `=` rather
than using the default carat versioning. This is meant to ensure that
`compiler-builtins` does not get updated as part of the weekly
`Cargo.lock` update, since updates to this crate need to be intentional:
changes to rust-lang/rust and rust-lang/compiler-builtins sometimes need
to be kept in lockstep, unlike most dependencies, and sometimes these
updates can be problematic.
[1]: https://github.com/rust-lang/compiler-builtins/pull/624
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.
Rc/Arc: don't leak the allocation if drop panics
Currently, when the last `Rc<T>` or `Arc<T>` is dropped and the destructor of `T` panics, the allocation will be leaked. This leak is unnecessary since the data cannot be (safely) accessed again and `Box` already deallocates in this case, so let's do the same for `Rc` and `Arc`, too.
Split `boxed.rs` into a few modules
I wanted to add an impl for `Box<_>`, but was quickly discouraged by the 3K file. This splits off a couple bits, making it at least a bit more manageable.
r? ````@workingjubilee```` (I think you are not bothered by refactorings like this?)
Const stability checks v2
The const stability system has served us well ever since `const fn` were first stabilized. It's main feature is that it enforces *recursive* validity -- a stable const fn cannot internally make use of unstable const features without an explicit marker in the form of `#[rustc_allow_const_fn_unstable]`. This is done to make sure that we don't accidentally expose unstable const features on stable in a way that would be hard to take back. As part of this, it is enforced that a `#[rustc_const_stable]` can only call `#[rustc_const_stable]` functions. However, some problems have been coming up with increased usage:
- It is baffling that we have to mark private or even unstable functions as `#[rustc_const_stable]` when they are used as helpers in regular stable `const fn`, and often people will rather add `#[rustc_allow_const_fn_unstable]` instead which was not our intention.
- The system has several gaping holes: a private `const fn` without stability attributes whose inherited stability (walking up parent modules) is `#[stable]` is allowed to call *arbitrary* unstable const operations, but can itself be called from stable `const fn`. Similarly, `#[allow_internal_unstable]` on a macro completely bypasses the recursive nature of the check.
Fundamentally, the problem is that we have *three* disjoint categories of functions, and not enough attributes to distinguish them:
1. const-stable functions
2. private/unstable functions that are meant to be callable from const-stable functions
3. functions that can make use of unstable const features
Functions in the first two categories cannot use unstable const features and they can only call functions from the first two categories.
This PR implements the following system:
- `#[rustc_const_stable]` puts functions in the first category. It may only be applied to `#[stable]` functions.
- `#[rustc_const_unstable]` by default puts functions in the third category. The new attribute `#[rustc_const_stable_indirect]` can be added to such a function to move it into the second category.
- `const fn` without a const stability marker are in the second category if they are still unstable. They automatically inherit the feature gate for regular calls, it can now also be used for const-calls.
Also, all the holes mentioned above have been closed. There's still one potential hole that is hard to avoid, which is when MIR building automatically inserts calls to a particular function in stable functions -- which happens in the panic machinery. Those need to be manually marked `#[rustc_const_stable_indirect]` to be sure they follow recursive const stability. But that's a fairly rare and special case so IMO it's fine.
The net effect of this is that a `#[unstable]` or unmarked function can be constified simply by marking it as `const fn`, and it will then be const-callable from stable `const fn` and subject to recursive const stability requirements. If it is publicly reachable (which implies it cannot be unmarked), it will be const-unstable under the same feature gate. Only if the function ever becomes `#[stable]` does it need a `#[rustc_const_unstable]` or `#[rustc_const_stable]` marker to decide if this should also imply const-stability.
Adding `#[rustc_const_unstable]` is only needed for (a) functions that need to use unstable const lang features (including intrinsics), or (b) `#[stable]` functions that are not yet intended to be const-stable. Adding `#[rustc_const_stable]` is only needed for functions that are actually meant to be directly callable from stable const code. `#[rustc_const_stable_indirect]` is used to mark intrinsics as const-callable and for `#[rustc_const_unstable]` functions that are actually called from other, exposed-on-stable `const fn`. No other attributes are required.
Also see the updated dev-guide at https://github.com/rust-lang/rustc-dev-guide/pull/2098.
I think in the future we may want to tweak this further, so that in the hopefully common case where a public function's const-stability just exactly mirrors its regular stability, we never have to add any attribute. But right now, once the function is stable this requires `#[rustc_const_stable]`.
### Open question
There is one point I could see we might want to do differently, and that is putting `#[rustc_const_unstable]` functions (but not intrinsics) in category 2 by default, and requiring an extra attribute for `#[rustc_const_not_exposed_on_stable]` or so. This would require a bunch of extra annotations, but would have the advantage that turning a `#[rustc_const_unstable]` into `#[rustc_const_stable]` will never change the way the function is const-checked. Currently, we often discover in the const stabilization PR that a function needs some other unstable const things, and then we rush to quickly deal with that. In this alternative universe, we'd work towards getting rid of the `rustc_const_not_exposed_on_stable` before stabilization, and once that is done stabilization becomes a trivial matter. `#[rustc_const_stable_indirect]` would then only be used for intrinsics.
I think I like this idea, but might want to do it in a follow-up PR, as it will need a whole bunch of annotations in the standard library. Also, we probably want to convert all const intrinsics to the "new" form (`#[rustc_intrinsic]` instead of an `extern` block) before doing this to avoid having to deal with two different ways of declaring intrinsics.
Cc `@rust-lang/wg-const-eval` `@rust-lang/libs-api`
Part of https://github.com/rust-lang/rust/issues/129815 (but not finished since this is not yet sufficient to safely let us expose `const fn` from hashbrown)
Fixes https://github.com/rust-lang/rust/issues/131073 by making it so that const-stable functions are always stable
try-job: test-various
Fundamentally, we have *three* disjoint categories of functions:
1. const-stable functions
2. private/unstable functions that are meant to be callable from const-stable functions
3. functions that can make use of unstable const features
This PR implements the following system:
- `#[rustc_const_stable]` puts functions in the first category. It may only be applied to `#[stable]` functions.
- `#[rustc_const_unstable]` by default puts functions in the third category. The new attribute `#[rustc_const_stable_indirect]` can be added to such a function to move it into the second category.
- `const fn` without a const stability marker are in the second category if they are still unstable. They automatically inherit the feature gate for regular calls, it can now also be used for const-calls.
Also, several holes in recursive const stability checking are being closed.
There's still one potential hole that is hard to avoid, which is when MIR
building automatically inserts calls to a particular function in stable
functions -- which happens in the panic machinery. Those need to *not* be
`rustc_const_unstable` (or manually get a `rustc_const_stable_indirect`) to be
sure they follow recursive const stability. But that's a fairly rare and special
case so IMO it's fine.
The net effect of this is that a `#[unstable]` or unmarked function can be
constified simply by marking it as `const fn`, and it will then be
const-callable from stable `const fn` and subject to recursive const stability
requirements. If it is publicly reachable (which implies it cannot be unmarked),
it will be const-unstable under the same feature gate. Only if the function ever
becomes `#[stable]` does it need a `#[rustc_const_unstable]` or
`#[rustc_const_stable]` marker to decide if this should also imply
const-stability.
Adding `#[rustc_const_unstable]` is only needed for (a) functions that need to
use unstable const lang features (including intrinsics), or (b) `#[stable]`
functions that are not yet intended to be const-stable. Adding
`#[rustc_const_stable]` is only needed for functions that are actually meant to
be directly callable from stable const code. `#[rustc_const_stable_indirect]` is
used to mark intrinsics as const-callable and for `#[rustc_const_unstable]`
functions that are actually called from other, exposed-on-stable `const fn`. No
other attributes are required.
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`
Optimize `Rc<T>::default`
The missing piece of https://github.com/rust-lang/rust/pull/131460.
Also refactored `Arc<T>::default` by using a safe `NonNull::from(Box::leak(_))` to replace the unnecessarily unsafe call to `NonNull::new_unchecked(Box::into_raw(_))`. The remaining unsafety is coming from `[Rc|Arc]::from_inner`, which is safe from the construction of `[Rc|Arc]Inner`.
better default capacity for str::replace
Adds smarter capacity for str::replace in cases where we know that the output will be at least as long as the original string.
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
Fix predicate signatures in retain_mut docs
This is my first PR here so let me know if I'm doing anything wrong.
The docs for `retain_mut` in `LinkedList` and `VecDeque` say the predicate takes `&e`, but it should be `&mut e` to match the actual signature. `Vec` [has it documented](https://doc.rust-lang.org/std/vec/struct.Vec.html#method.retain_mut) correctly already.
optimize str.replace
Adds a fast path for str.replace for the ascii to ascii case. This allows for autovectorizing the code. Also should this instead be done with specialization? This way we could remove one branch. I think it is the kind of branch that is easy to predict though.
Benchmark for the fast path (replace all "a" with "b" in the rust wikipedia article, using criterion) :
| N | Speedup | Time New (ns) | Time Old (ns) |
|----------|---------|---------------|---------------|
| 2 | 2.03 | 13.567 | 27.576 |
| 8 | 1.73 | 17.478 | 30.259 |
| 11 | 2.46 | 18.296 | 45.055 |
| 16 | 2.71 | 17.181 | 46.526 |
| 37 | 4.43 | 18.526 | 81.997 |
| 64 | 8.54 | 18.670 | 159.470 |
| 200 | 9.82 | 29.634 | 291.010 |
| 2000 | 24.34 | 81.114 | 1974.300 |
| 20000 | 30.61 | 598.520 | 18318.000 |
| 1000000 | 29.31 | 33458.000 | 980540.000 |
Implemented `FromStr` for `CString` and `TryFrom<CString>` for `String`
The motivation of this change is making it possible to use `CString` in generic methods with `FromStr` and `TryInto<String>` trait bounds. The same traits are already implemented for `OsString` which is an FFI type too.
remove const_cow_is_borrowed feature gate
The two functions guarded by this are still unstable, and there's no reason to require a separate feature gate for their const-ness -- we can just have `cow_is_borrowed` cover both kinds of stability.
Cc #65143
Port sort-research-rs test suite to Rust stdlib tests
This PR is a followup to https://github.com/rust-lang/rust/pull/124032. It replaces the tests that test the various sort functions in the standard library with a test-suite developed as part of https://github.com/Voultapher/sort-research-rs. The current tests suffer a couple of problems:
- They don't cover important real world patterns that the implementations take advantage of and execute special code for.
- The input lengths tested miss out on code paths. For example, important safety property tests never reach the quicksort part of the implementation.
- The miri side is often limited to `len <= 20` which means it very thoroughly tests the insertion sort, which accounts for 19 out of 1.5k LoC.
- They are split into to core and alloc, causing code duplication and uneven coverage.
- ~~The randomness is tied to a caller location, wasting the space exploration capabilities of randomized testing.~~ The randomness is not repeatable, as it relies on `std:#️⃣:RandomState::new().build_hasher()`.
Most of these issues existed before https://github.com/rust-lang/rust/pull/124032, but they are intensified by it. One thing that is new and requires additional testing, is that the new sort implementations specialize based on type properties. For example `Freeze` and non `Freeze` execute different code paths.
Effectively there are three dimensions that matter:
- Input type
- Input length
- Input pattern
The ported test-suite tests various properties along all three dimensions, greatly improving test coverage. It side-steps the miri issue by preferring sampled approaches. For example the test that checks if after a panic the set of elements is still the original one, doesn't do so for every single possible panic opportunity but rather it picks one at random, and performs this test across a range of input length, which varies the panic point across them. This allows regular execution to easily test inputs of length 10k, and miri execution up to 100 which covers significantly more code. The randomness used is tied to a fixed - but random per process execution - seed. This allows for fully repeatable tests and fuzzer like exploration across multiple runs.
Structure wise, the tests are previously found in the core integration tests for `sort_unstable` and alloc unit tests for `sort`. The new test-suite was developed to be a purely black-box approach, which makes integration testing the better place, because it can't accidentally rely on internal access. Because unwinding support is required the tests can't be in core, even if the implementation is, so they are now part of the alloc integration tests. Are there architectures that can only build and test core and not alloc? If so, do such platforms require sort testing? For what it's worth the current implementation state passes miri `--target mips64-unknown-linux-gnuabi64` which is big endian.
The test-suite also contains tests for properties that were and are given by the current and previous implementations, and likely relied upon by users but weren't tested. For example `self_cmp` tests that the two parameters `a` and `b` passed into the comparison function are never references to the same object, which if the user is sorting for example a `&mut [Mutex<i32>]` could lead to a deadlock.
Instead of using the hashed caller location as rand seed, it uses seconds since unix epoch / 10, which given timestamps in the CI should be reasonably easy to reproduce, but also allows fuzzer like space exploration.
---
Test run-time changes:
Setup:
```
Linux 6.10
rustc 1.83.0-nightly (f79a912d9 2024-09-18)
AMD Ryzen 9 5900X 12-Core Processor (Zen 3 micro-architecture)
CPU boost enabled.
```
master: e9df22f
Before core integration tests:
```
$ LD_LIBRARY_PATH=build/x86_64-unknown-linux-gnu/stage0-std/x86_64-unknown-linux-gnu/release/deps/ hyperfine build/x86_64-unknown-linux-gnu/stage0-std/x86_64-unknown-linux-gnu/release/deps/coretests-219cbd0308a49e2f
Time (mean ± σ): 869.6 ms ± 21.1 ms [User: 1327.6 ms, System: 95.1 ms]
Range (min … max): 845.4 ms … 917.0 ms 10 runs
# MIRIFLAGS="-Zmiri-disable-isolation" to get real time
$ MIRIFLAGS="-Zmiri-disable-isolation" ./x.py miri library/core
finished in 738.44s
```
After core integration tests:
```
$ LD_LIBRARY_PATH=build/x86_64-unknown-linux-gnu/stage0-std/x86_64-unknown-linux-gnu/release/deps/ hyperfine build/x86_64-unknown-linux-gnu/stage0-std/x86_64-unknown-linux-gnu/release/deps/coretests-219cbd0308a49e2f
Time (mean ± σ): 865.1 ms ± 14.7 ms [User: 1283.5 ms, System: 88.4 ms]
Range (min … max): 836.2 ms … 885.7 ms 10 runs
$ MIRIFLAGS="-Zmiri-disable-isolation" ./x.py miri library/core
finished in 752.35s
```
Before alloc unit tests:
```
LD_LIBRARY_PATH=build/x86_64-unknown-linux-gnu/stage0-std/x86_64-unknown-linux-gnu/release/deps/ hyperfine build/x86_64-unknown-linux-gnu/stage0-std/x86_64-unknown-linux-gnu/release/deps/alloc-19c15e6e8565aa54
Time (mean ± σ): 295.0 ms ± 9.9 ms [User: 719.6 ms, System: 35.3 ms]
Range (min … max): 284.9 ms … 319.3 ms 10 runs
$ MIRIFLAGS="-Zmiri-disable-isolation" ./x.py miri library/alloc
finished in 322.75s
```
After alloc unit tests:
```
LD_LIBRARY_PATH=build/x86_64-unknown-linux-gnu/stage0-std/x86_64-unknown-linux-gnu/release/deps/ hyperfine build/x86_64-unknown-linux-gnu/stage0-std/x86_64-unknown-linux-gnu/release/deps/alloc-19c15e6e8565aa54
Time (mean ± σ): 97.4 ms ± 4.1 ms [User: 297.7 ms, System: 28.6 ms]
Range (min … max): 92.3 ms … 109.2 ms 27 runs
$ MIRIFLAGS="-Zmiri-disable-isolation" ./x.py miri library/alloc
finished in 309.18s
```
Before alloc integration tests:
```
$ LD_LIBRARY_PATH=build/x86_64-unknown-linux-gnu/stage0-std/x86_64-unknown-linux-gnu/release/deps/ hyperfine build/x86_64-unknown-linux-gnu/stage0-std/x86_64-unknown-linux-gnu/release/deps/alloctests-439e7300c61a8046
Time (mean ± σ): 103.2 ms ± 1.7 ms [User: 135.7 ms, System: 39.4 ms]
Range (min … max): 99.7 ms … 107.3 ms 28 runs
$ MIRIFLAGS="-Zmiri-disable-isolation" ./x.py miri library/alloc
finished in 231.35s
```
After alloc integration tests:
```
$ LD_LIBRARY_PATH=build/x86_64-unknown-linux-gnu/stage0-std/x86_64-unknown-linux-gnu/release/deps/ hyperfine build/x86_64-unknown-linux-gnu/stage0-std/x86_64-unknown-linux-gnu/release/deps/alloctests-439e7300c61a8046
Time (mean ± σ): 379.8 ms ± 4.7 ms [User: 4620.5 ms, System: 1157.2 ms]
Range (min … max): 373.6 ms … 386.9 ms 10 runs
$ MIRIFLAGS="-Zmiri-disable-isolation" ./x.py miri library/alloc
finished in 449.24s
```
In my opinion the results don't change iterative library development or CI execution in meaningful ways. For example currently the library doc-tests take ~66s and incremental compilation takes 10+ seconds. However I only have limited knowledge of the various local development workflows that exist, and might be missing one that is significantly impacted by this change.
The `Box<T: Default>` impl currently calls `T::default()` before allocating
the `Box`.
Most `Default` impls are trivial, which should in theory allow
LLVM to construct `T: Default` directly in the `Box` allocation when calling
`<Box<T>>::default()`.
However, the allocation may fail, which necessitates calling `T's` destructor if it has one.
If the destructor is non-trivial, then LLVM has a hard time proving that it's
sound to elide, which makes it construct `T` on the stack first, and then copy it into the allocation.
Create an uninit `Box` first, and then write `T::default` into it, so that LLVM now only needs to prove
that the `T::default` can't panic, which should be trivial for most `Default` impls.
liballoc: introduce String, Vec const-slicing
This change `const`-qualifies many methods on `Vec` and `String`, notably `as_slice`, `as_str`, `len`. These changes are made behind the unstable feature flag `const_vec_string_slice`.
## Motivation
This is to support simultaneous variance over ownership and constness. I have an enum type that may contain either `String` or `&str`, and I want to produce a `&str` from it in a possibly-`const` context.
```rust
enum StrOrString<'s> {
Str(&'s str),
String(String),
}
impl<'s> StrOrString<'s> {
const fn as_str(&self) -> &str {
match self {
// In a const-context, I really only expect to see this variant, but I can't switch the implementation
// in some mode like #[cfg(const)] -- there has to be a single body
Self::Str(s) => s,
// so this is a problem, since it's not `const`
Self::String(s) => s.as_str(),
}
}
}
```
Currently `String` and `Vec` don't support this, but can without functional changes. Similar logic applies for `len`, `capacity`, `is_empty`.
## Changes
The essential thing enabling this change is that `Unique::as_ptr` is `const`. This lets us convert `RawVec::ptr` -> `Vec::as_ptr` -> `Vec::as_slice` -> `String::as_str`.
I had to move the `Deref` implementations into `as_{str,slice}` because `Deref` isn't `#[const_trait]`, but I would expect this change to be invisible up to inlining. I moved the `DerefMut` implementations as well for uniformity.
This change `const`-qualifies many methods on Vec and String, notably
`as_slice`, `as_str`, `len`. These changes are made behind the unstable
feature flag `const_vec_string_slice` with the following tracking issue:
https://github.com/rust-lang/rust/issues/129041
Mark some more types as having insignificant dtor
These were caught by https://github.com/rust-lang/rust/pull/129864#issuecomment-2376658407, which is implementing a lint for some changes in drop order for temporaries in tail expressions.
Specifically, the destructors of `CString` and the bitpacked repr for `std::io::Error` are insignificant insofar as they don't have side-effects on things like locking or synchronization; they just free memory.
See some discussion on #89144 for what makes a drop impl "significant"
This commit is a followup to https://github.com/rust-lang/rust/pull/124032. It
replaces the tests that test the various sort functions in the standard library
with a test-suite developed as part of
https://github.com/Voultapher/sort-research-rs. The current tests suffer a
couple of problems:
- They don't cover important real world patterns that the implementations take
advantage of and execute special code for.
- The input lengths tested miss out on code paths. For example, important safety
property tests never reach the quicksort part of the implementation.
- The miri side is often limited to `len <= 20` which means it very thoroughly
tests the insertion sort, which accounts for 19 out of 1.5k LoC.
- They are split into to core and alloc, causing code duplication and uneven
coverage.
- The randomness is not repeatable, as it
relies on `std:#️⃣:RandomState::new().build_hasher()`.
Most of these issues existed before
https://github.com/rust-lang/rust/pull/124032, but they are intensified by it.
One thing that is new and requires additional testing, is that the new sort
implementations specialize based on type properties. For example `Freeze` and
non `Freeze` execute different code paths.
Effectively there are three dimensions that matter:
- Input type
- Input length
- Input pattern
The ported test-suite tests various properties along all three dimensions,
greatly improving test coverage. It side-steps the miri issue by preferring
sampled approaches. For example the test that checks if after a panic the set of
elements is still the original one, doesn't do so for every single possible
panic opportunity but rather it picks one at random, and performs this test
across a range of input length, which varies the panic point across them. This
allows regular execution to easily test inputs of length 10k, and miri execution
up to 100 which covers significantly more code. The randomness used is tied to a
fixed - but random per process execution - seed. This allows for fully
repeatable tests and fuzzer like exploration across multiple runs.
Structure wise, the tests are previously found in the core integration tests for
`sort_unstable` and alloc unit tests for `sort`. The new test-suite was
developed to be a purely black-box approach, which makes integration testing the
better place, because it can't accidentally rely on internal access. Because
unwinding support is required the tests can't be in core, even if the
implementation is, so they are now part of the alloc integration tests. Are
there architectures that can only build and test core and not alloc? If so, do
such platforms require sort testing? For what it's worth the current
implementation state passes miri `--target mips64-unknown-linux-gnuabi64` which
is big endian.
The test-suite also contains tests for properties that were and are given by the
current and previous implementations, and likely relied upon by users but
weren't tested. For example `self_cmp` tests that the two parameters `a` and `b`
passed into the comparison function are never references to the same object,
which if the user is sorting for example a `&mut [Mutex<i32>]` could lead to a
deadlock.
Instead of using the hashed caller location as rand seed, it uses seconds since
unix epoch / 10, which given timestamps in the CI should be reasonably easy to
reproduce, but also allows fuzzer like space exploration.
Improve autovectorization of to_lowercase / to_uppercase functions
Refactor the code in the `convert_while_ascii` helper function to make it more suitable for auto-vectorization and also process the full ascii prefix of the string. The generic case conversion logic will only be invoked starting from the first non-ascii character.
The runtime on a microbenchmark with a small ascii-only input decreases from ~55ns to ~18ns per iteration. The new implementation also reduces the amount of unsafe code and encapsulates all unsafe inside the helper function.
Fixes#123712
update `compiler-builtins` to 0.1.126
this requires the addition of a bootstrap variant of the new `naked_asm!` macro
r? `@tgross35`
extracted from https://github.com/rust-lang/rust/pull/128651
Since the stabilization in #127679 has reached stage0, 1.82-beta, we can
start using `&raw` freely, and even the soft-deprecated `ptr::addr_of!`
and `ptr::addr_of_mut!` can stop allowing the unstable feature.
I intentionally did not change any documentation or tests, but the rest
of those macro uses are all now using `&raw const` or `&raw mut` in the
standard library.
Refactor the code in the `convert_while_ascii` helper function to make
it more suitable for auto-vectorization and also process the full ascii
prefix of the string. The generic case conversion logic will only be
invoked starting from the first non-ascii character.
The runtime on microbenchmarks with ascii-only inputs improves between
1.5x for short and 4x for long inputs on x86_64 and aarch64.
The new implementation also encapsulates all unsafe inside the
`convert_while_ascii` function.
Fixes#123712
Add str.as_str() for easy Deref to string slices
Working with `Box<str>` is cumbersome, because in places like `iter.filter()` it can end up being `&Box<str>` or even `&&Box<str>`, and such type doesn't always get auto-dereferenced as expected.
Dereferencing such box to `&str` requires ugly syntax like `&**boxed_str` or `&***boxed_str`, with the exact amount of `*`s.
`Box<str>` is [not easily comparable with other string types](https://github.com/rust-lang/rust/pull/129852) via `PartialEq`. `Box<str>` won't work for lookups in types like `HashSet<String>`, because `Borrow<String>` won't take types like `&Box<str>`. OTOH `set.contains(s.as_str())` works nicely regardless of levels of indirection.
`String` has a simple solution for this: the `as_str()` method, and `Box<str>` should too.
Avoid re-validating UTF-8 in `FromUtf8Error::into_utf8_lossy`
Part of the unstable feature `string_from_utf8_lossy_owned` - #129436
Refactor `FromUtf8Error::into_utf8_lossy` to copy valid UTF-8 bytes into the buffer, avoiding double validation of bytes.
Add tests that mirror the `String::from_utf8_lossy` tests.
Refactor `into_utf8_lossy` to copy valid UTF-8 bytes into the buffer,
avoiding double validation of bytes.
Add tests that mirror the `String::from_utf8_lossy` tests
[Clippy] Get rid of most `std` `match_def_path` usage, swap to diagnostic items.
Part of https://github.com/rust-lang/rust-clippy/issues/5393.
This was going to remove all `std` paths, but `SeekFrom` has issues being cleanly replaced with a diagnostic item as the paths are for variants, which currently cannot be diagnostic items.
This also, as a last step, categories the paths to help with future path removals.
Add new_cyclic_in for Rc and Arc
Currently, new_cyclic_in does not exist for Rc and Arc. This is an oversight according to https://github.com/rust-lang/wg-allocators/issues/132.
This PR adds new_cyclic_in for Rc and Arc. The implementation is almost the exact same as new_cyclic with some small differences to make it allocator-specific. new_cyclic's implementation has been replaced with a call to `new_cyclic_in(data_fn, Global)`.
Remaining questions:
* ~~Is requiring Allocator to be Clone OK? According to https://github.com/rust-lang/wg-allocators/issues/88, Allocators should be cheap to clone. I'm just hesitant to add unnecessary constraints, though I don't see an obvious workaround for this function since many called functions in new_cyclic_in expect an owned Allocator. I see Allocator.by_ref() as an option, but that doesn't work on when creating Weak { ptr: init_ptr, alloc: alloc.clone() }, because the type of Weak then becomes Weak<T, &A> which is incompatible.~~ Fixed, thank you `@zakarumych!` This PR no longer requires the allocator to be Clone.
* Currently, new_cyclic_in's documentation is almost entirely copy-pasted from new_cyclic, with minor tweaks to make it more accurate (e.g. Rc<T> -> Rc<T, A>). The example section is removed to mitigate redundancy and instead redirects to cyclic_in. Is this appropriate?
* ~~The comments in new_cyclic_in (and much of the implementation) are also copy-pasted from new_cyclic. Would it be better to make a helper method new_cyclic_in_internal that both functions call, with either Global or the custom allocator? I'm not sure if that's even possible, since the internal method would have to return Arc<T, Global> and I don't know if it's possible to "downcast" that to an Arc<T>. Maybe transmute would work here?~~ Done, thanks `@zakarumych`
* Arc::new_cyclic is #[inline], but Rc::new_cyclic is not. Which is preferred?
* nit: does it matter where in the impl block new_cyclic_in is defined?
Implement feature `string_from_utf8_lossy_owned` for lossy conversion from `Vec<u8>` to `String` methods
Accepted ACP: https://github.com/rust-lang/libs-team/issues/116
Tracking issue: #129436
Implement feature for lossily converting from `Vec<u8>` to `String`
- Add `String::from_utf8_lossy_owned`
- Add `FromUtf8Error::into_utf8_lossy`
---
Related to #64727, but unsure whether to mark it "fixed" by this PR.
That issue partly asks for in-place replacement of the original allocation. We fulfill the other half of that request with these functions.
closes#64727
Stabilize `&mut` (and `*mut`) as well as `&Cell` (and `*const Cell`) in const
This stabilizes `const_mut_refs` and `const_refs_to_cell`. That allows a bunch of new things in const contexts:
- Mentioning `&mut` types
- Creating `&mut` and `*mut` values
- Creating `&T` and `*const T` values where `T` contains interior mutability
- Dereferencing `&mut` and `*mut` values (both for reads and writes)
The same rules as at runtime apply: mutating immutable data is UB. This includes mutation through pointers derived from shared references; the following is diagnosed with a hard error:
```rust
#[allow(invalid_reference_casting)]
const _: () = {
let mut val = 15;
let ptr = &val as *const i32 as *mut i32;
unsafe { *ptr = 16; }
};
```
The main limitation that is enforced is that the final value of a const (or non-`mut` static) may not contain `&mut` values nor interior mutable `&` values. This is necessary because the memory those references point to becomes *read-only* when the constant is done computing, so (interior) mutable references to such memory would be pretty dangerous. We take a multi-layered approach here to ensuring no mutable references escape the initializer expression:
- A static analysis rejects (interior) mutable references when the referee looks like it may outlive the current MIR body.
- To be extra sure, this static check is complemented by a "safety net" of dynamic checks. ("Dynamic" in the sense of "running during/after const-evaluation, e.g. at runtime of this code" -- in contrast to "static" which works entirely by looking at the MIR without evaluating it.)
- After the final value is computed, we do a type-driven traversal of the entire value, and if we find any `&mut` or interior-mutable `&` we error out.
- However, the type-driven traversal cannot traverse `union` or raw pointers, so there is a second dynamic check where if the final value of the const contains any pointer that was not derived from a shared reference, we complain. This is currently a future-compat lint, but will become an ICE in #128543. On the off-chance that it's actually possible to trigger this lint on stable, I'd prefer if we could make it an ICE before stabilizing const_mut_refs, but it's not a hard blocker. This part of the "safety net" is only active for mutable references since with shared references, it has false positives.
Altogether this should prevent people from leaking (interior) mutable references out of the const initializer.
While updating the tests I learned that surprisingly, this code gets rejected:
```rust
const _: Vec<i32> = {
let mut x = Vec::<i32>::new(); //~ ERROR destructor of `Vec<i32>` cannot be evaluated at compile-time
let r = &mut x;
let y = x;
y
};
```
The analysis that rejects destructors in `const` is very conservative when it sees an `&mut` being created to `x`, and then considers `x` to be always live. See [here](https://github.com/rust-lang/rust/issues/65394#issuecomment-541499219) for a longer explanation. `const_precise_live_drops` will solve this, so I consider this problem to be tracked by https://github.com/rust-lang/rust/issues/73255.
Cc `@rust-lang/wg-const-eval` `@rust-lang/lang`
Cc https://github.com/rust-lang/rust/issues/57349
Cc https://github.com/rust-lang/rust/issues/80384
Add `NonNull` convenience methods to `Box` and `Vec`
Implements the ACP: https://github.com/rust-lang/libs-team/issues/418.
The docs for the added methods are mostly copied from the existing methods that use raw pointers instead of `NonNull`.
I'm new to this "contributing to rustc" thing, so I'm sorry if I did something wrong. In particular, I don't know what the process is for creating a new unstable feature. Please advise me if I should do something. Thank you.
some const cleanup: remove unnecessary attributes, add const-hack indications
I learned that we use `FIXME(const-hack)` on top of the "const-hack" label. That seems much better since it marks the right place in the code and moves around with the code. So I went through the PRs with that label and added appropriate FIXMEs in the code. IMO this means we can then remove the label -- Cc ``@rust-lang/wg-const-eval.``
I also noticed some const stability attributes that don't do anything useful, and removed them.
r? ``@fee1-dead``
Also emit `missing_docs` lint with `--test` to fulfil expectations
This PR removes the "test harness" suppression of the `missing_docs` lint to be able to fulfil `#[expect]` (expectations) as it is now "relevant".
I think the goal was to maybe avoid false-positive while linting on public items under `#[cfg(test)]` but with effective visibility we should no longer have any false-positive.
Another possibility would be to query the lint level and only emit the lint if it's of expect level, but that is even more hacky.
Fixes https://github.com/rust-lang/rust/issues/130021
try-job: x86_64-gnu-aux
enable -Zrandomize-layout in debug CI builds
This builds rustc/libs/tools with `-Zrandomize-layout` on *-debug CI runners.
Only a handful of tests and asserts break with that enabled, which is promising. One test was fixable, the rest is dealt with by disabling them through new cargo features or compiletest directives.
The config.toml flag `rust.randomize-layout` defaults to false, so it has to be explicitly enabled for now.
Rollup of 9 pull requests
Successful merges:
- #127474 (doc: Make block of inline Deref methods foldable)
- #129678 (Deny imports of `rustc_type_ir::inherent` outside of type ir + new trait solver)
- #129738 (`rustc_mir_transform` cleanups)
- #129793 (add extra linebreaks so rustdoc can identify the first sentence)
- #129804 (Fixed some typos in the standard library documentation/comments)
- #129837 (Actually parse stdout json, instead of using hacky contains logic.)
- #129842 (Fix LLVM ABI NAME for riscv64imac-unknown-nuttx-elf)
- #129843 (Mark myself as on vacation for triagebot)
- #129858 (Replace walk with visit so we dont skip outermost expr kind in def collector)
Failed merges:
- #129777 (Add `unreachable_pub`, round 4)
- #129868 (Remove kobzol vacation status)
r? `@ghost`
`@rustbot` modify labels: rollup
Apply size optimizations to panic machinery and some cold functions
* std dependencies gimli and addr2line are now built with opt-level=s
* various panic-related methods and `#[cold]` methods are now marked `#[optimize(size)]`
Panics should be cold enough that it doesn't make sense to optimize them for speed. The only tradeoff here is if someone does a lot of backtrace captures (without panics) and printing then the opt-level change might impact their perf.
Seems to be the first use of the optimize attribute. Tracking issue #54882
Re-enable android tests/benches in alloc/core
This is basically a revert of https://github.com/rust-lang/rust/pull/73729. These tests better work on android now; it's been 4 years and we don't use dlmalloc on that target anymore.
And I've validated that they should pass now with a try-build :)
Add fmt::Debug to sync::Weak<T, A>
Currently, `sync::Weak<T>` implements `Debug`, but `sync::Weak<T, A>` does not. This appears to be an oversight, as `rc::Weak<T, A>` implements `Debug`. (Note: `sync::Weak` is the weak for `Arc`, and `rc::Weak` is the weak for `Rc`.)
This PR adds the Debug trait for `sync::Weak<T, A>`. The issue was initially brought up here: https://github.com/rust-lang/wg-allocators/issues/131
A partial stabilization that only affects:
- AllocType<T>::new_uninit
- AllocType<T>::assume_init
- AllocType<[T]>::new_uninit_slice
- AllocType<[T]>::assume_init
where "AllocType" is Box, Rc, or Arc
library: Move unstable API of new_uninit to new features
- `new_zeroed` variants move to `new_zeroed_alloc`
- the `write` fn moves to `box_uninit_write`
The remainder will be stabilized in upcoming patches, as it was decided to only stabilize `uninit*` and `assume_init`.
- `new_zeroed` variants move to `new_zeroed_alloc`
- the `write` fn moves to `box_uninit_write`
The remainder will be stabilized in upcoming patches, as
it was decided to only stabilize `uninit*` and `assume_init`.
miri: make vtable addresses not globally unique
Miri currently gives vtables a unique global address. That's not actually matching reality though. So this PR enables Miri to generate different addresses for the same type-trait pair.
To avoid generating an unbounded number of `AllocId` (and consuming unbounded amounts of memory), we use the "salt" technique that we also already use for giving constants non-unique addresses: the cache is keyed on a "salt" value n top of the actually relevant key, and Miri picks a random salt (currently in the range `0..16`) each time it needs to choose an `AllocId` for one of these globals -- that means we'll get up to 16 different addresses for each vtable. The salt scheme is integrated into the global allocation deduplication logic in `tcx`, and also used for functions and string literals. (So this also fixes the problem that casting the same function to a fn ptr over and over will consume unbounded memory.)
r? `@saethlin`
Fixes https://github.com/rust-lang/miri/issues/3737
Apply "polymorphization at home" to RawVec
The idea here is to move all the logic in RawVec into functions with explicit size and alignment parameters. This should eliminate all the fussing about how tweaking RawVec code produces large swings in compile times.
This uncovered https://github.com/rust-lang/rust-clippy/issues/12979, so I've modified the relevant test in a way that tries to preserve the spirit of the test without tripping the ICE.
Improve `Ord` violation help
Recent experience in #128083 showed that the panic message when an Ord violation is detected by the new sort implementations can be confusing. So this PR aims to improve it, together with minor bug fixes in the doc comments for sort*, sort_unstable* and select_nth_unstable*.
Is it possible to get these changes into the 1.81 release? It doesn't change behavior and would greatly help when users encounter this panic for the first time, which they may after upgrading to 1.81.
Tagging `@orlp`
impl `Default` for collection iterators that don't already have it
There is a pretty strong precedent for implementing `Default` for collection iterators, and this does so for some where this implementation was missed.
I don't think this needs a separate ACP (since this precedent already exists, and these feel like they were just missed), however, it *will* need an FCP since these implementations are instantly stable.
Implement cursors for `BTreeSet`
Tracking issue: https://github.com/rust-lang/rust/issues/107540
This is a straightforward wrapping of the map API, except that map's `CursorMut` does not make sense, because there is no value to mutate. Hence, map's `CursorMutKey` is wrapped here as just `CursorMut`, since it's unambiguous for sets and we don't normally speak of "keys". On the other hand, I can see some potential for confusion with `CursorMut` meaning different things in each module. I'm happy to take suggestions to improve that.
r? ````@Amanieu````
Add `#[must_use]` to some `into_raw*` functions.
cc #121287
r? ``@cuviper``
Adds `#[must_use = "losing the pointer will leak memory"]`[^1] to `Box::into_raw(_with_allocator)`, `Vec::into_raw_parts(_with_alloc)`, `String::into_raw_parts`[^2], and `rc::{Rc, Weak}::into_raw_with_allocator` (Rc's normal `into_raw` and all of `Arc`'s `into_raw*`s are already `must_use`).
Adds `#[must_use = "losing the raw <resource name may leak resources"]` to `IntoRawFd::into_raw_fd`, `IntoRawSocket::into_raw_socket`, and `IntoRawHandle::into_raw_handle`.
[^1]: "*will* leak memory" may be too-strong wording (since `Box`/`Vec`/`String`/`rc::Weak` might not have a backing allocation), but I left it as-is for simplicity and consistency.
[^2]: `String::into_raw_parts`'s `must_use` message is changed from the previous (possibly misleading) "`self` will be dropped if the result is not used".
- Use if the implementation of [`Ord`] for `T`
language
- Link to total order wiki page
- Rework total order help and examples
- Improve language to be more precise and less
prone to misunderstandings.
- Fix usage of `sort_unstable_by` in `sort_by`
example
- Fix missing author mention
- Use more consistent example input for sort
- Use more idiomatic assert_eq! in examples
- Use more natural "comparison function" language
instead of "comparator function"
Optimize empty case in Vec::retain
While profiling some code that happens to call Vec::retain() in a tight loop, I noticed more runtime than expected in retain, even in a bench case where the vector was always empty. When I wrapped my call to retain in `if !myvec.is_empty()` I saw faster execution compared with doing retain on an empty vector.
On closer inspection, Vec::retain is doing set_len(0) on itself even when the vector is empty, and then resetting the length again in BackshiftOnDrop::drop.
Unscientific screengrab of a flamegraph illustrating how we end up spending time in set_len and drop:
Clean and enable `rustdoc::unescaped_backticks` for `core/alloc/std/test/proc_macro`
I am not sure if the lint is supposed to be "ready enough" (since it is `allow` by default), but it does catch a couple issues in `core` (`alloc`, `std`, `test` and `proc_macro` are already clean), so I propose making it `warn` in all the crates rendered in the website.
Cc: `@GuillaumeGomez`
Update compiler_builtins to 0.1.114
The `weak-intrinsics` feature was removed from compiler_builtins in https://github.com/rust-lang/compiler-builtins/pull/598, so dropped the `compiler-builtins-weak-intrinsics` feature from alloc/std/sysroot.
In https://github.com/rust-lang/compiler-builtins/pull/593, some builtins for f16/f128 were added. These don't work for all compiler backends, so add a `compiler-builtins-no-f16-f128` feature and disable it for cranelift and gcc.
The `weak-intrinsics` feature was removed from compiler_builtins in
https://github.com/rust-lang/compiler-builtins/pull/598, so dropped the
`compiler-builtins-weak-intrinsics` feature from alloc/std/sysroot.
In https://github.com/rust-lang/compiler-builtins/pull/593, some
builtins for f16/f128 were added. These don't work for all compiler
backends, so add a `compiler-builtins-no-f16-f128` feature and disable
it for cranelift and gcc. Also disable it for LLVM targets that don't
support it.
Stabilize `const_waker`
Closes: https://github.com/rust-lang/rust/issues/102012.
For `local_waker` and `context_ext` related things, I just ~~moved them to dedicated feature gates and reused their own tracking issue (maybe it's better to open a new one later, but at least they should not be tracked under https://github.com/rust-lang/rust/issues/102012 from the beginning IMO.)~~ reused their own feature gates as suggested by ``@tgross35.``
``@rustbot`` label: +T-libs-api
r? libs-api
Fix doc nits
Many tiny changes to stdlib doc comments to make them consistent (for example "Returns foo", rather than "Return foo"), adding missing periods, paragraph breaks, backticks for monospace style, and other minor nits.
from_ref, from_mut: clarify documentation
This was brought up [here](https://github.com/rust-lang/rust/issues/56604#issuecomment-2143193486). The domain of quantification is generally always constrained by the type in the type signature, and I am not sure it's always worth spelling that out explicitly as that makes things exceedingly verbose. But since this was explicitly brought up, let's clarify.
Gate `AsyncFn*` under `async_closure` feature
T-lang has not come to a consensus on the naming of async closure callable bounds, and as part of allowing the async closures RFC merge, we agreed to place `AsyncFn` under the same gate as `async Fn` so that these syntaxes can be evaluated in parallel.
See https://github.com/rust-lang/rfcs/pull/3668#issuecomment-2246435537
r? oli-obk
Replace some `mem::forget`'s with `ManuallyDrop`
> but I would like to see a larger effort to replace all uses of `mem::forget`.
_Originally posted by `@saethlin` in https://github.com/rust-lang/rust/issues/127584#issuecomment-2226087767_
So,
r? `@saethlin`
Sorry, I have finished writing all of this before I got your response.
Remove generic lifetime parameter of trait `Pattern`
Use a GAT for `Searcher` associated type because this trait is always implemented for every lifetime anyway.
cc #27721
Update tracking issue for `const_binary_heap_new_in`
This PR updates the tracking issue of `const_binary_heap_new_in` feature:
- Old issue: #112353
- New issue: #125961
Add missing try_new_uninit_slice_in and try_new_zeroed_slice_in
The methods for fallible slice allocation in a given allocator were missing from `Box`, which was an oversight according to https://github.com/rust-lang/wg-allocators/issues/130
This PR adds them as `try_new_uninit_slice_in` and `try_new_zeroed_slice_in`. I simply copy-pasted the implementations of `try_new_uninit_slice` and `try_new_zeroed_slice` and adusted doc comment, typings, and the allocator it uses internally.
Also adds missing punctuation to the doc comments of `try_new_uninit_slice` and `try_new_zeroed_slice`.
Related issue is https://github.com/rust-lang/rust/issues/32838 (Allocator traits and std::heap) *I think*. Also relevant is https://github.com/rust-lang/rust/issues/63291, but I did not add the corresponding `#[unstable]` proc macro, since `try_new_uninit_slice` and `try_new_zeroed_slice` are also not annotated with it.
When we do the big `use` reformatting there are a tiny number of cases
where rustfmt moves a comment from one `use` item to another in an
undesirable way. This commit pre-emptively rearranges things to prevent
this from happening.
Remove memory leaks in doctests in `core`, `alloc`, and `std`
cc `@RalfJung` https://github.com/rust-lang/rust/issues/126067https://github.com/rust-lang/miri/issues/3670
Should be no actual *documentation* changes[^1], all added/modified lines in the doctests are hidden with `#`,
This PR splits the existing memory leaks in doctests in `core`, `alloc`, and `std` into two general categories:
1. "Non-focused" memory leaks that are incidental to the thing being documented, and/or are easy to remove, i.e. they are only there because preventing the leak would make the doctest less clear and/or concise.
- These doctests simply have a comment like `# // Prevent leaks for Miri.` above the added line that removes the memory leak.
- [^2]Some of these would perhaps be better as part of the public documentation part of the doctest, to clarify that a memory leak can happen if it is not otherwise mentioned explicitly in the documentation (specifically the ones in `(A)Rc::increment_strong_count(_in)`).
2. "Focused" memory leaks that are intentional and documented, and/or are possibly fragile to remove.
- These doctests have a `# // FIXME` comment above the line that removes the memory leak, with a note that once `-Zmiri-disable-leak-check` can be applied at test granularity, these tests should be "un-unleakified" and have `-Zmiri-disable-leak-check` enabled.
- Some of these are possibly fragile (e.g. unleaking the result of `Vec::leak`) and thus should definitely not be made part of the documentation.
This should be all of the leaks currently in `core` and `alloc`. I only found one leak in `std`, and it was in the first category (excluding the modules `@RalfJung` mentioned in https://github.com/rust-lang/rust/issues/126067 , and reducing the number of iterations of [one test](https://github.com/rust-lang/rust/blob/master/library/std/src/sync/once_lock.rs#L49-L94) from 1000 to 10)
[^1]: assuming [^2] is not added
[^2]: backlink
Generalize `fn allocator` for Rc/Arc.
Split out from #119761
- For `Rc`/`Arc`, the existing associated `fn`s are changed to allow unsized pointees.
- For `Weak`s, new methods are added.
`````@rustbot````` label +A-allocators
Mark format! with must_use hint
Uses unstable feature https://github.com/rust-lang/rust/issues/94745
Part of #126475
First contribution to rust, please let me know if the blessing of tests is correct
Thanks `@bjorn3` for the help
Make casts of pointers to trait objects stricter
This is an attempt to `fix` https://github.com/rust-lang/rust/issues/120222 and https://github.com/rust-lang/rust/issues/120217.
This is done by adding restrictions on casting pointers to trait objects.
Before this PR the rules were as follows:
> When casting `*const X<dyn A>` -> `*const Y<dyn B>`, principal traits in `A` and `B` must refer to the same trait definition (or no trait).
With this PR the rules are changed to
> When casting `*const X<dyn Src>` -> `*const Y<dyn Dst>`
> - if `Dst` has a principal trait `DstP`,
> - `Src` must have a principal trait `SrcP`
> - `dyn SrcP` and `dyn DstP` must be the same type (modulo the trait object lifetime, `dyn T+'a` -> `dyn T+'b` is allowed)
> - Auto traits in `Dst` must be a subset of auto traits in `Src`
> - Not adhering to this is currently a FCW (warn-by-default + `FutureReleaseErrorReportInDeps`), instead of an error
> - if `Src` has a principal trait `Dst` must as well
> - this restriction will be removed in a follow up PR
This ensures that
1. Principal trait's generic arguments match (no `*const dyn Tr<A>` -> `*const dyn Tr<B>` casts, which are a problem for [#120222](https://github.com/rust-lang/rust/issues/120222))
2. Principal trait's lifetime arguments match (no `*const dyn Tr<'a>` -> `*const dyn Tr<'b>` casts, which are a problem for [#120217](https://github.com/rust-lang/rust/issues/120217))
3. No auto traits can be _added_ (this is a problem for arbitrary self types, see [this comment](https://github.com/rust-lang/rust/pull/120248#discussion_r1463835350))
Some notes:
- We only care about the metadata/last field, so you can still cast `*const dyn T` to `*const WithHeader<dyn T>`, etc
- The lifetime of the trait object itself (`dyn A + 'lt`) is not checked, so you can still cast `*mut FnOnce() + '_` to `*mut FnOnce() + 'static`, etc
- This feels fishy, but I couldn't come up with a reason it must be checked
The diagnostics are currently not great, to say the least, but as far as I can tell this correctly fixes the issues.
cc `@oli-obk` `@compiler-errors` `@lcnr`
Run alloc sync tests
I was browsing the code and this struck me as weird. We're not running some doc tests because, the comment says, Windows builders deadlock. That should absolutely not happen, at least with our current implementation. And if it does happen I'd like to know.
Just to be sure though I'll do some try builds.
try-job: x86_64-msvc
try-job: i686-msvc
try-job: i686-mingw
try-job: x86_64-mingw
