Do not allocate for ZST ThinBox (attempt 2 using const_allocate)
There's PR https://github.com/rust-lang/rust/pull/123184 which avoids allocation for ZST ThinBox.
That PR has an issue with unsoundness with padding in `MaybeUninit` (see comments in that PR). Also that PR relies on `Freeze` trait.
This PR is much simpler implementation which does not have this problem, but it uses `const_allocate` feature.
`@oli-obk` suggested that `const_allocate` should not be used for that feature. But I like how easy it to do this feature with `const_allocate`. Maybe it's OK to use `const_allocate` while `ThinBox` is unstable? Or, well, we can abandon this PR.
r? `@oli-obk`
The `thread_local!` examples use `RefCell` for `Copy` types. Update
examples to have one `Copy` and one non-`Copy` type using `Cell` and
`RefCell`, respectively.
Don't emit divide-by-zero panic paths in `StepBy::len`
I happened to notice today that there's actually two such calls emitted in the assembly: <https://rust.godbolt.org/z/1Wbbd3Ts6>
Since they're impossible, hopefully telling LLVM that will also help optimizations elsewhere.
Implement minimal, internal-only pattern types in the type system
rebase of https://github.com/rust-lang/rust/pull/107606
You can create pattern types with `std::pat::pattern_type!(ty is pat)`. The feature is incomplete and will panic on you if you use any pattern other than integral range patterns. The only way to create or deconstruct a pattern type is via `transmute`.
This PR's implementation differs from the MCP's text. Specifically
> This means you could implement different traits for different pattern types with the same base type. Thus, we just forbid implementing any traits for pattern types.
is violated in this PR. The reason is that we do need impls after all in order to make them usable as fields. constants of type `std::time::Nanoseconds` struct are used in patterns, so the type must be structural-eq, which it only can be if you derive several traits on it. It doesn't need to be structural-eq recursively, so we can just manually implement the relevant traits on the pattern type and use the pattern type as a private field.
Waiting on:
* [x] move all unrelated commits into their own PRs.
* [x] fix niche computation (see 2db07f94f44f078daffe5823680d07d4fded883f)
* [x] add lots more tests
* [x] T-types MCP https://github.com/rust-lang/types-team/issues/126 to finish
* [x] some commit cleanup
* [x] full self-review
* [x] remove 61bd325da19a918cc3e02bbbdce97281a389c648, it's not necessary anymore I think.
* [ ] ~~make sure we never accidentally leak pattern types to user code (add stability checks or feature gate checks and appopriate tests)~~ we don't even do this for the new float primitives
* [x] get approval that [the scope expansion to trait impls](https://rust-lang.zulipchat.com/#narrow/stream/326866-t-types.2Fnominated/topic/Pattern.20types.20types-team.23126/near/427670099) is ok
r? `@BoxyUwU`
This allows printing them in the Debug impl as well as getting them
again using the get_args() method. This allows programs that would
normally spawn another process to more easily show which program they
would have spawned if not for the fact that the target doesn't support
spawning child processes without requiring intrusive changes to keep the
args. For example rustc compiled to wasi will show the full linker
invocation that would have been done.
Documentation fix
Changed "It must not be an identical residual when interconversion is involved" to "The residual is not mandated to be identical when interconversion is involved." as the previous parenthetical appears to state that the residual is not permitted to be identical when interconversion is involved. However the intention of the original wording was to convey that the residual is not required to be identical when interconversion is involved, which makes more sense contextually.
extending filesystem support for Hermit
Extending `std` to create, change and read a directory for Hermit.
Hermit is a tier 3 platform and this PR changes only files, wich are related to the tier 3 platform.
Rollup of 2 pull requests
Successful merges:
- #123584 (Emit an error when `rustc_doc_primitive` has an unknown value)
- #123589 (sys_common::thread_local_key: make a note that this is not used on Windows)
r? `@ghost`
`@rustbot` modify labels: rollup
Use unchecked_sub in str indexing
https://github.com/rust-lang/rust/pull/108763 applied this logic to indexing for slices, but of course `str` has its own separate impl.
Found this by skimming over the codegen for https://github.com/oxidecomputer/hubris/; their dist builds enable overflow checks so the lack of `unchecked_sub` was producing an impossible-to-hit overflow check and also inhibiting some inlining.
r? scottmcm
Stabilize const Atomic*::into_inner
Partial stabilization for https://github.com/rust-lang/rust/issues/78729, for which the FCP has already completed.
The other `into_inner` functions in that tracking issue (`UnsafeCell`, `Cell`, `RefCell`) are blocked on https://github.com/rust-lang/rust/issues/73255 for now.
```console
error[E0493]: destructor of `UnsafeCell<T>` cannot be evaluated at compile-time
--> library/core/src/cell.rs:2076:29
|
2076 | pub const fn into_inner(self) -> T {
| ^^^^ the destructor for this type cannot be evaluated in constant functions
2077 | self.value
2078 | }
| - value is dropped here
```
Drop panic hook after running tests
Issue: https://github.com/rust-lang/rust/issues/119223
Previously we left the panic hook we allocated
on main termination. Doing so makes Valgrind
report it as a reachable unfreed block.
In order to fix that use `panic::take_hook()` before examining test results.
Example backtrace:
```
==146594== 16 bytes in 1 blocks are still reachable in loss record 1 of 1
==146594== at 0x4A390C5: malloc (vg_replace_malloc.c:442)
==146594== by 0x151336: alloc (alloc.rs:98)
==146594== by 0x151336: alloc_impl (alloc.rs:181)
==146594== by 0x151336: allocate (alloc.rs:241)
==146594== by 0x151336: exchange_malloc (alloc.rs:330)
==146594== by 0x151336: new<test::test_main::{closure_env#0}> (boxed.rs:217)
==146594== by 0x151336: test::test_main (lib.rs:124)
==146594== by 0x1522F9: test::test_main_static (lib.rs:160)
==146594== by 0x11E102: reachable_block_with_cargo_test::main (lib.rs:1)
==146594== by 0x11EABA: core::ops::function::FnOnce::call_once (function.rs:250)
==146594== by 0x11E76D: std::sys_common::backtrace::__rust_begin_short_backtrace (backtrace.rs:154)
==146594== by 0x11DFC0: std::rt::lang_start::{{closure}} (rt.rs:166)
==146594== by 0x177D3A: call_once<(), (dyn core::ops::function::Fn<(), Output=i32> + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe)> (function.rs:284)
==146594== by 0x177D3A: do_call<&(dyn core::ops::function::Fn<(), Output=i32> + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe), i32> (panicking.rs:504)
==146594== by 0x177D3A: try<i32, &(dyn core::ops::function::Fn<(), Output=i32> + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe)> (panicking.rs:468)
==146594== by 0x177D3A: catch_unwind<&(dyn core::ops::function::Fn<(), Output=i32> + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe), i32> (panic.rs:142)
==146594== by 0x177D3A: {closure#2} (rt.rs:148)
==146594== by 0x177D3A: do_call<std::rt::lang_start_internal::{closure_env#2}, isize> (panicking.rs:504)
==146594== by 0x177D3A: try<isize, std::rt::lang_start_internal::{closure_env#2}> (panicking.rs:468)
==146594== by 0x177D3A: catch_unwind<std::rt::lang_start_internal::{closure_env#2}, isize> (panic.rs:142)
==146594== by 0x177D3A: std::rt::lang_start_internal (rt.rs:148)
==146594== by 0x11DF99: std::rt::lang_start (rt.rs:165)
```
I happened to notice today that there's actually two such calls emitted in the assembly: <https://rust.godbolt.org/z/1Wbbd3Ts6>
Since they're impossible, hopefully telling LLVM that will also help optimizations elsewhere.
Previously we left the panic hook we allocated
on main termination. Doing so makes Valgrind
report it as a reachable unfreed block.
In order to fix that use `panic::take_hook()` before
examining test results.
Example backtrace:
```
==146594== 16 bytes in 1 blocks are still reachable in loss record 1 of 1
==146594== at 0x4A390C5: malloc (vg_replace_malloc.c:442)
==146594== by 0x151336: alloc (alloc.rs:98)
==146594== by 0x151336: alloc_impl (alloc.rs:181)
==146594== by 0x151336: allocate (alloc.rs:241)
==146594== by 0x151336: exchange_malloc (alloc.rs:330)
==146594== by 0x151336: new<test::test_main::{closure_env#0}> (boxed.rs:217)
==146594== by 0x151336: test::test_main (lib.rs:124)
==146594== by 0x1522F9: test::test_main_static (lib.rs:160)
==146594== by 0x11E102: reachable_block_with_cargo_test::main (lib.rs:1)
==146594== by 0x11EABA: core::ops::function::FnOnce::call_once (function.rs:250)
==146594== by 0x11E76D: std::sys_common::backtrace::__rust_begin_short_backtrace (backtrace.rs:154)
==146594== by 0x11DFC0: std::rt::lang_start::{{closure}} (rt.rs:166)
==146594== by 0x177D3A: call_once<(), (dyn core::ops::function::Fn<(), Output=i32> + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe)> (function.rs:284)
==146594== by 0x177D3A: do_call<&(dyn core::ops::function::Fn<(), Output=i32> + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe), i32> (panicking.rs:504)
==146594== by 0x177D3A: try<i32, &(dyn core::ops::function::Fn<(), Output=i32> + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe)> (panicking.rs:468)
==146594== by 0x177D3A: catch_unwind<&(dyn core::ops::function::Fn<(), Output=i32> + core::marker::Sync + core::panic::unwind_safe::RefUnwindSafe), i32> (panic.rs:142)
==146594== by 0x177D3A: {closure#2} (rt.rs:148)
==146594== by 0x177D3A: do_call<std::rt::lang_start_internal::{closure_env#2}, isize> (panicking.rs:504)
==146594== by 0x177D3A: try<isize, std::rt::lang_start_internal::{closure_env#2}> (panicking.rs:468)
==146594== by 0x177D3A: catch_unwind<std::rt::lang_start_internal::{closure_env#2}, isize> (panic.rs:142)
==146594== by 0x177D3A: std::rt::lang_start_internal (rt.rs:148)
==146594== by 0x11DF99: std::rt::lang_start (rt.rs:165)
```
Signed-off-by: Tal Gelbard <talgelbard1@gmail.com>
impl get_mut_or_init and get_mut_or_try_init for OnceCell and OnceLock
See also https://github.com/rust-lang/rust/issues/74465#issuecomment-1676522051
I'm trying to understand the process for such proposal. And I'll appreciate it if anyone can guide me the next step for consensus or adding tests.
Revert "Use OS thread name by default"
This reverts #121666 (Use the OS thread name by default if `THREAD_INFO` has not been initialized) due to #123495 (Thread names are not always valid UTF-8).
It's not a direct revert because there have been other changes since that PR.
Add aarch64-apple-visionos and aarch64-apple-visionos-sim tier 3 targets
Introduces `aarch64-apple-visionos` and `aarch64-apple-visionos-sim` as tier 3 targets. This allows native development for the Apple Vision Pro's visionOS platform.
This work has been tracked in https://github.com/rust-lang/compiler-team/issues/642. There is a corresponding `libc` change https://github.com/rust-lang/libc/pull/3568 that is not required for merge.
Ideally we would be able to incorporate [this change](https://github.com/gimli-rs/object/pull/626) to the `object` crate, but the author has stated that a release will not be cut for quite a while. Therefore, the two locations that would reference the xrOS constant from `object` are hardcoded to their MachO values of 11 and 12, accompanied by TODOs to mark the code as needing change. I am open to suggestions on what to do here to get this checked in.
# Tier 3 Target Policy
At this tier, the Rust project provides no official support for a target, so we place minimal requirements on the introduction of targets.
> A tier 3 target must have a designated developer or developers (the "target maintainers") on record to be CCed when issues arise regarding the target. (The mechanism to track and CC such developers may evolve over time.)
See [src/doc/rustc/src/platform-support/apple-visionos.md](e88379034a/src/doc/rustc/src/platform-support/apple-visionos.md)
> Targets must use naming consistent with any existing targets; for instance, a target for the same CPU or OS as an existing Rust target should use the same name for that CPU or OS. Targets should normally use the same names and naming conventions as used elsewhere in the broader ecosystem beyond Rust (such as in other toolchains), unless they have a very good reason to diverge. Changing the name of a target can be highly disruptive, especially once the target reaches a higher tier, so getting the name right is important even for a tier 3 target.
> * Target names should not introduce undue confusion or ambiguity unless absolutely necessary to maintain ecosystem compatibility. For example, if the name of the target makes people extremely likely to form incorrect beliefs about what it targets, the name should be changed or augmented to disambiguate it.
> * If possible, use only letters, numbers, dashes and underscores for the name. Periods (.) are known to cause issues in Cargo.
This naming scheme matches `$ARCH-$VENDOR-$OS-$ABI` which is matches the iOS Apple Silicon simulator (`aarch64-apple-ios-sim`) and other Apple targets.
> Tier 3 targets may have unusual requirements to build or use, but must not
create legal issues or impose onerous legal terms for the Rust project or for
Rust developers or users.
> - The target must not introduce license incompatibilities.
> - Anything added to the Rust repository must be under the standard Rust license (`MIT OR Apache-2.0`).
> - The target must not cause the Rust tools or libraries built for any other host (even when supporting cross-compilation to the target) to depend on any new dependency less permissive than the Rust licensing policy. This applies whether the dependency is a Rust crate that would require adding new license exceptions (as specified by the `tidy` tool in the rust-lang/rust repository), or whether the dependency is a native library or binary. In other words, the introduction of the target must not cause a user installing or running a version of Rust or the Rust tools to besubject to any new license requirements.
> - Compiling, linking, and emitting functional binaries, libraries, or other code for the target (whether hosted on the target itself or cross-compiling from another target) must not depend on proprietary (non-FOSS) libraries. Host tools built for the target itself may depend on the ordinary runtime libraries supplied by the platform and commonly used by other applications built for the target, but those libraries must not be required for code generation for the target; cross-compilation to the target must not require such libraries at all. For instance, `rustc` built for the target may depend on a common proprietary C runtime library or console output library, but must not depend on a proprietary code generation library or code optimization library. Rust's license permits such combinations, but the Rust project has no interest in maintaining such combinations within the scope of Rust itself, even at tier 3.
> - "onerous" here is an intentionally subjective term. At a minimum, "onerous" legal/licensing terms include but are *not* limited to: non-disclosure requirements, non-compete requirements, contributor license agreements (CLAs) or equivalent, "non-commercial"/"research-only"/etc terms, requirements conditional on the employer or employment of any particular Rust developers, revocable terms, any requirements that create liability for the Rust project or its developers or users, or any requirements that adversely affect the livelihood or prospects of the Rust project or its developers or users.
This contribution is fully available under the standard Rust license with no additional legal restrictions whatsoever. This PR does not introduce any new dependency less permissive than the Rust license policy.
The new targets do not depend on proprietary libraries.
> Tier 3 targets should attempt to implement as much of the standard libraries as possible and appropriate (core for most targets, alloc for targets that can support dynamic memory allocation, std for targets with an operating system or equivalent layer of system-provided functionality), but may leave some code unimplemented (either unavailable or stubbed out as appropriate), whether because the target makes it impossible to implement or challenging to implement. The authors of pull requests are not obligated to avoid calling any portions of the standard library on the basis of a tier 3 target not implementing those portions.
This new target mirrors the standard library for watchOS and iOS, with minor divergences.
> The target must provide documentation for the Rust community explaining how to build for the target, using cross-compilation if possible. If the target supports running binaries, or running tests (even if they do not pass), the documentation must explain how to run such binaries or tests for the target, using emulation if possible or dedicated hardware if necessary.
Documentation is provided in [src/doc/rustc/src/platform-support/apple-visionos.md](e88379034a/src/doc/rustc/src/platform-support/apple-visionos.md)
> Neither this policy nor any decisions made regarding targets shall create any binding agreement or estoppel by any party. If any member of an approving Rust team serves as one of the maintainers of a target, or has any legal or employment requirement (explicit or implicit) that might affect their decisions regarding a target, they must recuse themselves from any approval decisions regarding the target's tier status, though they may otherwise participate in discussions.
> * This requirement does not prevent part or all of this policy from being cited in an explicit contract or work agreement (e.g. to implement or maintain support for a target). This requirement exists to ensure that a developer or team responsible for reviewing and approving a target does not face any legal threats or obligations that would prevent them from freely exercising their judgment in such approval, even if such judgment involves subjective matters or goes beyond the letter of these requirements.
> Tier 3 targets must not impose burden on the authors of pull requests, or other developers in the community, to maintain the target. In particular, do not post comments (automated or manual) on a PR that derail or suggest a block on the PR based on a tier 3 target. Do not send automated messages or notifications (via any medium, including via `@)` to a PR author or others involved with a PR regarding a tier 3 target, unless they have opted into such messages.
> * Backlinks such as those generated by the issue/PR tracker when linking to an issue or PR are not considered a violation of this policy, within reason. However, such messages (even on a separate repository) must not generate notifications to anyone involved with a PR who has not requested such notifications.
> Patches adding or updating tier 3 targets must not break any existing tier 2 or tier 1 target, and must not knowingly break another tier 3 target without approval of either the compiler team or the maintainers of the other tier 3 target.
> * In particular, this may come up when working on closely related targets, such as variations of the same architecture with different features. Avoid introducing unconditional uses of features that another variation of the target may not have; use conditional compilation or runtime detection, as appropriate, to let each target run code supported by that target.
I acknowledge these requirements and intend to ensure that they are met.
This target does not touch any existing tier 2 or tier 1 targets and should not break any other targets.
There's PR https://github.com/rust-lang/rust/pull/123184
which avoids allocation for ZST ThinBox.
That PR has an issue with unsoundness with misuse of `MaybeUninit`
(see comments in that PR).
This PR is much simpler implementation which does not have this
problem, but it uses `const_allocate` feature.
Support running library tests in Miri
This adds a new bootstrap subcommand `./x.py miri` which can test libraries in Miri. This is in preparation for eventually doing that as part of bors CI, but this PR only adds the infrastructure, and doesn't enable it yet.
`@rust-lang/bootstrap` should this be `x.py test --miri library/core` or `x.py miri library/core`? The flag has the advantage that we don't have to copy all the arguments from `Subcommand::Test`. It has the disadvantage that most test steps just ignore `--miri` and still run tests the regular way. For clippy you went the route of making it a separate subcommand. ~~I went with a flag now as that seemed easier, but I can change this.~~ I made it a new subcommand. Note however that the regular cargo invocation would be `cargo miri test ...`, so `x.py` is still going to be different in that the `test` is omitted. That said, we could also make it `./x.py miri-test` to make that difference smaller -- that's in fact more consistent with the internal name of the command when bootstrap invokes cargo.
`@rust-lang/libs` ~~unfortunately this PR does some unholy things to the `lib.rs` files of our library crates.~~
`@m-ou-se` found a way that entirely avoids library-level hacks, except for some new small `lib.miri.rs` files that hopefully you will never have to touch. There's a new hack in cargo-miri but there it is in good company...
Avoid panicking unnecessarily on startup
On Windows, in `lang_start` we add an exception handler to catch stack overflows and we also reserve some stack space for the handler. Both of these are useful but they're not strictly necessary. The standard library has to work without them (e.g. if Rust is used from a foreign entry point) and the negative effect of not doing them is limited (i.e. you don't get the friendly stack overflow message).
As we really don't want to panic pre-main unless absolutely necessary, it now won't panic on failure. I've added some debug assertions so as to avoid programmer error.
Rename `expose_addr` to `expose_provenance`
`expose_addr` is a bad name, an address is just a number and cannot be exposed. The operation is actually about the provenance of the pointer.
This PR thus changes the name of the method to `expose_provenance` without changing its return type. There is sufficient precedence for returning a useful value from an operation that does something else without the name indicating such, e.g. [`Option::insert`](https://doc.rust-lang.org/nightly/std/option/enum.Option.html#method.insert) and [`MaybeUninit::write`](https://doc.rust-lang.org/nightly/std/mem/union.MaybeUninit.html#method.write).
Returning the address is merely convenient, not a fundamental part of the operation. This is implied by the fact that integers do not have provenance since
```rust
let addr = ptr.addr();
ptr.expose_provenance();
let new = ptr::with_exposed_provenance(addr);
```
must behave exactly like
```rust
let addr = ptr.expose_provenance();
let new = ptr::with_exposed_provenance(addr);
```
as the result of `ptr.expose_provenance()` and `ptr.addr()` is the same integer. Therefore, this PR removes the `#[must_use]` annotation on the function and updates the documentation to reflect the important part.
~~An alternative name would be `expose_provenance`. I'm not at all opposed to that, but it makes a stronger implication than we might want that the provenance of the pointer returned by `ptr::with_exposed_provenance`[^1] is the same as that what was exposed, which is not yet specified as such IIUC. IMHO `expose` does not make that connection.~~
A previous version of this PR suggested `expose` as name, libs-api [decided on](https://github.com/rust-lang/rust/pull/122964#issuecomment-2033194319) `expose_provenance` to keep the symmetry with `with_exposed_provenance`.
CC `@RalfJung`
r? libs-api
[^1]: I'm using the new name for `from_exposed_addr` suggested by #122935 here.
Provide cabi_realloc on wasm32-wasip2 by default
This commit provides a component model intrinsic in the standard library
by default on the `wasm32-wasip2` target. This intrinsic is not
required by the component model itself but is quite common to use, for
example it's needed if a wasm module receives a string or a list.
The intention of this commit is to provide an overridable definition in
the standard library through a weak definition of this function. That
means that downstream crates can provide their own customized and more
specific versions if they'd like, but the standard library's version
should suffice for general-purpose use.
Add `Context::ext`
This change enables `Context` to carry arbitrary extension data via a single `&mut dyn Any` field.
```rust
#![feature(context_ext)]
impl Context {
fn ext(&mut self) -> &mut dyn Any;
}
impl ContextBuilder {
fn ext(self, data: &'a mut dyn Any) -> Self;
fn from(cx: &'a mut Context<'_>) -> Self;
fn waker(self, waker: &'a Waker) -> Self;
}
```
Basic usage:
```rust
struct MyExtensionData {
executor_name: String,
}
let mut ext = MyExtensionData {
executor_name: "foo".to_string(),
};
let mut cx = ContextBuilder::from_waker(&waker).ext(&mut ext).build();
if let Some(ext) = cx.ext().downcast_mut::<MyExtensionData>() {
println!("{}", ext.executor_name);
}
```
Currently, `Context` only carries a `Waker`, but there is interest in having it carry other kinds of data. Examples include [LocalWaker](https://github.com/rust-lang/rust/issues/118959), [a reactor interface](https://github.com/rust-lang/libs-team/issues/347), and [multiple arbitrary values by type](https://docs.rs/context-rs/latest/context_rs/). There is also a general practice in the ecosystem of sharing data between executors and futures via thread-locals or globals that would arguably be better shared via `Context`, if it were possible.
The `ext` field would provide a low friction (to stabilization) solution to enable experimentation. It would enable experimenting with what kinds of data we want to carry as well as with what data structures we may want to use to carry such data.
Dedicated fields for specific kinds of data could still be added directly on `Context` when we have sufficient experience or understanding about the problem they are solving, such as with `LocalWaker`. The `ext` field would be for data for which we don't have such experience or understanding, and that could be graduated to dedicated fields once proven.
Both the provider and consumer of the extension data must be aware of the concrete type behind the `Any`. This means it is not possible for the field to carry an abstract interface. However, the field can carry a concrete type which in turn carries an interface. There are different ways one can imagine an interface-carrying concrete type to work, hence the benefit of being able to experiment with such data structures.
## Passing interfaces
Interfaces can be placed in a concrete type, such as a struct, and then that type can be casted to `Any`. However, one gotcha is `Any` cannot contain non-static references. This means one cannot simply do:
```rust
struct Extensions<'a> {
interface1: &'a mut dyn Trait1,
interface2: &'a mut dyn Trait2,
}
let mut ext = Extensions {
interface1: &mut impl1,
interface2: &mut impl2,
};
let ext: &mut dyn Any = &mut ext;
```
To work around this without boxing, unsafe code can be used to create a safe projection using accessors. For example:
```rust
pub struct Extensions {
interface1: *mut dyn Trait1,
interface2: *mut dyn Trait2,
}
impl Extensions {
pub fn new<'a>(
interface1: &'a mut (dyn Trait1 + 'static),
interface2: &'a mut (dyn Trait2 + 'static),
scratch: &'a mut MaybeUninit<Self>,
) -> &'a mut Self {
scratch.write(Self {
interface1,
interface2,
})
}
pub fn interface1(&mut self) -> &mut dyn Trait1 {
unsafe { self.interface1.as_mut().unwrap() }
}
pub fn interface2(&mut self) -> &mut dyn Trait2 {
unsafe { self.interface2.as_mut().unwrap() }
}
}
let mut scratch = MaybeUninit::uninit();
let ext: &mut Extensions = Extensions::new(&mut impl1, &mut impl2, &mut scratch);
// ext can now be casted to `&mut dyn Any` and back, and used safely
let ext: &mut dyn Any = ext;
```
## Context inheritance
Sometimes when futures poll other futures they want to provide their own `Waker` which requires creating their own `Context`. Unfortunately, polling sub-futures with a fresh `Context` means any properties on the original `Context` won't get propagated along to the sub-futures. To help with this, some additional methods are added to `ContextBuilder`.
Here's how to derive a new `Context` from another, overriding only the `Waker`:
```rust
let mut cx = ContextBuilder::from(parent_cx).waker(&new_waker).build();
```
rename ptr::from_exposed_addr -> ptr::with_exposed_provenance
As discussed on [Zulip](https://rust-lang.zulipchat.com/#narrow/stream/136281-t-opsem/topic/To.20expose.20or.20not.20to.20expose/near/427757066).
The old name, `from_exposed_addr`, makes little sense as it's not the address that is exposed, it's the provenance. (`ptr.expose_addr()` stays unchanged as we haven't found a better option yet. The intended interpretation is "expose the provenance and return the address".)
The new name nicely matches `ptr::without_provenance`.
De-LLVM the unchecked shifts [MCP#693]
This is just one part of the MCP (https://github.com/rust-lang/compiler-team/issues/693), but it's the one that IMHO removes the most noise from the standard library code.
Seems net simpler this way, since MIR already supported heterogeneous shifts anyway, and thus it's not more work for backends than before.
r? WaffleLapkin
Add `Ord::cmp` for primitives as a `BinOp` in MIR
Update: most of this OP was written months ago. See https://github.com/rust-lang/rust/pull/118310#issuecomment-2016940014 below for where we got to recently that made it ready for review.
---
There are dozens of reasonable ways to implement `Ord::cmp` for integers using comparison, bit-ops, and branches. Those differences are irrelevant at the rust level, however, so we can make things better by adding `BinOp::Cmp` at the MIR level:
1. Exactly how to implement it is left up to the backends, so LLVM can use whatever pattern its optimizer best recognizes and cranelift can use whichever pattern codegens the fastest.
2. By not inlining those details for every use of `cmp`, we drastically reduce the amount of MIR generated for `derive`d `PartialOrd`, while also making it more amenable to MIR-level optimizations.
Having extremely careful `if` ordering to μoptimize resource usage on broadwell (#63767) is great, but it really feels to me like libcore is the wrong place to put that logic. Similarly, using subtraction [tricks](https://graphics.stanford.edu/~seander/bithacks.html#CopyIntegerSign) (#105840) is arguably even nicer, but depends on the optimizer understanding it (https://github.com/llvm/llvm-project/issues/73417) to be practical. Or maybe [bitor is better than add](https://discourse.llvm.org/t/representing-in-ir/67369/2?u=scottmcm)? But maybe only on a future version that [has `or disjoint` support](https://discourse.llvm.org/t/rfc-add-or-disjoint-flag/75036?u=scottmcm)? And just because one of those forms happens to be good for LLVM, there's no guarantee that it'd be the same form that GCC or Cranelift would rather see -- especially given their very different optimizers. Not to mention that if LLVM gets a spaceship intrinsic -- [which it should](https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/Suboptimal.20inlining.20in.20std.20function.20.60binary_search.60/near/404250586) -- we'll need at least a rustc intrinsic to be able to call it.
As for simplifying it in Rust, we now regularly inline `{integer}::partial_cmp`, but it's quite a large amount of IR. The best way to see that is with 8811efa88b (diff-d134c32d028fbe2bf835fef2df9aca9d13332dd82284ff21ee7ebf717bfa4765R113) -- I added a new pre-codegen MIR test for a simple 3-tuple struct, and this PR change it from 36 locals and 26 basic blocks down to 24 locals and 8 basic blocks. Even better, as soon as the construct-`Some`-then-match-it-in-same-BB noise is cleaned up, this'll expose the `Cmp == 0` branches clearly in MIR, so that an InstCombine (#105808) can simplify that to just a `BinOp::Eq` and thus fix some of our generated code perf issues. (Tracking that through today's `if a < b { Less } else if a == b { Equal } else { Greater }` would be *much* harder.)
---
r? `@ghost`
But first I should check that perf is ok with this
~~...and my true nemesis, tidy.~~
This PR aims to pin down exactly what restricted_std is meant to achieve
and what it isn't.
This commit fixes https://github.com/rust-lang/wg-cargo-std-aware/issues/87
by explaining why the error appears and what the choices the user has.
The error describes how std cannot function without knowing about some
form of OS/platform support. Any features of std that work without an
OS should be moved to core/alloc (see https://github.com/rust-lang/rust/issues/27242https://github.com/rust-lang/rust/issues/103765).
Note that the message says "platform" and "environment" because, since
https://github.com/rust-lang/rust/pull/120232, libstd can be built for
some JSON targets. This is still unsupported (all JSON targets probably
should be unstable https://github.com/rust-lang/wg-cargo-std-aware/issues/90),
but a JSON target with the right configuration should hopefully have
some partial libstd support.
I propose closing https://github.com/rust-lang/wg-cargo-std-aware/issues/69
as "Won't fix" since any support of std without properly configured os,
vendor or env fields is very fragile considering future upgrades of Rust
or dependencies. In addition there's no likely path to it being fixed
long term (making std buildable for all targets being the only
solution). This is distinct from tier 3 platforms with limited std
support implemented (and as such aren't restricted_std) because these
platforms can conceptually work in the future and std support should
mainly improve over time.
The alternative to closing https://github.com/rust-lang/wg-cargo-std-aware/issues/69
is a new crate feature for std which escapes the restricted_std
mechanism in build.rs. It could be used with the -Zbuild-std-features
flag if we keep it permanently unstable, which I hope we can do anyway.
A minor side-effect in this scenario is that std wouldn't be marked as
unstable if documentation for it were generated with build-std.
Refactor stack overflow handling
Currently, every platform must implement a `Guard` that protects a thread from stack overflow. However, UNIX is the only platform that actually does so. Windows has a different mechanism for detecting stack overflow, while the other platforms don't detect it at all. Also, the UNIX stack overflow handling is split between `sys::pal::unix::stack_overflow`, which implements the signal handler, and `sys::pal::unix::thread`, which detects/installs guard pages.
This PR cleans this by getting rid of `Guard` and unifying UNIX stack overflow handling inside `stack_overflow` (commit 1). Therefore we can get rid of `sys_common::thread_info`, which stores `Guard` and the current `Thread` handle and move the `thread::current` TLS variable into `thread` (commit 2).
The second commit is not strictly speaking necessary. To keep the implementation clean, I've included it here, but if it causes too much noise, I can split it out without any trouble.
doc: describe panic conditions for SliceIndex implementations
Implementation note: The most probable place for users to find the documentation is at https://doc.rust-lang.org/std/slice/trait.SliceIndex.html
On that page, documentation added to specific methods will not be visible. As such, I opted to add the comments to the impl blocks directly.
Helps with #121568.
Implementation note: The most probable place for users to find
the documentation is at https://doc.rust-lang.org/std/slice/trait.SliceIndex.html
On that page, documentation added to specific methods will not
be visible. As such, I opted to add the comments to the impl blocks
directly.
Helps with #121568.
This is just one part of the MCP, but it's the one that IMHO removes the most noise from the standard library code.
Seems net simpler this way, since MIR already supported heterogeneous shifts anyway, and thus it's not more work for backends than before.
Remove len argument from RawVec::reserve_for_push
Removes `RawVec::reserve_for_push`'s `len` argument since it's always the same as capacity.
Also makes `Vec::insert` use `RawVec::reserve_for_push`.
Stabilize `unchecked_{add,sub,mul}`
Tracking issue: #85122
I think we might as well just stabilize these basic three. They're the ones that have `nuw`/`nsw` flags in LLVM.
Notably, this doesn't include the potentially-more-complex or -more-situational things like `unchecked_neg` or `unchecked_shr` that are under different feature flags.
To quote Ralf https://github.com/rust-lang/rust/issues/85122#issuecomment-1681669646,
> Are there any objections to stabilizing at least `unchecked_{add,sub,mul}`? For those there shouldn't be any surprises about what their safety requirements are.
*Semantially* these are [already available on stable, even in `const`, via](https://play.rust-lang.org/?version=stable&mode=debug&edition=2021&gist=bdb1ff889b61950897f1e9f56d0c9a36) `checked_*`+`unreachable_unchecked`. So IMHO we might as well just let people write them directly, rather than try to go through a `let Some(x) = x.checked_add(y) else { unsafe { hint::unreachable_unchecked() }};` dance.
I added additional text to each method to attempt to better describe the behaviour and encourage `wrapping_*` instead.
r? rust-lang/libs-api
Add detection of [Partial]Ord methods in the `ambiguous_wide_pointer_comparisons` lint
Partially addresses https://github.com/rust-lang/rust/issues/121264 by adding diagnostics items for PartialOrd and Ord methods, detecting such diagnostics items as "binary operation" and suggesting the correct replacement.
I also took the opportunity to change the suggestion to use new methods `.cast()` on `*mut T` an d `*const T`.
Because `HashMap::with_hasher` constness is being stabilized this will
in turn allow creating empty HashMap<K,V,BuildHasherDefault<H>> in const
context for any H: Default + Hasher.
Eliminate `UbChecks` for non-standard libraries
The purpose of this PR is to allow other passes to treat `UbChecks` as constants in MIR for optimization after #122629.
r? RalfJung
Codegen const panic messages as function calls
This skips emitting extra arguments at every callsite (of which there
can be many). For a librustc_driver build with overflow checks enabled,
this cuts 0.7MB from the resulting shared library (see [perf]).
A sample improvement from nightly:
```
leaq str.0(%rip), %rdi
leaq .Lalloc_d6aeb8e2aa19de39a7f0e861c998af13(%rip), %rdx
movl $25, %esi
callq *_ZN4core9panicking5panic17h17cabb89c5bcc999E@GOTPCREL(%rip)
```
to this PR:
```
leaq .Lalloc_d6aeb8e2aa19de39a7f0e861c998af13(%rip), %rdi
callq *_RNvNtNtCsduqIKoij8JB_4core9panicking11panic_const23panic_const_div_by_zero@GOTPCREL(%rip)
```
[perf]: https://perf.rust-lang.org/compare.html?start=a7e4de13c1785819f4d61da41f6704ed69d5f203&end=64fbb4f0b2d621ff46d559d1e9f5ad89a8d7789b&stat=instructions:u
`num::NonZero::get` can be 1 transmute instead of 2
Just something I noticed in passing. No need for a `match` in here to call `unreachable_unchecked`, as `transmute_unchecked` will add the appropriate `llvm.assume` <https://rust.godbolt.org/z/W5hjeETnc>.
Clarify atomic bit validity
The previous definition used the phrase "representation", which is ambiguous given the current state of memory model nomenclature in Rust. For integer types and for `AtomicPtr<T>`, the new wording clarifies that size and bit validity are guaranteed to match the corresponding native integer type/`*mut T`. For `AtomicBool`, the new wording clarifies that size, alignment, and bit validity are guaranteed to match `bool`.
Note that we use the phrase "size and alignment" rather than "layout" since the latter term also implies that the field types are the same. This isn't true - `AtomicXxx` doesn't store an `xxx`, but rather an `UnsafeCell<xxx>`. This distinction is important for some `unsafe` code, which needs to reason about the presence or absence of interior mutability in order to ensure that their code is sound (see e.g. https://github.com/google/zerocopy/issues/251).
Soft-destabilize `RustcEncodable` & `RustcDecodable`, remove from prelude in next edition
cc rust-lang/libs-team#272
Any use of `RustcEncodable` and `RustcDecodable` now triggers a deny-by-default lint. The derives have been removed from the 2024 prelude. I specifically chose **not** to document this in the module-level documentation, as the presence in existing preludes is not documented (which I presume is intentional).
This does not implement the proposed change for `rustfix`, which I will be looking into shortly.
With regard to the items in the preludes being stable, this should not be an issue because #15702 has been resolved.
r? libs-api
Update `RwLock` deadlock example to not use shadowing
Tweak variable names in the deadlock example to remove any potential confusion that the behavior is somehow shadowing-related.
Implement `Vec::pop_if`
This PR adds `Vec::pop_if` to the public API, behind the `vec_pop_if` feature.
```rust
impl<T> Vec<T> {
pub fn pop_if<F>(&mut self, f: F) -> Option<T>
where F: FnOnce(&mut T) -> bool;
}
```
Tracking issue: #122741
## Open questions
- [ ] Should the first unit test be split up?
- [ ] I don't see any guidance on ordering of methods in impl blocks, should I move the method elsewhere?
unix fs: Make hurd using explicit new rather than From
408c0ea216 ("unix time module now return result") dropped the From impl for SystemTime, breaking the hurd build (and probably the horizon build)
Fixes#123032
Fix doc link to BufWriter in std::fs::File documentation
It seems that doc link to `BufWriter` in `std::fs::File` doc leads to `BufReader`, not `BufWriter`.
See https://doc.rust-lang.org/std/fs/struct.File.html
Simplify proc macro bridge state
Currently, `proc_macro` uses a `ScopedCell` to store the client-side proc-macro bridge. Unfortunately, this requires the `Bridge`, which has non-negligible size, to be copied out and back again on every access. In some cases, the optimizer might be able to elide these copies, but in general, this is suboptimal.
This PR removes `ScopedCell` and employs a similar trick as in [`scoped_tls`](https://crates.io/crates/scoped-tls), meaning that the only thing stored in TLS is a pointer to the state, which now is a `RefCell`. Access to the pointer is then scoped so that it is always within the lifetime of the reference to the state. Unfortunately, `scoped_tls` requires the referenced type to be `'static`, which `Bridge` is not, therefore we cannot simply copy that macro but have to reimplement its TLS trick.
This removes the `#[forbid(unsafe_code)]` on the `client` module so that we do not have to export `Bridge`, which currently is private, to the whole crate. I can change that, if necessary.
Import the 2021 prelude in the core crate
The `core` crate currently imports the v1 prelude
b3df0d7e5e/library/core/src/lib.rs (L285-L287)
This recently caused an issue when updating the `portable-simd` subtree since it was using a trait that was added to the 2021 prelude: https://github.com/rust-lang/rust/pull/122905#discussion_r1536228822
To make it easier to have a consistent build environment for subtrees and submodules that get included in `core`, we will now import the 2021 prelude into `core`.
Fixes#122912
r? `@Nilstrieb`
warning: casting raw pointers to the same type and constness is unnecessary (`*mut V` -> `*mut V`)
--> library\alloc\src\collections\btree\map\entry.rs:357:31
|
357 | let val_ptr = root.borrow_mut().push(self.key, value) as *mut V;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `root.borrow_mut().push
(self.key, value)`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_cast
warning: casting to the same type is unnecessary (`usize` -> `usize`)
--> library\alloc\src\ffi\c_str.rs:411:56
|
411 | let slice = slice::from_raw_parts_mut(ptr, len as usize);
| ^^^^^^^^^^^^ help: try: `len`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_cast
warning: casting raw pointers to the same type and constness is unnecessary (`*mut T` -> `*mut T`)
--> library\alloc\src\slice.rs:516:25
|
516 | (buf.as_mut_ptr() as *mut T).add(buf.len()),
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `buf.as_mut_ptr()`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_cast
warning: casting raw pointers to the same type and constness is unnecessary (`*mut T` -> `*mut T`)
--> library\alloc\src\slice.rs:537:21
|
537 | (buf.as_mut_ptr() as *mut T).add(buf.len()),
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: try: `buf.as_mut_ptr()`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_cast
warning: casting raw pointers to the same type and constness is unnecessary (`*const ()` -> `*const ()`)
--> library\alloc\src\task.rs:151:13
|
151 | waker as *const (),
| ^^^^^^^^^^^^^^^^^^ help: try: `waker`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_cast
warning: casting raw pointers to the same type and constness is unnecessary (`*const ()` -> `*const ()`)
--> library\alloc\src\task.rs:323:13
|
323 | waker as *const (),
| ^^^^^^^^^^^^^^^^^^ help: try: `waker`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_cast
warning: casting to the same type is unnecessary (`usize` -> `usize`)
--> library\std\src\sys_common\net.rs:110:21
|
110 | assert!(len as usize >= mem::size_of::<c::sockaddr_in>());
| ^^^^^^^^^^^^ help: try: `len`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_cast
warning: casting to the same type is unnecessary (`usize` -> `usize`)
--> library\std\src\sys_common\net.rs:116:21
|
116 | assert!(len as usize >= mem::size_of::<c::sockaddr_in6>());
| ^^^^^^^^^^^^ help: try: `len`
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_cast
Clarify transmute example
The example claims using an iterator will copy the entire vector, but this is not true in practice thanks to internal specializations in the stdlib (see https://godbolt.org/z/cnxo3MYs5 for confirmation that this doesn't reallocate nor iterate over the vec's elements). Since neither the copy nor the optimization is guaranteed I opted for saying that they _may_ happen.
This saves some debug and scope metadata in every single function that calls it.
Normally wouldn't be worth it, but with the derives there's *so* many of these.
std:🧵 refine available_parallelism for solaris/illumos.
Rather than the system-wide available cpus fallback solution, we fetch the cpus bound to the current process.
panic-in-panic-hook: formatting a message that's just a string is risk-free
This slightly improves the output in the 'panic while processing panic' case if the panic message does not involve any formatting. Follow-up to https://github.com/rust-lang/rust/pull/122930.
r? ``@Amanieu``
Rename `Arguments::as_const_str` to `as_statically_known_str`
While `const` has a particular meaning about language guarantees, here
we need a fuzzier notion like whether constant propagation was
effective, and `statically_known` is the best term we have for now.
r? ``@RalfJung``
Fix compile of wasm64-unknown-unknown target
This target is a Tier 3 target so it's not tested on CI, and it's broken since last used so this commit fixes a small unwind-related issue that cropped up in the meantime.
While `const` has a particular meaning about language guarantees, here
we need a fuzzier notion like whether constant propagation was
effective, and `statically_known` is the best term we have for now.
Rollup of 9 pull requests
Successful merges:
- #121281 (regression test for #103626)
- #122168 (Fix validation on substituted callee bodies in MIR inliner)
- #122217 (Handle str literals written with `'` lexed as lifetime)
- #122379 (transmute: caution against int2ptr transmutation)
- #122840 (`rustdoc --test`: Prevent reaching the maximum size of command-line by using files for arguments if there are too many)
- #122907 (Uniquify `ReError` on input mode in canonicalizer)
- #122942 (Add test in higher ranked subtype)
- #122943 (add a couple more ice tests)
- #122963 (core/panicking: fix outdated comment)
r? `@ghost`
`@rustbot` modify labels: rollup
transmute: caution against int2ptr transmutation
This came up in https://github.com/rust-lang/rust/pull/121282.
Cc ```@saethlin``` ```@scottmcm```
Eventually we'll add a proper description of provenance that we can reference, but that's a bunch of work and it's unclear who will have the time to do that when. Meanwhile, let's at least do what we can without mentioning provenance explicitly.
refactor check_{lang,library}_ub: use a single intrinsic
This enacts the plan I laid out [here](https://github.com/rust-lang/rust/pull/122282#issuecomment-1996917998): use a single intrinsic, called `ub_checks` (in aniticpation of https://github.com/rust-lang/compiler-team/issues/725), that just exposes the value of `debug_assertions` (consistently implemented in both codegen and the interpreter). Put the language vs library UB logic into the library.
This makes it easier to do something like https://github.com/rust-lang/rust/pull/122282 in the future: that just slightly alters the semantics of `ub_checks` (making it more approximating when crates built with different flags are mixed), but it no longer affects whether these checks can happen in Miri or compile-time.
The first commit just moves things around; I don't think these macros and functions belong into `intrinsics.rs` as they are not intrinsics.
r? `@saethlin`
Rollup of 11 pull requests
Successful merges:
- #120577 (Stabilize slice_split_at_unchecked)
- #122698 (Cancel `cargo update` job if there's no updates)
- #122780 (Rename `hir::Local` into `hir::LetStmt`)
- #122915 (Delay a bug if no RPITITs were found)
- #122916 (docs(sync): normalize dot in fn summaries)
- #122921 (Enable more mir-opt tests in debug builds)
- #122922 (-Zprint-type-sizes: print the types of awaitees and unnamed coroutine locals.)
- #122927 (Change an ICE regression test to use the original reproducer)
- #122930 (add panic location to 'panicked while processing panic')
- #122931 (Fix some typos in the pin.rs)
- #122933 (tag_for_variant follow-ups)
r? `@ghost`
`@rustbot` modify labels: rollup
Stabilize slice_split_at_unchecked
Greetings!
I took the opportunity, and I tried to stabilize the `slice_split_at_unchecked` feature. I followed the guidelines, and I hope everything was done correctly 🤞 .
Closes#76014
Let codegen decide when to `mem::swap` with immediates
Making `libcore` decide this is silly; the backend has so much better information about when it's a good idea.
Thus this PR introduces a new `typed_swap` intrinsic with a fallback body, and replaces that fallback implementation when swapping immediates or scalar pairs.
r? oli-obk
Replaces #111744, and means we'll never need more libs PRs like #111803 or #107140
This skips emitting extra arguments at every callsite (of which there
can be many). For a librustc_driver build with overflow checks enabled,
this cuts 0.7MB from the resulting binary.
Remove SpecOptionPartialEq
With the recent LLVM bump, the specialization for Option::partial_eq on types with niches is no longer necessary. I kept the manual implementation as it still gives us better codegen than the derive (will look at this seperately).
Also implemented PartialOrd/Ord by hand as it _somewhat_ improves codegen for #49892: https://godbolt.org/z/vx5Y6oW4Y
Doc Guarantee: BTree(Set|Map): `IntoIter` Iterate in Sorted by key Order
This Doc-only PR adds text to the IntoIterator implementation and IntoIter type for both BTreeMap and BTreeSet that states that the returned items will be in sorted-by-key order, this is a guarantee that is made by the iter() and iter_mut() methods of BTreeMap/Set and BTreeMap respectively, but not on into_iter methods or types.
I don't know how the IntoIter iteration would not be sorted by key, and I would like to rely on that behavior for my prefix_array crate.
The text appended to IntoIter documentation is based on each types respective iter() method documentation, as is the text used in the IntoIterator documentation; they are slightly inconsistent between Set/Map, but they are consistent within their own types documentation.
select Vec::from_iter impls in a const block to optimize compile times
Ignoring whitespace diffs should make this easier to review.
This relies on the trick from #122301
Split out from #120682
Make `type_ascribe!` not a built-in
The only weird thing is the macro expansion note. I wonder if we should suppress these 🤔
r? ````@fmease```` since you told me about builtin# lol
Add `usize::MAX` arg tests for Vec
Tests to prevent recurrence of the UB from the rust-lang/rust#122760 issue.
I skipped the `with_capacity`, `drain`, `reserve`, etc. APIs because they actually had a good assortment of tests earlier in the same file.
r? Nilstrieb
Relax SeqCst ordering in standard library.
Every single SeqCst in the standard library is unnecessary. In all cases, Relaxed or Release+Acquire was sufficient.
As I [wrote](https://marabos.nl/atomics/memory-ordering.html#common-misconceptions) in my book on atomics:
> [..] when reading code, SeqCst basically tells the reader: "this operation depends on the total order of every single SeqCst operation in the program," which is an incredibly far-reaching claim. The same code would likely be easier to review and verify if it used weaker memory ordering instead, if possible. For example, Release effectively tells the reader: "this relates to an acquire operation on the same variable," which involves far fewer considerations when forming an understanding of the code.
>
> It is advisable to see SeqCst as a warning sign. Seeing it in the wild often means that either something complicated is going on, or simply that the author did not take the time to analyze their memory ordering related assumptions, both of which are reasons for extra scrutiny.
r? ````@Amanieu```` ````@joboet````
This target is a Tier 3 target so it's not tested on CI, and it's broken
since last used so this commit fixes a small unwind-related issue that
cropped up in the meantime.
fix OOB pointer formed in Vec::index
Move the length check to before using `index` with `ptr::add` to prevent an out of bounds pointer from being formed.
Fixes#122760
For async closures, cap closure kind, get rid of `by_mut_body`
Right now we have three `AsyncFn*` traits, and three corresponding futures that are returned by the `call_*` functions for them. This is fine, but it is a bit excessive, since the future returned by `AsyncFn` and `AsyncFnMut` are identical. Really, the only distinction we need to make with these bodies is "by ref" and "by move".
This PR removes `AsyncFn::CallFuture` and renames `AsyncFnMut::CallMutFuture` to `AsyncFnMut::CallRefFuture`. This simplifies MIR building for async closures, since we don't need to build an extra "by mut" body, but just a "by move" body which is materially different.
We need to do a bit of delicate handling of the ClosureKind for async closures, since we need to "cap" it to `AsyncFnMut` in some cases when we only care about what body we're looking for.
This also fixes a bug where `<{async closure} as Fn>::call` was returning a body that takes the async-closure receiver *by move*.
This also helps align the `AsyncFn` traits to the `LendingFn` traits' eventual designs.
Expose `ucred::peer_cred` on QNX targets to enable dist builds
After following https://doc.rust-lang.org/rustc/platform-support/nto-qnx.html I attempted to run the following `x.py` command:
```bash
export build_env='
CC_aarch64-unknown-nto-qnx710=qcc
CFLAGS_aarch64-unknown-nto-qnx710=-Vgcc_ntoaarch64le_cxx
CXX_aarch64-unknown-nto-qnx710=qcc
AR_aarch64_unknown_nto_qnx710=ntoaarch64-ar
CC_x86_64-pc-nto-qnx710=qcc
CFLAGS_x86_64-pc-nto-qnx710=-Vgcc_ntox86_64_cxx
CXX_x86_64-pc-nto-qnx710=qcc
AR_x86_64_pc_nto_qnx710=ntox86_64-ar'
env $build_env ./x.py --stage 2 dist rust-std --target aarch64-unknown-nto-qnx710,x86_64-pc-nto-qnx710,x86_64-unknown-linux-gnu
```
The result was the following error:
```
Compiling object v0.32.2
Compiling std_detect v0.1.5 (/home/ana/git/rust-lang/rust/library/stdarch/crates/std_detect)
Compiling addr2line v0.21.0
error: function `peer_cred` is never used
--> library/std/src/os/unix/net/ucred.rs:89:12
|
89 | pub fn peer_cred(socket: &UnixStream) -> io::Result<UCred> {
| ^^^^^^^^^
|
= note: `-D dead-code` implied by `-D warnings`
= help: to override `-D warnings` add `#[allow(dead_code)]`
error: could not compile `std` (lib) due to 1 previous error
Build completed unsuccessfully in 0:06:25
```
I contacted `@flba-eb` and `@gh-tr` over email and we confirmed that `peer_cred` here should be flagged on `nto` targets. This should enable the clean `x.py --stage 2 dist rust-std` command on these platforms.
various clippy fixes
We need to keep the order of the given clippy lint rules before passing them.
Since clap doesn't offer any useful interface for this purpose out of the box,
we have to handle it manually.
Additionally, this PR makes `-D` rules work as expected. Previously, lint rules were limited to `-W`. By enabling `-D`, clippy began to complain numerous lines in the tree, all of which have been resolved in this PR as well.
Fixes#121481
cc `@matthiaskrgr`
Makes the iterator 2*usize larger, but I doubt that matters much.
In exchange, we save a lot on instruction count.
In the absence of delegation syntax,
we must forward all the specialized impls manually…
Stabilize associated type bounds (RFC 2289)
This PR stabilizes associated type bounds, which were laid out in [RFC 2289]. This gives us a shorthand to express nested type bounds that would otherwise need to be expressed with nested `impl Trait` or broken into several `where` clauses.
### What are we stabilizing?
We're stabilizing the associated item bounds syntax, which allows us to put bounds in associated type position within other bounds, i.e. `T: Trait<Assoc: Bounds...>`. See [RFC 2289] for motivation.
In all position, the associated type bound syntax expands into a set of two (or more) bounds, and never anything else (see "How does this differ[...]" section for more info).
Associated type bounds are stabilized in four positions:
* **`where` clauses (and APIT)** - This is equivalent to breaking up the bound into two (or more) `where` clauses. For example, `where T: Trait<Assoc: Bound>` is equivalent to `where T: Trait, <T as Trait>::Assoc: Bound`.
* **Supertraits** - Similar to above, `trait CopyIterator: Iterator<Item: Copy> {}`. This is almost equivalent to breaking up the bound into two (or more) `where` clauses; however, the bound on the associated item is implied whenever the trait is used. See #112573/#112629.
* **Associated type item bounds** - This allows constraining the *nested* rigid projections that are associated with a trait's associated types. e.g. `trait Trait { type Assoc: Trait2<Assoc2: Copy>; }`.
* **opaque item bounds (RPIT, TAIT)** - This allows constraining associated types that are associated with the opaque without having to *name* the opaque. For example, `impl Iterator<Item: Copy>` defines an iterator whose item is `Copy` without having to actually name that item bound.
The latter three are not expressible in surface Rust (though for associated type item bounds, this will change in #120752, which I don't believe should block this PR), so this does represent a slight expansion of what can be expressed in trait bounds.
### How does this differ from the RFC?
Compared to the RFC, the current implementation *always* desugars associated type bounds to sets of `ty::Clause`s internally. Specifically, it does *not* introduce a position-dependent desugaring as laid out in [RFC 2289], and in particular:
* It does *not* desugar to anonymous associated items in associated type item bounds.
* It does *not* desugar to nested RPITs in RPIT bounds, nor nested TAITs in TAIT bounds.
This position-dependent desugaring laid out in the RFC existed simply to side-step limitations of the trait solver, which have mostly been fixed in #120584. The desugaring laid out in the RFC also added unnecessary complication to the design of the feature, and introduces its own limitations to, for example:
* Conditionally lowering to nested `impl Trait` in certain positions such as RPIT and TAIT means that we inherit the limitations of RPIT/TAIT, namely lack of support for higher-ranked opaque inference. See this code example: https://github.com/rust-lang/rust/pull/120752#issuecomment-1979412531.
* Introducing anonymous associated types makes traits no longer object safe, since anonymous associated types are not nameable, and all associated types must be named in `dyn` types.
This last point motivates why this PR is *not* stabilizing support for associated type bounds in `dyn` types, e.g, `dyn Assoc<Item: Bound>`. Why? Because `dyn` types need to have *concrete* types for all associated items, this would necessitate a distinct lowering for associated type bounds, which seems both complicated and unnecessary compared to just requiring the user to write `impl Trait` themselves. See #120719.
### Implementation history:
Limited to the significant behavioral changes and fixes and relevant PRs, ping me if I left something out--
* #57428
* #108063
* #110512
* #112629
* #120719
* #120584Closes#52662
[RFC 2289]: https://rust-lang.github.io/rfcs/2289-associated-type-bounds.html
core: document default attribute stabilization
As of now, the first release which stabilized the `#[default]` macro for the deriving the `Default` trait for enus is not documented.
I have had to search the [`RELEASES.md`](https://github.com/rust-lang/rust/blob/master/RELEASES.md) when making sure my code would be accepted by an older Rust compiler.
I just added a line in the doc comment since, as far as I know, there's no option to pass to the `#[stable()]` attribute.
I am open to improvements in the wording.
Making `libcore` decide this is silly; the backend has so much better information about when it's a good idea.
So introduce a new `typed_swap` intrinsic with a fallback body, but replace that implementation for immediates and scalar pairs.
Add as_(mut_)ptr and as_(mut_)slice to raw array pointers
Hey, first time contributing to the standard libraries so not completely sure about the process.
These functions are complementary to the ones being added in #74265 . I found them missing on array pointers.
See also:
- ACP: https://github.com/rust-lang/libs-team/issues/321
- Tracking issue: #119834
Optimize `ptr::replace`
#83022 optimized `mem::replace` to reduce the number of `memcpy`s. `ptr::replace`, which is [documented to behave just like `mem::replace`](https://doc.rust-lang.org/nightly/std/ptr/fn.replace.html), was not optimized however, leading to [worse code](https://godbolt.org/z/T3hdEEdfe) and missed optimizations. This PR simply forwards `ptr::replace` to `mem::replace` to take advantage of the better implementation.
Use `UnsafeCell` for fast constant thread locals
This uses `UnsafeCell` instead of `static mut` for fast constant thread locals. This changes the type of the TLS shims to return `&UnsafeCell<T>` instead of `*mut T` which means they are always non-null so LLVM can optimize away the check for `Some` in `LocalKey::with` if `T` has no destructor.
LLVM is currently unable to do this optimization as we lose the fact that `__getit` always returns `Some` as it gets optimized to just returning the value of the TLS shim.
Bump windows-bindgen to 0.55.0
windows-bindgen is the crate used to generate std's Windows API bindings.
Not many changes for us, it's mostly just simplifying the generate code (e.g. no more `-> ()`). The one substantial change is some structs now use `i8` byte arrays instead of `u8`. However, this only impacts one test.
Mention labelled blocks in `break` docs
`break` doesn't require a loop, so note this in the docs. This is covered in the linked sections of the rust reference, but this page implied that `break` is only for loops.
`break` doesn't require a loop, so note this in the docs.
This is covered in the linked sections of the rust reference,
but this page implied that `break` is only for loops.
Cursor.rs documentation fix
Reason:
I've been learning Rust std library and got confused. Seek trait documentation clearly states that negative indexes will cause an error. And the code in the Cursor example uses negative index. I found myself trying to understand what am I missing until I've actually executed the code and got error. I decided to submit small fix to the documentation.
Rollup of 10 pull requests
Successful merges:
- #117118 ([AIX] Remove AixLinker's debuginfo() implementation)
- #121650 (change std::process to drop supplementary groups based on CAP_SETGID)
- #121764 (Make incremental sessions identity no longer depend on the crate names provided by source code)
- #122212 (Copy byval argument to alloca if alignment is insufficient)
- #122322 (coverage: Initial support for branch coverage instrumentation)
- #122373 (Fix the conflict problem between the diagnostics fixes of lint `unnecessary_qualification` and `unused_imports`)
- #122479 (Implement `Duration::as_millis_{f64,f32}`)
- #122487 (Rename `StmtKind::Local` variant into `StmtKind::Let`)
- #122498 (Update version of cc crate)
- #122503 (Make `SubdiagMessageOp` well-formed)
r? `@ghost`
`@rustbot` modify labels: rollup
Update version of cc crate
Reason:
In order to build the Windows version of the Rust toolchain for the Android platform, the following patch to the cc is crate is required to avoid incorrectly determining that we are building with the Android NDK: 57853c4bf8
This patch is present in version 1.0.80 and newer versions of the cc crate. The rustc source distribution currently has 3 different versions of cc in the vendor directory, only one of which has the necessary fix.
We (the Android Rust toolchain) are currently maintaining local patches to upgrade the cc crate dependency versions, which we would like to upstream.
Implement `Duration::as_millis_{f64,f32}`
Implementation of #122451.
Linked const-unstability to #72440, so the post there should probably be updated to mentions the 2 new methods when/if this PR is merged.
change std::process to drop supplementary groups based on CAP_SETGID
A trivial rebase of #95982
Should fix#39186 (from what I can tell)
Original description:
> Fixes#88716
>
> * Before this change, when a process was given a uid via `std::os::unix::process::CommandExt.uid`, there would be a `setgroups` call (when the process runs) to clear supplementary groups for the child **if the parent was root** (to remove potentially unwanted permissions).
> * After this change, supplementary groups are cleared if we have permission to do so, that is, if we have the CAP_SETGID capability.
>
> This new behavior was agreed upon in #88716 but there was a bit of uncertainty from `@Amanieu` here: [#88716 (comment)](https://github.com/rust-lang/rust/issues/88716#issuecomment-973366600)
>
> > I agree with this change, but is it really necessary to ignore an EPERM from setgroups? If you have permissions to change UID then you should also have permissions to change groups. I would feel more comfortable if we documented set_uid as requiring both UID and GID changing permissions.
>
> The way I've currently written it, we ignore an EPERM as that's what #88716 originally suggested. I'm not at all an expert in any of this so I'd appreciate feedback on whether that was the right way to go.
Reason:
In order to build the Windows version of the Rust toolchain for the Android platform, the following patch to the cc is crate is required to avoid incorrectly determining that we are building with the Android NDK: 57853c4bf8
This patch is present in version 1.0.80 and newer versions of the cc crate. The rustc source distribution currently has 3 different versions of cc in the vendor directory, only one of which has the necessary fix.
We (the Android Rust toolchain) are currently maintaining local patches to upgrade the cc crate dependency versions, which we would like to upstream.
Avoid closing invalid handles
Documentation for [`HandleOrInvalid`] has this note:
> If holds a handle other than `INVALID_HANDLE_VALUE`, it will close the handle on drop.
Documentation for [`HandleOrNull`] has this note:
> If this holds a non-null handle, it will close the handle on drop.
Currently, both will call `CloseHandle` on their invalid handles as a result of using `OwnedHandle` internally, contradicting the above paragraphs. This PR adds destructors that match the documentation.
```@rustbot``` label A-io O-windows T-libs
[`HandleOrInvalid`]: https://doc.rust-lang.org/std/os/windows/io/struct.HandleOrInvalid.html
[`HandleOrNull`]: https://doc.rust-lang.org/std/os/windows/io/struct.HandleOrNull.html
Rollup of 9 pull requests
Successful merges:
- #104353 (Add CStr::bytes iterator)
- #119676 (rustdoc-search: search types by higher-order functions)
- #120699 (Document `TRACK_DIAGNOSTIC` calls.)
- #121899 (Document how removing a type's field can be bad and what to do instead)
- #122405 (Add methods to create StableMIR constant)
- #122416 (Various style improvements to `rustc_lint::levels`)
- #122421 (Improve `Step` docs)
- #122440 (const-eval: organize and extend tests for required-consts)
- #122461 (fix unsoundness in Step::forward_unchecked for signed integers)
Failed merges:
- #122397 (Various cleanups around the const eval query providers)
r? `@ghost`
`@rustbot` modify labels: rollup
fix unsoundness in Step::forward_unchecked for signed integers
Fixes#122420
```rust
pub fn foo(a: i8, b: u8) -> i8 {
unsafe { a.checked_add_unsigned(b).unwrap_unchecked() }
}
```
still compiles down to a single arithmetic instruction ([godbolt](https://rust.godbolt.org/z/qsd3xYWfE)).
But we may be losing some loop optimizations if llvm can no longer easily derive that it's a finite counted loop from the no-wrapping flags.
Improve `Step` docs
It [came up on urlo](https://users.rust-lang.org/t/implement-trait-step-in-1-76-0/108204?u=cad97) that the unstable reason string isn't helpful, so just remove it; there's nothing meaningful to add here.
Also makes a couple drive-by improvements to the method docs -- removes incorrect references, changes `forward_checked`'s invariant formulation to match `backward_checked`'s, and adds a helpful corollary that `step_unchecked(a, 0)` is always safe.
Add CStr::bytes iterator
See rust-lang/libs-team#135 for an ACP.
Since rust-lang/libs-team#134 was also accepted, this type is now `core::ffi::c_str::Bytes` instead of `core::ffi::CStrBytes`.
unix time module now return result
First try to fix#108277 without break anything.
if anyone who read this know tips to be able to check compilation for different target I could use some help. So far I installed many target with rustup but `./x check --all-targets` doesn't seem to use them.
TODO:
- [x] better error
- [ ] test, how ?
`@rustbot` label -S-waiting-on-author +S-waiting-on-review
This commit provides a component model intrinsic in the standard library
by default on the `wasm32-wasip2` target. This intrinsic is not
required by the component model itself but is quite common to use, for
example it's needed if a wasm module receives a string or a list.
The intention of this commit is to provide an overridable definition in
the standard library through a weak definition of this function. That
means that downstream crates can provide their own customized and more
specific versions if they'd like, but the standard library's version
should suffice for general-purpose use.
The ordering of targets in `pal/mod.rs` did not end up using the wasip2
implementation, so after reordering that I've edited the implementation
to compile correctly.
Use `min_exhaustive_patterns` in core & std
[`min_exhaustive_patterns`](https://github.com/rust-lang/rust/issues/119612) provides a subset of the functionality of [`exhaustive_patterns`](https://github.com/rust-lang/rust/issues/51085) which is likely to be stabilized much earlier than the full feature.
The subset covers all the compiler and std use cases. `compiler/` [already uses it](9dd6eda778); this PR switches `std` over.
The dead_code lint was previously eroneously missing this dead code.
Since this lint bug has been fixed, the unused field need
to be removed or marked as `#[allow(dead_code)]`.
These structures API is common to all platforms so the code cannot be
removed and is hence marked allow(dead_code).
The dead_code lint was previously eroneously missing this dead code.
Since this lint bug has been fixed, the unused field need
to be removed or marked as `#[allow(dead_code)]`.
Given the nature of this code, I don't feel confident removing the field
so it is only marked as allow(dead_code).
Test wasm32-wasip1 in CI, not wasm32-unknown-unknown
This commit changes CI to no longer test the `wasm32-unknown-unknown` target and instead test the `wasm32-wasip1` target. There was some discussion of this in a [Zulip thread], and the motivations for this PR are:
* Runtime failures on `wasm32-unknown-unknown` print nothing, meaning all you get is "something failed". In contrast `wasm32-wasip1` can print to stdout/stderr.
* The unknown-unknown target is missing lots of pieces of libstd, and while `wasm32-wasip1` is also missing some pieces (e.g. threads) it's missing fewer pieces. This means that many more tests can be run.
Overall my hope is to improve the debuggability of wasm failures on CI and ideally be a bit less of a maintenance burden.
This commit specifically removes the testing of `wasm32-unknown-unknown` and replaces it with testing of `wasm32-wasip1`. Along the way there were a number of other archiectural changes made as well, including:
* A new `target.*.runtool` option can now be specified in `config.toml` which is passed as `--runtool` to `compiletest`. This is used to reimplement execution of WebAssembly in a less-wasm-specific fashion.
* The default value for `runtool` is an ambiently located WebAssembly runtime found on the system, if any. I've implemented logic for Wasmtime.
* Existing testing support for `wasm32-unknown-unknown` and Emscripten has been removed. I'm not aware of Emscripten testing being run any time recently and otherwise `wasm32-wasip1` is in theory the focus now.
* I've added a new `//@ needs-threads` directive for `compiletest` and classified a bunch of wasm-ignored tests as needing threads. In theory these tests can run on `wasm32-wasi-preview1-threads`, for example.
* I've tried to audit all existing tests that are either `ignore-emscripten` or `ignore-wasm*`. Many now run on `wasm32-wasip1` due to being able to emit error messages, for example. Many are updated with comments as to why they can't run as well.
* The `compiletest` output matching for `wasm32-wasip1` automatically uses "match a subset" mode implemented in `compiletest`. This is because WebAssembly runtimes often add extra information on failure, such as the `unreachable` instruction in `panic!`, which isn't able to be matched against the golden output from native platforms.
* I've ported most existing `run-make` tests that use custom Node.js wrapper scripts to the new run-make-based-in-Rust infrastructure. To do this I added `wasmparser` as a dependency of `run-make-support` for the various wasm tests to use that parse wasm files. The one test that executed WebAssembly now uses `wasmtime`-the-CLI to execute the test instead. I have not ported over an exception-handling test as Wasmtime doesn't implement this yet.
* I've updated the `test` crate to print out timing information for WASI targets as it can do that (gets a previously ignored test now passing).
* The `test-various` image now builds a WASI sysroot for the WASI target and additionally downloads a fixed release of Wasmtime, currently the latest one at 18.0.2, and uses that for testing.
[Zulip thread]: https://rust-lang.zulipchat.com/#narrow/stream/131828-t-compiler/topic/Have.20wasm.20tests.20ever.20caused.20problems.20on.20CI.3F/near/424317944
This commit updates the libtest conditionals to use `std::time::Instant`
on WASI targets where it's implemented. Previously all wasm targets
wouldn't use this type.
std support for wasm32 panic=unwind
Tracking issue: #118168
This adds std support for `-Cpanic=unwind` on wasm, and with it slightly more fleshed out rustc support. Now, the stable default is still panic=abort without exception-handling, but if you `-Zbuild-std` with `RUSTFLAGS=-Cpanic=unwind`, you get wasm exception-handling try/catch blocks in the binary:
```rust
#[no_mangle]
pub fn foo_bar(x: bool) -> *mut u8 {
let s = Box::<str>::from("hello");
maybe_panic(x);
Box::into_raw(s).cast()
}
#[inline(never)]
#[no_mangle]
fn maybe_panic(x: bool) {
if x {
panic!("AAAAA");
}
}
```
```wat
;; snip...
(try $label$5
(do
(call $maybe_panic
(local.get $0)
)
(br $label$1)
)
(catch_all
(global.set $__stack_pointer
(local.get $1)
)
(call $__rust_dealloc
(local.get $2)
(i32.const 5)
(i32.const 1)
)
(rethrow $label$5)
)
)
;; snip...
```
bors