Elaborate on deriving vs implementing `Copy`
I was reading this documentation and this wasn't immediately clear to me.
In my mind, it seemed obvious that a type can only claim to be `Copy` if the bits it is storing can be `Copy`, and in the case of a generic struct that can only be the case if `T: Copy`. So the bound added by the derive seemed necessary at all times, and I thought what the documentation was trying to say is that the custom implementation allows you to add _additional bounds_.
Of course what it was actually trying to point out is that just because you have a generic parameter `T`, it doesn't necessarily mean you are storing the bits of `T`. And if you aren't, it may be the case that your own bits can be copied regardless of whether the bits of `T` can be safely copied.
Thought it may be worth elaborating to make that a bit more clear. Haven't tested/didn't try to figure out how to render this locally. Mainly not sure if the `PhantomData` back link is going to just work or need some extra stuff, but I figured someone else probably could just tell.
Stabilize `waker_getters`
Tracking issue: #96992
FCP completed on the tracking issue a while ago. It's not clear whether the libs-api team wanted the `RawWaker` methods moved to `Waker` or went back to the current API after further discussion. `@Amanieu` [wrote "This is just waiting for someone to submit a stabilization PR."](https://github.com/rust-lang/rust/issues/96992#issuecomment-2213685218) so I'm doing just that in hopes of nudging this along.
Edit: Moved the `data` and `vtable` methods from `RawWaker` to `Waker` and added `Waker::new` per https://github.com/rust-lang/rust/issues/96992#issuecomment-1941998046
```rs
impl Waker {
pub const unsafe fn new(data: *const (), vtable: &'static RawWakerVTable) -> Self;
pub fn data(&self) -> *const ();
pub fn vtable(&self) -> &'static RawWakerVTable;
}
```
Closes#96992
Add target support for RTEMS Arm
# `armv7-rtems-eabihf`
This PR adds a new target for the RTEMS RTOS. To get things started it focuses on Xilinx/AMD Zynq-based targets, but in theory it should also support other armv7-based board support packages in the future.
Given that RTEMS has support for many POSIX functions it is mostly enabling corresponding unix features for the new target.
I also previously started a PR in libc (https://github.com/rust-lang/libc/pull/3561) to add the needed OS specific C-bindings and was told that a PR in this repo is needed first. I will update the PR to the newest version after approval here.
I will probably also need to change one line in the backtrace repo.
Current status is that I could compile rustc for the new target locally (with the updated libc and backtrace) and could compile binaries, link, and execute a simple "Hello World" RTEMS application for the target hardware.
> A proposed target or target-specific patch that substantially changes code shared with other targets (not just target-specific code) must be reviewed and approved by the appropriate team for that shared code before acceptance.
There should be no breaking changes for existing targets. Main changes are adding corresponding `cfg` switches for the RTEMS OS and adding the C binding in libc.
# Tier 3 target policy
> - 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.)
I will do the maintenance (for now) further members of the RTEMS community will most likely join once the first steps have been done.
> - 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.
The proposed triple is `armv7-rtems-eabihf`
> - 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 be subject 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.
The tools consists of the cross-compiler toolchain (gcc-based). The RTEMS kernel (BSD license) and parts of the driver stack of FreeBSD (BSD license). All tools are FOSS and publicly available here: https://gitlab.rtems.org/rtems
There are also no new features or dependencies introduced to the Rust code.
> - 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.
N/A to me. I am not a reviewer nor Rust team member.
> - 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.
`core` and `std` compile. Some advanced features of the `std` lib might not work yet. However, the goal of this tier 3 target it to make it easier for other people to build and run test applications to better identify the unsupported features and work towards enabling them.
> - 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.
Building is described in platform support doc. Running simple unit tests works. Running the test suite of the stdlib is currently not that easy. Trying to work towards that after the this target has been added to the nightly.
> - 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.
Understood.
> - 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.
Ok
> - 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 think, I didn't add any breaking changes for any existing targets (see the comment regarding features above).
> - Tier 3 targets must be able to produce assembly using at least one of rustc's supported backends from any host target.
Can produce assembly code via the llvm backend (tested on Linux).
>
> If a tier 3 target stops meeting these requirements, or the target maintainers no longer have interest or time, or the target shows no signs of activity and has not built for some time, or removing the target would improve the quality of the Rust codebase, we may post a PR to remove it; any such PR will be CCed to the target maintainers (and potentially other people who have previously worked on the target), to check potential interest in improving the situation.GIAt this tier, the Rust project provides no official support for a target, so we place minimal requirements on the introduction of targets.
Understood.
r? compiler-team
Clarify language around ptrs in slice::raw
More specifically we explicitly mention that the pointer should be non-null as a top level requirement. Nullptrs are always valid for zero sized operations, so just validity (and alignment) does not guarantee non-nullness as implied in the existing docs.
We also explicitly call out ZSTs as an additional example where perhaps unintuitively alignment and non-nullness still have to hold.
Finally we change `data` in the range functions to `start`, which seems like a typo to me.
Touches docs for #89792
r? RalfJung
compiler_fence documentation: emphasize synchronization, not reordering
Our `fence` docs have at some point been update to explain that they are about synchronization, not about "preventing reordering". This updates the `compiler_fence` docs n the same vein, mostly by referring to the `fence` docs.
The old docs make it sound like I can put a compiler_fence in the middle of a bunch of non-atomic operations and that would achieve any kind of guarantee. It does not, atomic operations are still required to do synchronization.
I also slightly tweaked the `fence` docs, to put the synchronization first and the "prevent reordering" second.
Cc `@rust-lang/opsem` `@chorman0773` `@m-ou-se`
Fixes https://github.com/rust-lang/rust/issues/129189
Fixes https://github.com/rust-lang/rust/issues/54962
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
add extra linebreaks so rustdoc can identify the first sentence
there should probably be a lint against this in rustdoc, it causes too many lines to be shown in the short documentation overviews
expecially noticable for the slice primative type: https://doc.rust-lang.org/std/index.html
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
there should probably be a lint against this in rustdoc, it causes
too many lines to be shown in the short documentation overviews
expecially noticable for the slice primative type:
https://doc.rust-lang.org/std/index.html
refactor: standardize duplicate processes in parser
## Summary
This PR refactors the `read_number` function to standardize duplicate code, improve readability, and enhance efficiency.
## Changes
- Merged the logic for both `max_digits` cases into a single `read_atomically` closure
- Simplified control flow and reduced code duplication
core: use `compare_bytes` for more slice element types
`bool`, `NonZero<u8>`, `Option<NonZero<u8>>` and `ascii::Char` can be compared the same way as `u8`.
Rollup of 11 pull requests
Successful merges:
- #128523 (Add release notes for 1.81.0)
- #129605 (Add missing `needs-llvm-components` directives for run-make tests that need target-specific codegen)
- #129650 (Clean up `library/profiler_builtins/build.rs`)
- #129651 (skip stage 0 target check if `BOOTSTRAP_SKIP_TARGET_SANITY` is set)
- #129684 (Enable Miri to pass pointers through FFI)
- #129762 (Update the `wasm-component-ld` binary dependency)
- #129782 (couple more crash tests)
- #129816 (tidy: say which feature gate has a stability issue mismatch)
- #129818 (make the const-unstable-in-stable error more clear)
- #129824 (Fix code examples buttons not appearing on click on mobile)
- #129826 (library: Fix typo in `core::mem`)
r? `@ghost`
`@rustbot` modify labels: rollup
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 :)
* Use a lookup table for 8-bit integers and the Karatsuba square root
algorithm for larger integers.
* Include optimization hints that give the compiler the exact numeric
range of results.
* Choose test inputs more thoroughly and systematically.
* Check that `isqrt` and `checked_isqrt` have equivalent results for
signed types, either equivalent numerically or equivalent as a panic
and a `None`.
* Check that `isqrt` has numerically-equivalent results for unsigned
types and their `NonZero` counterparts.
* Reuse `ilog10` benchmarks, plus benchmarks that use a uniform
distribution.
Rollup of 11 pull requests
Successful merges:
- #129421 (add repr to the allowlist for naked functions)
- #129480 (docs: correct panic conditions for rem_euclid and similar functions)
- #129551 (ub_checks intrinsics: fall back to cfg(ub_checks))
- #129608 (const-eval: do not make UbChecks behavior depend on current crate's flags)
- #129613 (interpret: do not make const-eval query result depend on tcx.sess)
- #129641 (rustdoc: fix missing resource suffix on `crates.js`)
- #129657 (Rename `BikeshedIntrinsicFrom` to `TransmuteFrom`)
- #129666 (interpret: add missing alignment check in raw_eq)
- #129667 (Rustc driver cleanup)
- #129668 (Fix Pin::set bounds regression)
- #129686 (coverage: Rename `CodeRegion` to `SourceRegion`)
r? `@ghost`
`@rustbot` modify labels: rollup
Rename `BikeshedIntrinsicFrom` to `TransmuteFrom`
As our implementation of MCP411 nears completion and we begin to solicit testing, it's no longer reasonable to expect testers to type or remember `BikeshedIntrinsicFrom`. The name degrades the ease-of-reading of documentation, and the overall experience of using compiler safe transmute.
Tentatively, we'll instead adopt `TransmuteFrom`.
This name seems to be the one most likely to be stabilized, after discussion on Zulip [1]. We may want to revisit the ordering of `Src` and `Dst` before stabilization, at which point we'd likely consider `TransmuteInto` or `Transmute`.
[1] https://rust-lang.zulipchat.com/#narrow/stream/216762-project-safe-transmute/topic/What.20should.20.60BikeshedIntrinsicFrom.60.20be.20named.3F
Tracking Issue: https://github.com/rust-lang/rust/issues/99571
r? `@compiler-errors`
ub_checks intrinsics: fall back to cfg(ub_checks)
Not sure why the fallback body uses `debug_assertions`, probably a leftover from when `cfg!(ub_checks)` did not exist yet?
r? `@saethlin`
