Stabilize `naked_functions`
tracking issue: https://github.com/rust-lang/rust/issues/90957
request for stabilization on tracking issue: https://github.com/rust-lang/rust/issues/90957#issuecomment-2539270352
reference PR: https://github.com/rust-lang/reference/pull/1689
# Request for Stabilization
Two years later, we're ready to try this again. Even though this issue is already marked as having passed FCP, given the amount of time that has passed and the changes in implementation strategy, we should follow the process again.
## Summary
The `naked_functions` feature has two main parts: the `#[naked]` function attribute, and the `naked_asm!` macro.
An example of a naked function:
```rust
const THREE: usize = 3;
#[naked]
pub extern "sysv64" fn add_n(number: usize) -> usize {
// SAFETY: the validity of the used registers
// is guaranteed according to the "sysv64" ABI
unsafe {
core::arch::naked_asm!(
"add rdi, {}",
"mov rax, rdi",
"ret",
const THREE,
)
}
}
```
When the `#[naked]` attribute is applied to a function, the compiler won't emit a [function prologue](https://en.wikipedia.org/wiki/Function_prologue_and_epilogue) or epilogue when generating code for this function. This attribute is analogous to [`__attribute__((naked))`](https://developer.arm.com/documentation/100067/0608/Compiler-specific-Function--Variable--and-Type-Attributes/--attribute----naked---function-attribute) in C. The use of this feature allows the programmer to have precise control over the assembly that is generated for a given function.
The body of a naked function must consist of a single `naked_asm!` invocation, a heavily restricted variant of the `asm!` macro: the only legal operands are `const` and `sym`, and the only legal options are `raw` and `att_syntax`. In lieu of specifying operands, the `naked_asm!` within a naked function relies on the function's calling convention to determine the validity of registers.
## Documentation
The Rust Reference: https://github.com/rust-lang/reference/pull/1689
(Previous PR: https://github.com/rust-lang/reference/pull/1153)
## Tests
* [tests/run-make/naked-symbol-visiblity](https://github.com/rust-lang/rust/tree/master/tests/codegen/naked-fn) verifies that `pub`, `#[no_mangle]` and `#[linkage = "..."]` work correctly for naked functions
* [tests/codegen/naked-fn](https://github.com/rust-lang/rust/tree/master/tests/codegen/naked-fn) has tests for function alignment, use of generics, and validates the exact assembly output on linux, macos, windows and thumb
* [tests/ui/asm/naked-*](https://github.com/rust-lang/rust/tree/master/tests/ui/asm) tests for incompatible attributes, generating errors around incorrect use of `naked_asm!`, etc
## Interaction with other (unstable) features
### [fn_align](https://github.com/rust-lang/rust/issues/82232)
Combining `#[naked]` with `#[repr(align(N))]` works well, and is tested e.g. here
- https://github.com/rust-lang/rust/blob/master/tests/codegen/naked-fn/aligned.rs
- https://github.com/rust-lang/rust/blob/master/tests/codegen/naked-fn/min-function-alignment.rs
It's tested extensively because we do need to explicitly support the `repr(align)` attribute (and make sure we e.g. don't mistake powers of two for number of bytes).
## History
This feature was originally proposed in [RFC 1201](https://github.com/rust-lang/rfcs/pull/1201), filed on 2015-07-10 and accepted on 2016-03-21. Support for this feature was added in [#32410](https://github.com/rust-lang/rust/pull/32410), landing on 2016-03-23. Development languished for several years as it was realized that the semantics given in RFC 1201 were insufficiently specific. To address this, a minimal subset of naked functions was specified by [RFC 2972](https://github.com/rust-lang/rfcs/pull/2972), filed on 2020-08-07 and accepted on 2021-11-16. Prior to the acceptance of RFC 2972, all of the stricter behavior specified by RFC 2972 was implemented as a series of warn-by-default lints that would trigger on existing uses of the `naked` attribute; these lints became hard errors in [#93153](https://github.com/rust-lang/rust/pull/93153) on 2022-01-22. As a result, today RFC 2972 has completely superseded RFC 1201 in describing the semantics of the `naked` attribute.
More recently, the `naked_asm!` macro was added to replace the earlier use of a heavily restricted `asm!` invocation. The `naked_asm!` name is clearer in error messages, and provides a place for documenting the specific requirements of inline assembly in naked functions.
The implementation strategy was changed to emitting a global assembly block. In effect, an extern function
```rust
extern "C" fn foo() {
core::arch::naked_asm!("ret")
}
```
is emitted as something similar to
```rust
core::arch::global_asm!(
"foo:",
"ret"
);
extern "C" {
fn foo();
}
```
The codegen approach was chosen over the llvm naked function attribute because:
- the rust compiler can guarantee the behavior (no sneaky additional instructions, no inlining, etc.)
- behavior is the same on all backends (llvm, cranelift, gcc, etc)
Finally, there is now an allow list of compatible attributes on naked functions, so that e.g. `#[inline]` is rejected with an error. The `#[target_feature]` attribute on naked functions was later made separately unstable, because implementing it is complex and we did not want to block naked functions themselves on how target features work on them. See also https://github.com/rust-lang/rust/issues/138568.
relevant PRs for these recent changes
- https://github.com/rust-lang/rust/pull/127853
- https://github.com/rust-lang/rust/pull/128651
- https://github.com/rust-lang/rust/pull/128004
- https://github.com/rust-lang/rust/pull/138570
-
### Various historical notes
#### `noreturn`
[RFC 2972](https://github.com/rust-lang/rfcs/blob/master/text/2972-constrained-naked.md) mentions that naked functions
> must have a body which contains only a single asm!() statement which:
> iii. must contain the noreturn option.
Instead of `asm!`, the current implementation mandates that the body contain a single `naked_asm!` statement. The `naked_asm!` macro is a heavily restricted version of the `asm!` macro, making it easier to talk about and document the rules of assembly in naked functions and give dedicated error messages.
For `naked_asm!`, the behavior of the `asm!`'s `noreturn` option is implicit. The `noreturn` option means that it is UB for control flow to fall through the end of the assembly block. With `asm!`, this option is usually used for blocks that diverge (and thus have no return and can be typed as `!`). With `naked_asm!`, the intent is different: usually naked funtions do return, but they must do so from within the assembly block. The `noreturn` option was used so that the compiler would not itself also insert a `ret` instruction at the very end.
#### padding / `ud2`
A `naked_asm!` block that violates the safety assumption that control flow must not fall through the end of the assembly block is UB. Because no return instruction is emitted, whatever bytes follow the naked function will be executed, resulting in truly undefined behavior. There has been discussion whether rustc should emit an invalid instruction (e.g. `ud2` on x86) after the `naked_asm!` block to at least fail early in the case of an invalid `naked_asm!`. It was however decided that it is more useful to guarantee that `#[naked]` functions NEVER contain any instructions besides those in the `naked_asm!` block.
# unresolved questions
None
r? ``@Amanieu``
I've validated the tests on x86_64 and aarch64
replace broken links armv7-rtems-eabihf.md
Hi team , i found broken link in `src/doc/rustc/src/platform-support/armv7-rtems-eabihf.md` and replace
thanks
Put them all on the same line with just their GitHub handles to make it
very easy to copy and paste (with ctrl-shift-v!!!) the names.
We have no use for email, so I removed all the emails, we don't care
about people's full names either.
Co-authored-by: Thalia Archibald <thalia@archibald.dev>
Switch exploit mitigations to mdbook footnotes
This updates the exploit mitigations chapter in the rustc book to use the footnote feature of mdbook instead of manually implementing footnotes with HTML.
simd intrinsics with mask: accept unsigned integer masks, and fix some of the errors
It's not clear at all why the mask would have to be signed, it is anyway interpreted bitwise. The backend should just make sure that works no matter the surface-level type; our LLVM backend already does this correctly. The note of "the mask may be widened, which only has the correct behavior for signed integers" explains... nothing? Why can't the code do the widening correctly? If necessary, just cast to the signed type first...
Also while we are at it, fix the errors. For simd_masked_load/store, the errors talked about the "third argument" but they meant the first argument (the mask is the first argument there). They also used the wrong type for `expected_element`.
I have extremely low confidence in the GCC part of this PR.
See [discussion on Zulip](https://rust-lang.zulipchat.com/#narrow/channel/257879-project-portable-simd/topic/On.20the.20sign.20of.20masks)
Improve `clean_maybe_renamed_item` function code a bit
Follow-up of #139846.
This is what I tried to say in there: the `name` variable can be unwrapped in most cases so better do it directly once and for all if possible and move the cases where it's not possible above.
r? `@nnethercote`
skip llvm-config in autodiff check builds, when its unavailable
As you suggested, this indeed fixes `./x.py check` builds when autodiff is enabled.
r? ```@onur-ozkan```
closes#139936
Tracking:
- https://github.com/rust-lang/rust/issues/124509
Setup editor file associations for non-rs extensions
.gitattributes lists `*.fixed`, `*.pp`, and `*.mir` as file extensions which should be treated as Rust source code. Do the same for VS Code and Zed. This only does syntax highlighting, which is appropriate, as MIR isn't really Rust code.
At the same time, consistently order `rust-analyzer.linkedProjects` between editors. For some reason, Eglot didn't include `library/Cargo.toml`.
I have tested this with VS Code and Zed. I have not implemented it for Emacs/Eglot or Helix.
Do not remove trivial `SwitchInt` in analysis MIR
This PR ensures that we don't prematurely remove trivial `SwitchInt` terminators which affects both the borrow-checking and runtime semantics (i.e. UB) of the code. Previously the `SimplifyCfg` optimization was removing `SwitchInt` terminators when they was "trivial", i.e. when all arms branched to the same basic block, even if that `SwitchInt` terminator had the side-effect of reading an operand which (for example) may not be initialized or may point to an invalid place in memory.
This behavior is unlike all other optimizations, which are only applied after "analysis" (i.e. borrow-checking) is finished, and which Miri disables to make sure the compiler doesn't silently remove UB.
Fixing this code "breaks" (i.e. unmasks) code that used to borrow-check but no longer does, like:
```rust
fn foo() {
let x;
let (0 | _) = x;
}
```
This match expression should perform a read because `_` does not shadow the `0` literal pattern, and the compiler should have to read the match scrutinee to compare it to 0. I've checked that this behavior does not actually manifest in practice via a crater run which came back clean: https://github.com/rust-lang/rust/pull/139042#issuecomment-2767436367
As a side-note, it may be tempting to suggest that this is actually a good thing or that we should preserve this behavior. If we wanted to make this work (i.e. trivially optimize out reads from matches that are redundant like `0 | _`), then we should be enabling this behavior *after* fixing this. However, I think it's kinda unprincipled, and for example other variations of the code don't even work today, e.g.:
```rust
fn foo() {
let x;
let (0.. | _) = x;
}
```
This updates the exploit mitigations chapter in the rustc book to use
the footnote feature of mdbook instead of manually implementing
footnotes with HTML.
Clean UI tests 4 of n
Cleaned up some tests that have `issue` in the title. I kept the commits to be one per "`issue`" cleanup/rename to make it easier to check. I can rebase to one commit once the changes are approved.
Related Issues:
#73494#133895
r? jieyouxu
Add citool command for generating a test dashboard
This PR implements an initial version of a test suite dashboard, which shows which tests were executed on CI and which tests were ignored. This was discussed [here](https://rust-lang.zulipchat.com/#narrow/channel/238009-t-compiler.2Fmeetings/topic/.5Bsteering.5D.202025-04-11.20Dealing.20with.20disabled.20tests/with/512799036). The dashboard is still quite bare-bones, but I think that it could already be useful.
The next step is to create a job index, similarly to the post-merge report, and link from the individual tests to the job that executed them.
You can try it locally like this:
```bash
$ cargo run --manifest-path src/ci/citool/Cargo.toml --release \
-- test-dashboard 38c560ae68 --output-dir dashboard
```
and then open `dashboard/index.html` in a web browser.
CC ````@wesleywiser````
r? ````@jieyouxu````
Rewrite on_unimplemented format string parser.
This PR rewrites the format string parser for `rustc_on_unimplemented` and `diagnostic::on_unimplemented`. I plan on moving this code (and more) into the new attribute parsing system soon and wanted to PR it separately.
This PR introduces some minor differences though:
- `rustc_on_unimplemented` on trait *implementations* is no longer checked/used - this is actually never used (outside of some tests) so I plan on removing it in the future.
- for `rustc_on_unimplemented`, it introduces the `{This}` argument in favor of `{ThisTraitname}` (to be removed later). It'll be easier to parse.
- for `rustc_on_unimplemented`, `Self` can now consistently be used as a filter, rather than just `_Self`. It used to not match correctly on for example `Self = "[{integer}]"`
- Some error messages now have better spans.
Fixes https://github.com/rust-lang/rust/issues/130627
support config extensions
_Copied from the `rustc-dev-guide` addition:_
>When working on different tasks, you might need to switch between different bootstrap >configurations.
>Sometimes you may want to keep an old configuration for future use. But saving raw config >values in
>random files and manually copying and pasting them can quickly become messy, especially if >you have a
>long history of different configurations.
>
>To simplify managing multiple configurations, you can create config extensions.
>
>For example, you can create a simple config file named `cross.toml`:
>
>```toml
>[build]
>build = "x86_64-unknown-linux-gnu"
>host = ["i686-unknown-linux-gnu"]
>target = ["i686-unknown-linux-gnu"]
>
>
>[llvm]
>download-ci-llvm = false
>
>[target.x86_64-unknown-linux-gnu]
>llvm-config = "/path/to/llvm-19/bin/llvm-config"
>```
>
>Then, include this in your `bootstrap.toml`:
>
>```toml
>include = ["cross.toml"]
>```
>
>You can also include extensions within extensions recursively.
>
>**Note:** In the `include` field, the overriding logic follows a right-to-left order. For example,
in `include = ["a.toml", "b.toml"]`, extension `b.toml` overrides `a.toml`. Also, parent extensions
always overrides the inner ones.
try-job: x86_64-mingw-2
Make rustdoc JSON Span column 1-based, just like line numbers
Fixes https://github.com/rust-lang/rust/issues/139906.
This PR does two things:
1. It makes column 1-indexed as well, just like lines.
2. It updates documentation about them to mention that they are 1-indexed.
I think it's better for coherency to have them both 1-indexed instead of the weird mix we used to have. Docs for `line` and `col` fields can be found [here](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_span/struct.Loc.html#structfield.line).
And finally: it adds a regression test to ensure they are indeed 1-indexed.
r? `@aDotInTheVoid`
Deduplicate & clean up Nix shell
1. Deduplicate the flake and shell files
2. Remove flake-utils
3. Remove `with` statements
They are considered bad practice nowadays because the slow down the evalulator and have weird shadowing rules.
4. Use `env`
:3
5. use `callPackage`
It's the recommended way for derivations like these.
6. Use `packages` in the shell
There is no reason to use `buildInputs` for a mkShell (except in funny cases that will not be seen here), so the `packages` attr is recommended now days.
r? WaffleLapkin
Implement `pin!()` using `super let`
Tracking issue for super let: https://github.com/rust-lang/rust/issues/139076
This uses `super let` to implement `pin!()`.
This means we can remove [the hack](https://github.com/rust-lang/rust/pull/138717) we had to put in to fix https://github.com/rust-lang/rust/issues/138596.
It also means we can remove the original hack to make `pin!()` work, which used a questionable public-but-unstable field rather than a proper private field.
While `super let` is still unstable and subject to change, it seems safe to assume that future Rust will always have a way to express `pin!()` in a compatible way, considering `pin!()` is already stable.
It'd help [the experiment](https://github.com/rust-lang/rust/issues/139076) to have `pin!()` use `super let`, so we can get some more experience with it.
run-make: drop `os_pipe` workaround now that `anonymous_pipe` is stable on beta
Follow-up to #137537 where I had to include a temporary dep on `os_pipe` before `anonymous_pipe` was stabilized. Now that `anonymous_pipe` is stable on beta, we can get rid of this workaround.
Closes#137532. (Final cleanup item)
r? `@Kobzol`
rustdoc/clean: Fix lowering of fn params (fixes correctness & HIR vs. middle parity regressions)
**(0)** PR #136411 aimed to stop rendering unnamed params of fn ptr types as underscores in the common case (e.g., `fn(_: i32)` → `fn(i32)`) to make the rendered output stylistically more conventional.
**(0.a)** However, since the cleaning fn that the PR modified is also used for lowering the HIR params of foreign fns and required assoc fns in traits, it accidentally butchered the rendering of the latter two:
```rs
pub trait Trait { fn assoc_fn(_: i32); } // as well as (Rust 2015 only): fn assoc_fn(i32);
unsafe extern "C" { pub fn foreign_fn(_: i32); }
// Since 1.86 the fns above gets mis-rendered as:
pub fn assoc_fn(: i32) // <-- BUTCHERED
pub unsafe extern "C" fn foreign_fn(: i32) // <-- BUTCHERED
```
**(0.b)** Furthermore, it broke parity with middle cleaning (which includes inlined cross-crate re-exports) re-regressing parts of #44306 I once fixed in PR #103885.
**(1)** Lastly, PR #139035 introduced an ICE triggered by the following input file:
```rs
trait Trait { fn anon(()) {} } // internal error: entered unreachable code
```
---
This PR fixes all of these regressions and in the first commit renames several types and fns to be more ~~correct~~ descriptive and legible.
~~It also refactors `Param.name` to be of type `Option<Symbol>` instead `Symbol` (where `None` ~ `kw::Empty`), so rendering mistakes like that can no longer creep in like that (ignoring tests). CC #137978.~~ Independently done in PR #139846 a day prior.
Disable combining LLD with external llvm-config
When an external `llvm-config` is used, we don't really know anything about the external LLD, as we don't build it ourselves. Therefore, we probably shouldn't allow using `rust-lld` nor copy it to the target sysroot.
Fixes: https://github.com/rust-lang/rust/issues/139477
CC ``@cuviper``
r? ``@onur-ozkan``
try-job: dist-x86_64-linux
try-job: dist-aarch64-linux
sync::mpsc: prevent double free on `Drop`
This PR is fixing a regression introduced by #121646 that can lead to a double free when dropping the channel.
The details of the bug can be found in the corresponding crossbeam PR https://github.com/crossbeam-rs/crossbeam/pull/1187
rustdoc-json: Output target feature information
`#[target_feature]` attributes refer to a target-specific list of features. Enabling certain features can imply enabling other features. Certain features are always enabled on certain targets, since they are required by the target's ABI. Features can also be enabled indirectly based on other compiler flags.
Feature information is ultimately known to `rustc`. Rather than force external tools to track it – which may be wildly impractical due to `-C target-cpu` – have `rustdoc` output `rustc`'s feature data.
This change is motivated by https://github.com/obi1kenobi/cargo-semver-checks/issues/1246, which intends to detect semver hazards caused by `#[target_feature]`.
try-job: aarch64-gnu
try-job: armhf-gnu
try-job: test-various
try-job: x86_64-msvc-1
try-job: i686-msvc-1
try-job: x86_64-mingw-1
try-job: aarch64-apple
deref patterns: implement implicit deref patterns
This implements implicit deref patterns (per https://hackmd.io/4qDDMcvyQ-GDB089IPcHGg#Implicit-deref-patterns) and adds tests and an unstable book chapter.
Best reviewed commit-by-commit. Overall there's a lot of additions, but a lot of that is tests, documentation, and simple(?) refactoring.
Tracking issue: #87121
r? ``@Nadrieril``
Chris Denton