Update books
## rust-lang/book
1 commits in 4433c9f0cad8460bee05ede040587f8a1fa3f1de..8a6d44e45b7b564eeb6bae30507e1fbac439d72d
2025-06-18 17:06:36 UTC to 2025-06-18 17:06:36 UTC
- Chapter 12 from tech review (rust-lang/book#4410)
## rust-lang/reference
6 commits in d4c66b346f4b72d29e70390a3fa3ea7d4e064db1..50fc1628f36563958399123829c73755fa7a8421
2025-06-19 02:02:39 UTC to 2025-06-17 21:18:46 UTC
- Document inferred const args (`feature(generic_arg_infer)`) (rust-lang/reference#1835)
- const_eval: we allow references to statics and promoteds (rust-lang/reference#1858)
- Fix missing rule on destructors (rust-lang/reference#1861)
- Fix inconsistent heading depth (rust-lang/reference#1860)
- Fix recursive root-accessible grammar check (rust-lang/reference#1852)
- Fix grammar links (rust-lang/reference#1851)
## rust-lang/rust-by-example
1 commits in 9baa9e863116cb9524a177d5a5c475baac18928a..05c7d8bae65f23a1837430c5a19be129d414f5ec
2025-06-18 13:15:17 UTC to 2025-06-18 13:15:17 UTC
- Revert "introduce new ````@media```` query to set a higher content width on ultra wide screens" (rust-lang/rust-by-example#1939)
Reduce uses of `hir_crate`.
I tried rebasing my old incremental-HIR branch. This is a by-product, which is required if we want to get rid of `hir_crate` entirely.
The second commit is a drive-by cleanup. It can be pulled into its own PR.
r? ````@oli-obk````
Implement send_signal for unix child processes
Tracking issue: rust-lang/rust#141975
There are two main differences between my implementation and the Public API section of the tracking issue. ~First, `send_signal` requires a mutable reference, like `Child::kill`.~ Second, `ChildExt` has `Sealed` as a supertrait, bringing it more in line with other extension traits like `CommandExt`.
try-job: `dist-various*`
try-job: `test-various*`
Extract some shared code from codegen backend target feature handling
There's a bunch of code duplication between the GCC and LLVM backends in target feature handling. This moves that into new shared helper functions in `rustc_codegen_ssa`.
The first two commits should be purely refactoring. I am fairly sure the LLVM-side behavior stays the same; if the GCC side deliberately diverges from this then I may have missed that. I did account for one divergence, which I do not know is deliberate or not: GCC does not seem to use the `-Ctarget-feature` flag to populate `cfg(target_feature)`. That seems odd, since the `-Ctarget-feature` flag is used to populate the return value of `global_gcc_features` which controls the target features actually used by GCC. ``@GuillaumeGomez`` ``@antoyo`` is there a reason `target_config` ignores `-Ctarget-feature` but `global_gcc_features` does not? The second commit also cleans up a bunch of unneeded complexity added in https://github.com/rust-lang/rust/pull/135927.
The third commit extracts some shared logic out of the functions that populate `cfg(target_feature)` and the backend target feature set, respectively. This one actually has some slight functional changes:
- Before, with `-Ctarget-feature=-feat`, if there is some other feature `x` that implies `feat` we would *not* add `-x` to the backend target feature set. Now, we do. This fixesrust-lang/rust#134792.
- The logic that removes `x` from `cfg(target_feature)` in this case also changed a bit, avoiding a large number of calls to the (uncached) `sess.target.implied_target_features` (if there were a large number of positive features listed before a negative feature) but instead constructing a full inverse implication map when encountering the first negative feature. Ideally this would be done with queries but the backend target feature logic runs before `tcx` so we can't use that...
- Previously, if feature "a" implied "b" and "b" was unstable, then using `-Ctarget-feature=+a` would also emit a warning about `b`. I had to remove this since when accounting for negative implications, this emits a ton of warnings in a bunch of existing tests... I assume this was unintentional anyway.
The fourth commit increases consistency of the GCC backend with the LLVM backend.
The last commit does some further cleanup:
- Get rid of RUSTC_SPECIAL_FEATURES. It was only needed for s390x "backchain", but since LLVM 19 that is always a regular target feature so we don't need this hack any more. The hack also has various unintended side-effects so we don't want to keep it. Fixes https://github.com/rust-lang/rust/issues/142412.
- Move RUSTC_SPECIFIC_FEATURES handling into the shared parse_rust_feature_flag helper so all consumers of `-Ctarget-feature` that only care about actual target features (and not "crt-static") have it. Previously, we actually set `cfg(target_feature = "crt-static")` twice: once in the backend target feature logic, and once specifically for that one feature. IIUC, some targets are meant to ignore `-Ctarget-feature=+crt-static`, it seems like before this PR that flag still incorrectly enabled `cfg(target_feature = "crt-static")` (but I didn't test this).
- Move fixed_x18 handling together with retpoline handling.
- Forbid setting fixed_x18 as a regular target feature, even unstably. It must be set via the `-Z` flag.
``@bjorn3`` I did not touch the cranelift backend here, since AFAIK it doesn't really support target features. But if you ever do, please use the new helpers. :)
Cc ``@workingjubilee``
rewrite `optimize` attribute to use new attribute parsing infrastructure
r? ```@oli-obk```
I'm afraid we'll get quite a few of these PRs in the future. If we get a lot of trivial changes I'll start merging multiple into one PR. They should be easy to review :)
Waiting on #138165 first
Use jemalloc for Clippy
The tool macros are annoying, we should IMO just get rid of them, create separate steps for each tool and (re)use some builders in them to share the build code.
r? `@ghost`
Use a distinct `ToString` implementation for `u128` and `i128`
Part of https://github.com/rust-lang/rust/issues/135543.
Follow-up of rust-lang/rust#136264.
When working on https://github.com/rust-lang/rust/pull/142098, I realized that `i128` and `u128` could also benefit from a distinct `ToString` implementation so here it.
The last commit is just me realizing that I forgot to add the format tests for `usize` and `isize`.
Here is the bench comparison:
| bench name | last nightly | with this PR | diff |
|-|-|-|-|
| bench_i128 | 29.25 ns/iter (+/- 0.66) | 17.52 ns/iter (+/- 0.7) | -40.1% |
| bench_u128 | 34.06 ns/iter (+/- 0.21) | 16.1 ns/iter (+/- 0.6) | -52.7% |
I used this code to test:
```rust
#![feature(test)]
extern crate test;
use test::{Bencher, black_box};
#[inline(always)]
fn convert_to_string<T: ToString>(n: T) -> String {
n.to_string()
}
macro_rules! decl_benches {
($($name:ident: $ty:ident,)+) => {
$(
#[bench]
fn $name(c: &mut Bencher) {
c.iter(|| convert_to_string(black_box({ let nb: $ty = 20; nb })));
}
)+
}
}
decl_benches! {
bench_u128: u128,
bench_i128: i128,
}
```
Handle win32 separator for cygwin paths
This PR handles a issue that cygwin actually supports Win32 path, so we need to handle the Win32 prefix and separaters.
r? `@mati865`
cc `@jeremyd2019`
~~Not sure if I should handle the prefix like the windows target... Cygwin *does* support win32 paths directly going through the APIs, but I think it's not the recommended way.~~
Here I just use `cygwin_conv_path` because it handles both cygwin and win32 paths correctly and convert them into absolute POSIX paths.
UPDATE: Windows path prefix is handled.
Enable automatic cross-compilation in run-make tests
Supersedes rust-lang/rust#138066.
Blocker for rust-lang/rust#141856.
Based on rust-lang/rust#138066 plus `rustdoc()` cross-compile changes.
### Summary
This PR automatically specifies `--target` to `rustc()` and `rustdoc()` to have `rustc`/`rustdoc` produce cross-compiled artifacts in run-make tests by default, unless:
- `//@ ignore-cross-compile` is used, or
- `bare_{rustc,rustdoc}` are used, or
- Explicit `.target()` is specified, which overrides the default cross-compile target.
Some tests are necessarily modified:
- Tests that have `.target(target())` have that incantation removed (since this is now automatically the default).
- Some tests have `//@ needs-target-std`, but are a necessary-but-insufficient condition, and are changed to `//@ ignore-cross-compile` instead as host-only tests.
- A few tests received `//@ ignore-musl` that fail against `x86_64-unknown-linux-musl` because of inability to find `-lunwind`. AFAICT, they don't *need* to test cross-compiled artifacts.
- Some tests are constrained to host-only for now, because the effort to make them pass on cross-compile does not seem worth the complexity, and it's not really *meaningfully* improving test coverage.
try-job: dist-various-1
Rollup of 7 pull requests
Successful merges:
- rust-lang/rust#140247 (Don't build `ParamEnv` and do trait solving in `ItemCtxt`s when lowering IATs)
- rust-lang/rust#142507 (use `#[align]` attribute for `fn_align`)
- rust-lang/rust#142524 (Weekly `cargo update`)
- rust-lang/rust#142606 (AsyncDrop trait without sync Drop generates an error)
- rust-lang/rust#142639 (Add a missing colon at the end of the panic location details in location-detail-unwrap-multiline.rs)
- rust-lang/rust#142654 (library: Increase timeout on mpmc test to reduce flakes)
- rust-lang/rust#142692 (Assorted bootstrap cleanups (step 3))
r? `@ghost`
`@rustbot` modify labels: rollup
This does change the logic a bit: previously, we didn't forward reverse
implications of negated features to the backend, instead relying on the backend
to handle the implication itself.
Assorted bootstrap cleanups (step 3)
I keep failing to unwrap the gordic knot of the logic of checking tools in bootstrap 😖 So in the meantime I at least want to upstream some cleanups I did along the way.
Since some time ago, we have separate steps for Clippy, so it shouldn't ever happen again that the check steps would be invoked with `builder.kind == Clippy`.
r? `@jieyouxu`
library: Increase timeout on mpmc test to reduce flakes
This recently spuriously failed in a rollup, so I think we can afford to increase the base timeout and the amount of time slept for to provide a much wider margin for the timeout to be reached.
Add a missing colon at the end of the panic location details in location-detail-unwrap-multiline.rs
The `location-detail-unwrap-multiline` test was failing when trying to enable `aarch64-pc-windows-msvc` CI Runners: https://github.com/rust-lang/rust/pull/140136#issuecomment-2978175728
When debugging, the normalized stderr was:
```
thread 'main' panicked at $DIR/location-detail-unwrap-multiline.rs:11:10:
called `Option::unwrap()` on a `None` value
stack backtrace:
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.
```
Note the trailing colon at the end of the location details in the panic message. This was missing in the error pattern regex. No idea why it has been passing for all other targets and failed for `aarch64-pc-windows-msvc`, but with the trailing colon it is now passing for all.
AsyncDrop trait without sync Drop generates an error
When type implements `AsyncDrop` trait, it must also implement sync `Drop` trait to be used in sync context and unwinds.
This PR adds error generation in such a case.
Fixes: rust-lang/rust#140696
use `#[align]` attribute for `fn_align`
Tracking issue: https://github.com/rust-lang/rust/issues/82232https://github.com/rust-lang/rfcs/pull/3806 decides to add the `#[align]` attribute for alignment of various items. Right now it's used for functions with `fn_align`, in the future it will get more uses (statics, struct fields, etc.)
(the RFC finishes FCP today)
r? `@ghost`
Don't build `ParamEnv` and do trait solving in `ItemCtxt`s when lowering IATs
Fixesrust-lang/rust#108491Fixesrust-lang/rust#125879
This was due to updating inhabited predicate stuff which I had to do to make constructing ADTs with IATs in fields not ICE
Fixesrust-lang/rust#136678 (but no test added, I don't rly care about weird IAT edge cases under GCE)
Fixesrust-lang/rust#138131
Avoids doing "fully correct" candidate selection for IATs during hir ty lowering when in item signatures as it almost always leads to a query cycle from trying to build a `ParamEnv`. I replaced it with a use `DeepRejectCtxt` which should be able to handle this kind of conservative "could these types unify" while in a context where we don't want to do type equality.
This is a relatively simple scheme and should be forwards compatible with doing something more complex/powerful.
I'm not really sure how this interacts with rust-lang/rust#126651, though I'm also not really sure its super important to support projecting IATs from IAT self types given we don't even support `T::Assoc::Other` for trait-associated types so didn't give much thought to how this might fit in with that.
r? `@compiler-errors`
cc `@fmease`
{aarch64,x86_64}-pc-windows-gnullvm: build host tools
This is a temporary single-release workflow to create stage0 for these targets.
I opted for bootstrapping from Linux because that's the easiest host system to work with, but once this hits beta, having dedicated Windows runners would be sensible and probably preferable.
`--enable-full-tools` for whatever reason doesn't seem to work when cross-compiling, because LLVM tools for the new hosts are not copied into the expected directory.
https://github.com/rust-lang/compiler-team/issues/877
Rollup of 6 pull requests
Successful merges:
- rust-lang/rust#135656 (Add `-Z hint-mostly-unused` to tell rustc that most of a crate will go unused)
- rust-lang/rust#138237 (Get rid of `EscapeDebugInner`.)
- rust-lang/rust#141614 (lint direct use of rustc_type_ir )
- rust-lang/rust#142123 (Implement initial support for timing sections (`--json=timings`))
- rust-lang/rust#142377 (Try unremapping compiler sources)
- rust-lang/rust#142674 (remove duplicate crash test)
r? `@ghost`
`@rustbot` modify labels: rollup
remove duplicate crash test
I noticed near duplication between "library/alloctests/tests/testing/crash_test.rs" and "library/alloctests/testing/crash_test.rs" and wanted to try and remove that. The only difference is the path used to import `Debug`, but it seems not to matter. Perhaps my change is still wrong?
r? ```@bjorn3```
Implement initial support for timing sections (`--json=timings`)
This PR implements initial support for emitting high-level compilation section timings. The idea is to provide a very lightweight way of emitting durations of various compilation sections (frontend, backend, linker, or on a more granular level macro expansion, typeck, borrowck, etc.). The ultimate goal is to stabilize this output (in some form), make Cargo pass `--json=timings` and then display this information in the HTML output of `cargo build --timings`, to make it easier to quickly profile "what takes so long" during the compilation of a Cargo project. I would personally also like if Cargo printed some of this information in the interactive `cargo build` output, but the `build --timings` use-case is the main one.
Now, this information is already available with several other sources, but I don't think that we can just use them as they are, which is why I proposed a new way of outputting this data (`--json=timings`):
- This data is available under `-Zself-profile`, but that is very expensive and forever unstable. It's just a too big of a hammer to tell us the duration it took to run the linker.
- It could also be extracted with `-Ztime-passes`. That is pretty much "for free" in terms of performance, and it can be emitted in a structured form to JSON via `-Ztime-passes-format=json`. I guess that one alternative might be to stabilize this flag in some form, but that form might just be `--json=timings`? I guess what we could do in theory is take the already emitted time passes and reuse them for `--json=timings`. Happy to hear suggestions!
I'm sending this PR mostly for a vibeck, to see if the way I implemented it is passable. There are some things to figure out:
- How do we represent the sections? Originally I wanted to output `{ section, duration }`, but then I realized that it might be more useful to actually emit `start` and `end` events. Both because it enables to see the output incrementally (in case compilation takes a long time and you read the outputs directly, or Cargo decides to show this data in `cargo build` some day in the future), and because it makes it simpler to represent hierarchy (see below). The timestamps currently emit microseconds elapsed from a predetermined point in time (~start of rustc), but otherwise they are fully opaque, and should be only ever used to calculate the duration using `end - start`. We could also precompute the duration for the user in the `end` event, but that would require doing more work in rustc, which I would ideally like to avoid :P
- Do we want to have some form of hierarchy? I think that it would be nice to show some more granular sections rather than just frontend/backend/linker (e.g. macro expansion, typeck and borrowck as a part of the frontend). But for that we would need some way of representing hierarchy. A simple way would be something like `{ parent: "frontend" }`, but I realized that with start/end timestamps we get the hierarchy "for free", only the client will need to reconstruct it from the order of start/end events (e.g. `start A`, `start B` means that `B` is a child of `A`).
- What exactly do we want to stabilize? This is probably a question for later. I think that we should definitely stabilize the format of the emitted JSON objects, and *maybe* some specific section names (but we should also make it clear that they can be missing, e.g. you don't link everytime you invoke `rustc`).
The PR be tested e.g. with `rustc +stage1 src/main.rs --json=timings --error-format=json -Zunstable-options` on a crate without dependencies (it is not easy to use `--json` with stock Cargo, because it also passes this flag to `rustc`, so this will later need Cargo integration to be usable with it).
Zulip discussions: [#t-compiler > Outputting time spent in various compiler sections](https://rust-lang.zulipchat.com/#narrow/channel/131828-t-compiler/topic/Outputting.20time.20spent.20in.20various.20compiler.20sections/with/518850162)
MCP: https://github.com/rust-lang/compiler-team/issues/873
r? ``@nnethercote``
lint direct use of rustc_type_ir
cc rust-lang/rust#138449
As previously discussed with `@lcnr,` it is a lint to prevent direct use of rustc_type_ir, except for some internal crates (like next_trait_solver or rustc_middle for example).
Add `-Z hint-mostly-unused` to tell rustc that most of a crate will go unused
This hint allows the compiler to optimize its operation based on this assumption, in order to compile faster. This is a hint, and does not guarantee any particular behavior.
This option can substantially speed up compilation if applied to a large dependency where the majority of the dependency does not get used. This flag may slow down compilation in other cases.
Currently, this option makes the compiler defer as much code generation as possible from functions in the crate, until later crates invoke those functions. Functions that never get invoked will never have code generated for them. For instance, if a crate provides thousands of functions, but only a few of them will get called, this flag will result in the compiler only doing code generation for the called functions. (This uses the same mechanisms as cross-crate inlining of functions.) This does not affect `extern` functions, or functions marked as `#[inline(never)]`.
This option has already existed in nightly as `-Zcross-crate-inline-threshold=always` for some time, and has gotten testing in that form. However, this option is still unstable, to give an opportunity for wider testing in this form.
Some performance numbers, based on a crate with many dependencies having just *one* large dependency set to `-Z hint-mostly-unused` (using Cargo's `profile-rustflags` option):
A release build went from 4m07s to 2m04s.
A non-release build went from 2m26s to 1m28s.
