Stabilize C string literals #117472

jmillikin · 2023-11-01T00:19:04Z

RFC: https://rust-lang.github.io/rfcs/3348-c-str-literal.html

Tracking issue: #105723

Documentation PR (reference manual): rust-lang/reference#1423

Stabilization report

Stabilizes C string and raw C string literals (c"..." and cr#"..."#), which are expressions of type &CStr. Both new literals require Rust edition 2021 or later.

const HELLO: &core::ffi::CStr = c"Hello, world!";

C strings may contain any byte other than NUL (b'\x00'), and their in-memory representation is guaranteed to end with NUL.

Implementation

Originally implemented by PR #108801, which was reverted due to unintentional changes to lexer behavior in Rust editions < 2021.

The current implementation landed in PR #113476, which restricts C string literals to Rust edition >= 2021.

Resolutions to open questions from the RFC

Adding C character literals (c'.') of type c_char is not part of this feature.
- Support for c"..." literals does not prevent c'.' literals from being added in the future.
C string literals should not be blocked on making &CStr a thin pointer.
- It's possible to declare constant expressions of type &'static CStr in stable Rust (as of v1.59), so C string literals are not adding additional coupling on the internal representation of CStr.
The unstable concat_bytes! macro should not accept c"..." literals.
- C strings have two equally valid &[u8] representations (with or without terminal NUL), so allowing them to be used in concat_bytes! would be ambiguous.
Adding a type to represent C strings containing valid UTF-8 is not part of this feature.
- Support for a hypothetical &Utf8CStr may be explored in the future, should such a type be added to Rust.

rustbot · 2023-11-01T00:19:12Z

r? @TaKO8Ki

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rustbot · 2023-11-01T00:19:15Z

Some changes occurred in src/tools/clippy

cc @rust-lang/clippy

jmillikin · 2023-11-01T00:24:59Z

See comment #105723 (comment) regarding stabilization timeline -- I'm hoping this might pass FCP in time for v1.76, but acknowledge it might need to wait until the implementation has soaked a bit more.

tgross35 · 2023-11-01T00:27:55Z

@rustbot label +T-lang +needs-fcp
r? lang

compiler-errors · 2023-11-01T02:15:56Z

I think this PR needs a stabilization report -- this PR seems pretty bare.

Specifically, things that come to mind are: should mention the implementation history, how C str literals work in the lexer/parser, any outstanding questions about the implementation, the extent to which the feature has been tested, etc. Are there reference changes to be made here?

ehuss · 2023-11-01T02:57:26Z

Can you please post a PR to https://github.com/rust-lang/reference/ to update the documentation for this feature?

jmillikin · 2023-11-01T07:41:54Z

Added a brief stability report to document decisions for each of the RFC's open questions.

PR for the reference manual: rust-lang/reference#1423

jmillikin · 2023-11-08T01:51:25Z

Gentle ping -- the documentation PR seems to be making progress, but it can't pass on CI until c_str_literals stabilizes.

Is there anything else blocking the stabilization, or can the FCP be started now?

tgross35 · 2023-11-08T03:16:07Z

The I-lang-nominated label means it's a topic of discussion for an upcoming lang team meeting. It can take a few weeks to hear anything, the overall stabilization process (general discussion, team discussion, FCP proposal, FCP) is usually at least a month or so

rust-timer · 2023-12-01T17:07:57Z

Finished benchmarking commit (63d16b5): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

This benchmark run did not return any relevant results for this metric.

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	2.7%	[2.4%, 2.9%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Cycles

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	2.4%	[2.4%, 2.4%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 673.917s -> 672.331s (-0.24%)
Artifact size: 313.41 MiB -> 313.37 MiB (-0.01%)

…ilstrieb Stabilize C string literals RFC: https://rust-lang.github.io/rfcs/3348-c-str-literal.html Tracking issue: rust-lang#105723 Documentation PR (reference manual): rust-lang/reference#1423 # Stabilization report Stabilizes C string and raw C string literals (`c"..."` and `cr#"..."#`), which are expressions of type [`&CStr`](https://doc.rust-lang.org/stable/core/ffi/struct.CStr.html). Both new literals require Rust edition 2021 or later. ```rust const HELLO: &core::ffi::CStr = c"Hello, world!"; ``` C strings may contain any byte other than `NUL` (`b'\x00'`), and their in-memory representation is guaranteed to end with `NUL`. ## Implementation Originally implemented by PR rust-lang#108801, which was reverted due to unintentional changes to lexer behavior in Rust editions < 2021. The current implementation landed in PR rust-lang#113476, which restricts C string literals to Rust edition >= 2021. ## Resolutions to open questions from the RFC * Adding C character literals (`c'.'`) of type `c_char` is not part of this feature. * Support for `c"..."` literals does not prevent `c'.'` literals from being added in the future. * C string literals should not be blocked on making `&CStr` a thin pointer. * It's possible to declare constant expressions of type `&'static CStr` in stable Rust (as of v1.59), so C string literals are not adding additional coupling on the internal representation of `CStr`. * The unstable `concat_bytes!` macro should not accept `c"..."` literals. * C strings have two equally valid `&[u8]` representations (with or without terminal `NUL`), so allowing them to be used in `concat_bytes!` would be ambiguous. * Adding a type to represent C strings containing valid UTF-8 is not part of this feature. * Support for a hypothetical `&Utf8CStr` may be explored in the future, should such a type be added to Rust.

Property404 · 2024-01-08T21:40:28Z

FYI for people looking at this PR, I believe it's getting reverted here: #119528

SUPERCILEX · 2024-01-08T21:54:36Z

Dang, bummer. The gist is that NUL byte validation is being moved up to lexing (I think?) and then it'll try to be stabilized again.

…cote [beta] Revert rust-lang#117472: Stabilize C string literals Based on discussion in [#t-lang](https://rust-lang.zulipchat.com/#narrow/stream/213817-t-lang/topic/rfc.203349.3A.20mixed.20utf8.20literals), revert the stabilization of C string literals in Rust 1.76. I also reverted rust-lang#118566 as it uses the newly stabilized C string literals in various places.

wesleywiser · 2024-01-10T22:14:45Z

Adjusting milestone to 1.77 to account for the revert in 1.76.

eduardosm · 2024-01-11T18:48:56Z

I opened #119865 to bump version in compiler/rustc_feature/src/accepted.rs

new lint: `manual_c_str_literals` With rust-lang/rust#117472 merged and `c""` syntax stabilized, I think it'd be nice to have a lint for using `CStr::from_ptr` (and similar constructors) with a string literal as an argument. We can probably also lint `"foo\0".as_ptr()` and suggest `c"foo".as_ptr()`. I might add that to this PR tomorrow if I find the time. The byte string literal to c string literal rewriting is ugly but oh well. changelog: new lint: `manual_c_str_literals`

new lint: `manual_c_str_literals` With rust-lang/rust#117472 merged and `c""` syntax stabilized, I think it'd be nice to have a lint for using `CStr::from_ptr` (and similar constructors) with a string literal as an argument. We can probably also lint `"foo\0".as_ptr()` and suggest `c"foo".as_ptr()`. I might add that to this PR tomorrow if I find the time. The byte string literal to c string literal rewriting is ugly but oh well. changelog: new lint: `manual_c_str_literals` [#11919](#11919)

Pkgsrc changes: * Adapt checksums and patches. Upstream chnages: Version 1.77.0 (2024-03-21) ========================== - [Reveal opaque types within the defining body for exhaustiveness checking.] (rust-lang/rust#116821) - [Stabilize C-string literals.] (rust-lang/rust#117472) - [Stabilize THIR unsafeck.] (rust-lang/rust#117673) - [Add lint `static_mut_refs` to warn on references to mutable statics.] (rust-lang/rust#117556) - [Support async recursive calls (as long as they have indirection).] (rust-lang/rust#117703) - [Undeprecate lint `unstable_features` and make use of it in the compiler.] (rust-lang/rust#118639) - [Make inductive cycles in coherence ambiguous always.] (rust-lang/rust#118649) - [Get rid of type-driven traversal in const-eval interning] (rust-lang/rust#119044), only as a [future compatiblity lint] (rust-lang/rust#122204) for now. - [Deny braced macro invocations in let-else.] (rust-lang/rust#119062) Compiler -------- - [Include lint `soft_unstable` in future breakage reports.] (rust-lang/rust#116274) - [Make `i128` and `u128` 16-byte aligned on x86-based targets.] (rust-lang/rust#116672) - [Use `--verbose` in diagnostic output.] (rust-lang/rust#119129) - [Improve spacing between printed tokens.] (rust-lang/rust#120227) - [Merge the `unused_tuple_struct_fields` lint into `dead_code`.] (rust-lang/rust#118297) - [Error on incorrect implied bounds in well-formedness check] (rust-lang/rust#118553), with a temporary exception for Bevy. - [Fix coverage instrumentation/reports for non-ASCII source code.] (rust-lang/rust#119033) - [Fix `fn`/`const` items implied bounds and well-formedness check.] (rust-lang/rust#120019) - [Promote `riscv32{im|imafc}-unknown-none-elf` targets to tier 2.] (rust-lang/rust#118704) - Add several new tier 3 targets: - [`aarch64-unknown-illumos`] (rust-lang/rust#112936) - [`hexagon-unknown-none-elf`] (rust-lang/rust#117601) - [`riscv32imafc-esp-espidf`] (rust-lang/rust#119738) - [`riscv32im-risc0-zkvm-elf`] (rust-lang/rust#117958) Refer to Rust's [platform support page][platform-support-doc] for more information on Rust's tiered platform support. Libraries --------- - [Implement `From<&[T; N]>` for `Cow<[T]>`.] (rust-lang/rust#113489) - [Remove special-case handling of `vec.split_off (0)`.](rust-lang/rust#119917) Stabilized APIs --------------- - [`array::each_ref`] (https://doc.rust-lang.org/stable/std/primitive.array.html#method.each_ref) - [`array::each_mut`] (https://doc.rust-lang.org/stable/std/primitive.array.html#method.each_mut) - [`core::net`] (https://doc.rust-lang.org/stable/core/net/index.html) - [`f32::round_ties_even`] (https://doc.rust-lang.org/stable/std/primitive.f32.html#method.round_ties_even) - [`f64::round_ties_even`] (https://doc.rust-lang.org/stable/std/primitive.f64.html#method.round_ties_even) - [`mem::offset_of!`] (https://doc.rust-lang.org/stable/std/mem/macro.offset_of.html) - [`slice::first_chunk`] (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.first_chunk) - [`slice::first_chunk_mut`] (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.first_chunk_mut) - [`slice::split_first_chunk`] (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.split_first_chunk) - [`slice::split_first_chunk_mut`] (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.split_first_chunk_mut) - [`slice::last_chunk`] (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.last_chunk) - [`slice::last_chunk_mut`] (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.last_chunk_mut) - [`slice::split_last_chunk`] (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.split_last_chunk) - [`slice::split_last_chunk_mut`] (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.split_last_chunk_mut) - [`slice::chunk_by`] (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.chunk_by) - [`slice::chunk_by_mut`] (https://doc.rust-lang.org/stable/std/primitive.slice.html#method.chunk_by_mut) - [`Bound::map`] (https://doc.rust-lang.org/stable/std/ops/enum.Bound.html#method.map) - [`File::create_new`] (https://doc.rust-lang.org/stable/std/fs/struct.File.html#method.create_new) - [`Mutex::clear_poison`] (https://doc.rust-lang.org/stable/std/sync/struct.Mutex.html#method.clear_poison) - [`RwLock::clear_poison`] (https://doc.rust-lang.org/stable/std/sync/struct.RwLock.html#method.clear_poison) Cargo ----- - [Extend the build directive syntax with `cargo::`.] (rust-lang/cargo#12201) - [Stabilize metadata `id` format as `PackageIDSpec`.] (rust-lang/cargo#12914) - [Pull out as `cargo-util-schemas` as a crate.] (rust-lang/cargo#13178) - [Strip all debuginfo when debuginfo is not requested.] (rust-lang/cargo#13257) - [Inherit jobserver from env for all kinds of runners.] (rust-lang/cargo#12776) - [Deprecate rustc plugin support in cargo.] (rust-lang/cargo#13248) Rustdoc ----- - [Allows links in markdown headings.] (rust-lang/rust#117662) - [Search for tuples and unit by type with `()`.] (rust-lang/rust#118194) - [Clean up the source sidebar's hide button.] (rust-lang/rust#119066) - [Prevent JS injection from `localStorage`.] (rust-lang/rust#120250) Misc ---- - [Recommend version-sorting for all sorting in style guide.] (rust-lang/rust#115046) Internal Changes ---------------- These changes do not affect any public interfaces of Rust, but they represent significant improvements to the performance or internals of rustc and related tools. - [Add more weirdness to `weird-exprs.rs`.] (rust-lang/rust#119028)

rust-lang/rfcs#3348 rust-lang/rust#105723 rust-lang/rust#117472

Stabilize C string literals

0f41bc2

rustbot assigned TaKO8Ki Nov 1, 2023

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Nov 1, 2023

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Tracking Issue for c"…" string literals #105723

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rustbot added needs-fcp This change is insta-stable, so needs a completed FCP to proceed. T-lang Relevant to the language team, which will review and decide on the PR/issue. labels Nov 1, 2023

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jmillikin force-pushed the stable-c-str-literals branch from a624c8e to 56fe3f9 Compare November 1, 2023 01:22

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jmillikin force-pushed the stable-c-str-literals branch from 56fe3f9 to 0f41bc2 Compare November 1, 2023 02:01

compiler-errors added the I-lang-nominated The issue / PR has been nominated for discussion during a lang team meeting. label Nov 1, 2023

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Document C string literal tokens. rust-lang/reference#1423

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rfcbot added proposed-final-comment-period Proposed to merge/close by relevant subteam, see T-<team> label. Will enter FCP once signed off. disposition-merge This issue / PR is in PFCP or FCP with a disposition to merge it. labels Nov 8, 2023

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ehuss added the relnotes Marks issues that should be documented in the release notes of the next release. label Dec 2, 2023

jmillikin deleted the stable-c-str-literals branch December 2, 2023 22:55

MaxVerevkin mentioned this pull request Dec 3, 2023

proc_macro does not have a constructor for c string literals #118560

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JarvisCraft mentioned this pull request Dec 3, 2023

feat: make DialogFileBrowserOptions::new() use native initialization function flipperzero-rs/flipperzero#92

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y21 mentioned this pull request Dec 3, 2023

new lint: manual_c_str_literals rust-lang/rust-clippy#11919

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1.0 release planning bytecodealliance/rustix#753

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ehuss mentioned this pull request Dec 6, 2023

Add C-string literals. rust-lang/edition-guide#286

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CrazyboyQCD mentioned this pull request Dec 10, 2023

fn rav1d_log: Replace with safe write! calls to a fully safe Rav1dLogger memorysafety/rav1d#619

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kkysen mentioned this pull request Dec 11, 2023

Replace cstr! with c"" literals when 1.77 is released memorysafety/rav1d#623

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novafacing mentioned this pull request Jan 5, 2024

[feature request] Support Cstr literals rust-lang/rust-bindgen#2710

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novafacing mentioned this pull request Jan 8, 2024

Tracking Issue for proc_macro_c_str_literals #119750

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wesleywiser modified the milestones: 1.76.0, 1.77.0 Jan 10, 2024

lilizoey mentioned this pull request Mar 10, 2024

Tracking issue for planned features we may want to use godot-rust/gdext#642

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rhysd mentioned this pull request Mar 20, 2024

Support C string literals highlight rust-lang/rust.vim#508

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chocolate-pie added a commit to chocolate-pie/misskey-slacc that referenced this pull request Apr 27, 2024

refactor(darwin): Use c"…" string literals in src/macos.rs

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Stabilize C string literals #117472

Stabilize C string literals #117472

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jmillikin commented Nov 1, 2023 • edited

Stabilization report

Implementation

Resolutions to open questions from the RFC

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Overall result: no relevant changes - no action needed

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