mikros/rust
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

Auto merge of #117472 - jmillikin:stable-c-str-literals, r=Nilstrieb

Browse Source 
Stabilize C string literals

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

Tracking issue: https://github.com/rust-lang/rust/issues/105723

Documentation PR (reference manual): https://github.com/rust-lang/reference/pull/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 https://github.com/rust-lang/rust/pull/108801, which was reverted due to unintentional changes to lexer behavior in Rust editions < 2021.

The current implementation landed in PR https://github.com/rust-lang/rust/pull/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.
This commit is contained in:
bors 2023-12-01 13:33:55 +00:00
commit 63d16b5a98
19 changed files with 41 additions and 90 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
compiler/rustc_ast_passes/src/feature_gate.rs
View File

@ -515,7 +515,6 @@ macro_rules! gate_all {
}
};
}
gate_all!(c_str_literals, "`c\"..\"` literals are experimental");
gate_all!(
if_let_guard,
"`if let` guards are experimental",

4
compiler/rustc_builtin_macros/src/concat_bytes.rs
View File

@ -19,8 +19,8 @@ fn invalid_type_err(
let snippet = cx.sess.source_map().span_to_snippet(span).ok();
match ast::LitKind::from_token_lit(token_lit) {
Ok(ast::LitKind::CStr(_, _)) => {
// FIXME(c_str_literals): should concatenation of C string literals
// include the null bytes in the end?
// Avoid ambiguity in handling of terminal `NUL` by refusing to
// concatenate C string literals as bytes.
cx.emit_err(errors::ConcatCStrLit { span: span });
}
Ok(ast::LitKind::Char(_)) => {

2
compiler/rustc_feature/src/accepted.rs
View File

@ -77,6 +77,8 @@ macro_rules! declare_features {
(accepted, bindings_after_at, "1.56.0", Some(65490), None),
/// Allows empty structs and enum variants with braces.
(accepted, braced_empty_structs, "1.8.0", Some(29720), None),
/// Allows `c"foo"` literals.
(accepted, c_str_literals, "CURRENT_RUSTC_VERSION", Some(105723), None),
/// Allows `#[cfg_attr(predicate, multiple, attributes, here)]`.
(accepted, cfg_attr_multi, "1.33.0", Some(54881), None),
/// Allows the use of `#[cfg(doctest)]`, set when rustdoc is collecting doctests.

2
compiler/rustc_feature/src/unstable.rs
View File

@ -354,8 +354,6 @@ pub fn internal(&self, feature: Symbol) -> bool {
(unstable, async_fn_track_caller, "1.73.0", Some(110011), None),
/// Allows builtin # foo() syntax
(unstable, builtin_syntax, "1.71.0", Some(110680), None),
/// Allows `c"foo"` literals.
(unstable, c_str_literals, "1.71.0", Some(105723), None),
/// Treat `extern "C"` function as nounwind.
(unstable, c_unwind, "1.52.0", Some(74990), None),
/// Allows using C-variadics.

3
compiler/rustc_parse/src/lexer/mod.rs
View File

@ -223,9 +223,6 @@ fn next_token(&mut self) -> (Token, bool) {
rustc_lexer::TokenKind::Literal { kind, suffix_start } => {
let suffix_start = start + BytePos(suffix_start);
let (kind, symbol) = self.cook_lexer_literal(start, suffix_start, kind);
if let token::LitKind::CStr | token::LitKind::CStrRaw(_) = kind {
self.sess.gated_spans.gate(sym::c_str_literals, self.mk_sp(start, self.pos));
}
let suffix = if suffix_start < self.pos {
let string = self.str_from(suffix_start);
if string == "_" {

1
src/tools/clippy/tests/ui/needless_raw_string.fixed
View File

@ -1,6 +1,5 @@
#![allow(clippy::needless_raw_string_hashes, clippy::no_effect, unused)]
#![warn(clippy::needless_raw_strings)]
#![feature(c_str_literals)]
fn main() {
"aaa";

1
src/tools/clippy/tests/ui/needless_raw_string.rs
View File

@ -1,6 +1,5 @@
#![allow(clippy::needless_raw_string_hashes, clippy::no_effect, unused)]
#![warn(clippy::needless_raw_strings)]
#![feature(c_str_literals)]
fn main() {
r#"aaa"#;

14
src/tools/clippy/tests/ui/needless_raw_string.stderr
View File

@ -1,5 +1,5 @@
error: unnecessary raw string literal
--> $DIR/needless_raw_string.rs:6:5
--> $DIR/needless_raw_string.rs:5:5
|
LL | r#"aaa"#;
| ^^^^^^^^
@ -13,7 +13,7 @@ LL + "aaa";
|
error: unnecessary raw string literal
--> $DIR/needless_raw_string.rs:9:5
--> $DIR/needless_raw_string.rs:8:5
|
LL | br#"aaa"#;
| ^^^^^^^^^
@ -25,7 +25,7 @@ LL + b"aaa";
|
error: unnecessary raw string literal
--> $DIR/needless_raw_string.rs:12:5
--> $DIR/needless_raw_string.rs:11:5
|
LL | cr#"aaa"#;
| ^^^^^^^^^
@ -37,7 +37,7 @@ LL + c"aaa";
|
error: unnecessary raw string literal
--> $DIR/needless_raw_string.rs:16:5
--> $DIR/needless_raw_string.rs:15:5
|
LL | / r#"
LL | | a
@ -56,7 +56,7 @@ LL ~ ";
|
error: unnecessary raw string literal
--> $DIR/needless_raw_string.rs:22:5
--> $DIR/needless_raw_string.rs:21:5
|
LL | r"no hashes";
| ^^^^^^^^^^^^
@ -68,7 +68,7 @@ LL + "no hashes";
|
error: unnecessary raw string literal
--> $DIR/needless_raw_string.rs:23:5
--> $DIR/needless_raw_string.rs:22:5
|
LL | br"no hashes";
| ^^^^^^^^^^^^^
@ -80,7 +80,7 @@ LL + b"no hashes";
|
error: unnecessary raw string literal
--> $DIR/needless_raw_string.rs:24:5
--> $DIR/needless_raw_string.rs:23:5
|
LL | cr"no hashes";
| ^^^^^^^^^^^^^

1
src/tools/clippy/tests/ui/needless_raw_string_hashes.fixed
View File

@ -1,6 +1,5 @@
#![allow(clippy::no_effect, unused)]
#![warn(clippy::needless_raw_string_hashes)]
#![feature(c_str_literals)]
fn main() {
r"\aaa";

1
src/tools/clippy/tests/ui/needless_raw_string_hashes.rs
View File

@ -1,6 +1,5 @@
#![allow(clippy::no_effect, unused)]
#![warn(clippy::needless_raw_string_hashes)]
#![feature(c_str_literals)]
fn main() {
r#"\aaa"#;

30
src/tools/clippy/tests/ui/needless_raw_string_hashes.stderr
View File

@ -1,5 +1,5 @@
error: unnecessary hashes around raw string literal
--> $DIR/needless_raw_string_hashes.rs:6:5
--> $DIR/needless_raw_string_hashes.rs:5:5
|
LL | r#"\aaa"#;
| ^^^^^^^^^
@ -13,7 +13,7 @@ LL + r"\aaa";
|
error: unnecessary hashes around raw string literal
--> $DIR/needless_raw_string_hashes.rs:7:5
--> $DIR/needless_raw_string_hashes.rs:6:5
|
LL | r##"Hello "world"!"##;
| ^^^^^^^^^^^^^^^^^^^^^
@ -25,7 +25,7 @@ LL + r#"Hello "world"!"#;
|
error: unnecessary hashes around raw string literal
--> $DIR/needless_raw_string_hashes.rs:8:5
--> $DIR/needless_raw_string_hashes.rs:7:5
|
LL | r######" "### "## "# "######;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@ -37,7 +37,7 @@ LL + r####" "### "## "# "####;
|
error: unnecessary hashes around raw string literal
--> $DIR/needless_raw_string_hashes.rs:9:5
--> $DIR/needless_raw_string_hashes.rs:8:5
|
LL | r######" "aa" "# "## "######;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@ -49,7 +49,7 @@ LL + r###" "aa" "# "## "###;
|
error: unnecessary hashes around raw string literal
--> $DIR/needless_raw_string_hashes.rs:10:5
--> $DIR/needless_raw_string_hashes.rs:9:5
|
LL | br#"\aaa"#;
| ^^^^^^^^^^
@ -61,7 +61,7 @@ LL + br"\aaa";
|
error: unnecessary hashes around raw string literal
--> $DIR/needless_raw_string_hashes.rs:11:5
--> $DIR/needless_raw_string_hashes.rs:10:5
|
LL | br##"Hello "world"!"##;
| ^^^^^^^^^^^^^^^^^^^^^^
@ -73,7 +73,7 @@ LL + br#"Hello "world"!"#;
|
error: unnecessary hashes around raw string literal
--> $DIR/needless_raw_string_hashes.rs:12:5
--> $DIR/needless_raw_string_hashes.rs:11:5
|
LL | br######" "### "## "# "######;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@ -85,7 +85,7 @@ LL + br####" "### "## "# "####;
|
error: unnecessary hashes around raw string literal
--> $DIR/needless_raw_string_hashes.rs:13:5
--> $DIR/needless_raw_string_hashes.rs:12:5
|
LL | br######" "aa" "# "## "######;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@ -97,7 +97,7 @@ LL + br###" "aa" "# "## "###;
|
error: unnecessary hashes around raw string literal
--> $DIR/needless_raw_string_hashes.rs:14:5
--> $DIR/needless_raw_string_hashes.rs:13:5
|
LL | cr#"\aaa"#;
| ^^^^^^^^^^
@ -109,7 +109,7 @@ LL + cr"\aaa";
|
error: unnecessary hashes around raw string literal
--> $DIR/needless_raw_string_hashes.rs:15:5
--> $DIR/needless_raw_string_hashes.rs:14:5
|
LL | cr##"Hello "world"!"##;
| ^^^^^^^^^^^^^^^^^^^^^^
@ -121,7 +121,7 @@ LL + cr#"Hello "world"!"#;
|
error: unnecessary hashes around raw string literal
--> $DIR/needless_raw_string_hashes.rs:16:5
--> $DIR/needless_raw_string_hashes.rs:15:5
|
LL | cr######" "### "## "# "######;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@ -133,7 +133,7 @@ LL + cr####" "### "## "# "####;
|
error: unnecessary hashes around raw string literal
--> $DIR/needless_raw_string_hashes.rs:17:5
--> $DIR/needless_raw_string_hashes.rs:16:5
|
LL | cr######" "aa" "# "## "######;
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
@ -145,7 +145,7 @@ LL + cr###" "aa" "# "## "###;
|
error: unnecessary hashes around raw string literal
--> $DIR/needless_raw_string_hashes.rs:19:5
--> $DIR/needless_raw_string_hashes.rs:18:5
|
LL | / r#"
LL | | \a
@ -164,7 +164,7 @@ LL ~ ";
|
error: unnecessary hashes around raw string literal
--> $DIR/needless_raw_string_hashes.rs:25:5
--> $DIR/needless_raw_string_hashes.rs:24:5
|
LL | r###"rust"###;
| ^^^^^^^^^^^^^
@ -176,7 +176,7 @@ LL + r"rust";
|
error: unnecessary hashes around raw string literal
--> $DIR/needless_raw_string_hashes.rs:26:5
--> $DIR/needless_raw_string_hashes.rs:25:5
|
LL | r#"hello world"#;
| ^^^^^^^^^^^^^^^^

1
tests/ui/proc-macro/literal-to-string.rs
View File

@ -1,6 +1,5 @@
// check-pass
// edition: 2021
#![feature(c_str_literals)]
// aux-build: print-tokens.rs
extern crate print_tokens;

30
tests/ui/proc-macro/literal-to-string.stdout
View File

@ -3,91 +3,91 @@ TokenStream [
kind: Integer,
symbol: "1",
suffix: None,
span: #0 bytes(172..173),
span: #0 bytes(144..145),
},
Literal {
kind: Integer,
symbol: "17",
suffix: Some("u8"),
span: #0 bytes(182..186),
span: #0 bytes(154..158),
},
Literal {
kind: Float,
symbol: "42.",
suffix: None,
span: #0 bytes(195..198),
span: #0 bytes(167..170),
},
Literal {
kind: Float,
symbol: "3.14",
suffix: Some("f32"),
span: #0 bytes(207..214),
span: #0 bytes(179..186),
},
Literal {
kind: Byte,
symbol: "a",
suffix: None,
span: #0 bytes(223..227),
span: #0 bytes(195..199),
},
Literal {
kind: Byte,
symbol: "\xFF",
suffix: None,
span: #0 bytes(236..243),
span: #0 bytes(208..215),
},
Literal {
kind: Char,
symbol: "c",
suffix: None,
span: #0 bytes(252..255),
span: #0 bytes(224..227),
},
Literal {
kind: Char,
symbol: "\x32",
suffix: None,
span: #0 bytes(264..270),
span: #0 bytes(236..242),
},
Literal {
kind: Str,
symbol: "\\"str\\"",
suffix: None,
span: #0 bytes(279..288),
span: #0 bytes(251..260),
},
Literal {
kind: StrRaw(1),
symbol: "\"raw\" str",
suffix: None,
span: #0 bytes(297..311),
span: #0 bytes(269..283),
},
Literal {
kind: StrRaw(3),
symbol: "very ##\"raw\"## str",
suffix: None,
span: #0 bytes(320..347),
span: #0 bytes(292..319),
},
Literal {
kind: ByteStr,
symbol: "\\"byte\\" str",
suffix: None,
span: #0 bytes(356..371),
span: #0 bytes(328..343),
},
Literal {
kind: ByteStrRaw(1),
symbol: "\"raw\" \"byte\" str",
suffix: None,
span: #0 bytes(380..402),
span: #0 bytes(352..374),
},
Literal {
kind: CStr,
symbol: "\\"c\\" str",
suffix: None,
span: #0 bytes(411..423),
span: #0 bytes(383..395),
},
Literal {
kind: CStrRaw(1),
symbol: "\"raw\" \"c\" str",
suffix: None,
span: #0 bytes(432..451),
span: #0 bytes(404..423),
},
]
1

2
tests/ui/rfcs/rfc-3348-c-string-literals/basic.rs
View File

@ -1,8 +1,6 @@
// run-pass
// edition: 2021
#![feature(c_str_literals)]
fn main() {
assert_eq!(b"test\0", c"test".to_bytes_with_nul());
}

15
tests/ui/rfcs/rfc-3348-c-string-literals/gate.rs
View File

@ -1,15 +0,0 @@
// gate-test-c_str_literals
// known-bug: #113333
// edition: 2021
macro_rules! m {
($t:tt) => {}
}
fn main() {
c"foo";
// FIXME(c_str_literals): This should be ``c".."` literals are experimental`
m!(c"test");
// FIXME(c_str_literals): This should be ``c".."` literals are experimental`
}

21
tests/ui/rfcs/rfc-3348-c-string-literals/gate.stderr
View File

@ -1,21 +0,0 @@
error[E0658]: `c".."` literals are experimental
--> $DIR/gate.rs:10:5
|
LL | c"foo";
| ^^^^^^
|
= note: see issue #105723 <https://github.com/rust-lang/rust/issues/105723> for more information
= help: add `#![feature(c_str_literals)]` to the crate attributes to enable
error[E0658]: `c".."` literals are experimental
--> $DIR/gate.rs:13:8
|
LL | m!(c"test");
| ^^^^^^^
|
= note: see issue #105723 <https://github.com/rust-lang/rust/issues/105723> for more information
= help: add `#![feature(c_str_literals)]` to the crate attributes to enable
error: aborting due to 2 previous errors
For more information about this error, try `rustc --explain E0658`.

BIN
tests/ui/rfcs/rfc-3348-c-string-literals/no-nuls.rs
View File

Binary file not shown.

BIN
tests/ui/rfcs/rfc-3348-c-string-literals/no-nuls.stderr
View File

Binary file not shown.

2
tests/ui/rfcs/rfc-3348-c-string-literals/non-ascii.rs
View File

@ -1,8 +1,6 @@
// run-pass
// edition: 2021
#![feature(c_str_literals)]
fn main() {
assert_eq!(
c"\xEF\x80🦀\u{1F980}".to_bytes_with_nul(),