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 3a760909fa
6 changed files with 22 additions and 26 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
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
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
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
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
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
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"#;
| ^^^^^^^^^^^^^^^^