constify some `CStr` methods #100291

WaffleLapkin · 2022-08-08T23:36:52Z

This PR marks the following public APIs as const:

impl CStr {
    // feature(const_cstr_from_bytes)
    pub const fn from_bytes_until_nul(bytes: &[u8]) -> Result<&CStr, FromBytesUntilNulError>;
    pub const fn from_bytes_with_nul(bytes: &[u8]) -> Result<&Self, FromBytesWithNulError>;

    // feature(const_cstr_to_bytes)
    pub const fn to_bytes(&self) -> &[u8];
    pub const fn to_bytes_with_nul(&self) -> &[u8];
    pub const fn to_str(&self) -> Result<&str, str::Utf8Error>;
}

r? @oli-obk (use of const_eval_select :P )
cc @mina86 (you've asked for this <3 )

rust-highfive · 2022-08-08T23:36:55Z

r? @scottmcm

(rust-highfive has picked a reviewer for you, use r? to override)

WaffleLapkin · 2022-08-08T23:43:53Z

r? @oli-obk

rustbot · 2022-08-08T23:44:07Z

Hey! It looks like you've submitted a new PR for the library teams!

If this PR contains changes to any rust-lang/rust public library APIs then please comment with @rustbot label +T-libs-api -T-libs to tag it appropriately. If this PR contains changes to any unstable APIs please edit the PR description to add a link to the relevant API Change Proposal or create one if you haven't already. If you're unsure where your change falls no worries, just leave it as is and the reviewer will take a look and make a decision to forward on if necessary.

Examples of T-libs-api changes:

Stabilizing library features
Introducing insta-stable changes such as new implementations of existing stable traits on existing stable types
Introducing new or changing existing unstable library APIs (excluding permanently unstable features / features without a tracking issue)
Changing public documentation in ways that create new stability guarantees
Changing observable runtime behavior of library APIs

mina86 · 2022-08-09T00:08:40Z

Thanks. LGTM.

library/core/src/ffi/c_str.rs

oli-obk

Oops forgot to send off the review

oli-obk · 2022-08-24T15:03:38Z

library/core/src/ffi/c_str.rs

@@ -299,7 +299,8 @@ impl CStr {
    /// ```
    ///
    #[unstable(feature = "cstr_from_bytes_until_nul", issue = "95027")]
-    pub fn from_bytes_until_nul(bytes: &[u8]) -> Result<&CStr, FromBytesUntilNulError> {
+    #[rustc_const_unstable(feature = "const_cstr_from_bytes", issue = "none")]


use the same feature gate and issue as the regular unstable attribute, these can be stabilized together.

Should I open an issues for from_bytes_with_nul and to_bytes/to_bytes_with_nul/to_str? (they are stable, so I can't reuse the feature gate/issue)

Yea, I think it's best to track them. You could just munge them into a generic cstr_consts gate and make one issue for all of them

oli-obk · 2022-08-24T15:07:06Z

library/core/src/slice/memchr.rs

+            match bytes {
+                [] => break None,
+                &[y, ..] if x == y => break Some(i),
+                [_, rest @ ..] => {
+                    bytes = rest;
+                    i += 1;
+                }
+            }


I appreciate the ingenuity, but why not just while let i < bytes.len() and index with i?

I do not remember, probably because of a habit, I think there was a time when you couldn't index in const fns, but could use patterns.

oli-obk · 2022-09-12T15:54:52Z

@bors r+ rollup

bors · 2022-09-12T15:54:56Z

📌 Commit cb02b64 has been approved by oli-obk

It is now in the queue for this repository.

…=oli-obk constify some `CStr` methods This PR marks the following public APIs as `const`: ```rust impl CStr { // feature(const_cstr_from_bytes) pub const fn from_bytes_until_nul(bytes: &[u8]) -> Result<&CStr, FromBytesUntilNulError>; pub const fn from_bytes_with_nul(bytes: &[u8]) -> Result<&Self, FromBytesWithNulError>; // feature(const_cstr_to_bytes) pub const fn to_bytes(&self) -> &[u8]; pub const fn to_bytes_with_nul(&self) -> &[u8]; pub const fn to_str(&self) -> Result<&str, str::Utf8Error>; } ``` r? `@oli-obk` (use of `const_eval_select` :P ) cc `@mina86` (you've asked for this <3 )

…=oli-obk constify some `CStr` methods This PR marks the following public APIs as `const`: ```rust impl CStr { // feature(const_cstr_from_bytes) pub const fn from_bytes_until_nul(bytes: &[u8]) -> Result<&CStr, FromBytesUntilNulError>; pub const fn from_bytes_with_nul(bytes: &[u8]) -> Result<&Self, FromBytesWithNulError>; // feature(const_cstr_to_bytes) pub const fn to_bytes(&self) -> &[u8]; pub const fn to_bytes_with_nul(&self) -> &[u8]; pub const fn to_str(&self) -> Result<&str, str::Utf8Error>; } ``` r? ``@oli-obk`` (use of `const_eval_select` :P ) cc ``@mina86`` (you've asked for this <3 )

…llaumeGomez Rollup of 8 pull requests Successful merges: - rust-lang#100185 (Fix `ReErased` leaking into typeck due to `typeof(...)` recovery) - rust-lang#100291 (constify some `CStr` methods) - rust-lang#101677 (Add test for rust-lang#101211) - rust-lang#101723 (Impove diagnostic for `.await`ing non-futures) - rust-lang#101724 (Allow unauthenticated users to add the `const-hack` label) - rust-lang#101731 (rustdoc: improve rustdoc HTML suggestions handling of nested generics) - rust-lang#101732 (Feature gate the `rustdoc::missing_doc_code_examples` lint) - rust-lang#101735 (rustdoc: fix treatment of backslash-escaped HTML) Failed merges: r? `@ghost` `@rustbot` modify labels: rollup

rust-highfive assigned scottmcm Aug 8, 2022

rustbot added the T-libs Relevant to the library team, which will review and decide on the PR/issue. label Aug 8, 2022

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Aug 8, 2022

rust-highfive assigned oli-obk and unassigned scottmcm Aug 8, 2022

WaffleLapkin marked this pull request as ready for review August 8, 2022 23:44

reitermarkus reviewed Sep 9, 2022

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reitermarkus mentioned this pull request Sep 9, 2022

Add cstr! macro. #101607

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oli-obk requested changes Sep 9, 2022

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WaffleLapkin mentioned this pull request Sep 12, 2022

Tracking Issue for const_cstr_methods #101719

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3 tasks

constify CStr methods

cb02b64

WaffleLapkin force-pushed the cstr_const_methods branch from c54464a to cb02b64 Compare September 12, 2022 12:29

oli-obk approved these changes Sep 12, 2022

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bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Sep 12, 2022

GuillaumeGomez mentioned this pull request Sep 12, 2022

Rollup of 8 pull requests #101733

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This was referenced Sep 12, 2022

Rollup of 7 pull requests #101734

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Rollup of 8 pull requests #101736

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bors merged commit 7fc3183 into rust-lang:master Sep 13, 2022

rustbot added this to the 1.65.0 milestone Sep 13, 2022

WaffleLapkin deleted the cstr_const_methods branch September 13, 2022 13:26

reitermarkus mentioned this pull request Sep 13, 2022

Add cstr! macro for creating &'static CStrs. rust-lang/libs-team#103

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reitermarkus mentioned this pull request Oct 16, 2022

Make CStr::from_ptr const. #102961

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tgross35 mentioned this pull request Jul 1, 2023

Tracking Issue for const_cstr_from_ptr #113219

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constify some `CStr` methods #100291

constify some `CStr` methods #100291

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constify some CStr methods #100291

constify some CStr methods #100291

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constify some `CStr` methods #100291

constify some `CStr` methods #100291

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