Auto merge of rust-lang#140356 - tgross35:rollup-cvqvrg4, r=tgross35

Rollup of 8 pull requests

Successful merges:

 - rust-lang#137439 (Stabilise `std::ffi::c_str`)
 - rust-lang#139031 (Use char::is_whitespace directly in str::trim*)
 - rust-lang#139090 (fix docs for `Peekable::next_if{_eq}`)
 - rust-lang#140220 (Fix detection of main function if there are expressions around it)
 - rust-lang#140297 (Update example to use CStr::to_string_lossy)
 - rust-lang#140330 (Clarified bootstrap optimization "true" argument)
 - rust-lang#140339 (session: Cleanup `CanonicalizedPath::new`)
 - rust-lang#140348 (Update lint-docs to default to Rust 2024)

r? `@ghost`
`@rustbot` modify labels: rollup

Author: bors

bootstrap.example.toml

@@ -500,7 +500,7 @@
 # building without optimizations takes much longer than optimizing. Further, some platforms
 # fail to build without this optimization (c.f. #65352).
 # The valid options are:
-# true - Enable optimizations.
+# true - Enable optimizations (same as 3).
 # false - Disable optimizations.
 # 0 - Disable optimizations.
 # 1 - Basic optimizations.

compiler/rustc_interface/src/tests.rs

@@ -1,7 +1,7 @@
 #![allow(rustc::bad_opt_access)]
-use std::collections::{BTreeMap, BTreeSet};
+use std::collections::BTreeMap;
 use std::num::NonZero;
-use std::path::{Path, PathBuf};
+use std::path::PathBuf;
 use std::sync::atomic::AtomicBool;
 
 use rustc_abi::Align;
@@ -89,8 +89,8 @@ where
     S: Into<String>,
     I: IntoIterator<Item = S>,
 {
-    let locations: BTreeSet<CanonicalizedPath> =
-        locations.into_iter().map(|s| CanonicalizedPath::new(Path::new(&s.into()))).collect();
+    let locations =
+        locations.into_iter().map(|s| CanonicalizedPath::new(PathBuf::from(s.into()))).collect();
 
     ExternEntry {
         location: ExternLocation::ExactPaths(locations),

compiler/rustc_lint/src/builtin.rs

@@ -948,7 +948,7 @@ declare_lint! {
     ///
     /// ### Example
     ///
-    /// ```rust,compile_fail
+    /// ```rust,compile_fail,edition2021
     /// #[no_mangle]
     /// const FOO: i32 = 5;
     /// ```

compiler/rustc_lint/src/impl_trait_overcaptures.rs

@@ -41,7 +41,7 @@ declare_lint! {
     ///
     /// ### Example
     ///
-    /// ```rust,compile_fail
+    /// ```rust,compile_fail,edition2021
     /// # #![deny(impl_trait_overcaptures)]
     /// # use std::fmt::Display;
     /// let mut x = vec![];

compiler/rustc_lint_defs/src/builtin.rs

@@ -1424,7 +1424,7 @@ declare_lint! {
     ///
     /// ### Example
     ///
-    /// ```rust,compile_fail
+    /// ```rust,compile_fail,edition2021
     /// macro_rules! foo {
     ///    () => {};
     ///    ($name) => { };
@@ -4128,7 +4128,7 @@ declare_lint! {
     ///
     /// ### Example
     ///
-    /// ```rust,compile_fail
+    /// ```rust,compile_fail,edition2021
     /// #![deny(dependency_on_unit_never_type_fallback)]
     /// fn main() {
     ///     if true {

compiler/rustc_session/src/config.rs

@@ -2323,14 +2323,13 @@ pub fn parse_externs(
         let ExternOpt { crate_name: name, path, options } =
             split_extern_opt(early_dcx, unstable_opts, &arg).unwrap_or_else(|e| e.emit());
 
-        let path = path.map(|p| CanonicalizedPath::new(p.as_path()));
-
         let entry = externs.entry(name.to_owned());
 
         use std::collections::btree_map::Entry;
 
         let entry = if let Some(path) = path {
             // --extern prelude_name=some_file.rlib
+            let path = CanonicalizedPath::new(path);
             match entry {
                 Entry::Vacant(vacant) => {
                     let files = BTreeSet::from_iter(iter::once(path));

compiler/rustc_session/src/utils.rs

@@ -1,4 +1,4 @@
-use std::path::{Path, PathBuf};
+use std::path::PathBuf;
 use std::sync::OnceLock;
 
 use rustc_data_structures::profiling::VerboseTimingGuard;
@@ -104,8 +104,8 @@ pub struct CanonicalizedPath {
 }
 
 impl CanonicalizedPath {
-    pub fn new(path: &Path) -> Self {
-        Self { original: path.to_owned(), canonicalized: try_canonicalize(path).ok() }
+    pub fn new(path: PathBuf) -> Self {
+        Self { canonicalized: try_canonicalize(&path).ok(), original: path }
     }
 
     pub fn canonicalized(&self) -> &PathBuf {

library/alloc/src/ffi/c_str.rs

@@ -818,6 +818,7 @@ impl From<Vec<NonZero<u8>>> for CString {
     }
 }
 
+#[stable(feature = "c_string_from_str", since = "1.85.0")]
 impl FromStr for CString {
     type Err = NulError;
 
@@ -830,6 +831,7 @@ impl FromStr for CString {
     }
 }
 
+#[stable(feature = "c_string_from_str", since = "1.85.0")]
 impl TryFrom<CString> for String {
     type Error = IntoStringError;
 

library/alloc/src/ffi/mod.rs

@@ -87,5 +87,5 @@ pub use self::c_str::CString;
 #[stable(feature = "alloc_c_string", since = "1.64.0")]
 pub use self::c_str::{FromVecWithNulError, IntoStringError, NulError};
 
-#[unstable(feature = "c_str_module", issue = "112134")]
+#[stable(feature = "c_str_module", since = "CURRENT_RUSTC_VERSION")]
 pub mod c_str;

library/core/src/ffi/c_str.rs

@@ -79,8 +79,9 @@ use crate::{fmt, ops, slice, str};
 ///
 /// fn my_string_safe() -> String {
 ///     let cstr = unsafe { CStr::from_ptr(my_string()) };
-///     // Get copy-on-write Cow<'_, str>, then guarantee a freshly-owned String allocation
-///     String::from_utf8_lossy(cstr.to_bytes()).to_string()
+///     // Get a copy-on-write Cow<'_, str>, then extract the
+///     // allocated String (or allocate a fresh one if needed).
+///     cstr.to_string_lossy().into_owned()
 /// }
 ///
 /// println!("string: {}", my_string_safe());