Auto merge of rust-lang#127840 - tgross35:rollup-jfkg1dq, r=tgross35

Rollup of 9 pull requests

Successful merges:

 - rust-lang#125206 (Simplify environment variable examples)
 - rust-lang#126271 (Skip fast path for dec2flt when optimize_for_size)
 - rust-lang#126776 (Clean up more comments near use declarations)
 - rust-lang#127444 (`impl Send + Sync` and override `count` for the `CStr::bytes` iterator)
 - rust-lang#127512 (Terminate `--print link-args` output with newline)
 - rust-lang#127792 (std: Use `read_unaligned` for reads from DWARF)
 - rust-lang#127807 (Use futex.rs for Windows thread parking)
 - rust-lang#127833 (zkvm: add `#[forbid(unsafe_op_in_unsafe_fn)]` in `stdlib`)
 - rust-lang#127836 (std: Forbid unwrapped unsafe ops in xous and uefi modules)

Failed merges:

 - rust-lang#127813 (Prevent double reference in generic futex)

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

Author: bors

compiler/rustc_codegen_ssa/src/back/link.rs

@@ -750,7 +750,7 @@ fn link_natively(
 
     for print in &sess.opts.prints {
         if print.kind == PrintKind::LinkArgs {
-            let content = format!("{cmd:?}");
+            let content = format!("{cmd:?}\n");
             print.out.overwrite(&content, sess);
         }
     }

compiler/rustc_const_eval/src/interpret/validity.rs

@@ -34,7 +34,6 @@ use super::{
     Pointer, Projectable, Scalar, ValueVisitor,
 };
 
-// for the validation errors
 use super::InterpError::UndefinedBehavior as Ub;
 use super::InterpError::Unsupported as Unsup;
 use super::UndefinedBehaviorInfo::*;

compiler/rustc_lint/src/lib.rs

@@ -120,7 +120,6 @@ use types::*;
 use unit_bindings::*;
 use unused::*;
 
-/// Useful for other parts of the compiler / Clippy.
 pub use builtin::{MissingDoc, SoftLints};
 pub use context::{CheckLintNameResult, FindLintError, LintStore};
 pub use context::{EarlyContext, LateContext, LintContext};

compiler/rustc_pattern_analysis/src/lib.rs

@@ -21,9 +21,7 @@ rustc_fluent_macro::fluent_messages! { "../messages.ftl" }
 
 use std::fmt;
 
-// Re-exports to avoid rustc_index version issues.
-pub use rustc_index::Idx;
-pub use rustc_index::IndexVec;
+pub use rustc_index::{Idx, IndexVec}; // re-exported to avoid rustc_index version issues
 
 #[cfg(feature = "rustc")]
 use rustc_middle::ty::Ty;

compiler/rustc_smir/src/rustc_internal/internal.rs

@@ -4,6 +4,7 @@
 //! due to incomplete stable coverage.
 
 // Prefer importing stable_mir over internal rustc constructs to make this file more readable.
+
 use crate::rustc_smir::Tables;
 use rustc_middle::ty::{self as rustc_ty, Const as InternalConst, Ty as InternalTy, TyCtxt};
 use rustc_span::Symbol;

library/alloc/src/testing/crash_test.rs

@@ -1,5 +1,4 @@
-// We avoid relying on anything else in the crate, apart from the `Debug` trait.
-use crate::fmt::Debug;
+use crate::fmt::Debug; // the `Debug` trait is the only thing we use from `crate::fmt`
 use std::cmp::Ordering;
 use std::sync::atomic::{AtomicUsize, Ordering::SeqCst};
 

library/core/src/char/mod.rs

@@ -24,19 +24,17 @@ mod convert;
 mod decode;
 mod methods;
 
-// stable re-exports
 #[stable(feature = "try_from", since = "1.34.0")]
 pub use self::convert::CharTryFromError;
 #[stable(feature = "char_from_str", since = "1.20.0")]
 pub use self::convert::ParseCharError;
 #[stable(feature = "decode_utf16", since = "1.9.0")]
 pub use self::decode::{DecodeUtf16, DecodeUtf16Error};
 
-// perma-unstable re-exports
 #[unstable(feature = "char_internals", reason = "exposed only for libstd", issue = "none")]
-pub use self::methods::encode_utf16_raw;
+pub use self::methods::encode_utf16_raw; // perma-unstable
 #[unstable(feature = "char_internals", reason = "exposed only for libstd", issue = "none")]
-pub use self::methods::encode_utf8_raw;
+pub use self::methods::encode_utf8_raw; // perma-unstable
 
 use crate::ascii;
 use crate::error::Error;

library/core/src/ffi/c_str.rs

@@ -781,8 +781,15 @@ const unsafe fn strlen(ptr: *const c_char) -> usize {
 pub struct Bytes<'a> {
     // since we know the string is nul-terminated, we only need one pointer
     ptr: NonNull<u8>,
-    phantom: PhantomData<&'a u8>,
+    phantom: PhantomData<&'a [c_char]>,
 }
+
+#[unstable(feature = "cstr_bytes", issue = "112115")]
+unsafe impl Send for Bytes<'_> {}
+
+#[unstable(feature = "cstr_bytes", issue = "112115")]
+unsafe impl Sync for Bytes<'_> {}
+
 impl<'a> Bytes<'a> {
     #[inline]
     fn new(s: &'a CStr) -> Self {
@@ -815,7 +822,7 @@ impl Iterator for Bytes<'_> {
             if ret == 0 {
                 None
             } else {
-                self.ptr = self.ptr.offset(1);
+                self.ptr = self.ptr.add(1);
                 Some(ret)
             }
         }
@@ -825,6 +832,12 @@ impl Iterator for Bytes<'_> {
     fn size_hint(&self) -> (usize, Option<usize>) {
         if self.is_empty() { (0, Some(0)) } else { (1, None) }
     }
+
+    #[inline]
+    fn count(self) -> usize {
+        // SAFETY: We always hold a valid pointer to a C string
+        unsafe { strlen(self.ptr.as_ptr().cast()) }
+    }
 }
 
 #[unstable(feature = "cstr_bytes", issue = "112115")]

library/core/src/num/dec2flt/mod.rs

@@ -250,8 +250,10 @@ pub fn dec2flt<F: RawFloat>(s: &str) -> Result<F, ParseFloatError> {
         None => return Err(pfe_invalid()),
     };
     num.negative = negative;
-    if let Some(value) = num.try_fast_path::<F>() {
-        return Ok(value);
+    if !cfg!(feature = "optimize_for_size") {
+        if let Some(value) = num.try_fast_path::<F>() {
+            return Ok(value);
+        }
     }
 
     // If significant digits were truncated, then we can have rounding error

library/core/src/prelude/common.rs

@@ -2,6 +2,9 @@
 //!
 //! See the [module-level documentation](super) for more.
 
+// No formatting: this file is nothing but re-exports, and their order is worth preserving.
+#![cfg_attr(rustfmt, rustfmt::skip)]
+
 // Re-exported core operators
 #[stable(feature = "core_prelude", since = "1.4.0")]
 #[doc(no_inline)]
@@ -33,10 +36,7 @@ pub use crate::convert::{AsMut, AsRef, From, Into};
 pub use crate::default::Default;
 #[stable(feature = "core_prelude", since = "1.4.0")]
 #[doc(no_inline)]
-pub use crate::iter::{DoubleEndedIterator, ExactSizeIterator};
-#[stable(feature = "core_prelude", since = "1.4.0")]
-#[doc(no_inline)]
-pub use crate::iter::{Extend, IntoIterator, Iterator};
+pub use crate::iter::{DoubleEndedIterator, ExactSizeIterator, Extend, IntoIterator, Iterator};
 #[stable(feature = "core_prelude", since = "1.4.0")]
 #[doc(no_inline)]
 pub use crate::option::Option::{self, None, Some};