Rollup of 7 pull requests

compiler/rustc_codegen_ssa/src/target_features.rs

@@ -80,6 +80,7 @@ pub fn from_target_feature(
                 Some(sym::loongarch_target_feature) => rust_features.loongarch_target_feature,
                 Some(sym::lahfsahf_target_feature) => rust_features.lahfsahf_target_feature,
                 Some(sym::prfchw_target_feature) => rust_features.prfchw_target_feature,
+                Some(sym::x86_amx_intrinsics) => rust_features.x86_amx_intrinsics,
                 Some(name) => bug!("unknown target feature gate {}", name),
                 None => true,
             };

compiler/rustc_feature/src/unstable.rs

@@ -640,6 +640,8 @@ declare_features! (
     (unstable, unsized_tuple_coercion, "1.20.0", Some(42877)),
     /// Allows using the `#[used(linker)]` (or `#[used(compiler)]`) attribute.
     (unstable, used_with_arg, "1.60.0", Some(93798)),
+    /// Allows use of x86 `AMX` target-feature attributes and intrinsics
+    (unstable, x86_amx_intrinsics, "CURRENT_RUSTC_VERSION", Some(126622)),
     /// Allows `do yeet` expressions
     (unstable, yeet_expr, "1.62.0", Some(96373)),
     // !!!!    !!!!    !!!!    !!!!   !!!!    !!!!    !!!!    !!!!    !!!!    !!!!    !!!!

compiler/rustc_hir/src/hir.rs

@@ -2708,6 +2708,13 @@ impl PreciseCapturingArg<'_> {
             PreciseCapturingArg::Param(param) => param.hir_id,
         }
     }
+
+    pub fn name(self) -> Symbol {
+        match self {
+            PreciseCapturingArg::Lifetime(lt) => lt.ident.name,
+            PreciseCapturingArg::Param(param) => param.ident.name,
+        }
+    }
 }
 
 /// We need to have a [`Node`] for the [`HirId`] that we attach the type/const param

compiler/rustc_span/src/symbol.rs

@@ -2072,6 +2072,7 @@ symbols! {
         write_str,
         write_via_move,
         writeln_macro,
+        x86_amx_intrinsics,
         x87_reg,
         xer,
         xmm_reg,

compiler/rustc_target/src/target_features.rs

@@ -192,6 +192,11 @@ const X86_ALLOWED_FEATURES: &[(&str, Stability)] = &[
     // tidy-alphabetical-start
     ("adx", Stable),
     ("aes", Stable),
+    ("amx-bf16", Unstable(sym::x86_amx_intrinsics)),
+    ("amx-complex", Unstable(sym::x86_amx_intrinsics)),
+    ("amx-fp16", Unstable(sym::x86_amx_intrinsics)),
+    ("amx-int8", Unstable(sym::x86_amx_intrinsics)),
+    ("amx-tile", Unstable(sym::x86_amx_intrinsics)),
     ("avx", Stable),
     ("avx2", Stable),
     ("avx512bf16", Unstable(sym::avx512_target_feature)),

library/alloc/src/rc.rs

@@ -665,16 +665,6 @@ impl<T> Rc<T> {
 }
 
 impl<T, A: Allocator> Rc<T, A> {
-    /// Returns a reference to the underlying allocator.
-    ///
-    /// Note: this is an associated function, which means that you have
-    /// to call it as `Rc::allocator(&r)` instead of `r.allocator()`. This
-    /// is so that there is no conflict with a method on the inner type.
-    #[inline]
-    #[unstable(feature = "allocator_api", issue = "32838")]
-    pub fn allocator(this: &Self) -> &A {
-        &this.alloc
-    }
     /// Constructs a new `Rc` in the provided allocator.
     ///
     /// # Examples
@@ -1331,6 +1321,17 @@ impl<T: ?Sized> Rc<T> {
 }
 
 impl<T: ?Sized, A: Allocator> Rc<T, A> {
+    /// Returns a reference to the underlying allocator.
+    ///
+    /// Note: this is an associated function, which means that you have
+    /// to call it as `Rc::allocator(&r)` instead of `r.allocator()`. This
+    /// is so that there is no conflict with a method on the inner type.
+    #[inline]
+    #[unstable(feature = "allocator_api", issue = "32838")]
+    pub fn allocator(this: &Self) -> &A {
+        &this.alloc
+    }
+
     /// Consumes the `Rc`, returning the wrapped pointer.
     ///
     /// To avoid a memory leak the pointer must be converted back to an `Rc` using
@@ -2994,6 +2995,13 @@ impl<T: ?Sized> Weak<T> {
 }
 
 impl<T: ?Sized, A: Allocator> Weak<T, A> {
+    /// Returns a reference to the underlying allocator.
+    #[inline]
+    #[unstable(feature = "allocator_api", issue = "32838")]
+    pub fn allocator(&self) -> &A {
+        &self.alloc
+    }
+
     /// Returns a raw pointer to the object `T` pointed to by this `Weak<T>`.
     ///
     /// The pointer is valid only if there are some strong references. The pointer may be dangling,

library/alloc/src/sync.rs

@@ -677,16 +677,6 @@ impl<T> Arc<T> {
 }
 
 impl<T, A: Allocator> Arc<T, A> {
-    /// Returns a reference to the underlying allocator.
-    ///
-    /// Note: this is an associated function, which means that you have
-    /// to call it as `Arc::allocator(&a)` instead of `a.allocator()`. This
-    /// is so that there is no conflict with a method on the inner type.
-    #[inline]
-    #[unstable(feature = "allocator_api", issue = "32838")]
-    pub fn allocator(this: &Self) -> &A {
-        &this.alloc
-    }
     /// Constructs a new `Arc<T>` in the provided allocator.
     ///
     /// # Examples
@@ -1470,6 +1460,17 @@ impl<T: ?Sized> Arc<T> {
 }
 
 impl<T: ?Sized, A: Allocator> Arc<T, A> {
+    /// Returns a reference to the underlying allocator.
+    ///
+    /// Note: this is an associated function, which means that you have
+    /// to call it as `Arc::allocator(&a)` instead of `a.allocator()`. This
+    /// is so that there is no conflict with a method on the inner type.
+    #[inline]
+    #[unstable(feature = "allocator_api", issue = "32838")]
+    pub fn allocator(this: &Self) -> &A {
+        &this.alloc
+    }
+
     /// Consumes the `Arc`, returning the wrapped pointer.
     ///
     /// To avoid a memory leak the pointer must be converted back to an `Arc` using
@@ -2715,6 +2716,13 @@ impl<T: ?Sized> Weak<T> {
 }
 
 impl<T: ?Sized, A: Allocator> Weak<T, A> {
+    /// Returns a reference to the underlying allocator.
+    #[inline]
+    #[unstable(feature = "allocator_api", issue = "32838")]
+    pub fn allocator(&self) -> &A {
+        &self.alloc
+    }
+
     /// Returns a raw pointer to the object `T` pointed to by this `Weak<T>`.
     ///
     /// The pointer is valid only if there are some strong references. The pointer may be dangling,

library/core/src/ffi/c_str.rs

@@ -263,8 +263,6 @@ impl CStr {
     /// ```
     ///
     /// ```
-    /// #![feature(const_cstr_from_ptr)]
-    ///
     /// use std::ffi::{c_char, CStr};
     ///
     /// const HELLO_PTR: *const c_char = {
@@ -280,7 +278,7 @@ impl CStr {
     #[inline] // inline is necessary for codegen to see strlen.
     #[must_use]
     #[stable(feature = "rust1", since = "1.0.0")]
-    #[rustc_const_unstable(feature = "const_cstr_from_ptr", issue = "113219")]
+    #[rustc_const_stable(feature = "const_cstr_from_ptr", since = "CURRENT_RUSTC_VERSION")]
     pub const unsafe fn from_ptr<'a>(ptr: *const c_char) -> &'a CStr {
         // SAFETY: The caller has provided a pointer that points to a valid C
         // string with a NUL terminator less than `isize::MAX` from `ptr`.
@@ -542,7 +540,7 @@ impl CStr {
     #[must_use]
     #[doc(alias("len", "strlen"))]
     #[stable(feature = "cstr_count_bytes", since = "1.79.0")]
-    #[rustc_const_unstable(feature = "const_cstr_from_ptr", issue = "113219")]
+    #[rustc_const_stable(feature = "const_cstr_from_ptr", since = "CURRENT_RUSTC_VERSION")]
     pub const fn count_bytes(&self) -> usize {
         self.inner.len() - 1
     }
@@ -742,6 +740,9 @@ impl AsRef<CStr> for CStr {
 /// The pointer must point to a valid buffer that contains a NUL terminator. The NUL must be
 /// located within `isize::MAX` from `ptr`.
 #[inline]
+#[unstable(feature = "cstr_internals", issue = "none")]
+#[rustc_const_stable(feature = "const_cstr_from_ptr", since = "CURRENT_RUSTC_VERSION")]
+#[rustc_allow_const_fn_unstable(const_eval_select)]
 const unsafe fn const_strlen(ptr: *const c_char) -> usize {
     const fn strlen_ct(s: *const c_char) -> usize {
         let mut len = 0;

library/std/src/panicking.rs

@@ -253,16 +253,20 @@ fn default_hook(info: &PanicHookInfo<'_>) {
     let name = thread.as_ref().and_then(|t| t.name()).unwrap_or("<unnamed>");
 
     let write = |err: &mut dyn crate::io::Write| {
+        // Use a lock to prevent mixed output in multithreading context.
+        // Some platforms also require it when printing a backtrace, like `SymFromAddr` on Windows.
+        let mut lock = backtrace::lock();
         let _ = writeln!(err, "thread '{name}' panicked at {location}:\n{msg}");
 
         static FIRST_PANIC: AtomicBool = AtomicBool::new(true);
 
         match backtrace {
+            // SAFETY: we took out a lock just a second ago.
             Some(BacktraceStyle::Short) => {
-                drop(backtrace::print(err, crate::backtrace_rs::PrintFmt::Short))
+                drop(lock.print(err, crate::backtrace_rs::PrintFmt::Short))
             }
             Some(BacktraceStyle::Full) => {
-                drop(backtrace::print(err, crate::backtrace_rs::PrintFmt::Full))
+                drop(lock.print(err, crate::backtrace_rs::PrintFmt::Full))
             }
             Some(BacktraceStyle::Off) => {
                 if FIRST_PANIC.swap(false, Ordering::Relaxed) {

library/std/src/sys/backtrace.rs

@@ -7,44 +7,41 @@ use crate::fmt;
 use crate::io;
 use crate::io::prelude::*;
 use crate::path::{self, Path, PathBuf};
-use crate::sync::{Mutex, PoisonError};
+use crate::sync::{Mutex, MutexGuard, PoisonError};
 
 /// Max number of frames to print.
 const MAX_NB_FRAMES: usize = 100;
 
-pub fn lock() -> impl Drop {
+pub(crate) struct BacktraceLock<'a>(#[allow(dead_code)] MutexGuard<'a, ()>);
+
+pub(crate) fn lock<'a>() -> BacktraceLock<'a> {
     static LOCK: Mutex<()> = Mutex::new(());
-    LOCK.lock().unwrap_or_else(PoisonError::into_inner)
+    BacktraceLock(LOCK.lock().unwrap_or_else(PoisonError::into_inner))
 }
 
-/// Prints the current backtrace.
-pub fn print(w: &mut dyn Write, format: PrintFmt) -> io::Result<()> {
-    // There are issues currently linking libbacktrace into tests, and in
-    // general during std's own unit tests we're not testing this path. In
-    // test mode immediately return here to optimize away any references to the
-    // libbacktrace symbols
-    if cfg!(test) {
-        return Ok(());
-    }
-
-    // Use a lock to prevent mixed output in multithreading context.
-    // Some platforms also requires it, like `SymFromAddr` on Windows.
-    unsafe {
-        let _lock = lock();
-        _print(w, format)
-    }
-}
+impl BacktraceLock<'_> {
+    /// Prints the current backtrace.
+    ///
+    /// NOTE: this function is not Sync. The caller must hold a mutex lock, or there must be only one thread in the program.
+    pub(crate) fn print(&mut self, w: &mut dyn Write, format: PrintFmt) -> io::Result<()> {
+        // There are issues currently linking libbacktrace into tests, and in
+        // general during std's own unit tests we're not testing this path. In
+        // test mode immediately return here to optimize away any references to the
+        // libbacktrace symbols
+        if cfg!(test) {
+            return Ok(());
+        }
 
-unsafe fn _print(w: &mut dyn Write, format: PrintFmt) -> io::Result<()> {
-    struct DisplayBacktrace {
-        format: PrintFmt,
-    }
-    impl fmt::Display for DisplayBacktrace {
-        fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
-            unsafe { _print_fmt(fmt, self.format) }
+        struct DisplayBacktrace {
+            format: PrintFmt,
+        }
+        impl fmt::Display for DisplayBacktrace {
+            fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+                unsafe { _print_fmt(fmt, self.format) }
+            }
         }
+        write!(w, "{}", DisplayBacktrace { format })
     }
-    write!(w, "{}", DisplayBacktrace { format })
 }
 
 unsafe fn _print_fmt(fmt: &mut fmt::Formatter<'_>, print_fmt: PrintFmt) -> fmt::Result {

library/std/src/sys/pal/unix/linux/pidfd/tests.rs

@@ -1,7 +1,7 @@
 use crate::assert_matches::assert_matches;
 use crate::os::fd::{AsRawFd, RawFd};
-use crate::os::linux::process::{ChildExt, CommandExt};
-use crate::os::unix::process::ExitStatusExt;
+use crate::os::linux::process::{ChildExt, CommandExt as _};
+use crate::os::unix::process::{CommandExt as _, ExitStatusExt};
 use crate::process::Command;
 
 #[test]
@@ -21,6 +21,7 @@ fn test_command_pidfd() {
         let flags = super::cvt(unsafe { libc::fcntl(pidfd.as_raw_fd(), libc::F_GETFD) }).unwrap();
         assert!(flags & libc::FD_CLOEXEC != 0);
     }
+    assert!(child.id() > 0 && child.id() < -1i32 as u32);
     let status = child.wait().expect("error waiting on pidfd");
     assert_eq!(status.code(), Some(1));
 
@@ -42,6 +43,17 @@ fn test_command_pidfd() {
         .unwrap()
         .pidfd()
         .expect_err("pidfd should not have been created");
+
+    // exercise the fork/exec path since the earlier attempts may have used pidfd_spawnp()
+    let mut child =
+        unsafe { Command::new("false").pre_exec(|| Ok(())) }.create_pidfd(true).spawn().unwrap();
+
+    assert!(child.id() > 0 && child.id() < -1i32 as u32);
+
+    if pidfd_open_available {
+        assert!(child.pidfd().is_ok())
+    }
+    child.wait().expect("error waiting on child");
 }
 
 #[test]

library/std/src/sys/pal/unix/mod.rs

@@ -305,10 +305,13 @@ macro_rules! impl_is_minus_one {
 
 impl_is_minus_one! { i8 i16 i32 i64 isize }
 
+/// Convert native return values to Result using the *-1 means error is in `errno`*  convention.
+/// Non-error values are `Ok`-wrapped.
 pub fn cvt<T: IsMinusOne>(t: T) -> crate::io::Result<T> {
     if t.is_minus_one() { Err(crate::io::Error::last_os_error()) } else { Ok(t) }
 }
 
+/// `-1` → look at `errno` → retry on `EINTR`. Otherwise `Ok()`-wrap the closure return value.
 pub fn cvt_r<T, F>(mut f: F) -> crate::io::Result<T>
 where
     T: IsMinusOne,
@@ -323,6 +326,7 @@ where
 }
 
 #[allow(dead_code)] // Not used on all platforms.
+/// Zero means `Ok()`, all other values are treated as raw OS errors. Does not look at `errno`.
 pub fn cvt_nz(error: libc::c_int) -> crate::io::Result<()> {
     if error == 0 { Ok(()) } else { Err(crate::io::Error::from_raw_os_error(error)) }
 }