Auto merge of rust-lang#126319 - workingjubilee:rollup-lendnud, r=workingjubilee

Rollup of 16 pull requests

Successful merges:

 - rust-lang#123374 (DOC: Add FFI example for slice::from_raw_parts())
 - rust-lang#124514 (Recommend to never display zero disambiguators when demangling v0 symbols)
 - rust-lang#125978 (Cleanup: HIR ty lowering: Consolidate the places that do assoc item probing & access checking)
 - rust-lang#125980 (Nvptx remove direct passmode)
 - rust-lang#126187 (For E0277 suggest adding `Result` return type for function when using QuestionMark `?` in the body.)
 - rust-lang#126210 (docs(core): make more const_ptr doctests assert instead of printing)
 - rust-lang#126249 (Simplify `[T; N]::try_map` signature)
 - rust-lang#126256 (Add {{target}} substitution to compiletest)
 - rust-lang#126263 (Make issue-122805.rs big endian compatible)
 - rust-lang#126281 (set_env: State the conclusion upfront)
 - rust-lang#126286 (Make `storage-live.rs` robust against rustc internal changes.)
 - rust-lang#126287 (Update a cranelift patch file for formatting changes.)
 - rust-lang#126301 (Use `tidy` to sort crate attributes for all compiler crates.)
 - rust-lang#126305 (Make PathBuf less Ok with adding UTF-16 then `into_string`)
 - rust-lang#126310 (Migrate run make prefer rlib)
 - rust-lang#126314 (fix RELEASES: we do not support upcasting to auto traits)

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

Author: bors

Diff for: core/src/array/mod.rs

@@ -533,11 +533,9 @@ impl<T, const N: usize> [T; N] {
     /// assert_eq!(c, Some(a));
     /// ```
     #[unstable(feature = "array_try_map", issue = "79711")]
-    pub fn try_map<F, R>(self, f: F) -> ChangeOutputType<R, [R::Output; N]>
+    pub fn try_map<R>(self, f: impl FnMut(T) -> R) -> ChangeOutputType<R, [R::Output; N]>
     where
-        F: FnMut(T) -> R,
-        R: Try,
-        R::Residual: Residual<[R::Output; N]>,
+        R: Try<Residual: Residual<[R::Output; N]>>,
     {
         drain_array_with(self, |iter| try_from_trusted_iterator(iter.map(f)))
     }

Diff for: core/src/ops/try_trait.rs

@@ -363,7 +363,9 @@ pub trait Residual<O> {
 }
 
 #[unstable(feature = "pub_crate_should_not_need_unstable_attr", issue = "none")]
-pub(crate) type ChangeOutputType<T, V> = <<T as Try>::Residual as Residual<V>>::TryType;
+#[allow(type_alias_bounds)]
+pub(crate) type ChangeOutputType<T: Try<Residual: Residual<V>>, V> =
+    <T::Residual as Residual<V>>::TryType;
 
 /// An adapter for implementing non-try methods via the `Try` implementation.
 ///

Diff for: core/src/ptr/const_ptr.rs

@@ -330,7 +330,7 @@ impl<T: ?Sized> *const T {
     ///
     /// unsafe {
     ///     if let Some(val_back) = ptr.as_ref() {
-    ///         println!("We got back the value: {val_back}!");
+    ///         assert_eq!(val_back, &10);
     ///     }
     /// }
     /// ```
@@ -346,7 +346,7 @@ impl<T: ?Sized> *const T {
     ///
     /// unsafe {
     ///     let val_back = &*ptr;
-    ///     println!("We got back the value: {val_back}!");
+    ///     assert_eq!(val_back, &10);
     /// }
     /// ```
     #[stable(feature = "ptr_as_ref", since = "1.9.0")]
@@ -393,7 +393,7 @@ impl<T: ?Sized> *const T {
     /// let ptr: *const u8 = &10u8 as *const u8;
     ///
     /// unsafe {
-    ///     println!("We got back the value: {}!", ptr.as_ref_unchecked());
+    ///     assert_eq!(ptr.as_ref_unchecked(), &10);
     /// }
     /// ```
     // FIXME: mention it in the docs for `as_ref` and `as_uninit_ref` once stabilized.
@@ -439,7 +439,7 @@ impl<T: ?Sized> *const T {
     ///
     /// unsafe {
     ///     if let Some(val_back) = ptr.as_uninit_ref() {
-    ///         println!("We got back the value: {}!", val_back.assume_init());
+    ///         assert_eq!(val_back.assume_init(), 10);
     ///     }
     /// }
     /// ```
@@ -501,8 +501,8 @@ impl<T: ?Sized> *const T {
     /// let ptr: *const u8 = s.as_ptr();
     ///
     /// unsafe {
-    ///     println!("{}", *ptr.offset(1) as char);
-    ///     println!("{}", *ptr.offset(2) as char);
+    ///     assert_eq!(*ptr.offset(1) as char, '2');
+    ///     assert_eq!(*ptr.offset(2) as char, '3');
     /// }
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
@@ -573,19 +573,21 @@ impl<T: ?Sized> *const T {
     /// # Examples
     ///
     /// ```
+    /// # use std::fmt::Write;
     /// // Iterate using a raw pointer in increments of two elements
     /// let data = [1u8, 2, 3, 4, 5];
     /// let mut ptr: *const u8 = data.as_ptr();
     /// let step = 2;
     /// let end_rounded_up = ptr.wrapping_offset(6);
     ///
-    /// // This loop prints "1, 3, 5, "
+    /// let mut out = String::new();
     /// while ptr != end_rounded_up {
     ///     unsafe {
-    ///         print!("{}, ", *ptr);
+    ///         write!(&mut out, "{}, ", *ptr).unwrap();
     ///     }
     ///     ptr = ptr.wrapping_offset(step);
     /// }
+    /// assert_eq!(out.as_str(), "1, 3, 5, ");
     /// ```
     #[stable(feature = "ptr_wrapping_offset", since = "1.16.0")]
     #[must_use = "returns a new pointer rather than modifying its argument"]
@@ -988,8 +990,8 @@ impl<T: ?Sized> *const T {
     /// let ptr: *const u8 = s.as_ptr();
     ///
     /// unsafe {
-    ///     println!("{}", *ptr.add(1) as char);
-    ///     println!("{}", *ptr.add(2) as char);
+    ///     assert_eq!(*ptr.add(1), b'2');
+    ///     assert_eq!(*ptr.add(2), b'3');
     /// }
     /// ```
     #[stable(feature = "pointer_methods", since = "1.26.0")]
@@ -1073,8 +1075,8 @@ impl<T: ?Sized> *const T {
     ///
     /// unsafe {
     ///     let end: *const u8 = s.as_ptr().add(3);
-    ///     println!("{}", *end.sub(1) as char);
-    ///     println!("{}", *end.sub(2) as char);
+    ///     assert_eq!(*end.sub(1), b'3');
+    ///     assert_eq!(*end.sub(2), b'2');
     /// }
     /// ```
     #[stable(feature = "pointer_methods", since = "1.26.0")]
@@ -1155,19 +1157,21 @@ impl<T: ?Sized> *const T {
     /// # Examples
     ///
     /// ```
+    /// # use std::fmt::Write;
     /// // Iterate using a raw pointer in increments of two elements
     /// let data = [1u8, 2, 3, 4, 5];
     /// let mut ptr: *const u8 = data.as_ptr();
     /// let step = 2;
     /// let end_rounded_up = ptr.wrapping_add(6);
     ///
-    /// // This loop prints "1, 3, 5, "
+    /// let mut out = String::new();
     /// while ptr != end_rounded_up {
     ///     unsafe {
-    ///         print!("{}, ", *ptr);
+    ///         write!(&mut out, "{}, ", *ptr).unwrap();
     ///     }
     ///     ptr = ptr.wrapping_add(step);
     /// }
+    /// assert_eq!(out, "1, 3, 5, ");
     /// ```
     #[stable(feature = "pointer_methods", since = "1.26.0")]
     #[must_use = "returns a new pointer rather than modifying its argument"]
@@ -1234,19 +1238,21 @@ impl<T: ?Sized> *const T {
     /// # Examples
     ///
     /// ```
+    /// # use std::fmt::Write;
     /// // Iterate using a raw pointer in increments of two elements (backwards)
     /// let data = [1u8, 2, 3, 4, 5];
     /// let mut ptr: *const u8 = data.as_ptr();
     /// let start_rounded_down = ptr.wrapping_sub(2);
     /// ptr = ptr.wrapping_add(4);
     /// let step = 2;
-    /// // This loop prints "5, 3, 1, "
+    /// let mut out = String::new();
     /// while ptr != start_rounded_down {
     ///     unsafe {
-    ///         print!("{}, ", *ptr);
+    ///         write!(&mut out, "{}, ", *ptr).unwrap();
     ///     }
     ///     ptr = ptr.wrapping_sub(step);
     /// }
+    /// assert_eq!(out, "5, 3, 1, ");
     /// ```
     #[stable(feature = "pointer_methods", since = "1.26.0")]
     #[must_use = "returns a new pointer rather than modifying its argument"]

Diff for: core/src/slice/raw.rs

@@ -82,6 +82,39 @@ use crate::ub_checks;
 /// }
 /// ```
 ///
+/// ### FFI: Handling null pointers
+///
+/// In languages such as C++, pointers to empty collections are not guaranteed to be non-null.
+/// When accepting such pointers, they have to be checked for null-ness to avoid undefined
+/// behavior.
+///
+/// ```
+/// use std::slice;
+///
+/// /// Sum the elements of an FFI slice.
+/// ///
+/// /// # Safety
+/// ///
+/// /// If ptr is not NULL, it must be correctly aligned and
+/// /// point to `len` initialized items of type `f32`.
+/// unsafe extern "C" fn sum_slice(ptr: *const f32, len: usize) -> f32 {
+///     let data = if ptr.is_null() {
+///         // `len` is assumed to be 0.
+///         &[]
+///     } else {
+///         // SAFETY: see function docstring.
+///         unsafe { slice::from_raw_parts(ptr, len) }
+///     };
+///     data.into_iter().sum()
+/// }
+///
+/// // This could be the result of C++'s std::vector::data():
+/// let ptr = std::ptr::null();
+/// // And this could be std::vector::size():
+/// let len = 0;
+/// assert_eq!(unsafe { sum_slice(ptr, len) }, 0.0);
+/// ```
+///
 /// [valid]: ptr#safety
 /// [`NonNull::dangling()`]: ptr::NonNull::dangling
 #[inline]

Diff for: std/src/env.rs

@@ -323,8 +323,10 @@ impl Error for VarError {
 /// This function is also always safe to call on Windows, in single-threaded
 /// and multi-threaded programs.
 ///
-/// In multi-threaded programs on other operating systems, we strongly suggest
-/// not using `set_var` or `remove_var` at all. The exact requirement is: you
+/// In multi-threaded programs on other operating systems, the only safe option is
+/// to not use `set_var` or `remove_var` at all.
+///
+/// The exact requirement is: you
 /// must ensure that there are no other threads concurrently writing or
 /// *reading*(!) the environment through functions or global variables other
 /// than the ones in this module. The problem is that these operating systems
@@ -390,8 +392,10 @@ unsafe fn _set_var(key: &OsStr, value: &OsStr) {
 /// This function is also always safe to call on Windows, in single-threaded
 /// and multi-threaded programs.
 ///
-/// In multi-threaded programs on other operating systems, we strongly suggest
-/// not using `set_var` or `remove_var` at all. The exact requirement is: you
+/// In multi-threaded programs on other operating systems, the only safe option is
+/// to not use `set_var` or `remove_var` at all.
+///
+/// The exact requirement is: you
 /// must ensure that there are no other threads concurrently writing or
 /// *reading*(!) the environment through functions or global variables other
 /// than the ones in this module. The problem is that these operating systems

Diff for: std/src/sys/pal/windows/rand.rs

@@ -1,6 +1,6 @@
+use core::{mem, ptr};
+
 use crate::sys::c;
-use core::mem;
-use core::ptr;
 
 #[cfg(not(target_vendor = "win7"))]
 #[inline]

Diff for: std/src/sys_common/wtf8.rs

@@ -477,6 +477,9 @@ impl Wtf8Buf {
     /// Part of a hack to make PathBuf::push/pop more efficient.
     #[inline]
     pub(crate) fn as_mut_vec_for_path_buf(&mut self) -> &mut Vec<u8> {
+        // FIXME: this function should not even exist, as it implies violating Wtf8Buf invariants
+        // For now, simply assume that is about to happen.
+        self.is_known_utf8 = false;
         &mut self.bytes
     }
 }

Diff for: std/tests/windows.rs

@@ -0,0 +1,14 @@
+#![cfg(windows)]
+//! An external tests
+
+use std::{ffi::OsString, os::windows::ffi::OsStringExt, path::PathBuf};
+
+#[test]
+#[should_panic]
+fn os_string_must_know_it_isnt_utf8_issue_126291() {
+    let mut utf8 = PathBuf::from(OsString::from("utf8".to_owned()));
+    let non_utf8: OsString =
+        OsStringExt::from_wide(&[0x6e, 0x6f, 0x6e, 0xd800, 0x75, 0x74, 0x66, 0x38]);
+    utf8.set_extension(&non_utf8);
+    utf8.into_os_string().into_string().unwrap();
+}