Auto merge of #100100 - Dylan-DPC:rollup-llcaaq8, r=Dylan-DPC

Rollup of 5 pull requests

Successful merges:

 - #99371 (Remove synchronization from Windows `hashmap_random_keys`)
 - #99614 (do not claim that transmute is like memcpy)
 - #99738 (rustdoc: avoid inlining modules with duplicate names)
 - #99800 (Fix futex module imports on wasm+atomics)
 - #100079 (Replace `* -> vec` with `-> vec` in docs)

Failed merges:

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

library/core/src/intrinsics.rs

@@ -1207,29 +1207,34 @@ extern "rust-intrinsic" {
 
     /// Reinterprets the bits of a value of one type as another type.
     ///
-    /// Both types must have the same size. Neither the original, nor the result,
-    /// may be an [invalid value](../../nomicon/what-unsafe-does.html).
+    /// Both types must have the same size. Compilation will fail if this is not guaranteed.
     ///
     /// `transmute` is semantically equivalent to a bitwise move of one type
     /// into another. It copies the bits from the source value into the
-    /// destination value, then forgets the original. It's equivalent to C's
-    /// `memcpy` under the hood, just like `transmute_copy`.
+    /// destination value, then forgets the original. Note that source and destination
+    /// are passed by-value, which means if `T` or `U` contain padding, that padding
+    /// is *not* guaranteed to be preserved by `transmute`.
+    ///
+    /// Both the argument and the result must be [valid](../../nomicon/what-unsafe-does.html) at
+    /// their given type. Violating this condition leads to [undefined behavior][ub]. The compiler
+    /// will generate code *assuming that you, the programmer, ensure that there will never be
+    /// undefined behavior*. It is therefore your responsibility to guarantee that every value
+    /// passed to `transmute` is valid at both types `T` and `U`. Failing to uphold this condition
+    /// may lead to unexpected and unstable compilation results. This makes `transmute` **incredibly
+    /// unsafe**. `transmute` should be the absolute last resort.
+    ///
+    /// Transmuting pointers to integers in a `const` context is [undefined behavior][ub].
+    /// Any attempt to use the resulting value for integer operations will abort const-evaluation.
+    /// (And even outside `const`, such transmutation is touching on many unspecified aspects of the
+    /// Rust memory model and should be avoided. See below for alternatives.)
     ///
     /// Because `transmute` is a by-value operation, alignment of the *transmuted values
     /// themselves* is not a concern. As with any other function, the compiler already ensures
     /// both `T` and `U` are properly aligned. However, when transmuting values that *point
     /// elsewhere* (such as pointers, references, boxes…), the caller has to ensure proper
     /// alignment of the pointed-to values.
     ///
-    /// `transmute` is **incredibly** unsafe. There are a vast number of ways to
-    /// cause [undefined behavior][ub] with this function. `transmute` should be
-    /// the absolute last resort.
-    ///
-    /// Transmuting pointers to integers in a `const` context is [undefined behavior][ub].
-    /// Any attempt to use the resulting value for integer operations will abort const-evaluation.
-    ///
-    /// The [nomicon](../../nomicon/transmutes.html) has additional
-    /// documentation.
+    /// The [nomicon](../../nomicon/transmutes.html) has additional documentation.
     ///
     /// [ub]: ../../reference/behavior-considered-undefined.html
     ///

library/std/src/sys/wasm/mod.rs

@@ -52,9 +52,11 @@ cfg_if::cfg_if! {
         #[path = "../unix/locks"]
         pub mod locks {
             #![allow(unsafe_op_in_unsafe_fn)]
-            mod futex;
+            mod futex_condvar;
+            mod futex_mutex;
             mod futex_rwlock;
-            pub(crate) use futex::{Mutex, MovableMutex, Condvar, MovableCondvar};
+            pub(crate) use futex_condvar::{Condvar, MovableCondvar};
+            pub(crate) use futex_mutex::{Mutex, MovableMutex};
             pub(crate) use futex_rwlock::{RwLock, MovableRwLock};
         }
         #[path = "atomics/futex.rs"]

library/std/src/sys/windows/rand.rs

@@ -1,62 +1,9 @@
 use crate::io;
 use crate::mem;
-use crate::sync;
+use crate::ptr;
 use crate::sys::c;
 
-/// The kinds of HashMap RNG that may be available
-#[derive(Clone, Copy, Debug, PartialEq)]
-enum HashMapRng {
-    Preferred,
-    Fallback,
-}
-
 pub fn hashmap_random_keys() -> (u64, u64) {
-    match get_hashmap_rng() {
-        HashMapRng::Preferred => {
-            preferred_rng().expect("couldn't generate random bytes with preferred RNG")
-        }
-        HashMapRng::Fallback => {
-            fallback_rng().expect("couldn't generate random bytes with fallback RNG")
-        }
-    }
-}
-
-/// Returns the HashMap RNG that should be used
-///
-/// Panics if they are both broken
-fn get_hashmap_rng() -> HashMapRng {
-    // Assume that if the preferred RNG is broken the first time we use it, it likely means
-    // that: the DLL has failed to load, there is no point to calling it over-and-over again,
-    // and we should cache the result
-    static VALUE: sync::OnceLock<HashMapRng> = sync::OnceLock::new();
-    *VALUE.get_or_init(choose_hashmap_rng)
-}
-
-/// Test whether we should use the preferred or fallback RNG
-///
-/// If the preferred RNG is successful, we choose it. Otherwise, if the fallback RNG is successful,
-/// we choose that
-///
-/// Panics if both the preferred and the fallback RNG are both non-functional
-fn choose_hashmap_rng() -> HashMapRng {
-    let preferred_error = match preferred_rng() {
-        Ok(_) => return HashMapRng::Preferred,
-        Err(e) => e,
-    };
-
-    match fallback_rng() {
-        Ok(_) => return HashMapRng::Fallback,
-        Err(fallback_error) => panic!(
-            "preferred RNG broken: `{}`, fallback RNG broken: `{}`",
-            preferred_error, fallback_error
-        ),
-    }
-}
-
-/// Generate random numbers using the preferred RNG function (BCryptGenRandom)
-fn preferred_rng() -> Result<(u64, u64), io::Error> {
-    use crate::ptr;
-
     let mut v = (0, 0);
     let ret = unsafe {
         c::BCryptGenRandom(
@@ -66,22 +13,23 @@ fn preferred_rng() -> Result<(u64, u64), io::Error> {
             c::BCRYPT_USE_SYSTEM_PREFERRED_RNG,
         )
     };
-
-    if ret == 0 { Ok(v) } else { Err(io::Error::last_os_error()) }
+    if ret != 0 { fallback_rng() } else { v }
 }
 
 /// Generate random numbers using the fallback RNG function (RtlGenRandom)
 #[cfg(not(target_vendor = "uwp"))]
-fn fallback_rng() -> Result<(u64, u64), io::Error> {
+#[inline(never)]
+fn fallback_rng() -> (u64, u64) {
     let mut v = (0, 0);
     let ret =
         unsafe { c::RtlGenRandom(&mut v as *mut _ as *mut u8, mem::size_of_val(&v) as c::ULONG) };
 
-    if ret != 0 { Ok(v) } else { Err(io::Error::last_os_error()) }
+    if ret != 0 { v } else { panic!("fallback RNG broken: {}", io::Error::last_os_error()) }
 }
 
 /// We can't use RtlGenRandom with UWP, so there is no fallback
 #[cfg(target_vendor = "uwp")]
-fn fallback_rng() -> Result<(u64, u64), io::Error> {
-    Err(io::const_io_error!(io::ErrorKind::Unsupported, "RtlGenRandom() not supported on UWP"))
+#[inline(never)]
+fn fallback_rng() -> (u64, u64) {
+    panic!("fallback RNG broken: RtlGenRandom() not supported on UWP");
 }

src/librustdoc/clean/mod.rs

@@ -51,19 +51,24 @@ pub(crate) trait Clean<'tcx, T> {
 impl<'tcx> Clean<'tcx, Item> for DocModule<'tcx> {
     fn clean(&self, cx: &mut DocContext<'tcx>) -> Item {
         let mut items: Vec<Item> = vec![];
-        items.extend(
-            self.foreigns
-                .iter()
-                .map(|(item, renamed)| clean_maybe_renamed_foreign_item(cx, item, *renamed)),
-        );
-        items.extend(self.mods.iter().map(|x| x.clean(cx)));
+        let mut inserted = FxHashSet::default();
+        items.extend(self.foreigns.iter().map(|(item, renamed)| {
+            let item = clean_maybe_renamed_foreign_item(cx, item, *renamed);
+            if let Some(name) = item.name {
+                inserted.insert((item.type_(), name));
+            }
+            item
+        }));
+        items.extend(self.mods.iter().map(|x| {
+            inserted.insert((ItemType::Module, x.name));
+            x.clean(cx)
+        }));
 
         // Split up imports from all other items.
         //
         // This covers the case where somebody does an import which should pull in an item,
         // but there's already an item with the same namespace and same name. Rust gives
         // priority to the not-imported one, so we should, too.
-        let mut inserted = FxHashSet::default();
         items.extend(self.items.iter().flat_map(|(item, renamed)| {
             // First, lower everything other than imports.
             if matches!(item.kind, hir::ItemKind::Use(..)) {

src/librustdoc/html/static/js/main.js

@@ -816,7 +816,7 @@ function loadCss(cssFileName) {
              <code>enum</code>, <code>trait</code>, <code>type</code>, <code>macro</code>, \
              and <code>const</code>.",
             "Search functions by type signature (e.g., <code>vec -&gt; usize</code> or \
-             <code>* -&gt; vec</code>)",
+             <code>-&gt; vec</code>)",
             "Search multiple things at once by splitting your query with comma (e.g., \
              <code>str,u8</code> or <code>String,struct:Vec,test</code>)",
             "You can look for items with an exact name by putting double quotes around \

src/test/rustdoc/auxiliary/issue-99734-aux.rs

@@ -0,0 +1,11 @@
+pub struct Option;
+impl Option {
+    pub fn unwrap(self) {}
+}
+
+/// [`Option::unwrap`]
+pub mod task {}
+
+extern "C" {
+    pub fn main() -> std::ffi::c_int;
+}

src/test/rustdoc/issue-99734-multiple-foreigns-w-same-name.rs

@@ -0,0 +1,16 @@
+// aux-build:issue-99734-aux.rs
+// build-aux-docs
+// ignore-cross-compile
+
+#![crate_name = "foo"]
+
+#[macro_use]
+extern crate issue_99734_aux;
+
+pub use issue_99734_aux::*;
+
+// @count foo/index.html '//a[@class="fn"][@title="foo::main fn"]' 1
+
+extern "C" {
+    pub fn main() -> std::ffi::c_int;
+}

src/test/rustdoc/issue-99734-multiple-mods-w-same-name.rs

@@ -0,0 +1,14 @@
+// aux-build:issue-99734-aux.rs
+// build-aux-docs
+// ignore-cross-compile
+
+#![crate_name = "foo"]
+
+#[macro_use]
+extern crate issue_99734_aux;
+
+pub use issue_99734_aux::*;
+
+// @count foo/index.html '//a[@class="mod"][@title="foo::task mod"]' 1
+
+pub mod task {}