Auto merge of rust-lang#99422 - Dylan-DPC:rollup-htjofm6, r=Dylan-DPC

Rollup of 7 pull requests

Successful merges:

 - rust-lang#98839 (Add assertion that `transmute_copy`'s U is not larger than T)
 - rust-lang#98998 (Remove branch target prologues from `#[naked] fn`)
 - rust-lang#99198 (add missing null ptr check in alloc example)
 - rust-lang#99344 (rustdoc: avoid inlining items with duplicate `(type, name)`)
 - rust-lang#99351 (Use `typeck_results` to get accurate qpath res for arg mismatch error)
 - rust-lang#99378 (interpret/visitor: add missing early return)
 - rust-lang#99394 (Add regression test for rust-lang#95230)

Failed merges:

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

Author: bors

compiler/rustc_codegen_llvm/src/attributes.rs

@@ -299,6 +299,12 @@ pub fn from_fn_attrs<'ll, 'tcx>(
     }
     if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::NAKED) {
         to_add.push(AttributeKind::Naked.create_attr(cx.llcx));
+        // HACK(jubilee): "indirect branch tracking" works by attaching prologues to functions.
+        // And it is a module-level attribute, so the alternative is pulling naked functions into new LLVM modules.
+        // Otherwise LLVM's "naked" functions come with endbr prefixes per https://github.com/rust-lang/rust/issues/98768
+        to_add.push(AttributeKind::NoCfCheck.create_attr(cx.llcx));
+        // Need this for AArch64.
+        to_add.push(llvm::CreateAttrStringValue(cx.llcx, "branch-target-enforcement", "false"));
     }
     if codegen_fn_attrs.flags.contains(CodegenFnAttrFlags::ALLOCATOR) {
         // apply to return place instead of function (unlike all other attributes applied in this function)

compiler/rustc_codegen_llvm/src/llvm/ffi.rs

@@ -191,6 +191,7 @@ pub enum AttributeKind {
     StackProtect = 32,
     NoUndef = 33,
     SanitizeMemTag = 34,
+    NoCfCheck = 35,
 }
 
 /// LLVMIntPredicate

compiler/rustc_const_eval/src/interpret/visitor.rs

@@ -473,6 +473,9 @@ macro_rules! make_value_visitor {
                         // The second `Box` field is the allocator, which we recursively check for validity
                         // like in regular structs.
                         self.visit_field(v, 1, &alloc)?;
+
+                        // We visited all parts of this one.
+                        return Ok(());
                     }
                     _ => {},
                 };

compiler/rustc_llvm/llvm-wrapper/LLVMWrapper.h

@@ -84,6 +84,7 @@ enum LLVMRustAttribute {
   StackProtect = 32,
   NoUndef = 33,
   SanitizeMemTag = 34,
+  NoCfCheck = 35,
 };
 
 typedef struct OpaqueRustString *RustStringRef;

compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp

@@ -176,6 +176,8 @@ static Attribute::AttrKind fromRust(LLVMRustAttribute Kind) {
     return Attribute::NoAlias;
   case NoCapture:
     return Attribute::NoCapture;
+  case NoCfCheck:
+    return Attribute::NoCfCheck;
   case NoInline:
     return Attribute::NoInline;
   case NonNull:

compiler/rustc_typeck/src/check/fn_ctxt/checks.rs

@@ -443,17 +443,17 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         // Next, let's construct the error
         let (error_span, full_call_span, ctor_of) = match &call_expr.kind {
             hir::ExprKind::Call(
-                hir::Expr {
-                    span,
-                    kind:
-                        hir::ExprKind::Path(hir::QPath::Resolved(
-                            _,
-                            hir::Path { res: Res::Def(DefKind::Ctor(of, _), _), .. },
-                        )),
-                    ..
-                },
+                hir::Expr { hir_id, span, kind: hir::ExprKind::Path(qpath), .. },
                 _,
-            ) => (call_span, *span, Some(of)),
+            ) => {
+                if let Res::Def(DefKind::Ctor(of, _), _) =
+                    self.typeck_results.borrow().qpath_res(qpath, *hir_id)
+                {
+                    (call_span, *span, Some(of))
+                } else {
+                    (call_span, *span, None)
+                }
+            }
             hir::ExprKind::Call(hir::Expr { span, .. }, _) => (call_span, *span, None),
             hir::ExprKind::MethodCall(path_segment, _, span) => {
                 let ident_span = path_segment.ident.span;

library/alloc/src/alloc.rs

@@ -70,11 +70,14 @@ pub use std::alloc::Global;
 /// # Examples
 ///
 /// ```
-/// use std::alloc::{alloc, dealloc, Layout};
+/// use std::alloc::{alloc, dealloc, handle_alloc_error, Layout};
 ///
 /// unsafe {
 ///     let layout = Layout::new::<u16>();
 ///     let ptr = alloc(layout);
+///     if ptr.is_null() {
+///         handle_alloc_error(layout);
+///     }
 ///
 ///     *(ptr as *mut u16) = 42;
 ///     assert_eq!(*(ptr as *mut u16), 42);

library/core/src/mem/mod.rs

@@ -1040,6 +1040,8 @@ pub fn copy<T: Copy>(x: &T) -> T {
 #[stable(feature = "rust1", since = "1.0.0")]
 #[rustc_const_unstable(feature = "const_transmute_copy", issue = "83165")]
 pub const unsafe fn transmute_copy<T, U>(src: &T) -> U {
+    assert!(size_of::<T>() >= size_of::<U>(), "cannot transmute_copy if U is larger than T");
+
     // If U has a higher alignment requirement, src might not be suitably aligned.
     if align_of::<U>() > align_of::<T>() {
         // SAFETY: `src` is a reference which is guaranteed to be valid for reads.

library/core/tests/mem.rs

@@ -97,6 +97,46 @@ fn test_transmute_copy() {
     assert_eq!(1, unsafe { transmute_copy(&1) });
 }
 
+#[test]
+fn test_transmute_copy_shrink() {
+    assert_eq!(0_u8, unsafe { transmute_copy(&0_u64) });
+}
+
+#[test]
+fn test_transmute_copy_unaligned() {
+    #[repr(C)]
+    #[derive(Default)]
+    struct Unaligned {
+        a: u8,
+        b: [u8; 8],
+    }
+
+    let u = Unaligned::default();
+    assert_eq!(0_u64, unsafe { transmute_copy(&u.b) });
+}
+
+#[test]
+#[cfg(panic = "unwind")]
+fn test_transmute_copy_grow_panics() {
+    use std::panic;
+
+    let err = panic::catch_unwind(panic::AssertUnwindSafe(|| unsafe {
+        let _unused: u64 = transmute_copy(&1_u8);
+    }));
+
+    match err {
+        Ok(_) => unreachable!(),
+        Err(payload) => {
+            payload
+                .downcast::<&'static str>()
+                .and_then(|s| {
+                    if *s == "cannot transmute_copy if U is larger than T" { Ok(s) } else { Err(s) }
+                })
+                .unwrap_or_else(|p| panic::resume_unwind(p));
+        }
+    }
+}
+
 #[test]
 #[allow(dead_code)]
 fn test_discriminant_send_sync() {

src/librustdoc/clean/mod.rs

@@ -57,11 +57,43 @@ impl<'tcx> Clean<'tcx, Item> for DocModule<'tcx> {
                 .map(|(item, renamed)| clean_maybe_renamed_foreign_item(cx, item, *renamed)),
         );
         items.extend(self.mods.iter().map(|x| x.clean(cx)));
-        items.extend(
-            self.items
-                .iter()
-                .flat_map(|(item, renamed)| clean_maybe_renamed_item(cx, item, *renamed)),
-        );
+
+        // 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(..)) {
+                return Vec::new();
+            }
+            let v = clean_maybe_renamed_item(cx, item, *renamed);
+            for item in &v {
+                if let Some(name) = item.name {
+                    inserted.insert((item.type_(), name));
+                }
+            }
+            v
+        }));
+        items.extend(self.items.iter().flat_map(|(item, renamed)| {
+            // Now we actually lower the imports, skipping everything else.
+            if !matches!(item.kind, hir::ItemKind::Use(..)) {
+                return Vec::new();
+            }
+            let mut v = clean_maybe_renamed_item(cx, item, *renamed);
+            v.drain_filter(|item| {
+                if let Some(name) = item.name {
+                    // If an item with the same type and name already exists,
+                    // it takes priority over the inlined stuff.
+                    !inserted.insert((item.type_(), name))
+                } else {
+                    false
+                }
+            });
+            v
+        }));
 
         // determine if we should display the inner contents or
         // the outer `mod` item for the source code.