Auto merge of #106450 - albertlarsan68:fix-arc-ptr-eq, r=Amanieu

Make `{Arc,Rc,Weak}::ptr_eq` ignore pointer metadata

FCP completed in #103763 (comment)

Closes #103763

Author: bors

library/alloc/src/rc.rs

@@ -1169,7 +1169,7 @@ impl<T: ?Sized> Rc<T> {
     #[inline]
     #[stable(feature = "ptr_eq", since = "1.17.0")]
     /// Returns `true` if the two `Rc`s point to the same allocation in a vein similar to
-    /// [`ptr::eq`]. See [that function][`ptr::eq`] for caveats when comparing `dyn Trait` pointers.
+    /// [`ptr::eq`]. This function ignores the metadata of  `dyn Trait` pointers.
     ///
     /// # Examples
     ///
@@ -1184,7 +1184,7 @@ impl<T: ?Sized> Rc<T> {
     /// assert!(!Rc::ptr_eq(&five, &other_five));
     /// ```
     pub fn ptr_eq(this: &Self, other: &Self) -> bool {
-        this.ptr.as_ptr() == other.ptr.as_ptr()
+        this.ptr.as_ptr() as *const () == other.ptr.as_ptr() as *const ()
     }
 }
 
@@ -2466,8 +2466,8 @@ impl<T: ?Sized> Weak<T> {
     }
 
     /// Returns `true` if the two `Weak`s point to the same allocation similar to [`ptr::eq`], or if
-    /// both don't point to any allocation (because they were created with `Weak::new()`). See [that
-    /// function][`ptr::eq`] for caveats when comparing `dyn Trait` pointers.
+    /// both don't point to any allocation (because they were created with `Weak::new()`). However,
+    /// this function ignores the metadata of  `dyn Trait` pointers.
     ///
     /// # Notes
     ///
@@ -2508,7 +2508,7 @@ impl<T: ?Sized> Weak<T> {
     #[must_use]
     #[stable(feature = "weak_ptr_eq", since = "1.39.0")]
     pub fn ptr_eq(&self, other: &Self) -> bool {
-        self.ptr.as_ptr() == other.ptr.as_ptr()
+        ptr::eq(self.ptr.as_ptr() as *const (), other.ptr.as_ptr() as *const ())
     }
 }
 

library/alloc/src/sync.rs

@@ -1267,7 +1267,7 @@ impl<T: ?Sized> Arc<T> {
     }
 
     /// Returns `true` if the two `Arc`s point to the same allocation in a vein similar to
-    /// [`ptr::eq`]. See [that function][`ptr::eq`] for caveats when comparing `dyn Trait` pointers.
+    /// [`ptr::eq`]. This function ignores the metadata of  `dyn Trait` pointers.
     ///
     /// # Examples
     ///
@@ -1287,7 +1287,7 @@ impl<T: ?Sized> Arc<T> {
     #[must_use]
     #[stable(feature = "ptr_eq", since = "1.17.0")]
     pub fn ptr_eq(this: &Self, other: &Self) -> bool {
-        this.ptr.as_ptr() == other.ptr.as_ptr()
+        this.ptr.as_ptr() as *const () == other.ptr.as_ptr() as *const ()
     }
 }
 
@@ -2254,8 +2254,8 @@ impl<T: ?Sized> Weak<T> {
     }
 
     /// Returns `true` if the two `Weak`s point to the same allocation similar to [`ptr::eq`], or if
-    /// both don't point to any allocation (because they were created with `Weak::new()`). See [that
-    /// function][`ptr::eq`] for caveats when comparing `dyn Trait` pointers.
+    /// both don't point to any allocation (because they were created with `Weak::new()`). However,
+    /// this function ignores the metadata of  `dyn Trait` pointers.
     ///
     /// # Notes
     ///
@@ -2298,7 +2298,7 @@ impl<T: ?Sized> Weak<T> {
     #[must_use]
     #[stable(feature = "weak_ptr_eq", since = "1.39.0")]
     pub fn ptr_eq(&self, other: &Self) -> bool {
-        self.ptr.as_ptr() == other.ptr.as_ptr()
+        ptr::eq(self.ptr.as_ptr() as *const (), other.ptr.as_ptr() as *const ())
     }
 }
 

src/tools/clippy/clippy_lints/src/unnamed_address.rs

@@ -96,9 +96,7 @@ impl LateLintPass<'_> for UnnamedAddress {
             if let ExprKind::Call(func, [ref _left, ref _right]) = expr.kind;
             if let ExprKind::Path(ref func_qpath) = func.kind;
             if let Some(def_id) = cx.qpath_res(func_qpath, func.hir_id).opt_def_id();
-            if match_def_path(cx, def_id, &paths::PTR_EQ) ||
-                match_def_path(cx, def_id, &paths::RC_PTR_EQ) ||
-                match_def_path(cx, def_id, &paths::ARC_PTR_EQ);
+            if match_def_path(cx, def_id, &paths::PTR_EQ);
             let ty_param = cx.typeck_results().node_substs(func.hir_id).type_at(0);
             if ty_param.is_trait();
             then {

src/tools/clippy/clippy_utils/src/paths.rs

@@ -15,7 +15,6 @@ pub const APPLICABILITY_VALUES: [[&str; 3]; 4] = [
 ];
 #[cfg(feature = "internal")]
 pub const DIAGNOSTIC_BUILDER: [&str; 3] = ["rustc_errors", "diagnostic_builder", "DiagnosticBuilder"];
-pub const ARC_PTR_EQ: [&str; 4] = ["alloc", "sync", "Arc", "ptr_eq"];
 pub const BTREEMAP_CONTAINS_KEY: [&str; 6] = ["alloc", "collections", "btree", "map", "BTreeMap", "contains_key"];
 pub const BTREEMAP_INSERT: [&str; 6] = ["alloc", "collections", "btree", "map", "BTreeMap", "insert"];
 pub const BTREESET_ITER: [&str; 6] = ["alloc", "collections", "btree", "set", "BTreeSet", "iter"];
@@ -93,7 +92,6 @@ pub const PTR_WRITE_UNALIGNED: [&str; 3] = ["core", "ptr", "write_unaligned"];
 pub const PTR_WRITE_VOLATILE: [&str; 3] = ["core", "ptr", "write_volatile"];
 pub const PUSH_STR: [&str; 4] = ["alloc", "string", "String", "push_str"];
 pub const RANGE_ARGUMENT_TRAIT: [&str; 3] = ["core", "ops", "RangeBounds"];
-pub const RC_PTR_EQ: [&str; 4] = ["alloc", "rc", "Rc", "ptr_eq"];
 pub const REFCELL_REF: [&str; 3] = ["core", "cell", "Ref"];
 pub const REFCELL_REFMUT: [&str; 3] = ["core", "cell", "RefMut"];
 pub const REGEX_BUILDER_NEW: [&str; 5] = ["regex", "re_builder", "unicode", "RegexBuilder", "new"];

src/tools/clippy/tests/ui/vtable_address_comparisons.rs

@@ -23,12 +23,6 @@ fn main() {
     let b = &1 as &dyn Debug;
     ptr::eq(a, b);
 
-    let a: Rc<dyn Debug> = Rc::new(1);
-    Rc::ptr_eq(&a, &a);
-
-    let a: Arc<dyn Debug> = Arc::new(1);
-    Arc::ptr_eq(&a, &a);
-
     // These should be fine:
     let a = &1;
     ptr::eq(a, a);
@@ -39,6 +33,12 @@ fn main() {
     let a = Arc::new(1);
     Arc::ptr_eq(&a, &a);
 
+    let a: Rc<dyn Debug> = Rc::new(1);
+    Rc::ptr_eq(&a, &a);
+
+    let a: Arc<dyn Debug> = Arc::new(1);
+    Arc::ptr_eq(&a, &a);
+
     let a: &[u8] = b"";
     ptr::eq(a, a);
 }

src/tools/clippy/tests/ui/vtable_address_comparisons.stderr

@@ -63,21 +63,5 @@ LL |     ptr::eq(a, b);
    |
    = help: consider extracting and comparing data pointers only
 
-error: comparing trait object pointers compares a non-unique vtable address
-  --> $DIR/vtable_address_comparisons.rs:27:5
-   |
-LL |     Rc::ptr_eq(&a, &a);
-   |     ^^^^^^^^^^^^^^^^^^
-   |
-   = help: consider extracting and comparing data pointers only
-
-error: comparing trait object pointers compares a non-unique vtable address
-  --> $DIR/vtable_address_comparisons.rs:30:5
-   |
-LL |     Arc::ptr_eq(&a, &a);
-   |     ^^^^^^^^^^^^^^^^^^^
-   |
-   = help: consider extracting and comparing data pointers only
-
-error: aborting due to 10 previous errors
+error: aborting due to 8 previous errors