Merge from rustc

3 files changed, 14 insertions, 2 deletions

diff --git a/src/tools/miri/tests/pass/dyn-traits.rs b/src/tools/miri/tests/pass/dyn-traits.rs
index 908d521a0d8..f6220120968 100644
--- a/src/tools/miri/tests/pass/dyn-traits.rs
+++ b/src/tools/miri/tests/pass/dyn-traits.rs
@@ -141,7 +141,17 @@ fn unsized_dyn_autoderef() {
 }
 */
 
+fn vtable_ptr_eq() {
+    use std::{fmt, ptr};
+
+    // We don't always get the same vtable when casting this to a wide pointer.
+    let x = &2;
+    let x_wide = x as &dyn fmt::Display;
+    assert!((0..256).any(|_| !ptr::eq(x as &dyn fmt::Display, x_wide)));
+}
+
 fn main() {
     ref_box_dyn();
     box_box_trait();
+    vtable_ptr_eq();
 }
diff --git a/src/tools/miri/tests/pass/function_pointers.rs b/src/tools/miri/tests/pass/function_pointers.rs
index 2aa3ebf2dd0..a5c4bc5e0d9 100644
--- a/src/tools/miri/tests/pass/function_pointers.rs
+++ b/src/tools/miri/tests/pass/function_pointers.rs
@@ -82,7 +82,8 @@ fn main() {
     assert!(return_fn_ptr(i) == i);
     assert!(return_fn_ptr(i) as unsafe fn() -> i32 == i as fn() -> i32 as unsafe fn() -> i32);
     // Miri gives different addresses to different reifications of a generic function.
-    assert!(return_fn_ptr(f) != f);
+    // at least if we try often enough.
+    assert!((0..256).any(|_| return_fn_ptr(f) != f));
     // However, if we only turn `f` into a function pointer and use that pointer,
     // it is equal to itself.
     let f2 = f as fn() -> i32;
diff --git a/src/tools/miri/tests/pass/rc.rs b/src/tools/miri/tests/pass/rc.rs
index 6dd1b3aff9e..b1470dabc26 100644
--- a/src/tools/miri/tests/pass/rc.rs
+++ b/src/tools/miri/tests/pass/rc.rs
@@ -75,7 +75,8 @@ fn rc_fat_ptr_eq() {
     let p = Rc::new(1) as Rc<dyn Debug>;
     let a: *const dyn Debug = &*p;
     let r = Rc::into_raw(p);
-    assert!(a == r);
+    // Only compare the pointer parts, as the vtable might differ.
+    assert!(a as *const () == r as *const ());
     drop(unsafe { Rc::from_raw(r) });
 }