Auto merge of #3004 - RalfJung:borrow-tests, r=RalfJung

add some SB and TB tests

Also I realized the `direct_mut_to_const_raw` test can be enabled in TB, so let's do that.

src/tools/miri/tests/pass/stacked-borrows/stacked-borrows.rs

@@ -10,7 +10,7 @@ fn main() {
     mut_raw_mut();
     partially_invalidate_mut();
     drop_after_sharing();
-    direct_mut_to_const_raw();
+    // direct_mut_to_const_raw();
     two_raw();
     shr_and_raw();
     disjoint_mutable_subborrows();
@@ -19,6 +19,7 @@ fn main() {
     mut_below_shr();
     wide_raw_ptr_in_tuple();
     not_unpin_not_protected();
+    write_does_not_invalidate_all_aliases();
 }
 
 // Make sure that reading from an `&mut` does, like reborrowing to `&`,
@@ -110,14 +111,13 @@ fn drop_after_sharing() {
 }
 
 // Make sure that coercing &mut T to *const T produces a writeable pointer.
-fn direct_mut_to_const_raw() {
+// TODO: This is currently disabled, waiting on a decision on <https://github.com/rust-lang/rust/issues/56604>
-    // TODO: This is currently disabled, waiting on a decision on <https://github.com/rust-lang/rust/issues/56604>
+/*fn direct_mut_to_const_raw() {
-    /*let x = &mut 0;
+    let x = &mut 0;
     let y: *const i32 = x;
     unsafe { *(y as *mut i32) = 1; }
     assert_eq!(*x, 1);
-    */
+}*/
-}
 
 // Make sure that we can create two raw pointers from a mutable reference and use them both.
 fn two_raw() {
@@ -238,3 +238,28 @@ fn not_unpin_not_protected() {
         drop(unsafe { Box::from_raw(raw) });
     });
 }
+
+fn write_does_not_invalidate_all_aliases() {
+    mod other {
+        /// Some private memory to store stuff in.
+        static mut S: *mut i32 = 0 as *mut i32;
+
+        pub fn lib1(x: &&mut i32) {
+            unsafe {
+                S = (x as *const &mut i32).cast::<*mut i32>().read();
+            }
+        }
+
+        pub fn lib2() {
+            unsafe {
+                *S = 1337;
+            }
+        }
+    }
+
+    let x = &mut 0;
+    other::lib1(&x);
+    *x = 42; // a write to x -- invalidates other pointers?
+    other::lib2();
+    assert_eq!(*x, 1337); // oops, the value changed! I guess not all pointers were invalidated
+}

src/tools/miri/tests/pass/tree_borrows/tree-borrows.rs

@@ -10,6 +10,8 @@ fn main() {
     aliasing_read_only_mutable_refs();
     string_as_mut_ptr();
     two_mut_protected_same_alloc();
+    direct_mut_to_const_raw();
+    local_addr_of_mut();
 
     // Stacked Borrows tests
     read_does_not_invalidate1();
@@ -19,7 +21,6 @@ fn main() {
     mut_raw_mut();
     partially_invalidate_mut();
     drop_after_sharing();
-    direct_mut_to_const_raw();
     two_raw();
     shr_and_raw();
     disjoint_mutable_subborrows();
@@ -28,6 +29,18 @@ fn main() {
     mut_below_shr();
     wide_raw_ptr_in_tuple();
     not_unpin_not_protected();
+    write_does_not_invalidate_all_aliases();
+}
+
+#[allow(unused_assignments)]
+fn local_addr_of_mut() {
+    let mut local = 0;
+    let ptr = ptr::addr_of_mut!(local);
+    // In SB, `local` and `*ptr` would have different tags, but in TB they have the same tag.
+    local = 1;
+    unsafe { *ptr = 2 };
+    local = 3;
+    unsafe { *ptr = 4 };
 }
 
 // Tree Borrows has no issue with several mutable references existing
@@ -172,12 +185,12 @@ fn drop_after_sharing() {
 
 // Make sure that coercing &mut T to *const T produces a writeable pointer.
 fn direct_mut_to_const_raw() {
-    // TODO: This is currently disabled, waiting on a decision on <https://github.com/rust-lang/rust/issues/56604>
+    let x = &mut 0;
-    /*let x = &mut 0;
     let y: *const i32 = x;
-    unsafe { *(y as *mut i32) = 1; }
+    unsafe {
+        *(y as *mut i32) = 1;
+    }
     assert_eq!(*x, 1);
-    */
 }
 
 // Make sure that we can create two raw pointers from a mutable reference and use them both.
@@ -298,3 +311,31 @@ fn not_unpin_not_protected() {
         drop(unsafe { Box::from_raw(raw) });
     });
 }
+
+fn write_does_not_invalidate_all_aliases() {
+    // In TB there are other ways to do that (`addr_of!(*x)` has the same tag as `x`),
+    // but let's still make sure this SB test keeps working.
+
+    mod other {
+        /// Some private memory to store stuff in.
+        static mut S: *mut i32 = 0 as *mut i32;
+
+        pub fn lib1(x: &&mut i32) {
+            unsafe {
+                S = (x as *const &mut i32).cast::<*mut i32>().read();
+            }
+        }
+
+        pub fn lib2() {
+            unsafe {
+                *S = 1337;
+            }
+        }
+    }
+
+    let x = &mut 0;
+    other::lib1(&x);
+    *x = 42; // a write to x -- invalidates other pointers?
+    other::lib2();
+    assert_eq!(*x, 1337); // oops, the value changed! I guess not all pointers were invalidated
+}