address reviews

Author: JoJoDeveloping

tests/fail/tree_borrows/children-can-alias.rs

@@ -1,4 +1,3 @@
-//@revisions: default
 //@compile-flags: -Zmiri-tree-borrows
 #![allow(dangerous_implicit_autorefs)]
 use std::cell::{Cell, Ref, RefCell, RefMut, UnsafeCell};

tests/fail/tree_borrows/children-can-alias.stderr

@@ -1,4 +1,3 @@
-//@revisions: default
 //@compile-flags: -Zmiri-tree-borrows
 #![feature(allocator_api)]
 
@@ -11,6 +10,7 @@ fn main() {
     direct_mut_to_const_raw();
     local_addr_of_mut();
     returned_mut_is_usable();
+    raw_children_of_refmut_can_alias();
 
     // Stacked Borrows tests
     read_does_not_invalidate1();
@@ -356,3 +356,20 @@ fn write_does_not_invalidate_all_aliases() {
     other::lib2();
     assert_eq!(*x, 1337); // oops, the value changed! I guess not all pointers were invalidated
 }
+
+fn raw_children_of_refmut_can_alias() {
+    fn test_with_protector(x: &mut u8) {
+        unsafe {
+            let child1 = &raw mut *x;
+            let child2 = &raw mut *x;
+            // We create two raw aliases of `x`: they have the exact same
+            // tag and can be used interchangeably.
+            child1.write(1);
+            child2.write(2);
+            child1.write(1);
+            child2.write(2);
+        }
+    }
+
+    test_with_protector(&mut 42u8);
+}

tests/pass/tree_borrows/interior_mutability.rs

@@ -1,4 +1,3 @@
-//@revisions: default
 // We disable the GC for this test because it would change what is printed.
 //@compile-flags: -Zmiri-tree-borrows -Zmiri-provenance-gc=0
 
@@ -11,6 +10,8 @@ mod utils;
 use core::ptr::Unique;
 
 // Check general handling of Unique
+// Currently, this test just tests that Unique is not handled special in any way.
+// In particular, it remains `Active` throughout the test.
 
 fn main() {
     unsafe {
@@ -21,45 +22,17 @@ fn main() {
         let raw = &mut *base as *mut u8;
         name!(raw);
 
-        // We create a `Unique` and expect it to have a fresh tag
-        // and uninitialized permissions.
         let uniq = Unique::new_unchecked(raw);
 
-        // With `-Zmiri-unique-is-unique`, `Unique::as_ptr` (which is called by
-        // `Vec::as_ptr`) generates pointers with a fresh tag, so to name the actual
-        // `base` pointer we care about we have to walk up the tree a bit.
-        //
-        // We care about naming this specific parent tag because it is the one
-        // that stays `Active` during the entire execution, unlike the leaves
-        // that will be invalidated the next time `as_ptr` is called.
-        //
-        // (We name it twice so that we have an indicator in the output of
-        // whether we got the distance correct:
-        // If the output shows
-        //
-        //    |- <XYZ: uniq>
-        //    '- <XYZ: uniq>
-        //
-        // then `nth_parent` is not big enough.
-        // The correct value for `nth_parent` should be the minimum
-        // integer for which the output shows
-        //
-        //    '- <XYZ: uniq, uniq>
-        // )
-        //
-        // Ultimately we want pointers obtained through independent
-        // calls of `as_ptr` to be able to alias, which will probably involve
-        // a new permission that allows aliasing when there is no protector.
-        let nth_parent = if cfg!(uniq) { 2 } else { 0 };
-        name!(uniq.as_ptr()=>nth_parent, "uniq");
-        name!(uniq.as_ptr()=>nth_parent, "uniq");
+        name!(uniq.as_ptr(), "uniq");
         print_state!(alloc_id);
 
         // We can activate the Unique and use it mutably.
         *uniq.as_ptr() = 42;
         print_state!(alloc_id);
 
-        // Write through the raw parent disables the Unique
+        // Write through the raw parent does not disable the Unique,
+        // since both have the same tag.
         *raw = 42;
         print_state!(alloc_id);
     }

tests/pass/tree_borrows/tree-borrows.rs

@@ -3,19 +3,19 @@ Warning: this tree is indicative only. Some tags may have been hidden.
 0..   1
 | Act |    └─┬──<TAG=root of the allocation>
 | Res |      └─┬──<TAG=base>
-| Res |        └────<TAG=raw, uniq, uniq>
+| Res |        └────<TAG=raw, uniq>
 ──────────────────────────────────────────────────
 ──────────────────────────────────────────────────
 Warning: this tree is indicative only. Some tags may have been hidden.
 0..   1
 | Act |    └─┬──<TAG=root of the allocation>
 | Act |      └─┬──<TAG=base>
-| Act |        └────<TAG=raw, uniq, uniq>
+| Act |        └────<TAG=raw, uniq>
 ──────────────────────────────────────────────────
 ──────────────────────────────────────────────────
 Warning: this tree is indicative only. Some tags may have been hidden.
 0..   1
 | Act |    └─┬──<TAG=root of the allocation>
 | Act |      └─┬──<TAG=base>
-| Act |        └────<TAG=raw, uniq, uniq>
+| Act |        └────<TAG=raw, uniq>
 ──────────────────────────────────────────────────