TB: add missing interior_mutability test file

Author: RalfJung

src/tools/miri/tests/pass/tree_borrows/interior_mutability.rs

@@ -0,0 +1,177 @@
+//@revisions: default uniq
+//@compile-flags: -Zmiri-tree-borrows
+//@[uniq]compile-flags: -Zmiri-unique-is-unique
+use std::cell::{Cell, Ref, RefCell, RefMut, UnsafeCell};
+use std::mem::{self, MaybeUninit};
+
+fn main() {
+    aliasing_mut_and_shr();
+    aliasing_frz_and_shr();
+    into_interior_mutability();
+    unsafe_cell_2phase();
+    unsafe_cell_deallocate();
+    unsafe_cell_invalidate();
+    refcell_basic();
+    ref_protector();
+    ref_mut_protector();
+    rust_issue_68303();
+}
+
+fn aliasing_mut_and_shr() {
+    fn inner(rc: &RefCell<i32>, aliasing: &mut i32) {
+        *aliasing += 4;
+        let _escape_to_raw = rc as *const _;
+        *aliasing += 4;
+        let _shr = &*rc;
+        *aliasing += 4;
+        // also turning this into a frozen ref now must work
+        let aliasing = &*aliasing;
+        let _val = *aliasing;
+        let _escape_to_raw = rc as *const _; // this must NOT unfreeze
+        let _val = *aliasing;
+        let _shr = &*rc; // this must NOT unfreeze
+        let _val = *aliasing;
+    }
+
+    let rc = RefCell::new(23);
+    let mut bmut = rc.borrow_mut();
+    inner(&rc, &mut *bmut);
+    drop(bmut);
+    assert_eq!(*rc.borrow(), 23 + 12);
+}
+
+fn aliasing_frz_and_shr() {
+    fn inner(rc: &RefCell<i32>, aliasing: &i32) {
+        let _val = *aliasing;
+        let _escape_to_raw = rc as *const _; // this must NOT unfreeze
+        let _val = *aliasing;
+        let _shr = &*rc; // this must NOT unfreeze
+        let _val = *aliasing;
+    }
+
+    let rc = RefCell::new(23);
+    let bshr = rc.borrow();
+    inner(&rc, &*bshr);
+    assert_eq!(*rc.borrow(), 23);
+}
+
+// Getting a pointer into a union with interior mutability used to be tricky
+// business (https://github.com/rust-lang/miri/issues/615), but it should work
+// now.
+fn into_interior_mutability() {
+    let mut x: MaybeUninit<(Cell<u32>, u32)> = MaybeUninit::uninit();
+    x.as_ptr();
+    x.write((Cell::new(0), 1));
+    let ptr = unsafe { x.assume_init_ref() };
+    assert_eq!(ptr.1, 1);
+}
+
+// Two-phase borrows of the pointer returned by UnsafeCell::get() should not
+// invalidate aliases.
+fn unsafe_cell_2phase() {
+    unsafe {
+        let x = &UnsafeCell::new(vec![]);
+        let x2 = &*x;
+        (*x.get()).push(0);
+        let _val = (*x2.get()).get(0);
+    }
+}
+
+/// Make sure we can deallocate an UnsafeCell that was passed to an active fn call.
+/// (This is the fix for https://github.com/rust-lang/rust/issues/55005.)
+fn unsafe_cell_deallocate() {
+    fn f(x: &UnsafeCell<i32>) {
+        let b: Box<i32> = unsafe { Box::from_raw(x as *const _ as *mut i32) };
+        drop(b)
+    }
+
+    let b = Box::new(0i32);
+    f(unsafe { mem::transmute(Box::into_raw(b)) });
+}
+
+/// As a side-effect of the above, we also allow this -- at least for now.
+fn unsafe_cell_invalidate() {
+    fn f(_x: &UnsafeCell<i32>, y: *mut i32) {
+        // Writing to y invalidates x, but that is okay.
+        unsafe {
+            *y += 1;
+        }
+    }
+
+    let mut x = 0i32;
+    let raw1 = &mut x as *mut _;
+    let ref1 = unsafe { &mut *raw1 };
+    let raw2 = ref1 as *mut _;
+    // Now the borrow stack is: raw1, ref2, raw2.
+    // So using raw1 invalidates raw2.
+    f(unsafe { mem::transmute(raw2) }, raw1);
+}
+
+fn refcell_basic() {
+    let c = RefCell::new(42);
+    {
+        let s1 = c.borrow();
+        let _x: i32 = *s1;
+        let s2 = c.borrow();
+        let _x: i32 = *s1;
+        let _y: i32 = *s2;
+        let _x: i32 = *s1;
+        let _y: i32 = *s2;
+    }
+    {
+        let mut m = c.borrow_mut();
+        let _z: i32 = *m;
+        {
+            let s: &i32 = &*m;
+            let _x = *s;
+        }
+        *m = 23;
+        let _z: i32 = *m;
+    }
+    {
+        let s1 = c.borrow();
+        let _x: i32 = *s1;
+        let s2 = c.borrow();
+        let _x: i32 = *s1;
+        let _y: i32 = *s2;
+        let _x: i32 = *s1;
+        let _y: i32 = *s2;
+    }
+}
+
+// Adding a Stacked Borrows protector for `Ref` would break this
+fn ref_protector() {
+    fn break_it(rc: &RefCell<i32>, r: Ref<'_, i32>) {
+        // `r` has a shared reference, it is passed in as argument and hence
+        // a protector is added that marks this memory as read-only for the entire
+        // duration of this function.
+        drop(r);
+        // *oops* here we can mutate that memory.
+        *rc.borrow_mut() = 2;
+    }
+
+    let rc = RefCell::new(0);
+    break_it(&rc, rc.borrow())
+}
+
+fn ref_mut_protector() {
+    fn break_it(rc: &RefCell<i32>, r: RefMut<'_, i32>) {
+        // `r` has a shared reference, it is passed in as argument and hence
+        // a protector is added that marks this memory as inaccessible for the entire
+        // duration of this function
+        drop(r);
+        // *oops* here we can mutate that memory.
+        *rc.borrow_mut() = 2;
+    }
+
+    let rc = RefCell::new(0);
+    break_it(&rc, rc.borrow_mut())
+}
+
+/// Make sure we do not have bad enum layout optimizations.
+fn rust_issue_68303() {
+    let optional = Some(RefCell::new(false));
+    let mut handle = optional.as_ref().unwrap().borrow_mut();
+    assert!(optional.is_some());
+    *handle = true;
+}