add tests that fail due to SRW protectors

also do more iterations of weak mem consistency, since now that is no longer the slowest test ;)

Author: RalfJung

tests/pass/0concurrency_arc_drop.rs

@@ -0,0 +1,19 @@
+// ignore-windows: Concurrency on Windows is not supported yet.
+use std::sync::Arc;
+use std::thread;
+
+/// Test for Arc::drop bug (https://github.com/rust-lang/rust/issues/55005)
+fn main() {
+    // The bug seems to take up to 700 iterations to reproduce with most seeds (tested 0-9).
+    for _ in 0..700 {
+        let arc_1 = Arc::new(());
+        let arc_2 = arc_1.clone();
+        let thread = thread::spawn(|| drop(arc_2));
+        let mut i = 0;
+        while i < 256 {
+            i += 1;
+        }
+        drop(arc_1);
+        thread.join().unwrap();
+    }
+}

tests/pass/0weak_memory_consistency.rs

@@ -214,7 +214,7 @@ fn test_single_thread() {
 }
 
 pub fn main() {
-    for _ in 0..50 {
+    for _ in 0..75 {
         test_single_thread();
         test_mixed_access();
         test_load_buffering_acq_rel();

tests/pass/stacked-borrows/interior_mutability.rs

@@ -1,11 +1,14 @@
+// compile-flags: -Zmiri-tag-raw-pointers
 use std::cell::{Cell, RefCell, UnsafeCell};
-use std::mem::MaybeUninit;
+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();
 }
 
 fn aliasing_mut_and_shr() {
@@ -67,3 +70,33 @@ fn unsafe_cell_2phase() {
         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);
+}