Refer to GitHub issue on overwritten init value

Author: cbeuw

src/concurrency/data_race.rs

@@ -544,6 +544,7 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: MiriEvalContextExt<'mir, 'tcx> {
         // side effects from a read the program did not perform. So we have to initialise
         // the store buffer with the value currently being written
         // ONCE this is fixed please remove the hack in buffered_atomic_write() in weak_memory.rs
+        // https://github.com/rust-lang/miri/issues/2164
         this.buffered_atomic_write(val, dest, atomic, val)
     }
 

src/concurrency/weak_memory.rs

@@ -508,6 +508,7 @@ pub(super) trait EvalContextExt<'mir, 'tcx: 'mir>:
             // UGLY HACK: in write_scalar_atomic() we don't know the value before our write,
             // so init == val always. If the buffer is fresh then we would've duplicated an entry,
             // so we need to remove it.
+            // See https://github.com/rust-lang/miri/issues/2164
             let was_empty = matches!(
                 alloc_buffers
                     .store_buffers

src/machine.rs

@@ -638,8 +638,6 @@ impl<'mir, 'tcx> Machine<'mir, 'tcx> for Evaluator<'mir, 'tcx> {
             None
         };
         let buffer_alloc = if ecx.machine.weak_memory {
-            // FIXME: if this is an atomic obejct, we want to supply its initial value
-            // while allocating the store buffer here.
             Some(weak_memory::AllocExtra::new_allocation())
         } else {
             None

tests/compile-fail/weak_memory/cpp20_rwc_syncs.rs

@@ -25,6 +25,7 @@ fn reads_value(loc: &AtomicUsize, val: usize) -> usize {
 fn static_atomic(val: usize) -> &'static AtomicUsize {
     let ret = Box::leak(Box::new(AtomicUsize::new(val)));
     // A workaround to put the initialization value in the store buffer.
+    // See https://github.com/rust-lang/miri/issues/2164
     ret.load(Relaxed);
     ret
 }