chore: wip [skip ci]

Author: not-matthias

crates/runner-shared/src/artifacts/memtrack.rs

@@ -53,8 +53,8 @@ pub enum MemtrackEventKind {
     },
     Free,
     Realloc {
-        #[serde(default)]
-        old_addr: u64,
+        #[serde(default, skip_serializing_if = "Option::is_none")]
+        old_addr: Option<u64>,
         size: u64,
     },
     Calloc {
@@ -174,4 +174,28 @@ mod tests {
 
         Ok(())
     }
+
+    #[test]
+    fn test_deserialize_realloc_compat() -> anyhow::Result<()> {
+        // The file contains a single serialized event using the old format without `old_addr`:
+        // MemtrackEventKind::Realloc { size: 42 }
+        let buf = include_bytes!("../../testdata/realloc.MemtrackArtifact.msgpack");
+        assert_eq!(
+            MemtrackArtifact::decode_streamed(Cursor::new(buf))?.count(),
+            1
+        );
+
+        let event = MemtrackArtifact::decode_streamed(Cursor::new(buf))?
+            .next()
+            .unwrap();
+        assert!(matches!(
+            event.kind,
+            MemtrackEventKind::Realloc {
+                old_addr: None,
+                size: 42
+            }
+        ));
+
+        Ok(())
+    }
 }