From 8813e76bf8a1fa157cdbaff073c02820d33c3725 Mon Sep 17 00:00:00 2001
From: Peter Zhu <peter@peterzhu.ca>
Date: Sun, 4 Jan 2026 14:14:26 -0500
Subject: [PATCH] Assert pinning object is not moved

---
 gc/mmtk/src/pinning_registry.rs | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/gc/mmtk/src/pinning_registry.rs b/gc/mmtk/src/pinning_registry.rs
index 71cf73e..b498b50 100644
--- a/gc/mmtk/src/pinning_registry.rs
+++ b/gc/mmtk/src/pinning_registry.rs
@@ -110,6 +110,11 @@ impl GCWork<Ruby> for PinPinningChildren {
                 target_object
             );
             if pin {
+                debug_assert!(
+                    target_object.get_forwarded_object().is_none(),
+                    "Trying to pin {target_object} but has been moved"
+                );
+
                 pinned_objs.push(target_object);
             }
             target_object