From db2cfebff1ae78ec6cbe32d24dcaf236b178f6ca Mon Sep 17 00:00:00 2001
From: Jean Boussier <jean.boussier@gmail.com>
Date: Mon, 2 Jun 2025 14:45:02 +0200
Subject: [PATCH] Pin shape->edges

---
 shape.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/shape.c b/shape.c
index fe576f2f7f..5e96766eb5 100644
--- a/shape.c
+++ b/shape.c
@@ -324,7 +324,14 @@ shape_tree_mark(void *data)
     rb_shape_t *end = RSHAPE(GET_SHAPE_TREE()->next_shape_id);
     while (cursor < end) {
         if (cursor->edges && !SINGLE_CHILD_P(cursor->edges)) {
-            rb_gc_mark_movable(cursor->edges);
+            // FIXME: GC compaction may call `rb_shape_traverse_from_new_root`
+            // to migrate objects from one object slot to another.
+            // Because of this if we don't pin `cursor->edges` it might be turned
+            // into a T_MOVED during GC.
+            // We'd need to eliminate `SHAPE_T_OBJECT` so that GC never need to lookup
+            // shapes this way.
+            // rb_gc_mark_movable(cursor->edges);
+            rb_gc_mark(cursor->edges);
         }
         cursor++;
     }