Fix missing write barrier through M_TBL

When creating a new origin in ensure_origin, we need to fire a write
barrier after RCLASS_WRITE_ORIGIN. rb_class_set_super allocates, so GC
could happen there, either incrementally marking or promoting the newly
allocated class, and only after RCLASS_WRITE_ORIGIN will origin mark
object in the M_TBL.

1 files changed, 5 insertions, 0 deletions

diff --git a/class.c b/class.c
index bef54eae2f..5184a96ad9 100644
--- a/class.c
+++ b/class.c
@@ -1931,6 +1931,11 @@ ensure_origin(VALUE klass)
         rb_class_set_super(origin, RCLASS_SUPER(klass));
         rb_class_set_super(klass, origin); // writes origin into RCLASS_SUPER(klass)
         RCLASS_WRITE_ORIGIN(klass, origin);
+
+        // RCLASS_WRITE_ORIGIN marks origin as an origin, so this is the first
+        // point that it sees M_TBL and may mark it
+        rb_gc_writebarrier_remember(origin);
+
         class_clear_method_table(klass);
         rb_id_table_foreach(RCLASS_M_TBL(origin), cache_clear_refined_method, (void *)klass);
         rb_id_table_foreach(RCLASS_M_TBL(origin), move_refined_method, (void *)klass);