Marking from terminated fibers are not needed; ref
The old condition marks the top-level callinfo even after the
fiber is terminated.
MODIFY
src/gc.c
src/gc.c
@@ -801,10 +801,10 @@ obj_free(mrb_state *mrb, struct RBasic *obj, int end)
struct mrb_context *c = ((struct RFiber*)obj)->cxt;
if (c && c != mrb->root_c) {
+ if (!end && c->status != MRB_FIBER_TERMINATED) {
mrb_callinfo *ci = c->ci;
mrb_callinfo *ce = c->cibase;
- if (!end) {
while (ce <= ci) {
struct REnv *e = ci->env;
if (e && !is_dead(&mrb->gc, e) &&

Marking from terminated fibers are not needed; ref #4143

The old condition marks the top-level callinfo even after the
fiber is terminated.