Avoid recursion from `mark_context()`.
MODIFY
src/gc.c
src/gc.c
@@ -582,6 +582,7 @@ mark_context(mrb_state *mrb, struct mrb_context *c)
int i;
mrb_callinfo *ci;
+ start:
if (c->status == MRB_FIBER_TERMINATED) return;
/* mark VM stack */
@@ -603,7 +604,8 @@ mark_context(mrb_state *mrb, struct mrb_context *c)
/* mark fibers */
mrb_gc_mark(mrb, (struct RBasic*)c->fib);
if (c->prev) {
- mark_context(mrb, c->prev);
+ c = c->prev;
+ goto start;
}
}

Avoid recursion from `mark_context()`.