Need to mark fibers referenced from `env`; fix #3837

The issue #3837 is a regression of #3819. I was mistakenly removed
a important code to mark fibers from `env`.

1 files changed, 3 insertions, 0 deletions

diff --git a/src/gc.c b/src/gc.c
index a3a638ae3..4b83f454b 100644
--- a/src/gc.c
+++ b/src/gc.c
@@ -657,6 +657,9 @@ gc_mark_children(mrb_state *mrb, mrb_gc *gc, struct RBasic *obj)
       struct REnv *e = (struct REnv*)obj;
       mrb_int i, len;
 
+      if (MRB_ENV_STACK_SHARED_P(e) && e->cxt->fib) {
+        mrb_gc_mark(mrb, (struct RBasic*)e->cxt->fib);
+      }
       len = MRB_ENV_STACK_LEN(e);
       for (i=0; i<len; i++) {
         mrb_gc_mark_value(mrb, e->stack[i]);