Use MRB_ENV_STACK_SHARED_P to check `cioff` field of REnv.

1 files changed, 2 insertions, 2 deletions

diff --git a/src/gc.c b/src/gc.c
index 426a84514..4db640ff4 100644
--- a/src/gc.c
+++ b/src/gc.c
@@ -515,7 +515,7 @@ gc_mark_children(mrb_state *mrb, struct RBasic *obj)
     {
       struct REnv *e = (struct REnv*)obj;
 
-      if (e->cioff < 0) {
+      if (!MRB_ENV_STACK_SHARED_P(e)) {
         int i, len;
 
         len = (int)MRB_ENV_STACK_LEN(e);
@@ -612,7 +612,7 @@ obj_free(mrb_state *mrb, struct RBasic *obj)
     {
       struct REnv *e = (struct REnv*)obj;
 
-      if (e->cioff < 0) {
+      if (!MRB_ENV_STACK_SHARED_P(e)) {
         mrb_free(mrb, e->stack);
         e->stack = NULL;
       }