Save block argument position in e->cioff; fix #3593

1 files changed, 5 insertions, 0 deletions

diff --git a/src/vm.c b/src/vm.c
index 518323cf7..f67e73533 100644
--- a/src/vm.c
+++ b/src/vm.c
@@ -257,8 +257,13 @@ mrb_env_unshare(mrb_state *mrb, struct REnv *e)
 {
   size_t len = (size_t)MRB_ENV_STACK_LEN(e);
   mrb_value *p = (mrb_value *)mrb_malloc(mrb, sizeof(mrb_value)*len);
+  ptrdiff_t cioff = e->cioff;
 
   MRB_ENV_UNSHARE_STACK(e);
+  if (!e->c) {
+    /* save block argument position (negated) */
+    e->cioff = -mrb->c->cibase[cioff].argc-1;
+  }
   if (len > 0) {
     stack_copy(p, e->stack, len);
   }