stack semantics for reference types stack semantics for reference types stack semantics for reference types stack semantics for reference types stack semantics for reference types stack semantics for reference types stack semantics for reference types stack semantics for reference types stack semantics for reference types stack semantics for reference types stack semantics for reference types stack semantics for reference types stack semantics for reference types stack semantics for reference types stack semantics for reference types stack semantics for reference types stack semantics for reference types stack semantics for reference types stack semantics for reference types stack semantics for reference types stack semantics for reference types stack semantics for reference types stack semantics for reference types stack semantics for reference types stack semantics for reference types stack semantics for reference types stack semantics for reference types stack semantics for reference types stack semantics for reference types stack semantics for reference types stack semantics for reference types stack semantics for reference types stack semantics for reference types