When continuations are captured/restored in the middle of variable binding constructs, a hidden problem occurs. Binding constructs work by allocating an empty environment and then destructively extending it. Since the environment is not on the stack, but a referenced object, it doesn't get deep copied into a continuation. As the continuation is revived repeatedly, parts of the variable binding code are repeatedly re-executed, and keep pushing fresh bindings into the same environment object. Though the new bindings correctly shadow the old, the old bindings are there and potentially hang on to garbage. The solution taken here is to introduce a new kind of frame for handling the situation: a continuation copy handling frame. This frame allows functions to register objects to be copied more deeply if a continuation is captured/revived across them. * eval.c (copy_env): New static function. (copy_env_handler): New static function. (bind_args, bind_macro_params): Install continuation copy handling frame for cloning new_env. (struct bindings_helper_vars): New struct type. (copy_bh_env_handler): New static function. (bindings_helper): Install continuation copy handling frame for de and ne variables which hold environments. The variables are moved to a struct to facilitate access from the handler. * eval.h (copy_env): Declared. * unwind.c (uw_push_cont_copy): New function. (call_copy_handler): New static function. (revive_cont): When a continuation is being revived invoke the copying actions in its continuation copy handling frames, but not if it is only being temporarily revived for immediate unwinding. (capture_cont): After copying the continuation, invoke any continuation copying frames in the "parent": the original frames that were captured. * unwind.h (enum uw_frtype): New type, UW_CONT_COPY. (struct uw_cont_copy): New struct type. (union uw_frame): New member cp. (uw_push_cont_copy): Declared.