lvalue

#define current_binding_level                   \
  (cfun && cp_function_chain->bindings          \
   ? cp_function_chain->bindings                \
   : scope_chain->bindings)

gcc/cp/decl.c

 7826   if (decl_context == NORMAL && !toplevel_bindings_p ())
 7827     {
 7828       struct cp_binding_level *b = current_binding_level;
 7829       current_binding_level = b->level_chain;
 7830       if (current_binding_level != 0 && toplevel_bindings_p ())
 7831         decl_context = PARM;
 7832       current_binding_level = b;
 7833     }
 7834

#define current_binding_level                   \
  (*(cfun && cp_function_chain->bindings        \
   ? &cp_function_chain->bindings               \
   : &scope_chain->bindings))