pop_expression
pop_expression(&big_condition_stack);
pop_expression(&big_expression_stack);
pop_expression(&big_expression_stack);
pop_expression(&big_expression_stack);
pop_expression(&big_expression_stack);
struct expression *pop_expression(struct expression_list **estack);
pop_expression(&switch_expr_stack);
pop_expression(&big_expression_stack);
pop_expression(&switch_expr_stack);