即使稍后有回溯，也会触发语义操作.

Semantic actions fire even if there's backtracking later.

解析器表达式可能会抛出异常.

Parser expressions might throw.

仅出于这些原因，在语义操作中进行动态分配并不是一个好主意.如果需要，请使用智能指针(尽管这仍然效率低下).

For these reasons alone, it's not a good idea to do dynamic allocations in your semantic actions. If you need to, use smart pointers (though this will still be inefficient).

见

• 提升精神:语义动作是邪恶的"?莉>
• 如何使用多态属性boost::spirit::qi 解析器?