即使稍后回溯，也会触发语义动作.

Semantic actions fire even if there's backtracking later.

解析器表达式可能会抛出.

Parser expressions might throw.

仅出于这些原因，在语义动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(尽管这样做仍然效率低下).

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).

请参见

• Boost Spirit:语义行为是邪恶的"?
• 如何将多态属性与boost :: spirit :: qi解析器?

• Boost Spirit: "Semantic actions are evil"?
• How can I use polymorphic attributes with boost::spirit::qi parsers?