尝试抛出异常时出现c++模板化函数错误

Question

我有一些代码试图在模板化方法中抛出自定义异常。当我尝试编译它时，我收到以下警告:

there are no arguments to ‘Invalid_State_Exception’ that depend on a 
template parameter, so a  declaration of ‘Invalid_State_Exception’ must
be available 
note: (if you use ‘-fpermissive’, G++ will accept your code, but
allowing the use of an undeclared name is deprecated)

到目前为止，我还没有找到解决这个问题的办法。任何建议都会很棒。这是一些示例代码，解释了我所拥有的 (Foo.h):

 template <class T> class Foo
 {
     public:
         void do_stuff(T t)
         {
             if(bar == true)
             {
                 throw Invalid_State_Exception("FooBar error occurred");
             }
         }

      ....
};

class Invalid_State_Exception : public std::runtime_error
{
    public:
        Invalid_State_Exception(const std::string& msg) :
            std::runtime_error(msg) { }
};

Answer 1

将 Invalid_State_Exception 的声明移到 Foo 之上。