构造函数引用参数导致seg错误

Question

我在ROS应用程序中使用以下代码.

class RobotisController
{
private:
    ....
public:
    ros::NodeHandle pxxx;
}

RobotisController::RobotisController(ros::NodeHandle& nh) : pxxx(nh)
{
    packetHandlerList.push_back(PacketHandler::getPacketHandler(1.0));
    packetHandlerList.push_back(PacketHandler::getPacketHandler(2.0));
}


class RosWrapper {
protected:
    Robotis::RobotisController controller_;
    ros::NodeHandle nh_;
    ....

public:
    RosWrapper() :
            controller_(nh_) {}
}


main()  
{
    RosWrapper interface;
}

当我运行上面的代码时,它会导致SIGSEGV.我试图调试代码,当我到达RobotisController的构造函数时,我发现传递给构造函数的变量nh显示cannot access memory,但内存已经在类RosWrapper中分配.

Answer 1

成员变量将按类定义中的声明顺序初始化.这意味着nh_将在之后初始化controller_.所以传递一个未初始化的nh_因为初始化的参数controller_将导致UB.

您可以更改声明的顺序:

class RosWrapper {
protected:
    ros::NodeHandle nh_;  // nh_ will be initialized firstly
    Robotis::RobotisController controller_;
    ....

public:
    RosWrapper() :
            controller_(nh_) {}
}