画图class Plot:public QwtPlot{ Q_OBJECTpublic: Plot(QWidget *parent = NULL); virtual ~Plot(); //virtual void replot(); //double draw_square(int x);public Q_SLOTS: //void setIntervalLength(double);private: //void initGradient();private: //QwtInterval d_interval; //QwtPlotMarker *d_origin; //QwtPlotCurve *d_curve;};类 Plot继承与QwtPlot，在主程序里什么也没做，运行程序的时候出现“程序异常终止”，具体的编译信息：
d:/qt/qtcreator-2.4.1/mingw/bin/../lib/gcc/mingw32/4.4.0/../../../../mingw32/bin/ld.exe: warning: auto-importing has been activated without --enable-auto-import specified on the command line.
This should work unless it involves constant data structures referencing symbols from auto-imported DLLs.
如果这里的Plot我改为继承与QWidget就不会出现上面的错误，请高手帮忙解答下，都弄了一个晚上了，实在找不到解决方法！
