QML plugin don't work while using QDeclarativeView to load can work

[brucewuu]

today I tried the demo QML plugin of qt on winows 7 x64 , it is in examples/declarative/tutorials/extending/chapter6-plugins ,
at first I build with qmake , mingw32-make , it said error
libsupc++/vterminate.cc:91: undefined reference to `_imp___iob'
and I searched it with google , and found some people meet the same problem , and the solution is to copy this project to other disc , then
I copy to E://qt/demo , and build with qmake , mingw32-make , and but still it doesn't work , it seems everything is right , I can get the
dll output in lib , while when I run app.qml , it said PieChart is not a type "PieChart" .
then I tried to build them in main.cpp, see main.cpp
@
#include <QtDeclarative/QtDeclarative>
#include <QtGui/QtGui>
#include "piechart.h"
#include "pieslice.h"

int main(int argc,char **argv)
{
QApplication app(argc,argv);
qmlRegisterType<PieChart>("Bruce",1,0,"PieChart");
qmlRegisterType<PieSlice>("Bruce",1,0,"PieSlice");
QDeclarativeView view;
view.setSource(QUrl("Test.qml"));
view.show();
return app.exec();
}
@
and Tested , it works , why the plugins don't work , while using QDeclarativeView to load them can work .