QT Qlibrary can't load dll

#include #include #include #include "data.h" #include #include"SignalProcess.h" #include using namespace std; int main(int argc, char *argv[]) { QCoreApplication a(argc, argv); complex dft_v[1024] ; QLibrary mylib; mylib.setFileName("D:/dfl_prj/QT_prj/fft_test1.0/fft_test/SignalProcess.dll"); qDebug()<<mylib.errorString(); if (mylib.isLoaded()) { cout<< "success!"<<endl; } else {cout<< "defeat!"<<endl;} return a.exec(); }