Error LNK2019 at compile a program whit Serial Port class

  • Hi! I im trying to compile a program whit serial port comunication but it show me the Error LNK2019 file not found:main.obj

    this is the main.cpp code:

    #include "mainwindow.h"
    #include <QApplication>
    #include <QTextStream>
    #include <QCoreApplication>
    #include <QFile>
    #include <QtCore>
    #include <QStringList>
    #include <QIODevice>
    #include <iostream>
    #include <QtSerialPort/QSerialPort>
    #include <QDebug>
    #include <Windows.h>
    #include <QElapsedTimer>
    QSerialPort serial;
    int main(int argc, char *argv[])
        QElapsedTimer timer;
        QApplication a(argc, argv);
        QByteArray output;
        serial.setPortName ("COM3"); (QIODevice::ReadOnly);
        serial.setBaudRate (QSerialPort::Baud9600);
        serial.setDataBits (QSerialPort::Data8);
        serial.setStopBits (QSerialPort::OneStop);
        serial.setFlowControl (QSerialPort::NoFlowControl);
        while (!serial.isOpen());
        while (true) {
            output = "a";
        MainWindow w;;
        return a.exec();
    //your code here

    this is the mainwindow.cpp:

    #include "mainwindow.h"
    #include "ui_mainwindow.h"
    MainWindow::MainWindow(QWidget *parent) :
        ui(new Ui::MainWindow)
        delete ui;
    void MainWindow::on_mano_abierto_clicked()
    //your code here

    this is the mainwindow.h:

    #ifndef MAINWINDOW_H
    #define MAINWINDOW_H
    #include <QMainWindow>
    namespace Ui {
    class MainWindow;
    class MainWindow : public QMainWindow
        explicit MainWindow(QWidget *parent = 0);
    private slots:
        void on_mano_abierto_clicked();
        Ui::MainWindow *ui;
    #endif // MAINWINDOW_H
    //your code here

    and this is the .pro file:

    QT       += core gui
    QT += serialport
    greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
    TARGET = brazo_gui
    TEMPLATE = app
    SOURCES += main.cpp\
    HEADERS  += mainwindow.h
    FORMS    += mainwindow.ui
    //your code here

    and this is the error :

    main.obj:-1: error: LNK2019: unresolved external symbol "__declspec(dllimport) public: __cdecl QSerialPort::QSerialPort(class QObject *)" (_imp??0QSerialPort@@QEAA@PEAVQObject@@@Z) referenced in function "void __cdecl `dynamic initializer for 'serial''(void)" (??__Eserial@@YAXXZ)

    appear one of this for every line that include a funcion of the Serial Port class
    when i delete it the program compile without errors
    even if i only add the line QSerialPort serial; it not compile

    please, someone could help me and tell me what is the error and how compile it correctly?

  • Moderators

    Does your Qt installation contain Qt5SerialPort.dll?
    Is it a debug or release build?
    Another possible problem: you're declaring serial outside of main, so it is initialized before main is executed. You should move it to main (after QApplication a(argc, argv), same for timer).
    One note: you should include it like this (no need for QtSerialPort):

    #include <QSerialPort>

  • @jsulm
    It's a debug project and yes, the installation contains the Qt5SerialPort.dll. I've already put the QSerialPort serial; code line inside the main after the QApplication a(argc, argv); line but when i compile it the same problem continues.

  • Lifetime Qt Champion


    Why are you creating a static QSerialPort object ?

  • Moderators

    For debug build you need Qt5SerialPortd.dll. Do you have it?

Log in to reply

Looks like your connection to Qt Forum was lost, please wait while we try to reconnect.