Qt QTimeSpan Error LNK2019 - c++

Question

I am using Windows 7, QCreator, Qt 5.0 and my PC is x64.
I get the following errors while using QTimeSpan:
mainwindow.obj:-1: error: LNK2019: unresolved external symbol "__declspec(dllimport) public: __cdecl QTimeSpan::~QTimeSpan(void)" (__imp_??1QTimeSpan##QEAA#XZ) referenced in function "private: void __cdecl MainWindow::on_pushButton_clicked(void)" (?on_pushButton_clicked#MainWindow##AEAAXXZ)
mainwindow.obj:-1: error: LNK2019: unresolved external symbol "__declspec(dllimport) class QTimeSpan __cdecl operator*(class QTimeSpan const &,int)" (__imp_??D#YA?AVQTimeSpan##AEBV0#H#Z) referenced in function "class QTimeSpan __cdecl operator*(int,class QTimeSpan const &)" (??D#YA?AVQTimeSpan##HAEBV0##Z)
mainwindow.obj:-1: error: LNK2019: unresolved external symbol "__declspec(dllimport) class QTimeSpan __cdecl operator-(class QTime const &,class QTime const &)" (__imp_??G#YA?AVQTimeSpan##AEBVQTime##0#Z) referenced in function "private: void __cdecl MainWindow::on_pushButton_clicked(void)" (?on_pushButton_clicked#MainWindow##AEAAXXZ)
mainwindow.obj:-1: error: LNK2019: unresolved external symbol "__declspec(dllimport) class QTime __cdecl operator+(class QTime const &,class QTimeSpan const &)" (__imp_??H#YA?AVQTime##AEBV0#AEBVQTimeSpan###Z) referenced in function "private: void __cdecl MainWindow::on_pushButton_clicked(void)" (?on_pushButton_clicked#MainWindow##AEAAXXZ)
debug\Midpoint3_1.exe:-1: error: LNK1120: 4 unresolved externals
I have tried adding the Qt/libs directory to paths in my computer's 'Environment Variables' but failed.
Here's the source code:
//Midpoint3_1.pro
#-------------------------------------------------
#
# Project created by QtCreator 2013-07-01T03:58:17
#
#-------------------------------------------------
QT += core gui
QT += widgets
greaterThan(QT_MAJOR_VERSION, 4): QT += widgets
TARGET = Midpoint3_1
TEMPLATE = app
SOURCES += main.cpp\
mainwindow.cpp\
HEADERS += mainwindow.h \
../../../../../../../../Qt/Qt5.0.2/5.0.2/msvc2012_64/include/QTimeSpan/qtimespan.h
FORMS += \
mainwindow.ui
//mainwindow.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
private slots:
void on_pushButton_clicked();
private:
Ui::MainWindow *ui;
};
#endif // MAINWINDOW_H
//MainWindow.cpp
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QtGui>
#include <QtCore>
#include "QTimeSpan/qtimespan.h"
#include <QTime>
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
connect(ui->horizontalSlider,SIGNAL(valueChanged(int))
,ui->percentage,SLOT(setValue(int)));
}
void MainWindow::on_pushButton_clicked()
{
QTime vtime1 = ui->time1->time();
QTime vtime2 = ui->time2->time();
QTimeSpan vspan = vtime2 - vtime1;
int vpercentage = ui->percentage->value();
QTime vtime3 = vtime1 + (vpercentage/100) * vspan;
//ui->time3->setText(QString );
}
MainWindow::~MainWindow()
{
delete ui;
}
//main.h
#include "mainwindow.h"
#include <QApplication>
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
MainWindow w;
w.show();
return a.exec();
}
There's also a mainwindow.ui, here's the source code:
<?xml version="1.0" encoding="UTF-8"?>
<ui version="4.0">
<class>MainWindow</class>
<widget class="QMainWindow" name="MainWindow">
<property name="geometry">
<rect>
<x>0</x>
<y>0</y>
<width>284</width>
<height>259</height>
</rect>
</property>
<property name="windowTitle">
<string>Time Midpoint Calculator</string>
</property>
<widget class="QWidget" name="centralWidget">
<widget class="QWidget" name="layoutWidget">
<property name="geometry">
<rect>
<x>20</x>
<y>10</y>
<width>241</width>
<height>191</height>
</rect>
</property>
<layout class="QVBoxLayout" name="verticalLayout_2">
<item>
<layout class="QVBoxLayout" name="verticalLayout">
<item>
<layout class="QHBoxLayout" name="horizontalLayout">
<item>
<widget class="QLabel" name="label">
<property name="text">
<string>Time 1</string>
</property>
</widget>
</item>
<item>
<widget class="QTimeEdit" name="time1"/>
</item>
</layout>
</item>
<item>
<layout class="QHBoxLayout" name="horizontalLayout_2">
<item>
<widget class="QLabel" name="label_2">
<property name="text">
<string>Time 2</string>
</property>
</widget>
</item>
<item>
<widget class="QTimeEdit" name="time2">
<property name="time">
<time>
<hour>12</hour>
<minute>0</minute>
<second>0</second>
</time>
</property>
</widget>
</item>
</layout>
</item>
<item>
<widget class="QSlider" name="horizontalSlider">
<property name="minimumSize">
<size>
<width>128</width>
<height>19</height>
</size>
</property>
<property name="maximumSize">
<size>
<width>20000</width>
<height>19</height>
</size>
</property>
<property name="maximum">
<number>100</number>
</property>
<property name="singleStep">
<number>1</number>
</property>
<property name="value">
<number>50</number>
</property>
<property name="orientation">
<enum>Qt::Horizontal</enum>
</property>
</widget>
</item>
<item>
<layout class="QHBoxLayout" name="horizontalLayout_3">
<item>
<widget class="QLabel" name="label_3">
<property name="text">
<string>Percentage</string>
</property>
</widget>
</item>
<item>
<widget class="QSpinBox" name="percentage">
<property name="maximumSize">
<size>
<width>60</width>
<height>22</height>
</size>
</property>
<property name="value">
<number>50</number>
</property>
</widget>
</item>
</layout>
</item>
</layout>
</item>
<item>
<widget class="QPushButton" name="pushButton">
<property name="text">
<string>Calculate</string>
</property>
</widget>
</item>
<item>
<layout class="QHBoxLayout" name="horizontalLayout_4">
<item>
<widget class="QLabel" name="label_4">
<property name="text">
<string>Output Time</string>
</property>
</widget>
</item>
<item>
<widget class="QLabel" name="time3">
<property name="text">
<string>6:00:00 AM</string>
</property>
</widget>
</item>
</layout>
</item>
</layout>
</widget>
</widget>
<widget class="QMenuBar" name="menuBar">
<property name="geometry">
<rect>
<x>0</x>
<y>0</y>
<width>284</width>
<height>21</height>
</rect>
</property>
<widget class="QMenu" name="menuHelp">
<property name="title">
<string>Help</string>
</property>
<addaction name="actionThe_Algorithm"/>
<addaction name="actionThe_Algorithm_2"/>
<addaction name="actionAbout_Midpoint"/>
</widget>
<addaction name="menuHelp"/>
</widget>
<widget class="QToolBar" name="mainToolBar">
<attribute name="toolBarArea">
<enum>TopToolBarArea</enum>
</attribute>
<attribute name="toolBarBreak">
<bool>false</bool>
</attribute>
</widget>
<widget class="QStatusBar" name="statusBar"/>
<action name="actionThe_Algorithm">
<property name="text">
<string>What is 'Fraction'?</string>
</property>
</action>
<action name="actionThe_Algorithm_2">
<property name="text">
<string>The Algorithm</string>
</property>
</action>
<action name="actionAbout_Midpoint">
<property name="text">
<string>About Midpoint</string>
</property>
</action>
</widget>
<layoutdefault spacing="6" margin="11"/>
<resources/>
<connections/>
</ui>
See here for the source code for qtimespan.h.
And here's how the program looks like:

Answer 1

I think you are trying to include and link to "C" libraries in your C++ application. If your QT is a C library, then calling convention would be __cdecl, but C++ may be looking for linking with __stdcall or someother convention.
In such a scenario if you are sure you are using a C library to link with your CPP app, then include your C headers with
#ifdef _cplusplus
extern "C" {
#endif
#include < your hearder here > //for example QtGui and QTCore etc headers here
#ifdef _cplusplus
}
#endif
This will ensure you will be able to C library without any issues from CPP application