Qt compiler error: 'emit' was not declared in this scope - c++

Question

I am trying to create a Simple GUI which creates multiple threads and perform some operation at the background while the GUI being responsive all the time. I am using QThreads of QT framework to achieve this but I am facing above said issue. Below is the code.
//Threading.h
This is my threading.h file.
#ifndef THREADING
#define THREADING
#include <QThread>
#include <QObject>
class Threading : public QThread
{
Q_OBJECT
private:
int num;
public:
explicit Threading(QObject * parent = 0);
void run();
void set_num(int);
int get_num();
Q_SIGNALS:
void someSignal(int);
};
//This is threading.cpp file
#include "threading.h"
#include <QtCore>
Threading::Threading(QObject *parent) : QThread(parent)
{
}
void Threading:: run()
{
emit someSignal(get_num());
}
void Threading :: set_num(int num)
{
QMutex mutex;
mutex.lock();
this->num = num;
mutex.unlock();
}
int Threading :: get_num()
{
return num;
}
//Mainwindow.h
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
#include <QMainWindow>
#include <QtCore>
#include "threading.h"
typedef unsigned char byte;
namespace Ui {
class MainWindow;
}
class MainWindow : public QMainWindow
{
Q_OBJECT
public:
explicit MainWindow(QWidget *parent = 0);
~MainWindow();
Threading *threadPointer;
};
//Mainwindow.cpp
In this file I am starting thread.
#include "mainwindow.h"
#include "ui_mainwindow.h"
#include "global.h"
#include <QtCore>
#include <QObject>
MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui-> setupUi(this);
threadPointer = new Threading(this);
connect(threadPointer,SIGNAL(someSignal(int)),this,SLOT(onSomeSignal()));
}
void MainWindow::on_clicked()
{
threadPointer->set_num(0);
threadPointer->start();
}
I saw some video online which has exactly similar code which is strangely but working fine and mine is not. Does it have to do with version ? Any help would be appreciated.

Answer 1

You can bypass the issue using Q_EMIT in place of emit, or just call the signal as a normal function (emit is optional and is there just for code readability):
void Threading:: run()
{
someSignal(get_num());
}
emit is an empty macro defined in qobjectdefs.h. You should investigate further, and try to understand why it is not defined (e.g. if QT_NO_KEYWORDS is defined somewhere and why).
You may also want to check if a
CONFIG += no_keywords
line exists in your pro file, as explained at the very end of this.