Problem with Sharing resources among threads

[NarimanN2]

I wrote two classes called TextProducer and TextConsumer and they inherited from QThread. I want to Share some resources like Qchar between this two Threads, so I Created a header file called globs.h and put my resources in it.but I get this errors :

textproducer.obj:-1: error: LNK2005: "bool atEnd" (?atEnd@@3_NA) already defined in main.obj
textproducer.obj:-1: error: LNK2005: "class QChar * buffer" (?buffer@@3PAVQChar@@A) already defined in main.obj
textproducer.obj:-1: error: LNK2005: "class QSemaphore availableData" (?availableData@@3VQSemaphore@@A) already defined in main.obj
textproducer.obj:-1: error: LNK2005: "class QSemaphore freeSpace" (?freeSpace@@3VQSemaphore@@A) already defined in main.obj
textconsumer.obj:-1: error: LNK2005: "bool atEnd" (?atEnd@@3_NA) already defined in main.obj
textconsumer.obj:-1: error: LNK2005: "class QChar * buffer" (?buffer@@3PAVQChar@@A) already defined in main.obj
textconsumer.obj:-1: error: LNK2005: "class QSemaphore availableData" (?availableData@@3VQSemaphore@@A) already defined in main.obj

@#ifndef GLOBS_H
#define GLOBS_H
#include <QChar>
#include <QSemaphore>

const int bufferSize = 20;
QChar buffer[bufferSize];
QSemaphore freeSpace(bufferSize);
QSemaphore availableData(0);
bool atEnd = false;

#endif // GLOBS_H
@

@#ifndef TEXTCONSUMER_H
#define TEXTCONSUMER_H

#include <QThread>
#include <QtCore>

class TextConsumer : public QThread
{
public:
TextConsumer();
void run();
};

#endif // TEXTCONSUMER_H
@

@#ifndef TEXTPRODUCER_H
#define TEXTPRODUCER_H

#include <QThread>

class TextProducer : public QThread
{
public:
TextProducer(const QString &text);
void run();

private:
QString m_text;
};

#endif // TEXTPRODUCER_H
@

@#include "textconsumer.h"

TextConsumer::TextConsumer() : QThread()
{
}

void TextConsumer::run()
{
int i = 0;

while (!atEnd || availableData.available())
{
    availableData.acquire();
    qDebug() << buffer[i];
    i = (i + 1) % bufferSize;
    freeSpace.release();
}

}
@

@#include "textproducer.h"

TextProducer::TextProducer(const QString &text) : QThread()
{
m_text = text;
}

void TextProducer::run()
{
for (int i = 0; i < m_text.length(); ++i)
{
freeSpace.acquire();
buffer[i % bufferSize] = m_text[i];

    if (i == m_text.length() - 1)
    {
        atEnd = true;
    }

    availableData.release();
}

}
@

[Chris Kawa]

The problem has nothing to do with threads.
If you declare a variable in a header and then include that header in two different places then of course you've got a duplicated definition and it won't link because linker doesn't know which to choose.

It's a bad idea to put data definitions in a header anyway. Either use extern or a singleton or a proper OOP data scheme where you put data in a class which you can share with eg. QSharedPointer.