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Created July 21, 2011 20:25
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Singleton example in C++
* Example of a singleton design pattern.
* Copyright (C) 2011 Radek Pazdera
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* GNU General Public License for more details.
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <>.
#include <iostream>
class Singleton
/* Here will be the instance stored. */
static Singleton* instance;
/* Private constructor to prevent instancing. */
/* Static access method. */
static Singleton* getInstance();
/* Null, because instance will be initialized on demand. */
Singleton* Singleton::instance = 0;
Singleton* Singleton::getInstance()
if (instance == 0)
instance = new Singleton();
return instance;
int main()
//new Singleton(); // Won't work
Singleton* s = Singleton::getInstance(); // Ok
Singleton* r = Singleton::getInstance();
/* The addresses will be the same. */
std::cout << s << std::endl;
std::cout << r << std::endl;
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@SwarajKetan Your singleton gets never created. You could either add a new to your getInstance implementation or avoid pointers completely like here:

Singleton& Singleton::getInstance() {
    static Singleton instance;
    return instance;

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asdlei99 commented Jan 5, 2021

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I think you should use std::call_once to prevent multi-thread problems

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