volatile-1.cpp

/*
 * Example 1: exits on SIGINT
 */
#include <iostream>
#include <signal.h>
#include <unistd.h>

bool continueRunning = true;

void sighandler(int signum) {
	continueRunning = false;
}

int main() {
	signal(SIGINT, sighandler);

	while (continueRunning) {
		usleep(1000);
	}

	std::cout << "exit" << std::endl;
	return 0;
}

volatile-2.cpp

/*
 * Example 1: does not exit on SIGINT
 */
#include <iostream>
#include <signal.h>
#include <unistd.h>

bool continueRunning = true;

void sighandler(int signum) {
	continueRunning = false;
}

int main() {
	signal(SIGINT, sighandler);

	while (continueRunning) {
	}

	std::cout << "exit" << std::endl;
	return 0;
}

volatile-3.cpp

/*
 * Example 1: with volatile, exits on SIGINT
 */
#include <iostream>
#include <signal.h>
#include <unistd.h>

volatile bool continueRunning = true;

void sighandler(int signum) {
	continueRunning = false;
}

int main() {
	signal(SIGINT, sighandler);

	while (continueRunning) {
	}

	std::cout << "exit" << std::endl;
	return 0;
}