Question

How to pass reference to thread in C++

Answer 1

#include <iostream>
#include <thread>
#include <string>

using std::cout;
using std::endl;

void threadFunction(int const &n)
{
	int &i = const_cast<int &>(n);
	i++;
	
	cout << "threadFunction n = " << n << endl;
}
int main()
{
	int n = 10;

	cout << "main() n = " << n << endl;

	std::thread obj(threadFunction, n);
	obj.join();

	cout << "end main() n = " << n << endl;

	return 0;
}

/*
run:

main() n = 10
threadFunction n = 11
end main() n = 10

*/

 

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Answer 2

#include <iostream>
#include <thread>
#include <string>

using std::cout;
using std::endl;

void threadFunction(int const &n)
{
	int &i = const_cast<int &>(n);
	i++;
	
	cout << "threadFunction n = " << n << endl;
}
int main()
{
	int n = 10;

	cout << "main() n = " << n << endl;

	std::thread obj(threadFunction, std::ref(n)); // ref(n));
	obj.join();

	cout << "end main() n = " << n << endl;

	return 0;
}

/*
run:

main() n = 10
threadFunction n = 11
end main() n = 11

*/

 

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