boost enable shared from this

Code Example

#include <iostream>
#include <string>
#include <boost/shared_ptr.hpp>
#include <boost/enable_shared_from_this.hpp>

using namespace std;
using namespace boost;

/*
enable_shared_from_this has become part of C++ 11 standard.

https://blog.csdn.net/csfreebird/article/details/8282518
https://stackoverflow.com/questions/712279/what-is-the-usefulness-of-enable-shared-from-this
*/

class Y : public boost::enable_shared_from_this<Y>
{
public:

	Y()
	{
		cout << "Y::Y()" << endl;
	}

	~Y() 
	{
		cout << "Y::~Y()" << endl;
	}

	boost::shared_ptr<Y> f()
	{
		return shared_from_this();
	}

	boost::shared_ptr<Y> f_dangerous()
	{// lead to multiple release on same resouce
		return boost::shared_ptr<Y>(this);  // don't do this!
	}
};

void test_safe()
{
	boost::shared_ptr<Y> p(new Y);
	boost::shared_ptr<Y> q = p->f();
	assert(p == q);
	assert(!(p < q || q < p)); // p and q must share ownership

	/*
	Y::Y()
	Y::~Y()
	*/
}

void test_dangerous()
{
	boost::shared_ptr<Y> p(new Y);
	boost::shared_ptr<Y> q = p->f_dangerous();
	assert(p == q);
	assert(!(p < q || q < p)); // p and q must share ownership

	/*
	Y::Y()
	Y::~Y()
	Y::~Y()
	*/
}

int main()
{
	//test_safe();
	test_dangerous();
	return 0;
}

Reference

• what-is-the-usefulness-of-enable-shared-from-this

History

• 20180523: created.