shared_ptr是C++11标准中的智能指针（smart pointer）之一，通过使用shared_ptr，我们可以尽量减少手工维护动态内存，减少错误的发生。

代码示例如下，需要使用符合C++11标准的编译器编译：

#include <iostream>
#include <memory>
#include <string>
#include <vector>

using namespace std;

int main() {
	
	auto p1=make_shared<string>("Good evening");
	if(p1) {
		cout << *p1 << endl;
	}

	shared_ptr<string> s(new string("Good afternoon"));
	if(s) {
		cout << *s << endl;
	}

	shared_ptr<vector<int>> p2(new vector<int>);
	for(int i=0;i<10;i++) {
		p2->push_back(i);
	}
	for(auto x : *p2) {
		cout << x << "\t";
	}
	cout << endl;
	auto p3(p2);
	p3->push_back(100);
	for(auto x : *p2) {
		cout << x << "\t";
	}
	cout << endl;
	cout << "p2 use_count: " << p2.use_count() << endl;

	auto v=new vector<shared_ptr<string>>();
	auto str=make_shared<string>("Good morning");

	cout << "str use_count: " << str.use_count() << endl;
	v->push_back(str);
	cout << "str use_count: " << str.use_count() << endl;
	delete v;
	cout << "str use_count: " << str.use_count() << endl;
	if(str.unique()) {
		cout << "str is unique, reset it." << endl;
		str.reset();
		cout << "now str is null: " << str << endl;
	}
	
	return 0;
}

参考资料：

http://www.cplusplus.com/reference/memory/shared_ptr/