智能指针类模板[图] scoped_ptr[图] boost scoped_ptr的正确构造 boost shared_ptr[图] boost shared_ptr构建.png[图] boost shared_ptr可以多次引用指针 boost week ptr[图] boost week_ptr boost intrusive 侵入式指针 boost make_shared 省略显式的new boost enable_shared_from_this boost 循环引用,对象无法析构,内存泄漏 boost weak_ptr打破循环引用 boost pimpl 接口私有实现技术
智能指针类模板[图]
scoped_ptr[图]
boost scoped_ptr的正确构造
pi@raspberrypi:~/boost $ cat main.cpp
// * 操作符重载
// ->操作符重载
#include <iostream>
#include <boost/scoped_ptr.hpp>
using namespace std;
struct A
{
A() { cout << "A:A()" << endl;}
~A() { cout << "A:~A()" << endl;}
void f() { cout << "A:f()" <<endl;}
};
//智能指针正确的构造方式
int main()
{
boost::scoped_ptr<int>sp(new int(128));
cout << ++*sp <<endl;
//初始化的方式只有一种,只为独享
//boost::scoped_ptr<int>sp2(sp);//Compile Error
boost::scoped_ptr<A> ap(new A);
ap->f();
cout << "-------------------" << endl;
//演示double free
//A a; //栈区变量,离开作用域会自动析构
//boost::scoped_ptr<A>(&a);//离开作用域会自动析构
//Compile Error:note: previous declaration as ‘A a’
return 0;
}
pi@raspberrypi:~/boost $ g++ -Wall main.cpp &&./a.out
129
A:A()
A:f()
-------------------
A:~A()
pi@raspberrypi:~/boost $boost shared_ptr[图]
boost shared_ptr构建.png[图]
boost shared_ptr可以多次引用指针
pi@raspberrypi:~/boost $ cat main.cpp
#include <iostream>
#include <boost/shared_ptr.hpp>
using namespace std;
struct A
{
A() { cout << "A:A()" << endl;}
~A() { cout << "A:~A()" << endl;}
void f() { cout << "A:f()" <<endl;}
};
//智能指针正确的构造方式
int main()
{
boost::shared_ptr<int>sp(new int(128));
cout << ++*sp <<endl;
boost::shared_ptr<int>sp2(sp);//shared_ptr可以多次引用
cout << "sp2的引用次数:" << sp2.use_count() << endl;
boost::shared_ptr<A> ap(new A);
ap->f();
cout << "-------------------" << endl;
return 0;
}
pi@raspberrypi:~/boost $ g++ -Wall main.cpp &&./a.out
129
sp2的引用次数:2
A:A()
A:f()
-------------------
A:~A()
pi@raspberrypi:~/boost $boost week ptr[图]
boost week_ptr
pi@raspberrypi:~/boost $ cat main.cpp
#include <iostream>
#include <boost/shared_ptr.hpp>
#include <boost/weak_ptr.hpp>
using namespace std;
int main()
{
boost::shared_ptr<int>sp(new int(128));
cout << ++*sp <<endl;
boost::shared_ptr<int>sp2(sp);//shared_ptr可以多次引用
cout << "sp2的引用次数:" << sp2.use_count() << endl;
boost::weak_ptr<int> wp(sp2);
cout << "wp的引用次数:" <<wp.use_count() << endl;
cout << "wp.lock:" <<*wp.lock() << endl;//lock返回一个符合要求的shared_ptr
//wp->f();//weak没有->操作符重载,编译报错
cout << "-------------------" << endl;
return 0;
}
pi@raspberrypi:~/boost $ g++ -Wall main.cpp &&./a.out
129
sp2的引用次数:2
wp的引用次数:2
wp.lock:129
-------------------
pi@raspberrypi:~/boost $boost intrusive 侵入式指针
pi@raspberrypi:~/boost $ cat main.cpp
#include <iostream>
#include <boost/shared_ptr.hpp>
#include <boost/intrusive_ptr.hpp>
using namespace std;
class ReferenceCounter
{
public:
ReferenceCounter():refCount(0){}
virtual ~ReferenceCounter(){}
friend void intrusive_ptr_add_ref(ReferenceCounter *p)
{
++p->refCount;
}
friend void intrusive_ptr_release(ReferenceCounter *p)
{
if(--p->refCount == 0)
{
delete p;
}
}
int getRefCount() const
{
return refCount;
}
private:
int refCount;
};
class D:public ReferenceCounter
{
public:
D(){cout << "D:D()" << endl;}
~D(){cout << "D:~D()" << endl;}
};
int main()
{
D* dp = new D;
boost::intrusive_ptr<D> dp1(dp);
{//局域作用域
boost::intrusive_ptr<D> dp2(dp);
cout << "dp2 的引用:"<< dp2->getRefCount() << endl;
}
cout << "dp1 的引用:"<< dp1->getRefCount() << endl;
return 0;
}
pi@raspberrypi:~/boost $ g++ -Wall main.cpp &&./a.out
D:D()
dp2 的引用:2
dp1 的引用:1
D:~D()
pi@raspberrypi:~/boost $boost make_shared 省略显式的new
#include <iostream>
#include <boost/shared_ptr.hpp>
#include <boost/make_shared.hpp>
struct D
{
D(){ std::cout << "D:D()" << std::endl;}
D(int k,double d){std::cout << "k="<<k<<" d="<< d << std::endl;}
~D(){std::cout << "D:~D()" << std::endl;}
};
struct E
{
E(std::string s) {std::cout << "s=" <<s<< std::endl;}
~E(){std::cout << "E:~E()" << std::endl;}
};
int main()
{
boost::shared_ptr<D> dp1 = boost::make_shared<D>();
boost::shared_ptr<D> dp2 = boost::make_shared<D>(12,3.14);
boost::shared_ptr<E> ep1 = boost::make_shared<E>("Boost");
return 0;
}
pi@raspberrypi:~/boost $ g++ -Wall main.cpp &&./a.out
D:D()
k=12 d=3.14
s=Boost
E:~E()
D:~D()
D:~D()
pi@raspberrypi:~/boost $boost enable_shared_from_this
#include <boost/shared_ptr.hpp>
#include <boost/enable_shared_from_this.hpp>
//在一个类的内部使用shared_ptr
class A;
void func(boost::shared_ptr<A> p)
{
std::cout << "sizeof(p)="<<sizeof(p) <<std::endl;
}
class A:public boost::enable_shared_from_this<A>
{
public:
void f()
{
std::cout << "A f() \n";
func(shared_from_this());
}
void say_hi()
{
std::cout << "Hello Boost \n";
}
};
int main()
{
boost::shared_ptr <A> a(new A);
a->f();
return 0;
}
pi@raspberrypi:~/boost $ g++ -Wall main.cpp &&./a.out
A f()
sizeof(p)=8
pi@raspberrypi:~/boost $boost 循环引用,对象无法析构,内存泄漏
pi@raspberrypi:~/boost $ cat main.cpp
#include <iostream>
#include <boost/shared_ptr.hpp>
#include <boost/enable_shared_from_this.hpp>
struct B;
struct A
{
A() {std::cout <<"A()" <<std::endl;}
~A(){std::cout <<"~A()" <<std::endl;}
boost::shared_ptr<B> b;
};
struct B
{
B() {std::cout <<"B()" <<std::endl;}
~B(){std::cout <<"~B()" <<std::endl;}
boost::shared_ptr<A> a;
};
int main()
{
boost::shared_ptr<A> ap(new A);
boost::shared_ptr<B> bp(new B);
ap->b = bp;
bp->a = ap;
std::cout << "------------\n";
return 0;
}
pi@raspberrypi:~/boost $ g++ -Wall main.cpp &&./a.out
A()
B()
------------
pi@raspberrypi:~/boost $boost weak_ptr打破循环引用
pi@raspberrypi:~/boost $ cat main.cpp
#include <iostream>
#include <boost/shared_ptr.hpp>
#include <boost/enable_shared_from_this.hpp>
struct B;
struct A
{
A() {std::cout <<"A()" <<std::endl;}
~A(){std::cout <<"~A()" <<std::endl;}
boost::shared_ptr<B> b;
};
struct B
{
B() {std::cout <<"B()" <<std::endl;}
~B(){std::cout <<"~B()" <<std::endl;}
//boost::shared_ptr<A> a;
boost::weak_ptr<A> a;
};
int main()
{
boost::shared_ptr<A> ap(new A);
boost::shared_ptr<B> bp(new B);
ap->b = bp;
bp->a = ap;
std::cout << "------------\n";
return 0;
}
pi@raspberrypi:~/boost $ g++ -Wall main.cpp &&./a.out
A()
B()
------------
~A()
~B()
pi@raspberrypi:~/boost $boost pimpl 接口私有实现技术
pi@raspberrypi:~/boost $ cat Example.h
#ifndef EXAMPLE_H_
#define EXAMPLE_H_
#include <boost/shared_ptr.hpp>
class Example {
public:
Example();
void do_something();
private:
class implementation;
// hide implementation details
boost::shared_ptr<implementation> _imp;
};
#endif /* EXAMPLE_H_ */
pi@raspberrypi:~/boost $ cat Example.cpp
#include <iostream>
#include "Example.h"
class Example::implementation {
public:
~implementation() {
std::cout << "destroying implementation\n";
}
};
Example::Example():_imp(new implementation)
{
}
void Example::do_something()
{
std::cout << "use_count() is " << _imp.use_count() << "\n";
}
pi@raspberrypi:~/boost $ cat pimpl_test.cpp
#include "Example.h"
int main() {
Example a;
a.do_something();
Example b(a);
b.do_something();
Example c;
c = a;
c.do_something();
return 0;
}
pi@raspberrypi:~/boost $ g++ -Wall pimpl_test.cpp Example.cpp &&./a.out
use_count() is 1
use_count() is 2
destroying implementation
use_count() is 3
destroying implementation
pi@raspberrypi:~/boost $本文出自 “魂斗罗” 博客，谢绝转载！
原文地址：http://990487026.blog.51cto.com/10133282/1879969
