c++11新特性之移动语义

移动语义大大降低了对象转移的成本，通常右值转左值会触发移动语义，左值转左值触发复制语义

可以看看下面的输出是什么

#include <iostream>
#include <string>
#include <vector>
class CDemo
{
public:
    CDemo()
    {
        //std::cout << "构造函数" << std::endl;
    };
    CDemo(CDemo&& cur) noexcept
    {
        std::cout << "移动函数" << std::endl;
    };
    CDemo(CDemo& cur)
    {
        std::cout << "拷贝函数" << std::endl;
    };
    CDemo& operator=(const CDemo& cur)
    {
        std::cout << "赋值函数" << std::endl;
        return *this;
    }
    ~CDemo()
    {
        //std::cout << "析构函数" << std::endl;
    }
    void print(std::string str)
    {
        std::cout << "CDemo::print "<<str << std::endl;
    }
};
CDemo test()
{
    CDemo demo;
    return demo;
}
CDemo test5(CDemo&& demo)
{
    return demo;
}
CDemo test6(CDemo&& demo)
{
    return demo;
}
void test4(CDemo demo)
{
}
void test3(CDemo demo)
{
}
void test2(CDemo demo)
{
    std::cout << "call test3" << std::endl;
    test3(demo);

    std::cout << "call test4" << std::endl;
    test3(std::move(demo));
    return;
}
bool write(std::vector<char> data)
{
    return true;
}
int main()
{
    std::cout << "call test" << std::endl;
    CDemo ok=test();
    
    CDemo ok2;
    std::cout << "call =" << std::endl;
    ok2=ok;

    std::cout << "call test2" << std::endl;
    test2(ok);

    std::cout << "call test5" << std::endl;
    test5(std::move(ok2));//因为test5的参数声明为右值了 所以直接传入左值编译不过test5(ok2); 而test2则可以传入左值是调用复制，转入右值时调用移动
 
    std::cout << "call test6" << std::endl;
    ok = test6(std::move(ok));

    std::cout << "call test6" << std::endl;
    CDemo&& ok3 = test6(std::move(ok));
    return 0;
}

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下面是输出结果

call test
移动函数
call =
赋值函数
call test2
拷贝函数
call test3
拷贝函数
call test4
移动函数
call test5
移动函数
call test6
移动函数
赋值函数
call test6
移动函数