C++动态空间的申请

为什么C++的动态分配是new和delete？

因为malloc 函数和对应的free函数不能调用构造函数和析构函数，这破坏了空间分配、初始化的功能。所以引入了new和delete。

//============================================================================
// Name        : main.cpp
// Author      : ShiGuang
// Version     : www.zzzyk.com
// Copyright   : sg131971@qq.com
// Description : Hello World in C++, Ansi-style
//============================================================================

#include <iostream>
#include <string>
using namespace std;

class aa
{
public:
    aa(int a = 1)
    {
        cout << "aa is constructed." << endl;
        id = a;
    }
    int id;
    ~aa()
    {
        cout << "aa is completed." << endl;
    }
};

int main(int argc, char **argv)
{
    aa *p = new aa(9);
    cout << p->id << endl;
    delete p;

    cout << "" << endl;

    aa *q = (aa *) malloc(sizeof(aa));
    cout << q->id << endl;//随机数表明构造函数未调用
    free(q);//析构函数未调用
}
运行结果：

aa is constructed.
9
aa is completed.

3018824

堆空间不伴随函数动态释放，程序员要自主管理

//============================================================================
// Name        : main.cpp
// Author      : ShiGuang
// Version     :
// Copyright   : sg131971@qq.com
// Description : Hello World in C++, Ansi-style
//============================================================================

#include <iostream>
#include <string>
using namespace std;

class aa
{
public:
    aa(int a = 1)
    {
        cout << "aa is constructed." << endl;
        id = a;
    }
    ~aa()
    {
        cout << "aa is completed." << endl;
    }
    int id;
};

aa & m()
{
    aa *p = new aa(9);
    delete p;
    return (*p);
}

int main(int argc, char **argv)
{
    aa & s = m();
    cout << s.id;// 结果为随机数，表明被释放
}
运行结果：

aa is constructed.
aa is completed.
4984904
函数内部的申请空间要及时释放，否则容易造成内存重复申请和内存迷失。

//============================================================================
// Name        : main.cpp
// Author      : ShiGuang
// Version     :
// Copyright   : sg131971@qq.com
// Description : Hello World in C++, Ansi-style
//============================================================================

#include <iostream>
#include <string>
using namespace std;

class aa
{
public:
    aa(int a = 1)
    {
        cout << "aa is constructed." << endl;
        id = a;
    }
    ~aa()
    {
        cout << "aa is completed." << endl;
    }
    int id;
};

void p()
{
    aa *s = new aa[9999];
}

int main(int argc, char **argv)
{
    for (;;)
        p();
    return 0;
}

摘自 sg131971的学习笔记

补充：软件开发 , C++ ,