c++官方文档-动态内存

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

int main()
{

    /**
     * 动态内存
     * url: http://www.cplusplus.com/doc/tutorial/dynamic/
     * 关键字new用于在程序运行时动态开辟内存,内存开辟在堆空间.
     * 此关键字不保证内存一定开辟成功,如果开辟失败,抛出bad_alloc异常,如果此异常没有指定的异常handle,程序就会终止.
     */
    int * foo = nullptr;
    foo = new int[5];  // if allocation fails, an exception is thrown
    //另一个方法是nothrow,使用此方法,内存开辟失败,返回null,而不是抛出异常让程序终止
    //此方法声明在new文件头内
    foo = new (std::nothrow) int[5];
    if(foo == nullptr)
    {

    }
    else
    {

        foo[0] = 1;
        cout << foo[0] << endl;
        delete[] foo;
    }
    //内存不在使用,删除内存,delete
    int i, n;
    int *p;
    cout << "how many numbers would you like to type?\n";
    cin >> i;
    cout << "i=" << i << endl;
    p = new (std::nothrow) int[i];
    if(p == nullptr)
    {
        cout << "Error: memory could not be allocated" << endl;
    }
    else
    {
        for(n = 0; n < i; n++)
        {
            cout << "enter number:";
            cin >> p[n];
        }
        cout << "you have enter:";
        for(n = 0; n < i; n++)
            cout << p[n] << ", ";
        delete[] p;
    }
    return 0;
}