C++动态分配指针和数组

g++.png

1. 使用new对指针进行动态分配空间
   可以看到指针的地址和内存所在地址不相同（指针存储在自动分配区域，指针指向空间存储在动态空间）
   对指针和动态数组首个元素进行+1操作。
   指针是大小为8字节，对自身加一自然会对地址增加自身大小；
   动态数组首个元素指针结果为2，原因是short类型为2字节

#include <iostream>

int main()
{
        short *tell = new short[5];
        tell[0] = 1; tell[1] = 2; tell[2] = 3; tell [3] = 4; tell[4] = 5;

        std::cout << "short *tell = new short[5]\n";

        std::cout << "&tell = " << &tell << std::endl;
        std::cout << "&tell + 1 = " << &tell + 1 << std::endl;
        std::cout << "sizeof(&tell) = " << sizeof(&tell) << std::endl;

        std::cout << "&tell[0] = " << &tell[0] << std::endl;
        std::cout << "tell = "  << tell << std::endl;
        std::cout << "tell + 1 = " << tell + 1 << std::endl;
        std::cout << "sizeof(tell) = " << sizeof(tell) << std::endl;

        std::cout << "*tell = " << *tell << std::endl;
        std::cout << "*(tell + 1) = " << *(tell + 1) << std::endl;

        delete [] tell;
 }
//运行结果：
    short *tell = new short[5]
    &tell = 0x7ffd499400f0
    &tell + 1 = 0x7ffd499400f8
    sizeof(&tell) = 8
    &tell[0] = 0x1d43c20
    tell = 0x1d43c20
    tell + 1 = 0x1d43c22
    sizeof(tell) = 8
    *tell = 1
    *(tell + 1) = 2

2. 数组指针
   数组名指向main函数栈内存中的第一个元素
   对数组名+1操作和数组指针+1操作结果不同
   数组名为首元素地址，对其+1则增加一个short的字节；
   对数组地址+1则增加数组长度即5个short的长度，10

#include <iostream>

int main()
{
        short tell[5];
        tell[0] = 1; tell[1] = 2; tell[2] = 3; tell [3] = 4; tell[4] = 5;

        std::cout << "short tell[5]\n";

        std::cout << "&tell = " << &tell << std::endl;
        std::cout << "&tell + 1 = " << &tell + 1 << std::endl;
        std::cout << "sizeof(&tell) = " << sizeof(&tell) << std::endl;

        std::cout << "&tell[0] = " << &tell[0] << std::endl;
        std::cout << "tell = "  << tell << std::endl;
        std::cout << "tell + 1 = " << tell + 1 << std::endl;
        std::cout << "sizeof(tell) = " << sizeof(tell) << std::endl;

        std::cout << "*tell = " << *tell << std::endl;
        std::cout << "*(tell + 1) = " << *(tell + 1) << std::endl;
}
//结果
  short tell[5]
  &tell = 0x7ffffd379e20
  &tell + 1 = 0x7ffffd379e2a
  sizeof(&tell) = 8
  &tell[0] = 0x7ffffd379e20
  tell = 0x7ffffd379e20
  tell + 1 = 0x7ffffd379e22
  sizeof(tell) = 10
  *tell = 1
  *(tell + 1) = 2

综上可以看出，数组和动态分配的指针大小不同。动态分配的数组指针大小为普通short指针大小8字节，而数组指针大小为数组大小5*2=10个字节。