指针常量和常量指针的几种改变方式

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本文详细解析了C++中指针的基本概念，包括常量指针、指针常量的区别及应用，并通过实例演示了不同类型的指针如何操作变量。

// 常量指针

int const * p;

const int * p;

// 指针常量

int * const p;

#include <iostream>
using namespace std;

int main()
{
	char str1[] = "123"; //程序运行前就分配的内存空间
	char str2[] = "123";
	cout << (str1 == str2) << endl; // 0, 两个字符数组分配的地址空间肯定不一样

	char *str3 = "123";
	char *str4 = "123";
	const char *str5 = "123";
	 
	cout << "str5= " << str5 << endl;  
	char const *str6 = "123";
	char * const str7 = "123";

	cout << (str3 == str4) << endl; // 1
	cout << (str3 == str5) << endl; // 1
	cout << (str3 == str6) << endl; // 1
	cout << (str3 == str7) << endl; // 1

	int a = 200;
	const int * ppt = &a;
	cout << "ppt= " << *ppt << endl;
	
	int b = 100;
	ppt = &b; //指针ppt本身的值可以改变
	cout << "ppt= " << *ppt << endl;

	//*ppt = b;
	int * const cht = &a;
	cout << "cht= " << *cht << endl;
	*cht = b; // cht指向的对象值可以改变
	cout << "cht= " << *cht << endl;

	int const* const thr = &a;
	cout << "thr= " << *thr << endl;
	a = 900;  // 通过改变a的值来改变thr指向对象的值
	cout << "thr= " << *thr << endl;
	
	return 0;
}