C string/char*/char[]互相转换

#include"stdio.h"
#include "stdlib.h"
#include "string.h"
#include "string"
#include "c_char_string.h"

using namespace std;

int main()
{
    /*char[] -> char* */
	charS_2_charX();
	/*char* -> char[]*/
	charX_2_charS();
	/*string -> char* */
	string_2_charX();
	/*char* -> string */
	charX_2_string();
	/*string -> charS */
	string_2_charS();
	/*charS -> string */
	charS_2_string();
	return 0;
}

void charX_2_charS()
{
	char *c_x = "nihao";
	char s_z[8];
	int s_i = 0;
	while (*c_x != '\0')
	{
		s_z[s_i] = *c_x;
		s_i++;
		c_x++;
	}
	s_z[s_i] = '\0';
	printf("\nchar * -> char[]\n");
	printf("%s\n", s_z);
}

void charS_2_charX()
{
	char s_z[6] = { 'n','i','h','a','o' ,'\0'};
	char *c_x ;
	c_x = (char *)malloc(sizeof(char) * (sizeof(s_z) + 1));
	if (c_x == NULL)
	{
		return;
	}
	strcpy(c_x, s_z);
	printf("\nchar[] -> char*\n");
	printf("%s\n", c_x);
}

void string_2_charX()
{
	string str_s = "nihao";
	const char* const_c_x;
	const_c_x = str_s.c_str();
	char *c_x = (char *)(const_c_x);
	printf("\nstring -> char*\n");
	printf("%s\n", c_x);
}

void charX_2_string()
{
	char *c_x = "nihao";
	string str_s;
	str_s = c_x;
	printf("\nchar* -> string\n");
	printf("%s\n", str_s.c_str());
}

void string_2_charS()
{
	string str_s = "nihao";
	char s_z[6];
	int str_len = str_s.length();
	int i;
	for (i = 0; i < str_len; i++)
	{
		s_z[i] = str_s[i];
	}
	s_z[i] = '\0';
	printf("\nstring* -> charS \n");
	printf("%s\n", s_z);
}

void charS_2_string()
{
	char s_z[6] = { 'n','i','h','a','o' };
	string str_s;
	str_s = s_z;
	printf("\ncharS -> string\n");
	printf("%s\n", str_s.c_str());
}

c_char_string.h：内容如下

void charX_2_charS();
void charS_2_charX();
void string_2_charX(); 
void charX_2_string();
void string_2_charS();
void charS_2_string();