#include <iostream>

#include <stdio.h>

#include <stdlib.h>

using namespace std;

//测试大小端的宏

static union {char c[4];unsigned int l;} endian_test = {{'l','?','?','b'}};

#define ENDIANNESS ((char)endian_test.l)

#pragma pack(4)

struct MyStruct{

	char m_char;

	long  m_int;

};

class TestArray

{

public:

	TestArray()

	{

		cout<<"this is construct"<<endl;

	}

 ~TestArray()

 {

	cout<<"this is destruct"<<endl;

 }

}；

int main()

{

  ///测试new一个数组时的指针前几个个字节是保留了 数组的长度

       //当以下数组是int 或者MyStruct 时 向前取的值 完全是0

      //  所以得出只对 自定义的class 才有意义

	TestArray* pArray =  new TestArray[257];

	int* pPoint = (int*)pArray  - 2;

	cout<<"the pre 4 byte's value is "<< *pPoint<<endl;

	printf("the pre  address is %p\n",pPoint);

	printf("the array  address is %p\n",pArray);

	char* pChar = (char*)pPoint;

	int array[8] = {0};

	for(int i = 0 ; i < 8; ++i)

	{

		array[i] = *pChar;

		++pChar;

		cout<<"the " << i <<" byte 's value is " << array[i]<<endl;

	}

    return 0;

}