C++ 結構體嵌套、空結構體和空類

程序編寫環境：

編輯器：UltraEdit18編譯器：g++4.4.3、gcc4.4.3編譯環境：ubuntu10.0

作業練習：

簡單的C++結構體嵌套的使用，以及結構體大小和空結構體，使用g++編譯

#include //cout
#include 

#define NSIZE 128
using namespace std;

struct SubStruct
{
	char *str;
	double dVal;
};
#if 0
struct MyStruct
{
	void Hello();
	int ID;
	char *name;
	struct SubStruct sub;		
};

#endif //0

typedef struct MyStruct
{
	void Hello();
	int ID;
	char *name;
	struct SubStruct sub;		
}mystruct;

void MyStruct::Hello()
{
	cout << "hello struct, nice to me you!" << endl;
	cout << "my name is:" << name << '\t' << "my id is:" << ID << endl;
	cout << sub.str << endl;
}

/*結構體X、Y、Z*/
struct X
{
	int XID;
	char Xsymb;
	float Xf;
	
};

struct Y
{
	long Ysize;
	int YID;
	double Yd;
	
};

struct Z
{
	char Zsymb;
	double Zd;
	int ZID;
};

struct Empty
{
	
};
/****************/

/*空類大小*/
class CMyclass
{
	
};

/***********/
int main()
{
	
	MyStruct A;//mystruct C++中不需要typedef或struct MyStruct xxx
	A.ID = 10;
	A.name = (char *)"lqf";
	A.sub.str = (char *)"I am substruct";
	A.Hello();
	cout << A.sub.str << endl;

#if 0
	/*計算結構體X、Y、Z和MyStruct大小*/
	cout << "size of struct MyStruct:" << sizeof(struct MyStruct) << endl;//20
	cout << "size of struct X:" << sizeof(struct X) << endl;//12
	cout << "size of struct Y:" << sizeof(struct Y) << endl;//16
	cout << "size of struct Z:" << sizeof(struct Z) << endl;//16
	cout << "size of struct Empty:" << sizeof(struct Empty) << endl; //1
	cout << "size of class Empty:" << sizeof(class CMyclass) << endl; //1
	/**********************/	
#endif //0	

	return 0;
}

採用gcc編譯：

#include 

#define NSIZE 128

struct SubStruct
{
	char *str;
};

struct MyStruct
{
	int ID;
	char *name;
	struct SubStruct sub;		
};


/*結構體X、Y、Z*/
struct X
{
	int XID;
	char Xsymb;
	float Xf;
	
};

struct Y
{
	long Ysize;
	int YID;
	double Yd;
	
};

struct Z
{
	char Zsymb;
	double Zd;
	int ZID;
};

struct Empty
{
	
};
/****************/
int main()
{

	/*計算結構體X、Y、Z大小*/
	printf("size of struct X:%d\n",sizeof(struct X));
	printf("size of struct Y:%d\n",sizeof(struct Y));
	printf("size of struct Z:%d\n",sizeof(struct Z));
	printf("size of struct Empty:%d\n",sizeof(struct Empty));
	/**********************/	

	return 0;
}

空類或空結構體的存在，一般是起佔位的作用，在內存中開一塊空間，以便後續的開發。