sizeof 可變參數的模版特化 C++ templa

1 sizeof 測量函數傳回值大小的時候，是不執行函數的

2 可變參數清單可以沒有一個參數，隻是不能用參數了（這句不知到對不對）

3 可變參數清單再模版執行個體化過程中比較弱；

#include <iostream>

using namespace std;



long long fun1(...)
{
	cout << "in fun1 class" << endl;
	return 3l;
}

class MyClass{
public:
	typedef int x;
};



template <typename T>
char tmpfun1(typename T::x);

template <typename T>
long long tmpfun1(...);

#define has_member_of_X(T) (sizeof(tmpfun1<T>(0)) == 1)

int main()
{
	fun1(1);
	fun1("adfdf");
	cout << "sizeof(fun1) = " << sizeof(fun1(2)) << endl;

	if(has_member_of_X(int))
		cout << "int has type member x" << endl;
	else
		cout << "int has not member x" << endl;

	if(has_member_of_X(MyClass))
		cout << "MyClass has type member x"<< endl;
	else
		cout << "MyClass has not type member x" << endl;

	int i;
	cin >> i;
}