一个C++关于成员变量偏移地址的小Trick

Mon, 26 Aug 2013 14:16:37 +0000

今天看到一个小例子，发现了一个小trick。见代码：

#include 
#include 

class base_1
{
public:
 int a;
};

class base_2
{
public:
 int b;
};

class base_3: public base_1, public base_2
{
public:
 int c;
};

int main(int argc, char* argv[]) {

 printf("&base_1::a = %p\n", &base_1::a);
 printf("&base_2::b = %p\n", &base_2::b);
 printf("&base_3::a = %p\n", &base_3::a);
 printf("&base_3::b = %p\n", &base_3::b);
 printf("&base_3::c = %p\n", &base_3::c);


 base_3 t;
 t.a = 1;
 t.b = 2;
 t.c = 3;

 typedef int (base_3::*tip);
 tip pm = NULL;

 printf("base_3::a = %d\n", t.base_3::a);
 printf("base_3::b = %d\n", t.base_3::b);
 printf("base_3::c = %d\n", t.base_3::c);

 pm = &base_3::a;
 printf("base_3::a(%p) = %d(ptr)\n", pm, t.*pm);
 pm = &base_3::b;
 printf("base_3::b(%p) = %d(ptr)\n", pm, t.*pm);
 pm = &base_3::c;
 printf("base_3::c(%p) = %d(ptr)\n", pm, t.*pm);

 return 0;
}

猜猜看这个代码输出什么？答案是：

Trick on I'm OWenT

一个C++关于成员变量偏移地址的小Trick