天杀的内存对齐

#include<iostream> using namespace std; struct information { float f; int i; char c; }; struct info { double b; char c; }; int main() { double b; char c; cout << "sizeof( struct information) = " << sizeof ( struct information) << endl; cout << "sizeof( struct info) = " << sizeof( struct info) << endl; cout << "sizeof(b) = " << sizeof b << endl; cout << "sizeof (c) = " << sizeof c << endl; return 0; }

运行结果是：

sizeof( struct information) = 12
sizeof( struct info) = 16
sizeof(b) = 8
sizeof (c) = 1
请按任意键继续. . .

#include<iostream> using namespace std; class base { public: base(){ cout << "this is construction of base " << endl ; } ~base(){ cout << " this is destruction of base " << endl ; } private: int a ; float f ; }; class derived: public base{ public: derived(){ cout << " this is construction of derived" << endl ; } ~derived(){ cout << "this is destruction of derived " << endl ; } private: double d; char c; static int tp ; void fun(){ int a ; } }; int main(){ cout << "sizeof(class base) = " << sizeof(base) << endl ; cout << "sizeof(class derived)=" << sizeof(derived) << endl ; return 0 ; }

其结果是：

sizeof(class base) = 8
sizeof(class derived)=24
请按任意键继续. . .

关于内存对齐还有一点要注意的是：

sizeof不计算static变量，函数不占内存，但是虚函数就占内存了，而且无论多少虚函数，都只占4个字节。Just because there haveonly one vptr.