注意空域。unsigned默认是4个字节。
1 #include <iostream> 2 3 using namespace std; 4 struct B1{ 5 unsigned a:4; 6 unsigned b:4; 7 }; 8 9 struct B2{ 10 unsigned a:4; 11 unsigned :0; 12 unsigned b:4; 13 }; 14 15 struct B3{ 16 unsigned char a:4; 17 unsigned char b:4; 18 }; 19 20 struct B4{ 21 unsigned char a:4; 22 unsigned :0; 23 unsigned char b:4; 24 }; 25 26 struct B5{ 27 unsigned char a:4; 28 unsigned char b:4; 29 unsigned :0; 30 }; 31 32 struct B6{ 33 unsigned char a:4; 34 unsigned char b:5; 35 }; 36 int main(int argc, char** argv) { 37 cout << "sizeof(B1): " << sizeof(B1) << endl; 38 cout << "sizeof(B2): " << sizeof(B2) << endl; 39 cout << "sizeof(B3): " << sizeof(B3) << endl; 40 cout << "sizeof(B4): " << sizeof(B4) << endl; 41 cout << "sizeof(B5): " << sizeof(B5) << endl; 42 cout << "sizeof(B6): " << sizeof(B6) << endl; 43 return 0; 44 }
输出：
1 root@xxj-VirtualBox:~/interview# ./bitfield 2 sizeof(B1): 4 3 sizeof(B2): 8 4 sizeof(B3): 1 5 sizeof(B4): 5 6 sizeof(B5): 4 7 sizeof(B6): 2