菜鸟求助，为何这样写 可以获取map的value 结果b1就是b

Question

struct s_A
{...};
struct s_B
{...};

map<s_A,s_B> M;
s_A a;
s_B b;
M[a] = b;
s_B b1 = (s_B*)&a;

Answer 1

你这符号什么的，还有逻辑看是不是错了。