C++ 如何判断一个类型是POD

在C++11之前，可以使用std::is_pod模板类来判断一个类型是否是POD（Plain Old Data）类型。示例如下：

#include 
#include 

struct A {
    int x;
};

struct B {
    int x;
    int y;
};

int main() {
    bool is_A_pod = std::is_pod::value;
    bool is_B_pod = std::is_pod::value;

    std::cout << "A is POD: " << is_A_pod << std::endl;
    std::cout << "B is POD: " << is_B_pod << std::endl;

    return 0;
}

#include 
#include 

struct A {
    int x;
};

struct B {
    int x;
    int y;
};

int main() {
    bool is_A_pod = std::is_standard_layout::value && std::is_trivial::value;
    bool is_B_pod = std::is_standard_layout::value && std::is_trivial::value;

    std::cout << "A is POD: " << is_A_pod << std::endl;
    std::cout << "B is POD: " << is_B_pod << std::endl;

    return 0;
}