#include <iostream>

struct A
{
    int a = 0;
    void* ptr = nullptr;
    char data[16] {1,2,3,4};
};

int main()
{
    A a {0, nullptr, {1,2,3,4}};
    
    for (int i = 0; i < sizeof A::data; ++ i)
    {
       std::cout << int(a.data [i]) << ' ';
    }
}