#pragma pack(1)
struct MyStruct
{
    int a;
    bool b;
    const char* c;
};

void test(MyStruct* p)
{
    MyStruct* s = p;
    s->a = 0x1234;
    s->b = true;
    s->c = "Hello world";
}

int main()
{
    MyStruct s;
    test(&s);
    return s.a;
}

struct MyStruct
{
    int a;
    bool b;
    const char* c;
};