Question

Suppose there are two struct A and B. They have a common struct C.
I would like to know if it is safe to call reinterpret_cast to A or B to C.
if not, is there any way to do so without any performance impact?

struct C
{
    string m_c1;
    int32_t m_c2;
    double m_c3;
    string m_c4;
};

struct A
{
    C m_a1;
    string m_a2;
    int32_t m_a3;
};

struct B
{
    C m_b1;
    string m_b2;
    int32_t m_b3;
    double m_b4;
};
int main(int argc,char *argv[])
{
        A a;
        a.m_a1.m_c1="A";
        a.m_a1.m_c4="AA";

        B b;
        b.m_b1.m_c1="B";
        b.m_b1.m_c4="BB";

        C* pc = reinterpret_cast<C*>(&a);
        cout << pc->m_c1 << " " << pc->m_c4 << endl;

        pc = reinterpret_cast<C*>(&b);
        cout << pc->m_c1 << " " << pc->m_c4 << endl;

        return 1;
}

Answer 1

Why dont you inherit both A,B from C and then use static_cast instead? Should be safer/cleaner.

Indeed in your case, you shouldnt need a cast at all, you should be able to assign A or B ptrs to a C*