void function1(struct_a *a, struct_b *b, int i)
{
    cout << "abc";
}

void function1(struct_c *c, struct_d *d)
{
    cout << "def";
}

int main()
{
    struct_a *a = (struct_a *)<some-data-a>;
    struct_b *b = (struct_b *)<some-data-b>;
    struct_c *c = (struct_c *)<some-data-c>;
    struct_d *d = (struct_d *)<some-data-d>;

    function1(a, b, 1);
    return 0;
}