对C++下struct 和 类默认继承的认识

#include <iostream>
using namespace std;
struct  struct1{
    int data1 ;
    double data2 ;
    struct1(){
        (*this).data1 = data1 ;
        (*this).data2 = data2 ;
        cout<<"this is output by struct1 function !";
    }
    public : 
    void privateFunc(){
        cout<<"this is private function , so this massage should never show in console ! \n";
    }
};
struct struct2 : struct1{
    /*
    
    according the result in console , we can get the conclusion :
    
    the default inherit method of struct is public 

    */
};
class class1 : public  struct1 {
    /*
    
    if ignore 'public' identifiers , compile will show that privateFunc() in 35 line 
    
    can't access, this indicate that it is private inhert when subclass is a struct. 
    
    */
    string name ;
    public :
    class1(){
        name = "i'm a class !";
        cout<<"this is output by class1 !";
    }
};
class class2{
    public :
    void showClass2(){
        cout<<"this is output by class2 ! \n ";
    }
};
class class3 : class2{
    /*

    according to the result : showClass2 can't accessiable can prove class default 
    
    inherit method is private 

    */
};
struct struct4 : class2{
    /*

    default inherit is public 
    
    */
};
class class4 : struct1 {
    /*

    default inherit is private 
    */
}
int main(){
    //struct2 onestruct2 ;
    //onestruct2.privateFunc();    
    /* test class default inherit */
    //class3 * oneclass3 = class3;
    //oneclass3->showClass2();
    /* test struct inherit class */
    //struct4 onestruct4 ;
    //onestruct4.showClass2();
    class4 * oneclass4;
    oneclass4->privateFunc();
    return 0;
}