Возврат строк из функций

std::string func1()
{
    int n = rand() % 100;
    std::cout << "func1() gen: " << n << std::endl;
    std::string s = "number: " + std::to_string(n);
    return s;
}
 
std::string& func2()
{
    int n = rand() % 100;
    std::cout << "func2() gen: " << n << std::endl;
    static std::string s = "number: " + std::to_string(n);
    return s;
}
 
const std::string& func3()
{
    int n = rand() % 100;
    std::cout << "func3() gen: " << n << std::endl;
    static std::string s = "number: " + std::to_string(n);
    return s;
}
 
std::string func4()
{
    int n = rand() % 100;
    std::cout << "func4() gen: " << n << std::endl;
    static std::string s = "number: " + std::to_string(n);
    return s;
}
 
int main()
{
    std::string s1 = func1();
    std::string s1b = func1();
    std::string s2 = func2();
    std::string s2b = func2();
    std::string s3 = func3();
    std::string s3b = func3();
    std::string s4 = func4();
    std::string s4b = func4();
 
    std::cout << s1.c_str() << std::endl;
    std::cout << s1b.c_str() << std::endl;
    std::cout << s2.c_str() << std::endl;
    std::cout << s2b.c_str() << std::endl;
    std::cout << s3.c_str() << std::endl;
    std::cout << s3b.c_str() << std::endl;
    std::cout << s4.c_str() << std::endl;
    std::cout << s4b.c_str() << std::endl;
}

int func1()
{
    static int n;
    n = rand() % 100;
    std::cout << "func1() rand = " << n << std::endl;
 
    return n;
}
 
int func2()
{
    static int n = rand() % 100;
    std::cout << "func2() rand = " << n << std::endl;
 
    return n;
}
 
int main()
{
    for (int i = 0; i < 5; i++)
    {
        int n = func1();
        std::cout << n << std::endl;
    }

    static std::string s = "number: " + std::to_string(n);
 
    static std::string s;
    s = "number: " + std::to_string(n);