Do pointers created in a function block get deleted? c++

Question

I am trying to generate a code that is a phonebook, I have a person class with a name and number. I am generating the names and then later writing them to a file.

I create a vector of person pointers and then assign them in a separate function. I keep getting NULL though after the code executes. If I create this vector of person pointers and then pass it to a function that generates the person objects when the function ends do I lose these references? Shouldn't the new objects be created in the heap and still be there if they are referenced back to the vector? I would think the pointers get created in the stack of main and still be viable and then just get referenced to a place in the heap so I don't understand why I get NULL for all my values?

Here is my code:

int main(){
    vector<Person*> people(10);

    phone_gen(people);

   return 1;

}

void phone_gen(vector<Person*> a){

        cout << "Numbers generated \n";

        a[0] = new Person("Mike", 6044219901);
        a[1] = new Person("John" , 6041929402);
        a[2] = new Person("Ted"  , 6044211234);
        a[3] = new Person("Stern", 6044211233);
        a[4] = new Person("fred ", 6044211111);
        a[5] = new Person("ben  ", 6049999999);
        a[6] = new Person("timmy", 6044211113);
        a[7] = new Person("lowe ", 6044210908);
        a[8] = new Person("Glenn", 6044217112);
        a[9] = new Person("Danny", 6044211112);


    }

Answer 1

The problem here is that you pass the argument by value , meaning the vector gets copied and the function only works on the copy and not the original.

You should pass the argument by reference instead:

void phone_gen(vector<Person*>& a)
//                            ^
//                            |
//          Note ampersand here

Answer 2

In order to fill people vector in the phone_get function, you have to get it by reference:

void phone_get(vector<Person*>& a){...}

Otherwise, you will see 10 default constructed objects in the vector (10 null pointers)