Saving a pointer to heap created in the local area

Question

I made a "Planet" class and am trying to initialize a vector array based on this class in the client file of my project.

bool addPlanet(std::vector<Planet>& planets, std::string filePath)
{
    std::ifstream infile(filePath, std::ios_base::in);
 
    if (infile.fail()) {
        // File could not be opened
        return false;
    }
 
    std::string planetName, imagePath;
    float posX, posY, rotationZ, scaleX, scaleY;
    unsigned long long int planetMass;
 
    while (infile >> planetName >> posX >> posY >> rotationZ >> scaleX >> scaleY >> planetMass >> imagePath)
    {
        Planet* newPlanet = new Planet(sf::Vector2f(posX, posY), rotationZ, sf::Vector2f(scaleX, scaleY), planetMass, imagePath);
        
        planets.push_back(*newPlanet);
    }
 
    infile.close();
 
    return true;
}

But I can't figure out if the following piece of code is causing a memory leak:

while (infile >> planetName >> posX >> posY >> rotationZ >> scaleX >> scaleY >> planetMass >> imagePath)
{
    Planet* newPlanet = new Planet(sf::Vector2f(posX, posY), rotationZ, sf::Vector2f(scaleX, scaleY), planetMass, imagePath);
        
    planets.push_back(*newPlanet);
}

I think about it like this:

I allocate dynamic memory for a new instance of the "Planet" class. Using the push_back method — the vector 's internal iterator becomes a second pointer to the new instance. And when we exit the loop, there is still a pointer to the newly allocated heap in vector .

Do I understand everything correctly or am I just bad at reading the documentation?

Answer 1

Your code creates a Planet object:

Planet* newPlanet = new Planet(sf::Vector2f(posX, posY), rotationZ, sf::Vector2f(scaleX, scaleY), planetMass, imagePath);

Then, it copies this object into the vector:

planets.push_back(*newPlanet);

But it doesn't release the memory corresponding to the original object. The vector only owns the copy, not the original Planet object.

---

You can simply solve this issue but not using new at all:

Planet newPlanet(sf::Vector2f(posX, posY), rotationZ, sf::Vector2f(scaleX, scaleY), planetMass, imagePath);
planets.push_back(std::move(newPlanet));

Here, it is the code block the one who owns the newPlanet object.

However, you may want to directly use std::vector::emplace_back() instead of new and push_back():

planets.emplace_back(sf::Vector2f(posX, posY), rotationZ, sf::Vector2f(scaleX, scaleY), planetMass, imagePath);

This way, the vector acquires the ownership of the single Planet object that is created.