Question

I’ve a method in a class that get’s a pointer to another object (of a different class)and adds an object (of another different class) to a vector that is a member variable of the first object (the one that is passed as a parameter). This is the code:

ObstacleManager::ObstacleManager(Application *lApp)
{
    app=lApp;
    GLfloat obstacleVerts[12]={
    -0.1f,-0.2f,0.0f,
    0.1f,-0.2f,0.0f,
    -0.1f,0.2f,0.0f,
    0.1f,0.2f,0.0f
    };
    StandardObstacle obstacle(obstacleVerts,-0.7f,0.0f,4);
    obstacle.manager=this;
    lApp->characters.push_back(&obstacle);
}

I think the problem is that the obstacle object gets released when it shouldn’t, because if I change the code and create the obstacle with a “new” (if you create an object with new you have to manually delete it, don’t you?) It works. Like this:

ObstacleManager::ObstacleManager(Application *lApp)
{
    app=lApp;
    GLfloat obstacleVerts[12]={
    -0.1f,-0.2f,0.0f,
    0.1f,-0.2f,0.0f,
    -0.1f,0.2f,0.0f,
    0.1f,0.2f,0.0f
    };
    StandardObstacle *obstacle=new StandardObstacle(obstacleVerts,-0.7f,0.0f,4);
    obstacle->manager=this;
    lApp->characters.push_back(obstacle);
}

Is there a way to prevent this from happening?

Answer 1

You are passing the address of a local object to the vector, the local object does not exist once the constructor returns and your vector then has a pointer which points to invalidated memory.

You will have to make the object persist, possible ways are:
Just push the object by value or
Use dynamically allocated object but instead of raw pointer use a smart pointer like shared_ptr as the vector element type.