Memory in use issue using marmalade SDK - c++

Question

I have a bullet class. and I try to instantiate it by the following code:
I always get an assertion that there is a memory that is in use.. why?
In another class called ship:
if (g_Input.isKeyDown(s3eKeySpace))// && Canfire)
{
Bullet *bullet = new Bullet();
bullet->Init(SHIP_BULLET);
bullet->setPosition(Position.x, Position.y - 20);
Bullets->push_back(bullet);
Canfire = false;
}
This is called each frame which causes memory still in usage:
for (list<Bullet*>::iterator it = Bullets->begin(); it != Bullets->end();)
{
(*it)->Update(dt);
if ((*it)->IsDestroyed)
{
Canfire = true;
it = Bullets->erase(it);
}
else
{
it++;
Canfire = false;
}
}
the destructor of the Ship class
Ship::~Ship()
{
for (std::list<Bullet*>::iterator it = Bullets->begin(); it != Bullets->end(); ++it)
delete *it;
delete Bullets;
}
class Bullet
{
public:
Bullet();
~Bullet();
public:
void Init(BulletTypes bulletType);
void Update(float dt);
void Render();
CIw2DImage* Image; // curr image
}
void Bullet::Init(BulletTypes bulletType)
{
BulletType = bulletType;
if (BulletType == SHIP_BULLET)
{
Image = Iw2DCreateImage("textures/ship_bullet.png");
if (Image == nullptr)
return;
}
}
Bullet::~Bullet()
{
delete Image;
}

Answer 1

Executing this code causes the leak:
for (list<Bullet*>::iterator it = Bullets->begin(); it != Bullets->end();)
{
(*it)->Update(dt);
if ((*it)->IsDestroyed)
{
Canfire = true;
it = Bullets->erase(it);
}
else
{
it++;
Canfire = false;
}
}
What is going on is basically you removing a dynamically allocated element from a container, losing any reference to it thus you cannot free its memory anymore. Calling Ship destructor only frees the elements that are currently in the list, excluding the ones removed in the iteration, obviously.
I suggest this as a fix:
for (list<Bullet*>::iterator it = Bullets->begin(); it != Bullets->end();)
{
(*it)->Update(dt);
if ((*it)->IsDestroyed)
{
Canfire = true;
delete *it; // it now points to invalid address
it = Bullets->erase(it);
}
else
{
it++;
Canfire = false;
}
}
Another option would be to store all removed bullets in some other container in class Ship in case that a Bullet can be referenced after it was destroyed. Problem with this idea is that you have alot of destroyed bullets taking up memory and have to come up with a solution on how to remove them once they really prove useless.
If you get stuck with that, using std::shared_ptrs instead of raw pointers in the list could solve your issue (for slight performance penalty).