Vector keeps throwing assert failures

Question

 

Ok i have a very simple game engine that i made using VC++ 2003 which ran perfectly fine. Recently i moved over to VC++ 2008 and now every time the program is run it creates assert faliures withing 2 seconds of the vector in it being used.

 

Here is all the relevant source code.

 

BOOL GameEngine::CheckSpriteCollision(Sprite* pTestSprite)

{

// See if the sprite has collided with any other sprites

vector<Sprite*>::iterator siSprite;

for (siSprite = m_vSprites.begin(); siSprite != m_vSprites.end(); siSprite++)

{

// Make sure not to check for collision with itself

if (pTestSprite == (*siSprite))

continue;

// Test the collision

if (pTestSprite->TestCollision(*siSprite))

// Collision detected

return SpriteCollision((*siSprite), pTestSprite);

}

// No collision

return FALSE;

}

 

void GameEngine::AddSprite(Sprite* pSprite)

{

// Add a sprite to the sprite vector

if (pSprite != NULL)

{

// See if there are sprites already in the sprite vector

if (m_vSprites.size() > 0)

{

// Find a spot in the sprite vector to insert the sprite by its z-order

vector<Sprite*>::iterator siSprite;

for (siSprite = m_vSprites.begin(); siSprite != m_vSprites.end(); siSprite++)

if (pSprite->GetZOrder() < (*siSprite)->GetZOrder())

{

// Insert the sprite into the sprite vector

m_vSprites.insert(siSprite, pSprite);

return;

}

}

// The sprite's z-order is highest, so add it to the end of the vector

m_vSprites.push_back(pSprite);

}

}

void GameEngine:rawSprites(HDC hDC)

{

// Draw the sprites in the sprite vector

vector<Sprite*>::iterator siSprite;

for (siSprite = m_vSprites.begin(); siSprite != m_vSprites.end(); siSprite++)

(*siSprite)->Draw(hDC);

}

void GameEngine::UpdateSprites()

{

// Update the sprites in the sprite vector

RECT rcOldSpritePos;

SPRITEACTION saSpriteAction;

vector<Sprite*>::iterator siSprite;

for (siSprite = m_vSprites.begin(); siSprite != m_vSprites.end(); siSprite++)

{

// Bail if sprite is not valid

if((*siSprite) == NULL){

continue;

}

// Save the old sprite position in case we need to restore it

rcOldSpritePos = (*siSprite)->GetPosition();

// Update the sprite

saSpriteAction = (*siSprite)->Update();

// Handle the SA_ADDSPRITE sprite action

if (saSpriteAction & SA_ADDSPRITE)

// Allow the sprite to add its sprite

AddSprite((*siSprite)->AddSprite());

// Handle the SA_KILL sprite action

if (saSpriteAction & SA_KILL)

{

// Notify the game that the sprite is dying

SpriteDying(*siSprite);

// Kill the sprite

delete (*siSprite);

*siSprite = NULL;

m_vSprites.erase(siSprite);

siSprite--;

continue;

}

// See if the sprite collided with any others

if (CheckSpriteCollision((*siSprite))) //<- Normally Crashes Here

// Restore the old sprite position

(*siSprite)->SetPosition(rcOldSpritePos);

}

}

void GameEngine::CleanupSprites()

{

// Delete and remove the sprites in the sprite vector

vector<Sprite*>::iterator siSprite;

for (siSprite = m_vSprites.begin(); siSprite != m_vSprites.end(); siSprite++)

{

delete (*siSprite);

m_vSprites.erase(siSprite);

siSprite--;

}

}

Sprite* GameEngine::IsPointInSprite(int x, int y)

{

// See if the point is in a sprite in the sprite vector

vector<Sprite*>::reverse_iterator siSprite;

for (siSprite = m_vSprites.rbegin(); siSprite != m_vSprites.rend(); siSprite++)

if (!(*siSprite)->IsHidden() && (*siSprite)->IsPointInside(x, y))

return (*siSprite);

// The point is not in a sprite

return NULL;

}

Answer 1

I can not readily see where the crash is; however, I would suggest trying a forward facing iterator for the method GameEngine::IsPointInSprite.  It seems like I tried using reverse_iterators before and had problems with my iterator stopping in weird places.   It "could" be that VS2008 Express is allowing the siSprite iterators to become NULL before m_vSprites.rend() is ever reached [Just a wild guess.]

Also, I understand that you are probably trying to use iterators for efficiency reasons instead of the standard vector [] operator, but I can't think of any legitimate reason why the [] operator would be any slower than the ::iterator for a vector.  Unless VS 2008 Express provides a very poor implemenation of std::vector the [] operator should return in O(1) time because vectors are homogeneous in nature.  Given this understanding that [] "should" run just as fast as as ::iterator, I might even go as for as tranforming my iteration code to index based loops.

e.x.:
Sprite * mySpritePtr;
for (unsigned int i = 0; i < m_vSprites.size(); i++) {
   mySpritePtr = m_vSprites[i];
   if (!(mySpritePtr->IsHidden()) && (mySpritePtr->IsPointInside(x,y)) {
      return (mySpritePtr);
   }

   return NULL;
}

I don't "think" you will loose any efficiency by switching to the [] operator and the code should be slightly easier to troubleshoot and maintain. 

With Respect,

Shawn

Answer 2

Shawn -

Are you aware that you replied to a post which is almost two years old?

I hope Tomb332 isn't still waiting for a solution. ;-)

- Wayne