Question

Stepping through the debugger, the BBox object is okay at the entry of the function, but as soon as it enters the function, the vfptr object points to 0xccccc. I don’t get it.

1. What is causing this ?
2. Why is there a virtual table reference in there when the object is not derived from other class. (Though, it resides in GameObject from which my Player class inherits and I retrieve the BBox from within player. But, why does the BBox have the reference ? Shouldn’t it be player who should be maintained in that reference ?)

For 1; some code for reference:

A. I retrieve the bounding box from player. This returns a bounding box as expected. I then send its address to GetGridCells.

 const BoundingBox& l_Bbox = l_pPlayer->GetBoundingBox();

 boost::unordered_set < Cell*, CellPHash >& l_GridCells = GetGridCells ( &l_Bbox ); 

B. This is where a_pBoundingBox goes crazy and gets that garbage value.

 boost::unordered_set< Cell*, CellPHash > CollisionMgr::GetGridCells(const BoundingBox *a_pBoundingBox)
 {

I think the following code is also pertinent, so I’m sticking this in here anyways:

 const BoundingBox& Player::GetBoundingBox(void)
 {
 return BoundingBox( &GetBoundingSphere() );
 }

 const BoundingSphere& Player::GetBoundingSphere(void)
 {
 BoundingSphere& l_BSphere = m_pGeomMesh->m_BoundingSphere;

 l_BSphere.m_Center = GetPosition();

 return l_BSphere;
 }

 // BoundingBox Constructor
 BoundingBox(const BoundingSphere* a_pBoundingSphere);

Can anyone please give me some idea as to why this is happening? Also, if you want me to post more code, please do let me know.

Thanks!

Answer 1

 const BoundingBox& Player::GetBoundingBox(void)
 {
 return BoundingBox( &GetBoundingSphere() );
 }

Here, you’re returning a reference to a temporary BoundingBox object. That object goes out of scope as soon as the return statement ends.

Return a BoundingBox instead of a BoundingBox& instead.

---

Also:

 BoundingSphere& l_BSphere = m_pGeomMesh->m_BoundingSphere;

 l_BSphere.m_Center = GetPosition();

Here, you take a reference to the bounding sphere of the m_pGeomMesh, then modify the value it refers to. This will result in a modification of the original object. Are you sure this is what you want?

---

Also:

 // BoundingBox Constructor
 BoundingBox(const BoundingSphere* a_pBoundingSphere);

In the only place where using a reference makes a great deal of sense, you use a pointer instead. Why?