Thread: passing a vector to a function, getting negative length and size, aka segault

Hello,

I am writing a raytracer, and currently I'm working on creating a bounding volume hierarchy to accelerate the process. To do this, I am first creating a vector that holds each of the objects in the scene, and passing this vector to the constructor for my BVH.

Code:

//in header
BVH_Node* bvh;
//in main raytrace function
bvh = new BVH_Node(objList,0);

The BVH_Node constructor:

Code:

//here's how the beginning of it looks
BVH_Node::BVH_Node(vector<GeomObj*> list, int axis){
  int size = list.size(); //number of elements in list
  this->isObj = false;
  if(size == 1){
    this->left = makeLeaf(list[0]);
    this->right = makeLeaf(NULL);
    this->bb = list[0]->bb;
    return;
  }
  if(size == 2){
    this->left = makeLeaf(list[0]);
    this->right = makeLeaf(list[1]);
    this->bb = combineBoxes(list[0]->bb,list[1]->bb);
    return;
  }
//the rest of it
}

I am testing a scene that has only 2 objects, and so it goes to the size == 2 check. The first time it hits makeLeaf(), I segfault. I've used both gdb and valgrind, and of course it's a memory mapping error. gdb's backtrace tells me that the length of the vector I've passed in is -805305610 and the capacity is -21, and that it is inside my makeLeaf() function that the error occurs. Here's the function:

Code:

BVH_Node* BVH_Node::makeLeaf(GeomObj* v){
  BVH_Node* node;
  node->obj = v;
  node->isObj = true;
  return node;
}

The segfault happens at

Code:

node->obj = v;

Could someone help me understand why this is happening? If I run my raytracer without a BVH, the objList works perfectly.

Thanks