Bug 1190 – Reference becoming null

The following code is part of a LOD terrain engine I'm coding and the code fails on a split operation, where references to Nodes are updated (copied) to generate child nodes. The code has been ported from C++ (I can post it as well) and all lines has been checked and re-checked for errors on the implementation. The code has been striped of all unnecessary methods to improve readability and reduce dependencies. When compiled with "dmd -g -debug teste.d" the program fails to generate a viable mesh, crashing on an assert. This assert can be removed and the code would generate a mesh, but with null Nodes, if could not be rendered (Access Violation if attempted). The assert occurs in both Windows and Linux, the only platforms available for testing. The line in which the assert fails is 307, when the current node's right neighbor's base neighbor is set to current node's right child node. Before that line, both are asserted as NOT being null. I tried to analyze the disassembled code, but I couldn't find the source of the error. ------------------ teste.d ------------------------- ///Contains all declarations concerning the terrain engine import std.string; import std.stream; import std.math; alias std.string.toString strfy; alias std.stdio.writefln Log; private static const ubyte PatchSize=64; //must be power of 2 //const ubyte MAX_DEPTH=cast(ubyte)(2*sqrt(PatchSize)+1); private static const MaxDepth=4;//17 private struct CamInfo { uint x, y, z; } private CamInfo camInfo; /** The Terrain engine class. */ public final class Terrain { ///The TreeNode class is used to store information about the patch tree private final class TreeNode { private TreeNode lChild, rChild, bNeigh, lNeigh, rNeigh; public this() { reset(); } public void reset() { lChild=rChild=bNeigh=lNeigh=rNeigh=null; } } ///Patch Class. A terrain is composed of several patches private final class Patch { this (ushort x, ushort y) { this.x=x; this.y=y; visible=true; rNode=new TreeNode(); //these never get reassigned lNode=new TreeNode(); //they're const, remmember? assert(rNode !is null); assert(lNode !is null); //nodes come already clean rNode.bNeigh=lNode; lNode.bNeigh=rNode; calcError(); } ///Resets the patch. It becomes undivided and ready for the next tesselation. void reset() { rNode.reset(); lNode.reset(); rNode.bNeigh=lNode; lNode.bNeigh=rNode; //TODO: check visibility here visible=true; } ///Tesselates this patch and it becomes ready for rendering void update() { std.gc.disable(); cError[]=lError; tesselate(lNode, x, cast(ushort)(y+PatchSize), cast(ushort)(x+PatchSize), y, x, y, 1); cError[]=rError; tesselate(rNode, cast(ushort)(x+PatchSize), y, x, cast(ushort)(y+PatchSize), cast(ushort)(x+PatchSize), cast(ushort)(y+PatchSize), 1); std.gc.enable(); } ///This patch's error measure is updated from the data on hData. void calcError() { Calculate(x, cast(ushort)(y+PatchSize), cast(ushort)(x+PatchSize), y, x, y, 1); lError[]=cError; //copy the error data Calculate(cast(ushort)(x+PatchSize), y, x, cast(ushort)(y+PatchSize), cast(ushort)(x+PatchSize), cast(ushort)(y+PatchSize), 1); rError[]=cError; return; } ~this() { delete rNode; delete lNode; } //no need to protect this vars because this class won't be accessed from the exterior const ushort x, y; //coordinates aren't expected to change bool visible; ///Result of lastest cull check ushort[MaxDepth] lError, rError; const TreeNode rNode, lNode; } public: this(in File file, float detail) in { assert(file !is null); assert(detail>=0); //negative error values make no sense. 0 values are purely debugging technices } body { debug Log("Creating terrain object"); this.detail=detail; file.read(sizeX); file.read(sizeY); assert((sizeX>0)&&(sizeY>0)); HMult=1; //TODO: Replace with resolution from file hData=new ushort[][](sizeX, sizeY); //initialize data debug Log(" * Loading terrain data..."); foreach (stripe; hData) foreach (inout vertex; stripe) { file.read(vertex); vertex*=HMult; } maxH=0; //Maximum height present on the map. Used somewhere in debug code foreach (stripe; hData) foreach (vertex; stripe) if (vertex>maxH) maxH=vertex; xPatch=cast(ubyte)(sizeX/PatchSize); yPatch=cast(ubyte)(sizeY/PatchSize); nodes.length=(sizeX*sizeY/PatchSize); debug Log(" * Creating terrain nodes ("~strfy(nodes.length)~")..."); foreach(inout node; nodes) node=new TreeNode; debug Log(" * Creating patches..."); patches.length=xPatch;//how many columns will we have? Patch[col][row] foreach (size_t row, inout Patch[] strip; patches) { assert(strip.length==0, "Oups! Redefining a length of a strip"); strip.length=yPatch; //How many rows? foreach (size_t col, inout Patch patch; strip) patch=new Patch(cast(ushort)(col*PatchSize), cast(ushort)(row*PatchSize)); } debug Log("Terrain creation complete"); } public float heightAt(in float x, in float y) out(result) { assert((result>=0.0f)||(result==float.nan)); } body { if ((x<0.0)||(y<0.0f)) return float.nan; //triangulate height at the given point return 0.0f; } ///Makes the terrain ready for rendering. Tesselates all the patches. void update() body { //reset the engine first currNode=0; //reset current node foreach (size_t row, inout Patch[] strip; patches) foreach (size_t col, inout Patch patch; strip) { patch.reset(); //Recalculate the visibility flag if (patch.visible) //bail on non-visible patches { if (col>0) patch.lNode.lNeigh=patches[col-1][row].rNode; else patch.lNode.lNeigh=null; if (col<(xPatch-1)) patch.rNode.lNeigh=patches[col+1][row].lNode; else patch.rNode.lNeigh=null; if (row>0) patch.lNode.rNeigh=patches[col][row-1].rNode; else patch.lNode.rNeigh=null; if (row<(yPatch-1)) patch.rNode.rNeigh=patches[col][row+1].lNode; else patch.rNode.rNeigh=null; } } //Unfloatize camera information. Remember the case in which the coords are <0 foreach (Patch[] strip; patches) foreach (Patch patch; strip) if (patch.visible) patch.update(); return; } ~this() { /*Since the terrain is the last thing to be deleted when a game is over, a gc.fullCollect() will be preformed sometime soon, so it is not necessary to clean up manually*/ foreach (inout stripe; hData) { stripe.length=0; delete stripe; } hData.length=0; foreach (inout Patch[] strip; patches) foreach (inout Patch patch; strip) delete patch; foreach(inout node; nodes) delete node; nodes.length=0; } private: ///Returns the next available TreeNode. Creates a new one if there are no more available. TreeNode newNode() out(result) { assert(result !is null, "newNode() attempted to return a null TreeNode."); } body { assert(currNode<=nodes.length, "currNode advanced too much"); if (currNode==nodes.length) { nodes~=new TreeNode; //no more nodes available, create another one debug Log("Insufficient TreeNodes for current tesselation (detail="~strfy(detail)~"). Increasing TreeNode pool (currNode="~strfy(currNode)~")."); } TreeNode ret=nodes[currNode]; //get a new node ret.reset(); //clear new node's affiliations currNode++; return ret; } ///To be used by functions of the class, returns raw height value. ushort heightAt(ushort x, ushort y) { if ((x==sizeX)||(y==sizeY)) return 0; //Out of bounds values are not drawn (taken has void in game) assert(x<sizeX, "Out of bounds value requested"); assert(y<sizeY, "Out of bounds value requested"); return hData[x][y]; } ushort Calculate(ushort lX, ushort lY, ushort rX, ushort rY, ushort aX, ushort aY, ushort node) { //Calculate hipotenuse ushort cX=cast(ushort)((rX+lX)/2); ushort cY=cast(ushort)((rY+lY)/2); ushort cZ=heightAt(cX, cY); ushort rZ=heightAt(rX, rY); ushort lZ=heightAt(lX, lY); ushort errRatio=cast(ushort)abs(cZ-((lZ+rZ)/2)); //this iteraction's primary error ratio if (errRatio==0) return 0; //reached perfectness if ((abs((rX-lX))>=2)||(abs(rY-lY))>=2) //smaller than 2x2 { //calculate the error of one of the child triangles ushort tempErrRatio=Calculate(aX, aY, lX, lY, cX, cY, cast(ushort)(node*2)); if (errRatio<tempErrRatio) errRatio=tempErrRatio; //error is greater, adopt it //and then try the other child tempErrRatio=Calculate(rX, rY, aX, aY, cX, cY, cast(ushort)(node*2+1)); if (errRatio<tempErrRatio) errRatio=tempErrRatio; //error is greater, adopt it } //TODO: this "if" may not need to be here: required for range check, nothing else if (node<MaxDepth) cError[node]=errRatio; //store error ratio as we descend on the tree return errRatio; //return this levels error ratio } ///Splits a TreeNode, used by Patch sub-class void split(inout TreeNode myNode) in { assert(myNode !is null, "Attempted to split a null node"); } body { if (myNode.lChild !is null) return; //already split //Check to see if current triangle is diamond with bNeigh if ((myNode.bNeigh !is null)&&(myNode.bNeigh.bNeigh !is myNode)) { split(myNode.bNeigh); //it has to be split, so that current triangle can be a diamond with it's bNeigh assert(myNode.bNeigh.lChild !is null, "Split failed!"); } //asserts that I am a diamond with my bNeigh, or I'm a border node assert ((myNode.bNeigh is null)||(myNode.bNeigh.bNeigh is myNode), "Attempted to split a node that is not part of a diamond"); myNode.lChild=newNode(); myNode.rChild=newNode(); //with (myNode) //in this block, all the relations of myNode are updated { myNode.lChild.bNeigh=myNode.lNeigh; myNode.lChild.lNeigh=myNode.rChild; myNode.rChild.bNeigh=myNode.rNeigh; myNode.rChild.rNeigh=myNode.lChild; if (myNode.lNeigh !is null) //I have a left neigh { if (myNode.lNeigh.bNeigh is myNode) myNode.lNeigh.bNeigh=myNode.lChild; else { if (myNode.lNeigh.lNeigh is myNode) myNode.lNeigh.lNeigh=myNode.lChild; else if (myNode.lNeigh.rNeigh is myNode) myNode.lNeigh.rNeigh=myNode.lChild; } } assert((myNode.lChild !is null)&&(myNode.rChild !is null), "Children died at lNeigh update"); //The following if block causes the children to become null if (myNode.rNeigh !is null) //I have a right neigh { if (myNode.rNeigh.bNeigh is myNode) { assert(myNode.lChild !is null); assert(myNode.rChild !is null); assert(myNode.rNeigh.bNeigh !is null); myNode.rNeigh.bNeigh=myNode.rChild; //This causes the children (both) to die assert(myNode.lChild !is null); //crash here assert(myNode.rChild !is null); } else { if (myNode.rNeigh.rNeigh is myNode) myNode.rNeigh.rNeigh=myNode.rChild; else if (myNode.rNeigh.lNeigh is myNode) myNode.rNeigh.lNeigh=myNode.rChild; } } assert((myNode.lChild !is null)&&(myNode.rChild !is null), "Children died at rNeigh update"); if (myNode.bNeigh !is null) //I have a base neigh { if (myNode.bNeigh.lChild !is null) //My bNeigh is already split { assert(myNode.bNeigh.rChild !is null, "bNeigh is only partially split, cannot update relations."); myNode.bNeigh.lChild.rNeigh=myNode.rChild; myNode.bNeigh.rChild.lNeigh=myNode.lChild; myNode.lChild.rNeigh=myNode.bNeigh.rChild; myNode.rChild.lNeigh=myNode.bNeigh.lChild; } else split(myNode.bNeigh); //Split my base. He'll take care of Neigh relations } else //I don't have bNeigh { myNode.lChild.rNeigh=null; myNode.rChild.lNeigh=null; } assert((myNode.lChild !is null)&&(myNode.rChild !is null), "Children died at bNeigh update"); } //updates to myNode are over assert((myNode.lChild !is null)&&(myNode.rChild !is null), "Node children have been lost!"); return; } void tesselate (TreeNode myNode, ushort lX, ushort lY, ushort rX, ushort rY, ushort aX, ushort aY, ushort node) in { assert(myNode !is null, "Attempted to tesselate a null node"); } body { //Calculate hipotenuse ushort cX=cast(ushort)((rX+lX)/2); ushort cY=cast(ushort)((rY+lY)/2); ushort cZ=heightAt(cX, cY); ulong distance=(cX-camInfo.x)*(cX-camInfo.x)+(cY-camInfo.y)*(cY-camInfo.y)+(cZ-camInfo.z)*(cZ-camInfo.z); ulong threshold=cError[node]*cError[node]; if ((threshold*detail)>distance) //should this triangle be split? { split(myNode); //won't fail because TreeNodes will not go out //I have children and they aren't too small, //TODO: Unnecessary check: split never fails: (myNode.lChild !is null)&&(myNode.rChild !is null)&& if ((node<cast(ushort)(MaxDepth/2))&&((abs(lX-rX)>=2)||(abs(lY-rY)>=2))) { tesselate(myNode.lChild, aX, aY, lX, lY, cX, cY, cast(ushort)(node*2)); tesselate(myNode.rChild, rX, rY, aX, aY, cX, cY, cast(ushort)(node*2+1)); } } } const ushort maxH; float detail; ///Detail Threshold TreeNode nodes[]; ///Node pool size_t currNode; ///Current node being assigned const ushort sizeX, sizeY; const ubyte xPatch, yPatch; ushort hData[][]; ///The Height Data static ushort[MaxDepth] cError; //error buffer const ubyte HMult; ///Height multiplier, determines the resolution of the terrain const Patch patches[][]; ///The pathes that compose the terrain. } void main() { File este=new File("novomapa.raw", FileMode.In); Terrain terrain=new Terrain(este, 2500); delete este; std.stdio.writefln("Preparing for rendering..."); terrain.update(); delete terrain; }

Created attachment 142 This file contains the terrain height data Unzip this file to the exe's directory.

This bug still exists on version 1.15, in spite of the corrections made to the GC.

I'd try: 1) removing the delete statements -or- 2) disabling the gc and see if either of those affect the results.

Tried that, didn't work. I also added a debug printf on the TreeNode destructor and it didn't get called.

Please keep the version at the oldest possible: http://www.digitalmars.com/d/archives/digitalmars/D/bugs/bugzilla_usage_tips_10071.html

I've noticed that your code create something like : myNode.rNeigh.bNeigh == myNode So I assume it's your code fault, if you can't provide a smaller test case. import std.string; import std.stream; import std.math; alias std.string.toString strfy; alias std.stdio.writefln Log; int staticc; private static const ubyte PatchSize=64; //must be power of 2 //const ubyte MAX_DEPTH=cast(ubyte)(2*sqrt(PatchSize)+1); private static const MaxDepth=4;//17 private struct CamInfo { uint x, y, z; } private CamInfo camInfo; /** The Terrain engine class. */ public final class Terrain { ///The TreeNode class is used to store information about the patch tree private final class TreeNode { private TreeNode lChild, rChild, bNeigh, lNeigh, rNeigh; public this() { reset(); } public void reset() { lChild=rChild=bNeigh=lNeigh=rNeigh=null; } } ///Patch Class. A terrain is composed of several patches private final class Patch { this (ushort x, ushort y) { this.x=x; this.y=y; visible=true; rNode=new TreeNode(); //these never get reassigned lNode=new TreeNode(); //they're const, remmember? assert(rNode !is null); assert(lNode !is null); //nodes come already clean rNode.bNeigh=lNode; lNode.bNeigh=rNode; calcError(); } ///Resets the patch. It becomes undivided and ready for the next tesselation. void reset() { rNode.reset(); lNode.reset(); rNode.bNeigh=lNode; lNode.bNeigh=rNode; //TODO: check visibility here visible=true; } ///Tesselates this patch and it becomes ready for rendering void update() { std.gc.disable(); cError[]=lError; tesselate(lNode, x, cast(ushort)(y+PatchSize), cast(ushort)(x+PatchSize), y, x, y, 1); cError[]=rError; tesselate(rNode, cast(ushort)(x+PatchSize), y, x, cast(ushort)(y+PatchSize), cast(ushort)(x+PatchSize), cast(ushort)(y+PatchSize), 1); std.gc.enable(); } ///This patch's error measure is updated from the data on hData. void calcError() { Calculate(x, cast(ushort)(y+PatchSize), cast(ushort)(x+PatchSize), y, x, y, 1); lError[]=cError; //copy the error data Calculate(cast(ushort)(x+PatchSize), y, x, cast(ushort)(y+PatchSize), cast(ushort)(x+PatchSize), cast(ushort)(y+PatchSize), 1); rError[]=cError; return; } ~this() { delete rNode; delete lNode; } //no need to protect this vars because this class won't be accessed from the exterior const ushort x, y; //coordinates aren't expected to change bool visible; ///Result of lastest cull check ushort[MaxDepth] lError, rError; const TreeNode rNode, lNode; } public: this(in File file, float detail) in { assert(file !is null); assert(detail>=0); //negative error values make no sense. 0 values are purely debugging technices } body { debug Log("Creating terrain object"); this.detail=detail; file.read(sizeX); file.read(sizeY); assert((sizeX>0)&&(sizeY>0)); HMult=1; //TODO: Replace with resolution from file hData=new ushort[][](sizeX, sizeY); //initialize data debug Log(" * Loading terrain data..."); foreach (stripe; hData) foreach (inout vertex; stripe) { file.read(vertex); vertex*=HMult; } maxH=0; //Maximum height present on the map. Used somewhere in debug code foreach (stripe; hData) foreach (vertex; stripe) if (vertex>maxH) maxH=vertex; xPatch=cast(ubyte)(sizeX/PatchSize); yPatch=cast(ubyte)(sizeY/PatchSize); nodes.length=(sizeX*sizeY/PatchSize); debug Log(" * Creating terrain nodes ("~strfy(nodes.length)~")..."); foreach(inout node; nodes) node=new TreeNode; debug Log(" * Creating patches..."); patches.length=xPatch;//how many columns will we have? Patch[col][row] foreach (size_t row, inout Patch[] strip; patches) { assert(strip.length==0, "Oups! Redefining a length of a strip"); strip.length=yPatch; //How many rows? foreach (size_t col, inout Patch patch; strip) patch=new Patch(cast(ushort)(col*PatchSize), cast(ushort)(row*PatchSize)); } debug Log("Terrain creation complete"); } public float heightAt(in float x, in float y) out(result) { assert((result>=0.0f)||(result==float.nan)); } body { if ((x<0.0)||(y<0.0f)) return float.nan; //triangulate height at the given point return 0.0f; } ///Makes the terrain ready for rendering. Tesselates all the patches. void update() body { //reset the engine first currNode=0; //reset current node foreach (size_t row, inout Patch[] strip; patches) foreach (size_t col, inout Patch patch; strip) { patch.reset(); //Recalculate the visibility flag if (patch.visible) //bail on non-visible patches { if (col>0) patch.lNode.lNeigh=patches[col-1][row].rNode; else patch.lNode.lNeigh=null; if (col<(xPatch-1)) patch.rNode.lNeigh=patches[col+1][row].lNode; else patch.rNode.lNeigh=null; if (row>0) patch.lNode.rNeigh=patches[col][row-1].rNode; else patch.lNode.rNeigh=null; if (row<(yPatch-1)) patch.rNode.rNeigh=patches[col][row+1].lNode; else patch.rNode.rNeigh=null; } } //Unfloatize camera information. Remember the case in which the coords are <0 foreach (Patch[] strip; patches) foreach (Patch patch; strip) if (patch.visible) patch.update(); return; } ~this() { /*Since the terrain is the last thing to be deleted when a game is over, a gc.fullCollect() will be preformed sometime soon, so it is not necessary to clean up manually*/ foreach (inout stripe; hData) { stripe.length=0; delete stripe; } hData.length=0; foreach (inout Patch[] strip; patches) foreach (inout Patch patch; strip) delete patch; foreach(inout node; nodes) delete node; nodes.length=0; } private: ///Returns the next available TreeNode. Creates a new one if there are no more available. TreeNode newNode() out(result) { assert(result !is null, "newNode() attempted to return a null TreeNode."); } body { assert(currNode<=nodes.length, "currNode advanced too much"); if (currNode==nodes.length) { nodes~=new TreeNode; //no more nodes available, create another one debug Log("Insufficient TreeNodes for current tesselation (detail="~strfy(detail)~"). Increasing TreeNode pool (currNode="~strfy(currNode)~")."); } TreeNode ret=nodes[currNode]; //get a new node ret.reset(); //clear new node's affiliations currNode++; return ret; } ///To be used by functions of the class, returns raw height value. ushort heightAt(ushort x, ushort y) { if ((x==sizeX)||(y==sizeY)) return 0; //Out of bounds values are not drawn (taken has void in game) assert(x<sizeX, "Out of bounds value requested"); assert(y<sizeY, "Out of bounds value requested"); return hData[x][y]; } ushort Calculate(ushort lX, ushort lY, ushort rX, ushort rY, ushort aX, ushort aY, ushort node) { //Calculate hipotenuse ushort cX=cast(ushort)((rX+lX)/2); ushort cY=cast(ushort)((rY+lY)/2); ushort cZ=heightAt(cX, cY); ushort rZ=heightAt(rX, rY); ushort lZ=heightAt(lX, lY); ushort errRatio=cast(ushort)abs(cZ-((lZ+rZ)/2)); //this iteraction's primary error ratio if (errRatio==0) return 0; //reached perfectness if ((abs((rX-lX))>=2)||(abs(rY-lY))>=2) //smaller than 2x2 { //calculate the error of one of the child triangles ushort tempErrRatio=Calculate(aX, aY, lX, lY, cX, cY, cast(ushort)(node*2)); if (errRatio<tempErrRatio) errRatio=tempErrRatio; //error is greater, adopt it //and then try the other child tempErrRatio=Calculate(rX, rY, aX, aY, cX, cY, cast(ushort)(node*2+1)); if (errRatio<tempErrRatio) errRatio=tempErrRatio; //error is greater, adopt it } //TODO: this "if" may not need to be here: required for range check, nothing else if (node<MaxDepth) cError[node]=errRatio; //store error ratio as we descend on the tree return errRatio; //return this levels error ratio } ///Splits a TreeNode, used by Patch sub-class void split(inout TreeNode myNode) in { if (myNode.rNeigh !is null) assert(myNode.rNeigh.bNeigh !is myNode); assert(myNode !is null, "Attempted to split a null node"); } body { if (myNode.lChild !is null) return; //already split //Check to see if current triangle is diamond with bNeigh if ((myNode.bNeigh !is null)&&(myNode.bNeigh.bNeigh !is myNode)) { split(myNode.bNeigh); //it has to be split, so that current triangle can be a diamond with it's bNeigh assert(myNode.bNeigh.lChild !is null, "Split failed!"); } //asserts that I am a diamond with my bNeigh, or I'm a border node assert ((myNode.bNeigh is null)||(myNode.bNeigh.bNeigh is myNode), "Attempted to split a node that is not part of a diamond"); myNode.lChild=newNode(); myNode.rChild=newNode(); //with (myNode) //in this block, all the relations of myNode are updated { myNode.lChild.bNeigh=myNode.lNeigh; myNode.lChild.lNeigh=myNode.rChild; myNode.rChild.bNeigh=myNode.rNeigh; myNode.rChild.rNeigh=myNode.lChild; if (myNode.lNeigh !is null) //I have a left neigh { if (myNode.lNeigh.bNeigh is myNode) myNode.lNeigh.bNeigh=myNode.lChild; else { if (myNode.lNeigh.lNeigh is myNode) myNode.lNeigh.lNeigh=myNode.lChild; else if (myNode.lNeigh.rNeigh is myNode) myNode.lNeigh.rNeigh=myNode.lChild; } } assert((myNode.lChild !is null)&&(myNode.rChild !is null), "Children died at lNeigh update"); //The following if block causes the children to become null if (myNode.rNeigh !is null) //I have a right neigh { if (myNode.rNeigh.bNeigh is myNode) { assert(myNode.lChild !is null); assert(myNode.rChild !is null); assert(myNode.rNeigh.bNeigh !is null); assert(myNode.rNeigh.bNeigh !is myNode); myNode.rNeigh.bNeigh=myNode.rChild; //This causes the children (both) to die assert(myNode.lChild !is myNode.rNeigh.bNeigh); assert(myNode.lChild !is null); //crash here assert(myNode.rChild !is null); } else { if (myNode.rNeigh.rNeigh is myNode) myNode.rNeigh.rNeigh=myNode.rChild; else if (myNode.rNeigh.lNeigh is myNode) myNode.rNeigh.lNeigh=myNode.rChild; } } assert((myNode.lChild !is null)&&(myNode.rChild !is null), "Children died at rNeigh update"); if (myNode.bNeigh !is null) //I have a base neigh { if (myNode.bNeigh.lChild !is null) //My bNeigh is already split { assert(myNode.bNeigh.rChild !is null, "bNeigh is only partially split, cannot update relations."); myNode.bNeigh.lChild.rNeigh=myNode.rChild; myNode.bNeigh.rChild.lNeigh=myNode.lChild; myNode.lChild.rNeigh=myNode.bNeigh.rChild; myNode.rChild.lNeigh=myNode.bNeigh.lChild; } else split(myNode.bNeigh); //Split my base. He'll take care of Neigh relations } else //I don't have bNeigh { myNode.lChild.rNeigh=null; myNode.rChild.lNeigh=null; } assert((myNode.lChild !is null)&&(myNode.rChild !is null), "Children died at bNeigh update"); } //updates to myNode are over assert((myNode.lChild !is null)&&(myNode.rChild !is null), "Node children have been lost!"); return; } void tesselate (TreeNode myNode, ushort lX, ushort lY, ushort rX, ushort rY, ushort aX, ushort aY, ushort node) in { if (myNode.rNeigh !is null) assert(myNode.rNeigh.bNeigh !is myNode); assert(myNode !is null, "Attempted to tesselate a null node"); } body { //Calculate hipotenuse ushort cX=cast(ushort)((rX+lX)/2); ushort cY=cast(ushort)((rY+lY)/2); ushort cZ=heightAt(cX, cY); ulong distance=(cX-camInfo.x)*(cX-camInfo.x)+(cY-camInfo.y)*(cY-camInfo.y)+(cZ-camInfo.z)*(cZ-camInfo.z); ulong threshold=cError[node]*cError[node]; if ((threshold*detail)>distance) //should this triangle be split? { split(myNode); //won't fail because TreeNodes will not go out //I have children and they aren't too small, //TODO: Unnecessary check: split never fails: (myNode.lChild !is null)&&(myNode.rChild !is null)&& if ((node<cast(ushort)(MaxDepth/2))&&((abs(lX-rX)>=2)||(abs(lY-rY)>=2))) { tesselate(myNode.lChild, aX, aY, lX, lY, cX, cY, cast(ushort)(node*2)); tesselate(myNode.rChild, rX, rY, aX, aY, cX, cY, cast(ushort)(node*2+1)); } } } const ushort maxH; float detail; ///Detail Threshold TreeNode nodes[]; ///Node pool size_t currNode; ///Current node being assigned const ushort sizeX, sizeY; const ubyte xPatch, yPatch; ushort hData[][]; ///The Height Data static ushort[MaxDepth] cError; //error buffer const ubyte HMult; ///Height multiplier, determines the resolution of the terrain const Patch patches[][]; ///The pathes that compose the terrain. } void main() { File este=new File("novomapa.raw", FileMode.In); Terrain terrain=new Terrain(este, 2500); delete este; std.stdio.writefln("Preparing for rendering..."); terrain.update(); delete terrain; }

(In reply to comment #6) > I've noticed that your code create something like : > myNode.rNeigh.bNeigh == myNode > So I assume it's your code fault, if you can't provide a smaller test case. There is no such comparison on the code. All comparisons between nodes are made with the "is" keyword. No "==" comparisons are performed on references and you can confirm by searching all "==" on the code. And as I said on the main post, I have tracked the problem to a single line (marked in the source as "//This causes the children (both) to die"). Decompilation of the source lines gives out terrain.d:334 assert(myNode.rChild !is null); 00403402: 8b5d08 mov ebx, [ebp+0x8] 00403405: 8b0b mov ecx, [ebx] 00403407: 83790c00 cmp dword [ecx+0xc], 0x0 0040340b: 750a jnz 0x403417 MFKC7terrain7Terrain8TreeNodeZv terrain.Terrain.split terrain.d:336 0040340d: b84e010000 mov eax, 0x14e 00403412: e849040000 call 0x403860 void terrain.__assert(int) terrain.d:423 terrain.d:336 myNode.rNeigh.bNeigh=myNode.rChild; 00403417: 8b13 mov edx, [ebx] 00403419: 8b720c mov esi, [edx+0xc] 0040341c: 8b7a18 mov edi, [edx+0x18] 0040341f: 897710 mov [edi+0x10], esi terrain.d:337 assert(myNode.rChild !is null); 00403422: 8b0b mov ecx, [ebx] 00403424: 83790c00 cmp dword [ecx+0xc], 0x0 00403428: 750a jnz 0x403434 MFKC7terrain7Terrain8TreeNodeZv terrain.Terrain.split terrain.d:337 0040342a: b851010000 mov eax, 0x151 0040342f: e82c040000 call 0x403860 void terrain.__assert(int) terrain.d:423 00403434: eb3c jmp 0x403472 MFKC7terrain7Terrain8TreeNodeZv terrain.Terrain.split terrain.d:342 terrain.d:339 else if (myNode.rNeigh.rNeigh is myNode) myNode.rNeigh.rNeigh=myNode.rChild; 00403436: 8b5508 mov edx, [ebp+0x8] 00403439: 8b1a mov ebx, [edx] 0040343b: 8b7318 mov esi, [ebx+0x18] 0040343e: 8b4e18 mov ecx, [esi+0x18] 00403441: 3bcb cmp ecx, ebx 00403443: 7510 jnz 0x403455 MFKC7terrain7Terrain8TreeNodeZv terrain.Terrain.split terrain.d:340 00403445: 8b4508 mov eax, [ebp+0x8] 00403448: 8b10 mov edx, [eax] 0040344a: 8b5a0c mov ebx, [edx+0xc] 0040344d: 8b7218 mov esi, [edx+0x18] 00403450: 895e18 mov [esi+0x18], ebx 00403453: eb1d jmp 0x403472 MFKC7terrain7Terrain8TreeNodeZv terrain.Terrain.split terrain.d:342 You can confirm the code with ddbg. The problem isn't with my code, as I have said on the original post, the code was copied from my functional implementation on C (which I can provide if necessary) and I have confimed that EVERY LINE was been correctly ported. A single "copy" operation is cause two references to become null, references which are only read, not written to, on the faulty operation.

This seems to be a bad interaction between inout parameters and a tangly web of pointers. In your case, I don't think you need to pass the TreeNode by reference (inout) to split, because nowhere in that function is the parameter assigned to directly. So I think just removing "inout" on that function will fix your problem. (I got another error after removing it, but it got past the trouble spot). But this still may be a bug. You've got a graph like this basically: bNeigh-----> null<---rNeigh[root] [tree]bNeigh---> null <------rNeigh and you pass in root.bNeigh by reference, then you try to set tree.rNeigh.bNeigh, which is the same as tree. I'll attach a simplified test case.

Created attachment 175 Simpler test case

The Simpler test case just should access violation as Bill said in his last comment. Kill the ref keyword, the simpler test case goes fine. But without inout the original code fails at an assertion. And I'm kind enough to illustrate the new problem for you. :) Here is the code with a little bit correction, and illustrate the new assertion fail reason: import std.string; import std.stream; import std.math; alias std.string.toString strfy; alias std.stdio.writefln Log; int staticc; private static const ubyte PatchSize=64; //must be power of 2 //const ubyte MAX_DEPTH=cast(ubyte)(2*sqrt(PatchSize)+1); private static const MaxDepth=4;//17 private struct CamInfo { uint x, y, z; } private CamInfo camInfo; /** The Terrain engine class. */ public final class Terrain { ///The TreeNode class is used to store information about the patch tree private final class TreeNode { private TreeNode lChild, rChild, bNeigh, lNeigh, rNeigh; public this() { reset(); } public void reset() { lChild=rChild=bNeigh=lNeigh=rNeigh=null; } } ///Patch Class. A terrain is composed of several patches private final class Patch { this (ushort x, ushort y) { this.x=x; this.y=y; visible=true; rNode=new TreeNode(); //these never get reassigned lNode=new TreeNode(); //they're const, remmember? assert(rNode !is null); assert(lNode !is null); //nodes come already clean rNode.bNeigh=lNode; lNode.bNeigh=rNode; calcError(); } ///Resets the patch. It becomes undivided and ready for the next tesselation. void reset() { rNode.reset(); lNode.reset(); rNode.bNeigh=lNode; lNode.bNeigh=rNode; //TODO: check visibility here visible=true; } ///Tesselates this patch and it becomes ready for rendering void update() { std.gc.disable(); cError[]=lError; tesselate(lNode, x, cast(ushort)(y+PatchSize), cast(ushort)(x+PatchSize), y, x, y, 1); cError[]=rError; tesselate(rNode, cast(ushort)(x+PatchSize), y, x, cast(ushort)(y+PatchSize), cast(ushort)(x+PatchSize), cast(ushort)(y+PatchSize), 1); std.gc.enable(); } ///This patch's error measure is updated from the data on hData. void calcError() { Calculate(x, cast(ushort)(y+PatchSize), cast(ushort)(x+PatchSize), y, x, y, 1); lError[]=cError; //copy the error data Calculate(cast(ushort)(x+PatchSize), y, x, cast(ushort)(y+PatchSize), cast(ushort)(x+PatchSize), cast(ushort)(y+PatchSize), 1); rError[]=cError; return; } ~this() { delete rNode; delete lNode; } //no need to protect this vars because this class won't be accessed from the exterior const ushort x, y; //coordinates aren't expected to change bool visible; ///Result of lastest cull check ushort[MaxDepth] lError, rError; const TreeNode rNode, lNode; } public: this(in File file, float detail) in { assert(file !is null); assert(detail>=0); //negative error values make no sense. 0 values are purely debugging technices } body { debug Log("Creating terrain object"); this.detail=detail; file.read(sizeX); file.read(sizeY); assert((sizeX>0)&&(sizeY>0)); HMult=1; //TODO: Replace with resolution from file hData=new ushort[][](sizeX, sizeY); //initialize data debug Log(" * Loading terrain data..."); foreach (stripe; hData) foreach (inout vertex; stripe) { file.read(vertex); vertex*=HMult; } maxH=0; //Maximum height present on the map. Used somewhere in debug code foreach (stripe; hData) foreach (vertex; stripe) if (vertex>maxH) maxH=vertex; xPatch=cast(ubyte)(sizeX/PatchSize); yPatch=cast(ubyte)(sizeY/PatchSize); nodes.length=(sizeX*sizeY/PatchSize); debug Log(" * Creating terrain nodes ("~strfy(nodes.length)~")..."); foreach(inout node; nodes) node=new TreeNode; debug Log(" * Creating patches..."); patches.length=xPatch;//how many columns will we have? Patch[col][row] foreach (size_t row, inout Patch[] strip; patches) { assert(strip.length==0, "Oups! Redefining a length of a strip"); strip.length=yPatch; //How many rows? foreach (size_t col, inout Patch patch; strip) patch=new Patch(cast(ushort)(col*PatchSize), cast(ushort)(row*PatchSize)); } debug Log("Terrain creation complete"); } public float heightAt(in float x, in float y) out(result) { assert((result>=0.0f)||(result==float.nan)); } body { if ((x<0.0)||(y<0.0f)) return float.nan; //triangulate height at the given point return 0.0f; } ///Makes the terrain ready for rendering. Tesselates all the patches. void update() body { //reset the engine first currNode=0; //reset current node foreach (size_t row, inout Patch[] strip; patches) foreach (size_t col, inout Patch patch; strip) { patch.reset(); //Recalculate the visibility flag if (patch.visible) //bail on non-visible patches { if (col>0) patch.lNode.lNeigh=patches[col-1][row].rNode; else patch.lNode.lNeigh=null; if (col<(xPatch-1)) patch.rNode.lNeigh=patches[col+1][row].lNode; else patch.rNode.lNeigh=null; if (row>0) patch.lNode.rNeigh=patches[col][row-1].rNode; else patch.lNode.rNeigh=null; if (row<(yPatch-1)) patch.rNode.rNeigh=patches[col][row+1].lNode; else patch.rNode.rNeigh=null; } } //Unfloatize camera information. Remember the case in which the coords are <0 foreach (Patch[] strip; patches) foreach (Patch patch; strip) if (patch.visible) patch.update(); return; } ~this() { /*Since the terrain is the last thing to be deleted when a game is over, a gc.fullCollect() will be preformed sometime soon, so it is not necessary to clean up manually*/ foreach (inout stripe; hData) { stripe.length=0; delete stripe; } hData.length=0; foreach (inout Patch[] strip; patches) foreach (inout Patch patch; strip) delete patch; foreach(inout node; nodes) delete node; nodes.length=0; } private: ///Returns the next available TreeNode. Creates a new one if there are no more available. TreeNode newNode() out(result) { assert(result !is null, "newNode() attempted to return a null TreeNode."); } body { assert(currNode<=nodes.length, "currNode advanced too much"); if (currNode==nodes.length) { nodes~=new TreeNode; //no more nodes available, create another one debug Log("Insufficient TreeNodes for current tesselation (detail="~strfy(detail)~"). Increasing TreeNode pool (currNode="~strfy(currNode)~")."); } TreeNode ret=nodes[currNode]; //get a new node ret.reset(); //clear new node's affiliations currNode++; return ret; } ///To be used by functions of the class, returns raw height value. ushort heightAt(ushort x, ushort y) { if ((x==sizeX)||(y==sizeY)) return 0; //Out of bounds values are not drawn (taken has void in game) assert(x<sizeX, "Out of bounds value requested"); assert(y<sizeY, "Out of bounds value requested"); return hData[x][y]; } ushort Calculate(ushort lX, ushort lY, ushort rX, ushort rY, ushort aX, ushort aY, ushort node) { //Calculate hipotenuse ushort cX=cast(ushort)((rX+lX)/2); ushort cY=cast(ushort)((rY+lY)/2); ushort cZ=heightAt(cX, cY); ushort rZ=heightAt(rX, rY); ushort lZ=heightAt(lX, lY); ushort errRatio=cast(ushort)abs(cZ-((lZ+rZ)/2)); //this iteraction's primary error ratio if (errRatio==0) return 0; //reached perfectness if ((abs((rX-lX))>=2)||(abs(rY-lY))>=2) //smaller than 2x2 { //calculate the error of one of the child triangles ushort tempErrRatio=Calculate(aX, aY, lX, lY, cX, cY, cast(ushort)(node*2)); if (errRatio<tempErrRatio) errRatio=tempErrRatio; //error is greater, adopt it //and then try the other child tempErrRatio=Calculate(rX, rY, aX, aY, cX, cY, cast(ushort)(node*2+1)); if (errRatio<tempErrRatio) errRatio=tempErrRatio; //error is greater, adopt it } //TODO: this "if" may not need to be here: required for range check, nothing else if (node<MaxDepth) cError[node]=errRatio; //store error ratio as we descend on the tree return errRatio; //return this levels error ratio } ///Splits a TreeNode, used by Patch sub-class void split(TreeNode myNode) in { if (myNode.rNeigh !is null) // assert(myNode.rNeigh.bNeigh !is myNode); assert(myNode !is null, "Attempted to split a null node"); } body { if (myNode.lChild !is null) return; //already split //Check to see if current triangle is diamond with bNeigh if ((myNode.bNeigh !is null)&&(myNode.bNeigh.bNeigh !is myNode)) { TreeNode v=myNode.bNeigh; split(myNode.bNeigh); //it has to be split, so that current triangle can be a diamond with it's bNeigh if (myNode.bNeigh !is v){ printf("oh my god!"); } assert(myNode.bNeigh.lChild !is null, "Split failed!"); } //asserts that I am a diamond with my bNeigh, or I'm a border node assert ((myNode.bNeigh is null)||(myNode.bNeigh.bNeigh is myNode), "Attempted to split a node that is not part of a diamond"); myNode.lChild=newNode(); myNode.rChild=newNode(); //with (myNode) //in this block, all the relations of myNode are updated { myNode.lChild.bNeigh=myNode.lNeigh; myNode.lChild.lNeigh=myNode.rChild; myNode.rChild.bNeigh=myNode.rNeigh; myNode.rChild.rNeigh=myNode.lChild; if (myNode.lNeigh !is null) //I have a left neigh { if (myNode.lNeigh.bNeigh is myNode) myNode.lNeigh.bNeigh=myNode.lChild; else { if (myNode.lNeigh.lNeigh is myNode) myNode.lNeigh.lNeigh=myNode.lChild; else if (myNode.lNeigh.rNeigh is myNode) myNode.lNeigh.rNeigh=myNode.lChild; } } assert((myNode.lChild !is null)&&(myNode.rChild !is null), "Children died at lNeigh update"); //The following if block causes the children to become null if (myNode.rNeigh !is null) //I have a right neigh { if (myNode.rNeigh.bNeigh is myNode) { assert(myNode.lChild !is null); assert(myNode.rChild !is null); assert(myNode.rNeigh.bNeigh !is null); // assert(myNode.rNeigh.bNeigh !is myNode); myNode.rNeigh.bNeigh=myNode.rChild; //This causes the children (both) to die assert(myNode.lChild !is myNode.rNeigh.bNeigh); assert(myNode.lChild !is null); //crash here assert(myNode.rChild !is null); } else { if (myNode.rNeigh.rNeigh is myNode) myNode.rNeigh.rNeigh=myNode.rChild; else if (myNode.rNeigh.lNeigh is myNode) myNode.rNeigh.lNeigh=myNode.rChild; } } assert((myNode.lChild !is null)&&(myNode.rChild !is null), "Children died at rNeigh update"); if (myNode.bNeigh !is null) //I have a base neigh { if (myNode.bNeigh.lChild !is null) //My bNeigh is already split { assert(myNode.bNeigh.rChild !is null, "bNeigh is only partially split, cannot update relations."); myNode.bNeigh.lChild.rNeigh=myNode.rChild; myNode.bNeigh.rChild.lNeigh=myNode.lChild; myNode.lChild.rNeigh=myNode.bNeigh.rChild; myNode.rChild.lNeigh=myNode.bNeigh.lChild; } else split(myNode.bNeigh); //Split my base. He'll take care of Neigh relations } else //I don't have bNeigh { myNode.lChild.rNeigh=null; myNode.rChild.lNeigh=null; } assert((myNode.lChild !is null)&&(myNode.rChild !is null), "Children died at bNeigh update"); } //updates to myNode are over assert((myNode.lChild !is null)&&(myNode.rChild !is null), "Node children have been lost!"); // this assertion doesn't test the problem actually , in this scope testing myNode is useless // you should test the copy of myNode return; } void tesselate (TreeNode myNode, ushort lX, ushort lY, ushort rX, ushort rY, ushort aX, ushort aY, ushort node) in { if (myNode.rNeigh !is null) assert(myNode.rNeigh.bNeigh !is myNode); assert(myNode !is null, "Attempted to tesselate a null node"); } body { //Calculate hipotenuse ushort cX=cast(ushort)((rX+lX)/2); ushort cY=cast(ushort)((rY+lY)/2); ushort cZ=heightAt(cX, cY); ulong distance=(cX-camInfo.x)*(cX-camInfo.x)+(cY-camInfo.y)*(cY-camInfo.y)+(cZ-camInfo.z)*(cZ-camInfo.z); ulong threshold=cError[node]*cError[node]; if ((threshold*detail)>distance) //should this triangle be split? { split(myNode); //won't fail because TreeNodes will not go out //I have children and they aren't too small, //TODO: Unnecessary check: split never fails: (myNode.lChild !is null)&&(myNode.rChild !is null)&& if ((node<cast(ushort)(MaxDepth/2))&&((abs(lX-rX)>=2)||(abs(lY-rY)>=2))) { tesselate(myNode.lChild, aX, aY, lX, lY, cX, cY, cast(ushort)(node*2)); tesselate(myNode.rChild, rX, rY, aX, aY, cX, cY, cast(ushort)(node*2+1)); } } } const ushort maxH; float detail; ///Detail Threshold TreeNode nodes[]; ///Node pool size_t currNode; ///Current node being assigned const ushort sizeX, sizeY; const ubyte xPatch, yPatch; ushort hData[][]; ///The Height Data static ushort[MaxDepth] cError; //error buffer const ubyte HMult; ///Height multiplier, determines the resolution of the terrain const Patch patches[][]; ///The pathes that compose the terrain. } void main() { File este=new File("novomapa.raw", FileMode.In); Terrain terrain=new Terrain(este, 2500); delete este; std.stdio.writefln("Preparing for rendering..."); terrain.update(); delete terrain; }

If you're going to add gigantic gobs of code to bugzilla, please do it as an attachment so that the lines don't get all wrapped.