<div dir="ltr">Cornelius,<div><br></div><div>Thank you for the detailed bug report and your findings! <a href="mailto:vtk-developers@vtk.org">vtk-developers@vtk.org</a> (CC'ed) is a more appropriate list for this problem as it is VTK code in question, but no worries. I have filed an issue with your message in the VTK bug tracker for further tracking of this issue:</div><div><br></div><div><a href="https://gitlab.kitware.com/vtk/vtk/issues/17153">https://gitlab.kitware.com/vtk/vtk/issues/17153</a><br></div><div><br></div><div>Thanks!</div><div><br></div><div>Cory</div></div><div class="gmail_extra"><br><div class="gmail_quote">On Sun, Oct 22, 2017 at 9:25 AM, Cornelis Bockemühl <span dir="ltr"><<a href="mailto:cornelis.bockemuehl@gmail.com" target="_blank">cornelis.bockemuehl@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr">Dear VTK developers,<div><br></div><div>First of all: Am I posting this maybe in the wrong mailing list??</div><div><br></div><div>Anyway, here I go: In some project I am using the vtkIntersectPolyData filter. This works as expected many times, but from time to time I had crashes. I managed to track down these crashes to a little bug in that class that can be fixed by a very little change:</div><div><br></div><div>in vtkIntersectionPolyDataFilter.<wbr>cxx(14'1), replace</div><div><br></div><div><pre style="margin-top:0px;margin-bottom:0px"><span style="color:rgb(9,46,100)">  lineBool</span><span style="color:rgb(192,192,192)"> </span>=<span style="color:rgb(192,192,192)"> </span><span style="color:rgb(128,128,0)">new</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(128,128,0)">bool</span>[<span style="color:rgb(9,46,100)">pd</span>-><span style="font-style:italic;color:rgb(0,103,124)">GetNumberOfCells</span>()];</pre></div><div><br></div><div>by</div><div><pre style="margin-top:0px;margin-bottom:0px"><span style="color:rgb(9,46,100)"><br></span></pre><pre style="margin-top:0px;margin-bottom:0px"><span style="color:rgb(9,46,100)">  lineBool</span><span style="color:rgb(192,192,192)"> </span>=<span style="color:rgb(192,192,192)"> </span><span style="color:rgb(128,128,0)">new</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(128,128,0)">bool</span>[<span style="color:rgb(9,46,100)">pd</span>-><span style="font-style:italic;color:rgb(0,103,124)">GetNumberOfCells</span>()<span style="color:rgb(192,192,192)"> </span>+<span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,0,128)">1</span>];</pre></div><div><br></div><div>The crash happened when this array was released (heap corruption), and it turned out that indeed under some circumstances the program writes one element more than there is allocated memory. This happens if further down in the GetSingleLoop function the "else if" branch is chosen inside the "if -- else if -- else" construct: Here the pd cells array is extended by one element.</div><div><br></div><div>With the above fix the crash goes indeed away, but then later on the program throws an exception at vtkCellLinks.h(171):</div><div><br></div><div><pre style="margin-top:0px;margin-bottom:0px"><span style="color:rgb(192,192,192)">  </span><span style="color:rgb(0,0,128)">/**</span></pre>
<pre style="margin-top:0px;margin-bottom:0px"><span style="color:rgb(192,192,192)">   </span><span style="color:rgb(0,0,128)">*</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,0,128)">Increment</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,0,128)">the</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,0,128)">count</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,0,128)">of</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,0,128)">the</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,0,128)">number</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,0,128)">of</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,0,128)">cells</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,0,128)">using</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,0,128)">the</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,0,128)">point.</span></pre>
<pre style="margin-top:0px;margin-bottom:0px"><span style="color:rgb(192,192,192)">   </span><span style="color:rgb(0,0,128)">*/</span></pre>
<pre style="margin-top:0px;margin-bottom:0px"><span style="color:rgb(192,192,192)">  </span><span style="color:rgb(128,128,0)">void</span><span style="color:rgb(192,192,192)"> </span><span style="font-weight:600;color:rgb(0,103,124)">IncrementLinkCount</span>(<span style="color:rgb(128,0,128)">vtkIdType</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(9,46,100)">ptId</span>)<span style="color:rgb(192,192,192)"> </span>{<span style="color:rgb(192,192,192)"> </span><span style="color:rgb(128,128,0)">this</span>-><span style="color:rgb(128,0,0)">Array</span>[<span style="color:rgb(9,46,100)">ptId</span>].<span style="color:rgb(128,0,0)">ncells</span>++;};</pre>
<pre style="margin-top:0px;margin-bottom:0px"><br></pre><pre style="margin-top:0px;margin-bottom:0px">call stack at this point:</pre><pre style="margin-top:0px;margin-bottom:0px"><br></pre><pre style="margin-top:0px;margin-bottom:0px">1   vtkCellLinks::<wbr>IncrementLinkCount                     vtkCellLinks.h                          171  0x7feced1c91a 
2   vtkCellLinks::BuildLinks                             vtkCellLinks.cxx                        153  0x7feced1a89a 
3   vtkPolyData::BuildLinks                              vtkPolyData.cxx                         1096 0x7fecf022ff1 
4   debug_<wbr>vtkIntersectionPolyDataFilter:<wbr>:Impl::SplitCell debug_<wbr>vtkIntersectionPolyDataFilter.<wbr>cxx 1007 0x7fec0c994e2 
5   debug_<wbr>vtkIntersectionPolyDataFilter:<wbr>:Impl::SplitMesh debug_<wbr>vtkIntersectionPolyDataFilter.<wbr>cxx 630  0x7fec0c971cc 
6   debug_<wbr>vtkIntersectionPolyDataFilter:<wbr>:RequestData     debug_<wbr>vtkIntersectionPolyDataFilter.<wbr>cxx 2590 0x7fec0c94531 
7   vtkPolyDataAlgorithm::<wbr>ProcessRequest                 vtkPolyDataAlgorithm.cxx                90   0x7fecf556116 
8   vtkExecutive::CallAlgorithm                          vtkExecutive.cxx                        775  0x7fecf50eb55 
9   vtkDemandDrivenPipeline::<wbr>ExecuteData                 vtkDemandDrivenPipeline.cxx             491  0x7fecf50477c 
10  vtkCompositeDataPipeline::<wbr>ExecuteData                vtkCompositeDataPipeline.cxx            179  0x7fecf4fc560 
11  vtkDemandDrivenPipeline::<wbr>ProcessRequest              vtkDemandDrivenPipeline.cxx             274  0x7fecf503343 
12  vtkStreamingDemandDrivenPipeli<wbr>ne::ProcessRequest     vtkStreamingDemandDrivenPipeli<wbr>ne.cxx    328  0x7fecf588f67 
13  vtkDemandDrivenPipeline::<wbr>UpdateData                  vtkDemandDrivenPipeline.cxx             444  0x7fecf5042da 
14  vtkStreamingDemandDrivenPipeli<wbr>ne::Update             vtkStreamingDemandDrivenPipeli<wbr>ne.cxx    403  0x7fecf589412 
15  vtkStreamingDemandDrivenPipeli<wbr>ne::Update             vtkStreamingDemandDrivenPipeli<wbr>ne.cxx    366  0x7fecf58916c 
16  vtkAlgorithm::Update                                 vtkAlgorithm.cxx                        1457 0x7fecf4e5348 
17  vtkAlgorithm::Update                                 vtkAlgorithm.cxx                        1451 0x7fecf4e53b3 
18  vtkCemTestIntersectionFilter::<wbr>RequestData            vtkCemTestIntersectionFilter.<wbr>cxx        252  0x7fec0c84e7f 
19  vtkPolyDataAlgorithm::<wbr>ProcessRequest                 vtkPolyDataAlgorithm.cxx                90   0x7fecf556116 
20  vtkExecutive::CallAlgorithm                          vtkExecutive.cxx                        775  0x7fecf50eb55 
... <More>                                                                                                          
</pre></div><div><br></div><div>Note that debug_<wbr>vtkIntersectionPolyDataFilter is a copy of vtkIntersectionPolyDataFilter that I prepared to do my testing and add some debug output stuff etc. without interfering with the original code.</div><div><br></div><div>I guess that the exception is again a consequence of adding that "cell" in GetSingleLoop, but now I must admit that my understanding of the internals of these geometric object classes is not yet good enough to see what went wrong! The code that needs checking by an expert seems to me the following</div><div><br></div><div>vtkIntersectionPolyDataFilter.<wbr>cxx(1536..1555):</div><div><br></div><div><pre style="margin-top:0px;margin-bottom:0px"><span style="color:rgb(192,192,192)">    </span><span style="color:rgb(0,128,0)">//There</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,128,0)">is</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,128,0)">one</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,128,0)">line</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,128,0)">attached</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,128,0)">to</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,128,0)">point.</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,128,0)">This</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,128,0)">means</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,128,0)">the</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,128,0)">intersection</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,128,0)">has</span></pre>
<pre style="margin-top:0px;margin-bottom:0px"><span style="color:rgb(192,192,192)">    </span><span style="color:rgb(0,128,0)">//an</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,128,0)">open</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,128,0)">intersection</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,128,0)">loop</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,128,0)">(i.e.</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,128,0)">the</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,128,0)">surfaces</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,128,0)">are</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,128,0)">open</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,128,0)">and</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,128,0)">one</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,128,0)">does</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,128,0)">not</span></pre>
<pre style="margin-top:0px;margin-bottom:0px"><span style="color:rgb(192,192,192)">    </span><span style="color:rgb(0,128,0)">//completeley</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,128,0)">intersect</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,128,0)">the</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,128,0)">other.</span></pre>
<pre style="margin-top:0px;margin-bottom:0px"><span style="color:rgb(192,192,192)">    </span><span style="color:rgb(0,128,0)">//Make</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,128,0)">an</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,128,0)">artificial</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,128,0)">triangle</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,128,0)">loop</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,128,0)">in</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,128,0)">this</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,128,0)">case</span></pre>
<pre style="margin-top:0px;margin-bottom:0px"><span style="color:rgb(192,192,192)">    </span><span style="color:rgb(128,128,0)">else</span><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(128,128,0)">if</span><span style="color:rgb(192,192,192)"> </span>(<span style="color:rgb(9,46,100)">pointCells</span>-><span style="color:rgb(0,103,124)">GetNumberOfIds</span>()<span style="color:rgb(192,192,192)"> </span><<span style="color:rgb(192,192,192)"> </span><span style="color:rgb(0,0,128)">2</span>)</pre>
<pre style="margin-top:0px;margin-bottom:0px"><span style="color:rgb(192,192,192)">    </span>{</pre>
<pre style="margin-top:0px;margin-bottom:0px">      <span style="font-family:arial,sans-serif;color:rgb(128,0,128)">vtkSmartPointer</span><span style="font-family:arial,sans-serif"><</span><span style="font-family:arial,sans-serif;color:rgb(128,0,128)">vtkPolyData</span><span style="font-family:arial,sans-serif">></span><span style="font-family:arial,sans-serif;color:rgb(192,192,192)"> </span><span style="font-family:arial,sans-serif;color:rgb(9,46,100)">currentpd</span><span style="font-family:arial,sans-serif;color:rgb(192,192,192)"> </span><span style="font-family:arial,sans-serif">=</span><br></pre>
<pre style="margin-top:0px;margin-bottom:0px"><span style="color:rgb(192,192,192)">        </span><span style="color:rgb(128,0,128)">vtkSmartPointer</span><<span style="color:rgb(128,0,128)">vtkPolyData</span>>::<span style="color:rgb(0,103,124)"><wbr>New</span>();</pre>
<pre style="margin-top:0px;margin-bottom:0px"><span style="color:rgb(192,192,192)">      </span><span style="color:rgb(128,0,128)">vtkSmartPointer</span><<span style="color:rgb(128,0,128)">vtkCellArray</span>><span style="color:rgb(192,192,192)"> </span><span style="color:rgb(9,46,100)">currentcells</span><span style="color:rgb(192,192,192)"> </span>=</pre>
<pre style="margin-top:0px;margin-bottom:0px"><span style="color:rgb(192,192,192)">        </span><span style="color:rgb(128,0,128)">vtkSmartPointer</span><<span style="color:rgb(128,0,128)">vtkCellArray</span>>:<wbr>:<span style="color:rgb(0,103,124)">New</span>();</pre>
<pre style="margin-top:0px;margin-bottom:0px"><span style="color:rgb(192,192,192)">      </span><span style="color:rgb(9,46,100)">currentcells</span><span style="color:rgb(192,192,192)"> </span>=<span style="color:rgb(192,192,192)"> </span><span style="color:rgb(9,46,100)">pd</span>-><span style="color:rgb(0,103,124)">GetLines</span>();</pre>
<pre style="margin-top:0px;margin-bottom:0px"><span style="color:rgb(192,192,192)">      </span><span style="color:rgb(9,46,100)">currentcells</span>-><span style="color:rgb(0,103,124)">InsertNextCell</span>(<span style="color:rgb(0,0,128)">2</span><wbr>);</pre>
<pre style="margin-top:0px;margin-bottom:0px"><span style="color:rgb(192,192,192)">      </span><span style="color:rgb(9,46,100)">currentcells</span>-><span style="color:rgb(0,103,124)">InsertCellPoint</span>(<span style="color:rgb(9,46,100)"><wbr>nextPt</span>);</pre>
<pre style="margin-top:0px;margin-bottom:0px"><span style="color:rgb(192,192,192)">      </span><span style="color:rgb(9,46,100)">currentcells</span>-><span style="color:rgb(0,103,124)">InsertCellPoint</span>(<span style="color:rgb(9,46,100)"><wbr>startPt</span>);</pre>
<pre style="margin-top:0px;margin-bottom:0px"><span style="color:rgb(192,192,192)">      </span><span style="color:rgb(9,46,100)">nextCell</span><span style="color:rgb(192,192,192)"> </span>=<span style="color:rgb(192,192,192)"> </span><span style="color:rgb(9,46,100)">currentcells</span>-><span style="font-style:italic;color:rgb(0,103,124)">GetNumberOfCells</span><wbr>()-<span style="color:rgb(0,0,128)">1</span>;</pre>
<pre style="margin-top:0px;margin-bottom:0px"><span style="color:rgb(192,192,192)">      </span><span style="color:rgb(9,46,100)">currentpd</span>-><span style="color:rgb(0,103,124)">SetLines</span>(<span style="color:rgb(9,46,100)">currentcel<wbr>ls</span>);</pre>
<pre style="margin-top:0px;margin-bottom:0px"><span style="color:rgb(192,192,192)">      </span><span style="color:rgb(9,46,100)">currentpd</span>-><span style="font-style:italic;color:rgb(0,103,124)">SetPoints</span>(<span style="color:rgb(9,46,100)">pd</span>-><span style="font-style:italic;color:rgb(0,103,124)">GetPo<wbr>ints</span>());</pre>
<pre style="margin-top:0px;margin-bottom:0px"><span style="color:rgb(192,192,192)">      </span><span style="color:rgb(9,46,100)">pd</span>-><span style="font-style:italic;color:rgb(0,103,124)">DeepCopy</span>(<span style="color:rgb(9,46,100)">currentpd</span>);</pre>
<pre style="margin-top:0px;margin-bottom:0px"><span style="color:rgb(192,192,192)">      </span><span style="color:rgb(9,46,100)">pd</span>-><span style="color:rgb(0,103,124)">BuildLinks</span>();</pre>
<pre style="margin-top:0px;margin-bottom:0px"><span style="color:rgb(192,192,192)">    </span>}</pre>
<pre style="margin-top:0px;margin-bottom:0px"><br></pre></div><div>My guess is that this code is not yet good enough to properly insert the "cell" into pd...</div><div><br></div><div>Any idea?</div><div><br></div><div>Regards,</div><div>Cornelis</div><span class="HOEnZb"><font color="#888888"><div><div><br></div>-- <br><div class="m_-4996734613498183939gmail_signature">Cornelis Bockemühl<br>Basel, Schweiz<br></div>
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