[MOAB-dev] read polygon mesh from vtk file

[Huayi Wei]

Hi, Moab Dev,

I have a polygon mesh saved in vtk format, see attachment. I can show it 
by paraview. But when loading it into moab, I meet `Segmentation fault 
(core dumped)`
error. I don't know how to fixed it. Please help me, thanks very much.

Here is the cpp file.
```
#include "moab/Core.hpp"
#include <iostream>
#include <assert.h>

using namespace moab;
using namespace std;

int main(int argc, char ** argv)
{
     string file = s"/poly8-10.vtk";
     Interface * imesh = new Core;

     ErrorCode rval =  imesh->load_mesh(file.c_str());
     assert(rval == MB_SUCCESS);

     return 0;
}
```

And here is the information of core:
```
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
Core was generated by `./readpolygon_test'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0  0x00007f3fee79cd3b in moab::Range::front (this=0xffffffffffffffe0)
     at ./moab/Range.hpp:824
824      { return mHead.mNext->first; }
(gdb) list
819    inline Range::const_iterator 
Range::const_iterator::start_of_block() const
820      { return Range::const_iterator( mNode, mNode->first ); }
821
822      //! get first entity in range
823    inline const EntityHandle& Range::front() const
824      { return mHead.mNext->first; }
825      //! get last entity in range
826    inline const EntityHandle& Range::back() const
827      { return mHead.mPrev->second; }
828
```

Best

Huayi
-------------- next part --------------
# vtk DataFile Version 3.0
MOAB 4.7.0pre
ASCII
DATASET POLYDATA
POINTS 26 double 
3.073901530231682e-06 2.977455744718462e-01 0.000000000000000e+00 
-7.071067811865476e-01 7.071067811865475e-01 0.000000000000000e+00 
-1.715691137876366e-01 3.536798274750831e-01 0.000000000000000e+00 
-4.719776146377113e-01 1.857355490854607e-01 0.000000000000000e+00 
-8.508854127205038e-01 3.599944589578263e-01 0.000000000000000e+00 
2.775557561562891e-16 1.000000000000000e+00 0.000000000000000e+00 
-3.406715072241552e-01 8.588892413936710e-01 0.000000000000000e+00 
1.715662369808998e-01 3.536768053562428e-01 0.000000000000000e+00 
4.719754417201190e-01 1.857347459630188e-01 0.000000000000000e+00 
-4.719756118732749e-01 -1.857348097293946e-01 0.000000000000000e+00 
-1.000000000000000e+00 1.110223024625157e-16 0.000000000000000e+00 
-8.508847507623047e-01 -3.599960570662885e-01 0.000000000000000e+00 
7.071067811865476e-01 7.071067811865476e-01 0.000000000000000e+00 
3.406701269292776e-01 8.588898131305294e-01 0.000000000000000e+00 
8.508845922027242e-01 3.599964398629780e-01 0.000000000000000e+00 
-7.071067811865476e-01 -7.071067811865476e-01 0.000000000000000e+00 
4.719777412790575e-01 -1.857356073815120e-01 0.000000000000000e+00 
7.071067811865472e-01 -7.071067811865477e-01 0.000000000000000e+00 
-3.051853356210140e-16 -1.000000000000000e+00 0.000000000000000e+00 
1.715687253344436e-01 -3.536802010232855e-01 0.000000000000000e+00 
-3.319925237351595e-06 -2.977459818644166e-01 0.000000000000000e+00 
-1.715662714497118e-01 -3.536770586038507e-01 0.000000000000000e+00 
-3.406707216059742e-01 -8.588895668073767e-01 0.000000000000000e+00 
3.406712167592965e-01 -8.588893617081550e-01 0.000000000000000e+00 
1.000000000000000e+00 -2.775557561562891e-17 0.000000000000000e+00 
8.508853951409249e-01 -3.599945013986841e-01 0.000000000000000e+00 
POLYGONS 10 64
6 21 22 18 23 19 20 
6 20 0 7 8 16 19 
5 10 4 3 9 11 
5 12 13 7 8 14 
5 24 14 8 16 25 
5 21 9 11 15 22 
6 7 0 2 6 5 13 
5 19 23 17 25 16 
5 3 4 1 6 2 
6 21 9 3 2 0 20