CGAL users discussion list

["Laurent Rineau (CGAL/GeometryFactory)" <>]

Le Wednesday, January 4, 2017 10:59:46 AM CET Thomas Holzmann a écrit :
> Hi,
> 
> I'm having a (non-constrianed) triangulation and am dividing cells in
> several new ones. Therefore, I'm having a mapping from old to new cells:
> 
> map<Cell_handle, vector<Cell_handle> > oldToNewCells;
> 
> Now I want to check if a cell was already procesed:
> 
> vector<Cell_handle> cellAlreadyProcessed;
> try{
>      cellAlreadyProcessed = oldToNewCells.at(cell);
> }
> catch(out_of_range){}
> 
> This generally works. However, when I compile with -O0, I get this error
> in case the cell is not in the mapping:
> 
> CGAL ERROR: precondition violation!
> Expr: ( i >= 0 && i < 4 ) && ( j >= 0 && j < 4 ) && ( i != j )
> File: /home/holzi/tools/CGAL-4.9/include/CGAL/Triangulation_utils_3.h
> Line: 67
> 
> Could someone explain to me, why this error happens and no out_of_range
> exception is thrown?

Why do you think that precondition violation is related to the small code 
excerpt you show us?

That exception was triggered because there was a logic error in your code. 
Those checks are only applied if the macros CGAL_NDEBUG and NDEBUG are not 
defined. That is not related to the optimizations flags -O0, or -O3. 
Probably, the way you created the triangulation, or the way your split those 
cells invalidated invariant of the triangulation and make it invalid. You can 
check the value of `tr.is_valid(true)`, to be sure.

-- 
Laurent Rineau, PhD
R&D Engineer at GeometryFactory           http://www.geometryfactory.com/
Release Manager of the CGAL Project       http://www.cgal.org/