Infinite loop in orient_polygon_soup in a degenerate case

[sloriot]

I'm filling an issue as I observe an Infinite loop in orient_polygon_soup() in the function void duplicate_singular_vertices() that is extracting links of vertices to detect if a vertex is non-manifold (singular). I cannot reproduce the error in an isolated program, only in a complex one.

The problem happens here:

        if (next==v_id){
          /// turn the otherway round
          next = neighbors[0];
          do{
            P_ID other_p_id;
            std::tie(next, other_p_id) = next_ccw_vertex_around_target(next, v_id, polygons, edges, marked_edges);
            if (next==v_id) break;
            visited_polygons.insert(other_p_id);
            if(nb_link_ccs != 1)
              vertices_to_duplicate.back().second.push_back(other_p_id);
          }
          while(true);
        }

the pb happens because of a face having a degenerate edge, with the duplicated vertex being a T junction:

B----------------A
|                |
|                |
C-------DD-------E
|        |       |
|        |       |
|        |       |
F------- G-------H

f0: A-B-C-D-D-E
f1: E-D-G-H
f2: D-C-F-G

I'm not even sure we want to support such cases.

[VivekPrakashNitH]

Hello Sloriot,
I want to know more about the problem what is the issue and how can I help you. I want to contribute in the GSOC 2025 programme form CGAL . What is the issue and what is the problem and what are you trying to achieve in this particular issue can you explain me in detail I am new here . What are the things I need to refer to understand this project and how can I contribute to this Project

Regards
Vivek Prakash Yadav