CGAL::random_polygon_2 infinite loop

main.cpp

#define CGAL_DONT_SHUFFLE_IN_RANDOM_POLYGON_2

#include <CGAL/Exact_predicates_exact_constructions_kernel.h>
#include <CGAL/Polygon_2.h>
#include <CGAL/point_generators_2.h>
#include <CGAL/random_polygon_2.h>

#include <vector>

typedef CGAL::Exact_predicates_exact_constructions_kernel K;
typedef K::Point_2                                        Point_2;
typedef std::vector<Point_2>                              Container;
typedef CGAL::Polygon_2<K, Container>                     Polygon_2;


// Point generator that let's us generate a point from a vector instead of randomly
class PointGeneratorFromSequence : public CGAL::Generator_base<Point_2> {
    void generate_point();
private:
    std::vector<Point_2> points;
    size_t cur_index;
public:
    typedef PointGeneratorFromSequence This;
    PointGeneratorFromSequence(std::vector<Point_2> &points) : points(points), cur_index(0) { generate_point(); };
    This& operator++() {
        generate_point();
        return *this;
    }
    This  operator++(int) {
        This tmp = *this;
        ++(*this);
        return tmp;
    }
};

typedef PointGeneratorFromSequence Point_generator;

void PointGeneratorFromSequence::generate_point() {
    assert(this->points.size() > cur_index);
    this->d_item = points[cur_index];
    this->cur_index++;
}

int main() {
    std::vector<Point_2> points;
    points.push_back(Point_2(0,1));
    points.push_back(Point_2(2,2));
    points.push_back(Point_2(2,1));
    points.push_back(Point_2(3,1));
    // Note that the last point is not used, it's just needed here because random_polygon_2 eats one extra unused
    // point from the point generator due to how the loop in random_polygon_2.h:copy_n_unique is written.
    points.push_back(Point_2(0,0));

    Polygon_2 polygon;
    
    // The following call will never return:
    CGAL::random_polygon_2(points.size() - 1, std::back_inserter(polygon), Point_generator(points));
    
    return 0;
}