sym_difference yields bad result for int polygons

[vschoech@…]

My "_TPolygon" type is actually a multi-polygon, based on a polygon type that is oriented counter-clockwise and open (not closed). Please consider the following example, which apparently works fine:

tc::geo::polygon<double> polygonA; // tc::geo::polygon<...> is actually a MULTIPOLYGON, with polygons oriented COUNTER-CLOCKWISE and OPEN (not closed).
boost::geometry::read_wkt("MULTIPOLYGON(((564 2394,1548 2850,2526 2916,2526 1073741823,564 1073741823,564 2394)))", polygonA); // does not throw
boost::geometry::is_valid(polygonA); // returns true

tc::geo::polygon<double> polygonB;
boost::geometry::read_wkt("MULTIPOLYGON(((564 3252,2526 3252,2526 1073741823,564 1073741823,564 3252)))", polygonB); // does not throw
boost::geometry::is_valid(polygonB); // returns true

tc::geo::polygon<double> polygonC;
boost::geometry::sym_difference(polygonA, polygonB, polygonC); // does not throw
boost::geometry::is_valid(polygonC); // returns true
// polygonC is now "MULTIPOLYGON(((564 3252,564 2394,1548 2850,2526 2916,2526 3252,564 3252)))"

Note: std::numeric_limits<int>::max()/2 == 1073741823 Now, simply replace double by int:

tc::geo::polygon<int> polygonA; // tc::geo::polygon<...> is actually a MULTIPOLYGON, with polygons oriented COUNTER-CLOCKWISE and OPEN (not closed).
boost::geometry::read_wkt("MULTIPOLYGON(((564 2394,1548 2850,2526 2916,2526 1073741823,564 1073741823,564 2394)))", polygonA); // does not throw
boost::geometry::is_valid(polygonA); // returns true

tc::geo::polygon<int> polygonB;
boost::geometry::read_wkt("MULTIPOLYGON(((564 3252,2526 3252,2526 1073741823,564 1073741823,564 3252)))", polygonB); // does not throw
boost::geometry::is_valid(polygonB); // returns true

tc::geo::polygon<int> polygonC;
boost::geometry::sym_difference(polygonA, polygonB, polygonC); // does not throw
boost::geometry::is_valid(polygonC); // returns true
TRACE( "===================== polygonC2=" << polygonC );
// polygonC is now "MULTIPOLYGON(((564 3252,564 2394,1548 2850,2526 2916,2526 *!*333412*!*,564 3252)))"

As you can see, one value is completely off. This seems to happen reliably whenever the input is based on int and contains large numbers.

This issue may be related to Ticket #10658.

[sghanta05@…]

Hey I am new to boost and I would like to work on this bug. Could someone guide me?