Crash resulting from polygons with overlapping parallel segments

[Chad Parker]

pcb crashes under certain conditions when a polygon, or a segment of a polygon has zero area. For example, creating a polygon with the following six points:

 1 ______ 6
  |******|
  |******|
 3|******|
  |\*****|
  |*\****|
  |**\___|
 2 4 5

(*'s are used so that the auto-formatting doesn't cause the ASCII art to collapse)

If you then attempt to move point 2, pcb will die. Obviously this is not a shape that people are frequently interested in, but, a simpler case could happen accidentally quite easily:

1,3 ----------- 2

While debugging something else, I stumbled on this. In a debug build, there is failed assertion in polygon1.c:

Assertion failed: (poly_Valid (np)), function original_poly, file ../../src/polygon.c, line 329.

This appears to check the number of points in a polygon against the number of items found in an r_search.

[Peter Clifton (pcjc2)]

Hi, Doesn't crash for me - but the asserts are only enabled during debug builds.

It is quite possible to create an inconsistent (self intersecting) polygon geometry which will have the same effect if debug is enabled.

[Chad Parker (parker-charles)]

This only seems to be an issue when building with the DEBUG flag is set.