unexpected seg fault during union

[jandrejevic12]

Hello,

I was testing a union in the following small C++ example when I encountered an unexpected seg fault:

Paths64 subject;
subject.push_back(MakePath({3333339, -61588000, 31148604, -61588000, -2296358, -43414476, -922323, -72134223}));
subject.push_back(MakePath({750923, -61588000, 28566188, -61588000, -4878774, -43414476, -3504739, -72134223}));
subject.push_back(MakePath({28720589, -50574319, 28566188, -61588000, 31148604, -61588000}));
Paths64 result = Union(subject, FillRule::NonZero);

There are a few exactly touching vertices among the polygons, and perturbing them does resolve the issue. I tried to pinpoint the precise location of the seg fault, and the issue arises inside ClipperBase::Split line 2746 (e.next_in_ael->join_with = JoinWith::None;) where e.next_in_ael evaluates to nullptr thus producing the seg fault. Do you have any thoughts on why this might be the case? Thanks for your help!

[AngusJohnson]

Replace:

Clipper2/CPP/Clipper2Lib/src/clipper.engine.cpp

Lines 2761 to 2762 in bc5855a

	if (IsOpen(e) || !IsHotEdge(e) || !prev ||
	IsOpen(*prev) || !IsHotEdge(*prev)) return;

Clipper2/CPP/Clipper2Lib/src/clipper.engine.cpp

Lines 2787 to 2788 in bc5855a

	if (IsOpen(e) || !IsHotEdge(e) ||
	!next || IsOpen(*next) || !IsHotEdge(*next)) return;

with:

    if ( IsOpen(e) || !IsHotEdge(e) || !prev || IsHorizontal(e) ||
      IsOpen(*prev) || !IsHotEdge(*prev) || IsHorizontal(*prev) ) return;

    if ( IsOpen(e) || !IsHotEdge(e) || IsHorizontal(e) ||
      !next || IsOpen(*next) || !IsHotEdge(*next) || IsHorizontal(*next) ) return;

[jandrejevic12]

Thank you so much, that fixed the issue! :)