Compilation bug in >= 1.76 from detail::overlay::collinear::handle_as_equal

[kb0n]

I experience some problems when adapting Lanelet2 library to boost v1.78.0 , one of which is caused by a bug introduced with release v1.76.0 and has not been fixed yet.

When was this introduced

Introduced with 84d3a8d, specifically this line: 84d3a8d#diff-21d011ddccb292362e430e14bebe3673bfa5e10f432ee3a85ede067fe8f140c6R993 which is still existing in the latest boost version as well.

Identified issue

You're using a conditional operator, but range_q and range_p can be of a different type.

In my case, they were Eigen::Matrix<double, 2, 1> and Eigen::Matrix<double, 2, 1, 2>, i.e. aligned and non-aligned 2D Eigen-vectors.

Proposed fix

The fix is quite simple. This would be a proposal for the current version, but applicable to all other releases as well

-        auto const dm = fun::distance_measure(info.intersections[1],
-                arrival_p == 1 ? range_q.at(1) : range_p.at(1));
+        auto const dm = arrival_p == 1
+               ? fun::distance_measure(info.intersections[1], range_q.at(1))
+               : fun::distance_measure(info.intersections[1], range_p.at(1));

It would be nice if this could be backported to all affected revisions as well with a patch-release. I personally would be happy if this was provided "only" from v1.78.0 onward.

[kb0n]

Of course this is only what I have perceived so far.

I'll re-trigger this error for a more precise error-message.

[barendgehrels]

Hi, I cannot reproduce that. Can you verify it still occurs in 1.82?
However, I have no problems applying your fix and will do.
But we won't backport it, because we cannot update previous versions of the whole Boost library because of this bug.

[barendgehrels]

Now I can reproduce it, if coordinate type is also different. But get more (similar) problems. Will be fixed.