workaround for IntervalMap empty intersections

[danmatichuk]

The function IntervalMap.intersecting is incorrectly returning nonempty results when given an empty interval. This works around the issue by explicitly adding an isEmpty check.

This resolves an issue where ElfLoader would error, saying "Found section header that overlaps with program header.", if presented with a segment that has zero file size.

[RyanGlScott]

The function IntervalMap.intersecting is incorrectly returning nonempty results when given an empty interval.

Huh. Can you provide an example of some IntervalMap code that returns incorrect results? It sounds like we ought to file a bug report against IntervalMap, assuming that someone else hasn't already done so before.

[danmatichuk]

I've posted an issue to the github project for IntervalMap here bokesan/IntervalMap#9, which contains an example.

[RyanGlScott]

Thanks! I think it would be worth leaving a comment next to the code that explains why we bother to include this unusual special case, citing the issue alongside it.

Also, I did some limited testing, and this issues appears to fix #302! Can you add that as a test case? Alternatively, perhaps you have a test case of your own?

[RyanGlScott]

Now that IntervalMap-0.6.2.0 is on Hackage with a fix for bokesan/IntervalMap#9, perhaps we should just bump the lower version bounds on IntervalMap to >= 1.6.2. That way, we can drop the workaround entirely.

[danmatichuk]

Agreed. I'll roll back this change in favor of jump bumping the revision and then add your test to the repo.