Reproducing a GCC 8.1 ABI compatibility bug

I was reading about GCC and noticed this very suspicious warning line about an accidental compatibility break:

I thought it would be interesting to reproduce this. I reprodcued this specific scenario they outline and compiled two translations units, one with GCC 8.1, one with an earlier version (GCC 7) and observed the segfault that happens when two incompatible calling conventions interact with each other.

Any thoughts?