The missing source is ok, in [above](https://github.com/geany/geany-plugins/pull/1170#issuecomment-1148048143) you stepped into `tcgetattr()` stepped along a bit which was fine even if no source was shown, then did `next` not `step`. I would guess `tcgetattr()` does a trap to the kernal, and thats probably not tracable by GDB, which then gets very confused trying to do `next`. Debugging _should_ work ok if you step over the call to `tcgetattr()` not into it.