Thank you @certik for the quick response.
Concerning iso_c_binding, you are right. I actually have two versions of LFortran installed, and I compiled using the old one by mistake. I apologize for the false statement above, which got the strikethrough it deserved. I got rid of the old version so this mistake won’t happen again.
Many things using iso_c_binding work as expected. The progress is impressive. But I have issues interfacing existing C libraries (not C functions themselves, e.g. intefacing c_strlen works.) Will report accordingly at the right place.