I’ve updated the darktable (with the last merge), overwritten lightroom.c modified and compiled again.
I’ve got a working dt ! 
Thanks for your help !
The normal lightroom import features work but I don’t see the effects of my changes yet.
I’ll work on this and probably come back here to get some more support.
I see 2 main difficulties for the time being:
- where have I to restart the cmake process once I’ve modified the source file (lightroom.c) and maybe avoid to redo everything ?
- how to make the log work ? At least to see the existing log messages. That would be the best way for me to try to understand what does happen (or not).
Edit: I see some logs in the log file, but none which could correspond to those in lightroom.c. Is there something like-d luato activate them ?