Using a debug version of CuraEngine

Launch Cura with the --external-backend option. (On macOS, you can find the cura executable in Ultimaker Cura.app/Contents/MacOS.)

Run the debug CuraEngine with ./CuraEngine connect 127.0.0.1:49674. To find the correct port number, you can use lsof -Pan -p [cura PID] -i or similar.

If you wish to run CuraEngine in verbose mode, put -v at the end of the command line.