As I'm currently trying to debug an issue with my SPI link, which is addressed through pigpio, I'd like to make pigpiod write warnings and debug messages (if such occur) to stderr.
Errors are reported to
/dev/pigerr on the Pi running the daemon.
cat /dev/pigerr may provide useful information.
You can enable tracing of the API by using the pigs csi command.
Numbers 1 to 7 should uncover more tracing.
Try something like
pigs csi 5 or
pigs csi 6.
The results will be sent to