[LAD] suil error: Unable to open UI library

[Phil CM]

Hello LADs

I'm trying to make a GUI for a LV2 synth based on so-404. In fact, I'm 
trying to learn C / C++.

I got everything to build OK, but I'm stuck on a hard to read execution 
error ; when I load the plugin in jalv, it loads it OK, but fails to 
load the UI and says :

suil error: Unable to open UI library 
/usr/local/lib/lv2/kis.lv2/kis_gui.so 
(/usr/local/lib/lv2/kis.lv2/kis_gui.so: undefined symbol: 
_Z17instantiateSO_404PK15_LV2_DescriptordPKcPKPK12_LV2_Feature)

(The architecture is based on 
https://github.com/harryhaaren/lv2/tree/master/plugins/eg-sinsynth.lv2 
in fact it is exactly the same : synth.c/h, synth_gui.cpp, widget.cpp/h, 
built as synth.so synth_gui.so synth.ttl and manifest.ttl using waf).

I must say I'm still to fully understand the concept of descriptors... 
Can somebody see what I'm doing wrong?

Thanks

--Philippe "xaccrocheur" Coatmeur