[LAD] suil error: Unable to open UI library

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