Yep, I found the bad function....
[simplemsp~] don't use CLASS_ATTR_LABEL ! The definition has changed :
Max 6 :
#define CLASS_ATTR_LABEL(c,attrname,flags,labelstr)
CLASS_ATTR_ATTR_FORMAT(c,attrname,"label",USESYM(symbol),flags,"s",gensym_tr(labelstr))
Max 5 :
#define CLASS_ATTR_LABEL(c,attrname,flags,labelstr)
CLASS_ATTR_ATTR_FORMAT(c,attrname,"label",USESYM(symbol),flags,"s",gensym(labelstr))
Small differences that matter!