Aside from other warnings, I've spotted some of these. Given that they are around the path effects, there might be something to them.
./live_effects/effect.h:99: warning: 'virtual NArtBpath* Inkscape::LivePathEffect::Effect::doEffect(NArtBpath*)' was hidden ./live_effects/lpe-slant.h:27: warning: by 'virtual void Inkscape::LivePathEffect::LPESlant::doEffect(SPCurve*)' ./live_effects/effect.h:101: warning: 'virtual std::vector<Geom::Path, std::allocatorGeom::Path > Inkscape::LivePathEffect::Effect::doEffect(std::vector<Geom::Path, std::allocatorGeom::Path >&)\ ' was hidden ./live_effects/lpe-slant.h:27: warning: by 'virtual void Inkscape::LivePathEffect::LPESlant::doEffect(SPCurve*)' ./live_effects/effect.h:103: warning: 'virtual Geom::Piecewise<Geom::D2Geom::SBasis > Inkscape::LivePathEffect::Effect::doEffect (Geom::Piecewise<Geom::D2Geom::SBasis >&)' was hidden ./live_effects/lpe-slant.h:27: warning: by 'virtual void Inkscape::LivePathEffect::LPESlant::doEffect(SPCurve*)'