gnome-canvas needs gnome-canvas-path-def and registeres it with GType
rb-gnomecanvas then tries to create its own gnome-canvas-path-def GType with the same name (which fails), so renaming it in gnomecanvas/src/rbgnome-canvas-path-def.c to _Rb_GnomeCanvasPathDef (add the part between the lines) helps.
So the bug is that:
rb-gnomecanvas initializes gnome-canvas
gnome-canvas needs gnome-canvas- path-def and registeres it with GType
rb-gnomecanvas then tries to create its own gnome-canvas- path-def GType with the same name (which fails), so renaming it in gnomecanvas/ src/rbgnome- canvas- path-def. c to _Rb_GnomeCanvas PathDef (add the part between the lines) helps.