/usr/include/libgnomecanvasmm-2.6/libgnomecanvasmm/private/ is in libgnomecanvasmm-2.6-dev 2.26.0-2+b1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/libgnomecanvasmm-2.6/libgnomecanvasmm/private/bpath_p.h
/usr/include/libgnomecanvasmm-2.6/libgnomecanvasmm/private/canvas_p.h
/usr/include/libgnomecanvasmm-2.6/libgnomecanvasmm/private/ellipse_p.h
/usr/include/libgnomecanvasmm-2.6/libgnomecanvasmm/private/group_p.h
/usr/include/libgnomecanvasmm-2.6/libgnomecanvasmm/private/item_p.h
/usr/include/libgnomecanvasmm-2.6/libgnomecanvasmm/private/line_p.h
/usr/include/libgnomecanvasmm-2.6/libgnomecanvasmm/private/path-def_p.h
/usr/include/libgnomecanvasmm-2.6/libgnomecanvasmm/private/pixbuf_p.h
/usr/include/libgnomecanvasmm-2.6/libgnomecanvasmm/private/polygon_p.h
/usr/include/libgnomecanvasmm-2.6/libgnomecanvasmm/private/rect-ellipse_p.h
/usr/include/libgnomecanvasmm-2.6/libgnomecanvasmm/private/rect_p.h
/usr/include/libgnomecanvasmm-2.6/libgnomecanvasmm/private/rich-text_p.h
/usr/include/libgnomecanvasmm-2.6/libgnomecanvasmm/private/shape_p.h
/usr/include/libgnomecanvasmm-2.6/libgnomecanvasmm/private/text_p.h
/usr/include/libgnomecanvasmm-2.6/libgnomecanvasmm/private/widget_p.h