I don't like all the major mode bindings. So I usually just
(setq the-map-in-question (make-sparse-keymap)) each time I come across a new major mode.
But for c++-mode-map, it does not remain empty.
help-fns+.el to display the bindings of the keymap. When I open emacs,
c++-mode-map is indeed empty. But as soon as I open a C++ file, the following bindings in the keymap (in the picture) appears.
I still don't know how to fix this issue though.