Minor modes not working with derived mode from c++-mode

Question

I created a derived mode (using define-derived-mode) based on c++-mode to include new keywords, etc.

The mode is working great, but I'm having problems with other minor modes that stop working with my derived mode.

For example, flycheck and company-mode, the first stops telling me when there is broken code in the buffer, and the second will not complete (it will always say No completion found).

If I load the c++-mode in the buffer, all these minor modes start working again.

So, my question is how can I make these modes see my derived mode as if it was c++-mode.

Thanks!

Answer 1

company-mode is just a framework. If you want completions from company-clang, try adding your major mode to company-clang-modes.

But if you only created a new major mode for minor reasons like new font-lock keywords, maybe you would be better served by moving that logic to a new minor mode instead (and adding it to c++-mode-hook).

Answer 2

Flycheck provides flycheck-add-mode to register syntax checkers for new major modes, e.g.

(dolist (checker '(c/c++-clang c/c++-gcc c/c++-cppcheck))
  (flycheck-add-mode checker 'my-derived-mode))

This will add your my-derived-mode to all C/C++ syntax checkers in Flycheck. After evaluating this expression, Flycheck will check buffers in your derived mode just like buffers in the default C and C++ modes.