Automatically load c++ mode for HPP and CPP files - emacs

Question

I found this thread, but the accepted solution does not work for me. I still need to manually load c++-mode for indentation (!) (not syntax highlighting, however. But that worked before anyway) to be set to c++-mode. In my init I have this code:
(setq
c-default-style "stroustrup"
)
(add-to-list 'auto-mode-alist '("\\.cpp\\'" . c++-mode))
(add-to-list 'auto-mode-alist '("\\.hpp\\'" . c++-mode))
(defun my-c++-mode-hook ()
(setq c-basic-offset 4)
(c-set-offset 'substatement-open 0))
(add-hook 'c++-mode-hook 'my-c++-mode-hook)
and my entire init looks like this:
(require 'package)
(add-to-list 'package-archives
'("melpa" . "http://melpa.milkbox.net/packages/") t)
(package-initialize)
(setq gc-cons-threshold 100000000)
(setq inhibit-startup-message t)
(defalias 'yes-or-no-p 'y-or-n-p)
(defconst demo-packages
'(anzu
company
duplicate-thing
;; ggtags
;; helm
;; helm-gtags
;; helm-projectile
;; helm-swoop
;; function-args
clean-aindent-mode
comment-dwim-2
;; dtrt-indent
ws-butler
;; iedit
yasnippet
smartparens
;; projectile
;; volatile-highlights
;; undo-tree
zygospore))
(defun install-packages ()
"Install all required packages."
(interactive)
(unless package-archive-contents
(package-refresh-contents))
(dolist (package demo-packages)
(unless (package-installed-p package)
(package-install package))))
(install-packages)
;; this variables must be set before load helm-gtags
;; you can change to any prefix key of your choice
;; (setq helm-gtags-prefix-key "\C-cg")
(add-to-list 'load-path "~/.emacs.d/custom")
;; (require 'setup-helm)
;; (require 'setup-helm-gtags)
;; (require 'setup-ggtags)
(require 'setup-cedet)
(require 'setup-editing)
(windmove-default-keybindings)
;; function-args
;; (require 'function-args)
;; (fa-config-default)
;; (define-key c-mode-map [(tab)] 'company-complete)
;; (define-key c++-mode-map [(tab)] 'company-complete)
;; company
(require 'company)
(add-hook 'after-init-hook 'global-company-mode)
(delete 'company-semantic company-backends)
;; (define-key c-mode-map [(tab)] 'company-complete)
;; (define-key c++-mode-map [(tab)] 'company-complete)
;; (define-key c-mode-map [(control tab)] 'company-complete)
(define-key c++-mode-map [(control tab)] 'company-complete)
;; company-c-headers
(add-to-list 'company-backends 'company-c-headers)
;; hs-minor-mode for folding source code
(add-hook 'c-mode-common-hook 'hs-minor-mode)
;; Available C style:
;; “gnu”: The default style for GNU projects
;; “k&r”: What Kernighan and Ritchie, the authors of C used in their book
;; “bsd”: What BSD developers use, aka “Allman style” after Eric Allman.
;; “whitesmith”: Popularized by the examples that came with Whitesmiths C, an early commercial C compiler.
;; “stroustrup”: What Stroustrup, the author of C++ used in his book
;; “ellemtel”: Popular C++ coding standards as defined by “Programming in C++, Rules and Recommendations,” Erik Nyquist and Mats Henricson, Ellemtel
;; “linux”: What the Linux developers use for kernel development
;; “python”: What Python developers use for extension modules
;; “java”: The default style for java-mode (see below)
;; “user”: When you want to define your own style
(setq
c-default-style "stroustrup"
)
(add-to-list 'auto-mode-alist '("\\.cpp\\'" . c++-mode))
(add-to-list 'auto-mode-alist '("\\.hpp\\'" . c++-mode))
(defun my-c++-mode-hook ()
(setq c-basic-offset 4)
(c-set-offset 'substatement-open 0))
(add-hook 'c++-mode-hook 'my-c++-mode-hook)
(global-set-key (kbd "RET") 'newline-and-indent) ; automatically indent when press RET
;; activate whitespace-mode to view all whitespace characters
(global-set-key (kbd "C-c w") 'whitespace-mode)
;; show unncessary whitespace that can mess up your diff
(add-hook 'prog-mode-hook (lambda () (interactive) (setq show-trailing-whitespace 1)))
;; use space to indent by default
(setq-default indent-tabs-mode nil)
;; set appearance of a tab that is represented by 4 spaces
(setq-default tab-width 4)
;; Compilation
(global-set-key (kbd "<f5>") (lambda ()
(interactive)
(setq-local compilation-read-command nil)
(call-interactively 'compile)))
;; setup GDB
(setq
;; use gdb-many-windows by default
gdb-many-windows t
;; Non-nil means display source file containing the main routine at startup
gdb-show-main t
)
;; Package: clean-aindent-mode
(require 'clean-aindent-mode)
(add-hook 'prog-mode-hook 'clean-aindent-mode)
;; Package: dtrt-indent
(require 'dtrt-indent)
(dtrt-indent-mode 1)
;; Package: ws-butler
(require 'ws-butler)
(add-hook 'prog-mode-hook 'ws-butler-mode)
;; Package: yasnippet
(require 'yasnippet)
(yas-global-mode 1)
;; Package: smartparens
(require 'smartparens-config)
(setq sp-base-key-bindings 'paredit)
(setq sp-autoskip-closing-pair 'always)
(setq sp-hybrid-kill-entire-symbol nil)
(sp-use-paredit-bindings)
(show-smartparens-global-mode +1)
(smartparens-global-mode 1)
;; Package: projejctile
(require 'projectile)
(projectile-global-mode)
(setq projectile-enable-caching t)
;; (require 'helm-projectile)
;; (helm-projectile-on)
;; (setq projectile-completion-system 'helm)
;; (setq projectile-indexing-method 'alien)
;; Package zygospore
(global-set-key (kbd "C-x 1") 'zygospore-toggle-delete-other-windows)
(require 'ggtags)
(add-hook 'c-mode-common-hook
(lambda ()
(when (derived-mode-p 'c-mode 'c++-mode 'java-mode 'asm-mode)
(ggtags-mode 1))))
(define-key ggtags-mode-map (kbd "C-c g s") 'ggtags-find-other-symbol)
(define-key ggtags-mode-map (kbd "C-c g h") 'ggtags-view-tag-history)
(define-key ggtags-mode-map (kbd "C-c g r") 'ggtags-find-reference)
(define-key ggtags-mode-map (kbd "C-c g f") 'ggtags-find-file)
(define-key ggtags-mode-map (kbd "C-c g c") 'ggtags-create-tags)
(define-key ggtags-mode-map (kbd "C-c g u") 'ggtags-update-tags)
(define-key ggtags-mode-map (kbd "M-,") 'pop-tag-mark)
I got it from here: http://tuhdo.github.io/c-ide.html
And currently I am altering it to fit my needs better.
Any idea what might be conflicting here, causing
(add-to-list 'auto-mode-alist '("\\.cpp\\'" . c++-mode))
(add-to-list 'auto-mode-alist '("\\.hpp\\'" . c++-mode))
not to work?

Answer 1

No idea why but commenting out
(require 'dtrt-indent)
(dtrt-indent-mode 1)
and
(require 'setup-editing)
fixed it.