indentation (with multiline comments) in batch processing

Question

i'm trying to indent a couple of C++-files (and untabify them; and remove trailing whitespace), so i thought about using emacs in batch mode.

Since I'm pretty much a noob when it comes to elpa (or lisp in general), i searched the web and came up with something like this:

$ cat myscript.el
(defun myindent ()
   "Format the whole buffer."
   (c-set-style "stroustrup")
   (indent-region (point-min) (point-max) nil)
   (untabify (point-min) (point-max))
   (delete-trailing-whitespace)
   (save-buffer)
)
$ emacs -batch "somefile.cpp" -l $(pwd)/myscript.el -f myindent

This kind of works.

However, all of my header files contain a boilerplate in a C-style multiline comment, which is nicely formatted. Something like:

/*-----------------------------------------------------------------
LOG
    Foo Bar - the Pizza man

    Copyright (c) 1997-2017 Me, You and others
    For information on usage and redistribution, and for a DISCLAIMER OF ALL
    WARRANTIES, see the file "LICENSE.txt".

    CLASS
        Onion
        smells and bits like an onion

    KEYWORDS
        ingredients, vegetable

    DESCRIPTION
        hum, hmm...later

-----------------------------------------------------------------*/

now when i run my scrip on that file, all the pre-formatting is lost, and it ends up as:

/*-----------------------------------------------------------------
  LOG
  Foo Bar - the Pizza man

  Copyright (c) 1997-2017 Me, You and others
  For information on usage and redistribution, and for a DISCLAIMER OF ALL
  WARRANTIES, see the file "LICENSE.txt".

  CLASS
  Onion
  smells and bits like an onion

  KEYWORDS
  ingredients, vegetable

  DESCRIPTION
  hum, hmm...later

  -----------------------------------------------------------------*/

So the question is: Is there a way to indent my files in batch mode and preserve the formatting within multiline comments (and strings)?

I've tried using (indent-code-rigidly (point-min) (point-max) 0) instead of indent-region which leaves the comments intact, but I preservers too much of the original indentation of the code. So I guess I'd like something inbetween indent-region and indent-code-rigidly)

Answer 1

Should just be a matter of setting the comment offset to always choose the current indentation:

(defun myindent ()
   "Format the whole buffer."
   (c-set-style "stroustrup")
   ;; `c' is for comment.
   (c-set-offset 'c (lambda (_syntax) (current-indentation)))
   (setq indent-tabs-mode nil) ; No new tabs.
   (indent-region (point-min) (point-max) nil)
   (untabify (point-min) (point-max)) ; Remove any remaining old tabs.
   (delete-trailing-whitespace)
   (save-buffer))

Answer 2

While I haven't found a solution (yet) to do-what-i-want withing emacs, I ended up by doing the indentation with astyle instead.

This was acceptable, as for now I'm really interested into a one-time conversion to enforce a common indentation across all files.

I'm still interested in a real emacs solution though.