In cc-mode, I want a way set all syntax highlight colours to slightly more desaturated versions when inside a #if 0 ... #endif block. If that would be troublesome/hard to maintain (having to set all the colours manually), just setting all the text inside the block to a single colour would be fine too. I've tried this, but is intended for use with a single keyword.

I'm using spacemacs [email protected]

1 Answer 1


Emacs has a built-in package for ifdefs. To quote from https://www.gnu.org/software/emacs/manual/html_node/emacs/Other-C-Commands.html:

 ‘M-x hide-ifdef-mode’
      Hide-ifdef minor mode hides selected code within ‘#if’ and ‘#ifdef’
      preprocessor blocks.  If you change the variable
      ‘hide-ifdef-shadow’ to ‘t’, Hide-ifdef minor mode shadows
      preprocessor blocks by displaying them with a less prominent face,
      instead of hiding them entirely.  See the documentation string of
      ‘hide-ifdef-mode’ for more information.
  • I will read the doc more later, but it seems that it is what I'm looking for, thanks.
    – Luctins
    Commented Jan 19, 2021 at 13:17
  • Can it update automatically, or do i need to call hide-ifdefs to update?
    – Luctins
    Commented Jan 20, 2021 at 13:08

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