Emacs 24.x and 25.x have a bug in CC Mode which can result in some operations failing with the error

Invalid search bound (wrong side of point)

For example, I can reproduce it with the following file a.c:

#if defined(FOO) || \

and running

emacs -Q -nw a.c --eval '(occur "FOO")'

(Running M-x occur RET FOO RET after that works. I have a bigger file where this doesn't work.)

This is a known bug: #28850. The fix is in two commits 46540a1c7adb1b89b6c2f6c9150fe8680c3a5fba and ad68bbd0da4ed90117f09dc2344c0c3d9d728851 which were first released in Emacs 26.1. I can confirm that Emacs 26.3 works with both the minimal example above and my real file.

The machines I use most often run Emacs 24.5.1 or Emacs 25.2.2, so I need a workaround for Emacs 24.x and 25.x. My init file has several hot fixes for Emacs bug and I'm fine with adding one more. I normally hot-fix in an eval-after-load form, either by advising a function or by replacing its definition.

But here there's a bug in the function c-make-font-lock-search-form which, if I understand correctly, is used at compile time. This is the relevant part of cc-fonts.el:

  (defun c-make-font-lock-search-form (regexp highlights)
    ;; this code needs to be patched
  (defun c-make-font-lock-context-search-function (normal &rest state-stanzas)
    (c-make-font-lock-search-form …)) ;; this call needs to be patched

(c-lang-defconst c-cpp-matchers
  t `( … ,(c-make-font-lock-context-search-function …)))

So cc-fonts.elc contains buggy byte-compiled code. Merely fixing the buggy function after cc-fonts.elc is loaded won't help. Even fixing the function before cc-fonts.elc wouldn't help.

How can I work around this bug? The workaround needs to work on Emacs 24.x and 25.x. The workaround needs to fix the "Invalid search bound" error, without disabling fontification. I don't mind if there's a slight loss of performance or accuracy compared to the official fix.

  • Scanning the bug report, does it help to turn off jit-lock-stealth?
    – Drew
    Commented Oct 28, 2019 at 20:12
  • @Drew Isn't it off by default? jit-lock-stealth-time defaults to nil, it's nil in my configuration, and its documentation states “If nil, stealth fontification is never performed.”. I don't do anything special regarding jit-lock-mode, so it's turned on with default parameters. I think Jit Lock is just the way the reporter happened to trigger the bug. With me the trigger was occur. Commented Oct 29, 2019 at 18:55
  • Dunno. The bug report seemed to be about the problem happening when it's non-nil.
    – Drew
    Commented Oct 29, 2019 at 20:47

1 Answer 1


A big-hammer approach is to add cc-mode to your config, as it is maintained externally and tends to be very backwards-compatible.

The latest version says "CC Mode 5.34 should work out of the box with Emacs >= 24.5 ... It may well work on earlier versions."

The 5.33 release notes say "The minimum versions supported ... Emacs 23.2".

  • 1
    n.b. M-x c-version says Emacs 26.3 comes with CC Mode version 5.33.2
    – phils
    Commented Oct 28, 2019 at 21:34

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.