I recently notice that there's some strange behaviours of the font-lock of the c++-mode.

Let's start emacs by `emacs -Q` in the terminal, edit a new file `test.cpp` and save the following contents



Then put the cursor two lines above the `int main` line, type `int test`, you will find that the color of word `main` changes from *blue* to *black*



Backspace the current line to `in` or `i`, you will see that the color of `main` change back to *blue*



This is not a very big problem under this test, but I use color theme that the function names are in *bold* type. So when I add a function above another function, the font-lock of the below one keep changing all the time which is really annoying.

Is this a emacs bug ? I want *bold* function name and other *bold* keywords but how can I get rid of it ? Any help will be appreciated.


In GNU Emacs 25.1.1 (x86_64-apple-darwin13.4.0, NS appkit-1265.21 Version 10.9.5 (Build 13F1911))
of 2016-07-25 built on builder10-9.porkrind.org
Windowing system distributor 'Apple', version 10.3.1404
Configured using:
'configure --with-ns '--enable-locallisppath=/Library/Application
Support/Emacs/${version}/site-lisp:/Library/Application
Support/Emacs/site-lisp''

Configured features:
NOTIFY ACL LIBXML2 ZLIB TOOLKIT_SCROLL_BARS NS

Important settings:
  value of $LC_ALL: en_US.UTF-8
  value of $LC_CTYPE: UTF-8
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

Minor modes in effect:
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  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
Entering debugger...
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Type C-x 1 to delete the help window.
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Memory information:
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