Subject: bug#20711: 25.0.50; Emacs 24.5 regression: C++ font lock displays incorrectly when pasting

From: Alan Mackenzie <[email-masked]>
Date: 2 Jun 2015 13:41:59 -0000

Hello, Barry.

In article <[email-masked]> you wrote:
> [-- text/plain, encoding 7bit, charset: UTF-8, 88 lines --]

> Create ~/tmp/foo.cc with file contents:

>  //

Did you create it using Emacs?  If so, C++ Mode will automatically have
added a linefeed at the end of the bare line.

> Start Emacs 24.5 by:

>  emacs -Q ~/tmp/foo.cc

> Type 42 in some other X11 window (eg Chrome), and select it. In the Emacs
> window, paste it with the middle mouse button (mouse-yank-primary). The
> number 4 is not fontified.

That's a pretty crisp recipe, thanks.  I can't reproduce it, though.  I'm
in XFCE in X-Windows, and the program I used to get "42" into the
mouse-yank-primary buffer was vim running on xfce4-terminal.

I'm assuming that the "//" is at the beginning of the line, that there is
no trailing space after it, but there is a linefeed at the end of the
line.  I yanked in the "42" just after the second "/".

Could there be anything unusual about the "42" you got from Chrome?

What's your desktop environment?

Is there anything else you can think of in your setup that might be
influencing the bug?  Does the bug happen every time you try it,
sometimes, or did it only happen once?

> Try the same with Emacs 24.4 and all fontification is correct.

As a matter of interest, would you reproduce your Emacs configuration
line, please (M-: system-configuration-options).

> In GNU Emacs 25.0.50.1 (x86_64-unknown-linux-gnu, GTK+ Version 2.24.23)
> of 2015-05-12 on REDACTED

This is Emacs 25.0.50.  What is the connection, if any, between the debug
info you included below, and the test you ran on 24.5?

> Windowing system distributor `The X.Org Foundation', version 11.0.11501000
> System Description: Ubuntu 14.04 LTS (upgraded from: Ubuntu 12.04.4 LTS)

> Configured features:
> XPM JPEG TIFF GIF PNG SOUND GSETTINGS NOTIFY FREETYPE XFT ZLIB

> Important settings:
>  value of $LANG: en_US.UTF-8
>  value of $XMODIFIERS: @im=ibus
>  locale-coding-system: utf-8-unix

> Major mode: C++/l

[ .... ]

-- 
Alan Mackenzie (Nuremberg, Germany).