> From: Chris Gregory <czipperz@gmail.com>
> Date: Mon, 26 Dec 2016 22:55:54 -0600
>
> This patch changes string_from_display_spec (a static function in
> xdisp.c) to use a do while loop instead of a while loop.  The
> precondition is checked by the if statement and is redundant in the
> first iteration.  This redundancy is now removed.

The indenting for 'do-while' wasn't using the usual GNU style, and while fixing 
that I noticed that the code could be further simplified, so I installed the 
attached further patch.