After

commit daf434b40d61e8cc99485988017a4a95ff475922
Author: Paul Eggert <eggert@cs.ucla.edu>
Date:   Thu Aug 24 16:15:59 2017 -0700

     Prefer ‘double’ for FP temps in xterm.c

     * src/xterm.c (xm_scroll_callback, xaw_jump_callback)
     (x_set_toolkit_scroll_bar_thumb)
     (x_set_toolkit_horizontal_scroll_bar_thumb): Prefer ‘double’ to
     ‘float’ for individual local floating-point temporaries.

I get scrollbar warnings for the Motif build on Debian GNU/Linux, see
the attached screnshot.  I observed this when testing server/client
interactions where in a first terminal I did

emacs -Q -nw -xrm "emacs.synchronous: true" -f server-start

and in a second terminal I did

emacsclient -c

The warning appears in the first terminal's Emacs window after the GUI
window pops up.  I have no idea why text, mode line and echo area of
that window are completely mangled by that warning.  I have to resize
the terminal window in order to get its display working again.

martin