Odd block highlighting [master build]

[Kaushal Modi <kaushal.modi@gmail.com>]

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Lately I have been seeing this odd block highlighting issue in the master
build. Unfortunately I do not know how to recreate the issue, and the rough
estimate from when this started happening is also bad (some time last
month).

The best way to explain this issue is this gif:

http://i.imgur.com/yXLBoLO.gifv

For some reason, the region between lines 24 and 42 gets highlighted (not
selected) when the mouse cursor hovers on any text in that region. These
two points are not fixed; this could happen at random in different files.

I cannot make this go away by reverting the buffer or disabling *all* the
minor modes or changing the major mode to fundamental mode.

The only ways this gets 'fixed' is if I kill the buffer and re-open the
file, or if the file is modified outside of emacs and I revert the buffer.

But then this issue can repeat at any time in future.

Questions:

- Does this behavior look familiar to any recent commit to anyone?
- Where can I start looking so that I can provide a useful bug report? As
even disabling all minor modes and changing to fundamental mode retains
this issue, I do not what else to look at.

Here is my emacs build info:

Emacs version: GNU Emacs 25.1.1 (x86_64-unknown-linux-gnu, GTK+ Version
2.24.23)
 of 2016-09-18, built using commit 1229cc4ae640ea1fd9fafbb0bd64e72fc07994f8.

./configure options:
  --with-modules --prefix=/home/kmodi/usr_local/apps/6/emacs/emacs-25
'CPPFLAGS=-fgnu89-inline -I/home/kmodi/usr_local/6/include
-I/usr/include/freetype2 -I/usr/include' 'CFLAGS=-O2 -march=native'
'LDFLAGS=-L/home/kmodi/usr_local/6/lib -L/home/kmodi/usr_local/6/lib64'
PKG_CONFIG_PATH=/home/kmodi/usr_local/6/lib/pkgconfig:/home/kmodi/usr_local/6/lib64/pkgconfig:/cad/adi/apps/gnu/linux/x86_64/6/lib/pkgconfig:/cad/adi/apps/gnu/linux/x86_64/6/lib64/pkgconfig:/usr/lib/pkgconfig:/usr/lib64/pkgconfig:/usr/share/pkgconfig:/lib/pkgconfig:/lib64/pkgconfig

Features:
  XPM JPEG TIFF GIF PNG RSVG IMAGEMAGICK SOUND GPM DBUS GCONF GSETTINGS
NOTIFY ACL LIBSELINUX GNUTLS LIBXML2 FREETYPE LIBOTF XFT ZLIB
TOOLKIT_SCROLL_BARS GTK2 X11 MODULES


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Kaushal Modi

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