Just a reminder to myself, for the next time I need to compile a classic GNU tool :

git clone --recurse-submodules https://git.savannah.gnu.org/git/grep.git
./bootstrap  # no need to install gnulib or call autoreconf -vif & cie
./configure && make

I was checking if a bug still existed in latest source code of grep.
It does not in v3.1.43, but the following hangs forever with grep 2.16 under Ubuntu:

 env -i LANG=en_US.UTF-8 src/grep -Fq $'\377\302' ../ludochaordic/content/images/2015/05/Strip-SVN-800-final.jpg

It did not git bisect to find out when the bug was solved.