Dear Tetsuo Koyama,
A few weeks ago you introduced [[fallthrough]] in a few places of Getfem.
I completely agree with your intention but the problem with this feature is that
it's supported only as of C++17. Many users including us are not yet capable to
upgrade to the compilers that support this standard. Default compilation of getfem
is currently at C++ 11, but may be GCC supports it (I don't know).
May I ask you to replace [[fallthrough]] with some kind of macro that is only triggered
when standard 17 is being used?