http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60708
--- Comment #2 from Ville Voutilainen <ville.voutilainen at gmail dot com> --- Well, no - the error that 4.7 gives is caused by my using a C++14 deduced return type for a function there. 4.9 supports those with --std=c++1y.
