https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82354
--- Comment #2 from David Malcolm <dmalcolm at gcc dot gnu.org> --- Note: the pertinent extension appears to be documented here: https://gcc.gnu.org/onlinedocs/gcc-7.2.0/gcc/Variable-Length.html#index-parameter-forward-declaration (see @cindex parameter forward declaration within extend.texi)
