[Bug c++/85110] Missing underlines for some bad arguments

[dmalcolm at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=85110

--- Comment #4 from David Malcolm <dmalcolm at gcc dot gnu.org> ---
Candidate patch:
  https://gcc.gnu.org/ml/gcc-patches/2018-04/msg00342.html