I can also confirm success when compiling a file with a path "ömlaut/asdf.cpp". ...

I can also confirm success when compiling a file with a path "ömlaut/asdf.cpp".

  $ g++ --version | head -n 1
  g++ (Gentoo Hardened 4.9.3 p1.1, pie-0.6.2) 4.9.3
  $ uname -r -m
  4.1.6-hardened i686
  $ echo $LANG
  en_US.UTF-8
  $ bash --version | head -n 1
  GNU bash, version 4.3.42(1)-release (i686-pc-linux-gnu)