print_ext_c() { echo "c h"; }
print_ext_cxx() { echo "cxx cpp cc h hh hpp ipp tpp"; }

locate_source_files() {
  local sources=($(eval print_ext_${1:1}))
  eval find "${@:2}" -type f \
    \\\( \
      -name '__blank__' \
      $(printf " -o -name '*.%s'" "${sources[@]}") \
    \\\)
}