https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104552
--- Comment #25 from Roland Illig <roland.illig at gmx dot de> --- >From cp/module.cc: inform (loc, "compiler is %sversion %s%s%s", IS_EXPERIMENTAL (my_ver) ? "experimental " : "", my_string, reject_p ? "" : flag_module_version_ignore ? ", be it on your own head!" : ", close enough?", reject_p ? "" : " \xc2\xaf\\_(\xe3\x83\x84)_/\xc2\xaf"); Are you sure that you want to output this UTF-8 sequence in locale "C"? Furthermore, the conditional strings must be translatable. See the GCC diagnostics guidelines for more information.