since my libc is musl, tar is using builtin argp implementation, which will
pass NULL as msgid to dgettext without additional checks.

but according to
https://www.gnu.org/software/gettext/manual/html_node/Interface-to-gettext.html,
passing NULL to gettext is undefined. and, musl chose to crash..

could you please check if msgid is NULL before passing it to dgettext? the
problem code is located at argp-help.c.

 related links: https://www.openwall.com/lists/musl/2017/03/24/10.

-- 
Best regards,
xhe