XS.xs: In function ‘decode_utf8’:
XS.xs:207:5: warning: ‘Perl_utf8n_to_uvuni’ is deprecated [-Wdeprecated-declarations]
  207 |     return utf8n_to_uvuni (s, len, clen, UTF8_CHECK_ONLY);
      |     ^~~~~~
In file included from /usr/lib/perl5/5.42.2/core_perl/CORE/perl.h:6160,
                 from XS.xs:2:
/usr/lib/perl5/5.42.2/core_perl/CORE/proto.h:6133:1: note: declared here
 6133 | Perl_utf8n_to_uvuni(pTHX_ const U8 *s, STRLEN curlen, STRLEN *retlen, U32 flags)
      | ^~~~~~~~~~~~~~~~~~~