PERL_CALLCONV char* Perl_sv_pv(pTHX_ SV *sv);
PERL_CALLCONV char* Perl_sv_pvutf8(pTHX_ SV *sv);
PERL_CALLCONV char* Perl_sv_pvbyte(pTHX_ SV *sv);
-PERL_CALLCONV void Perl_sv_utf8_upgrade(pTHX_ SV *sv);
+PERL_CALLCONV STRLEN Perl_sv_utf8_upgrade(pTHX_ SV *sv);
PERL_CALLCONV bool Perl_sv_utf8_downgrade(pTHX_ SV *sv, bool fail_ok);
PERL_CALLCONV void Perl_sv_utf8_encode(pTHX_ SV *sv);
PERL_CALLCONV bool Perl_sv_utf8_decode(pTHX_ SV *sv);