fixup don't UTF8-upgrade caller argument strings

Author: leonerd

pp.c

@@ -7995,9 +7995,11 @@ PP(pp_multiparam)
                 val = svp ? *svp : &PL_sv_undef;
             }
 
-            /* namepv / namelen are always UTF-8 */
             STRLEN namelen;
-            const char *namepv = SvPVutf8(name, namelen);
+            const char *namepv = SvPV(name, namelen);
+            /* namepv / namelen are always UTF-8 */
+            if(!SvUTF8(name))
+                namepv = (const char *)bytes_to_utf8_temp_pv((const U8 *)namepv, &namelen);
 
             U32 namehash;
             PERL_HASH(namehash, namepv, namelen);

t/op/signatures.t

@@ -989,7 +989,9 @@ is eval("tnamed07(w => 'W', x => 'X', y => 'Y', z => 'Z')"), "x=X y=Y";
     sub tnamed09 (:$café) { return $café; }
 }
 # "café" = "caf\x{e9}"
-is eval('tnamed09("caf\x{e9}", "Ritz")'), "Ritz";
+my $nonutf8 = "caf\x{e9}";
+is eval('tnamed09($nonutf8, "Ritz")'), "Ritz";
+ok !utf8::is_utf8($nonutf8), 'Non-UTF8 parameter names do not get upgraded in caller';
 
 # Named params in anonymous subs
 {