+STATIC void
+S_mro_gather_and_rename(pTHX_ HV * const stashes, HV * const seen_stashes,
+ HV *stash, HV *oldstash, SV *namesv)
+{
+ XPVHV* xhv;
+ HE *entry;
+ I32 riter = -1;
+ I32 items = 0;
+ const bool stash_had_name = stash && HvENAME(stash);
+ bool fetched_isarev = FALSE;
+ HV *seen = NULL;
+ HV *isarev = NULL;
+ SV **svp = NULL;
+
+ PERL_ARGS_ASSERT_MRO_GATHER_AND_RENAME;
+
+ /* We use the seen_stashes hash to keep track of which packages have
+ been encountered so far. This must be separate from the main list of
+ stashes, as we need to distinguish between stashes being assigned
+ and stashes being replaced/deleted. (A nested stash can be on both
+ sides of an assignment. We cannot simply skip iterating through a
+ stash on the right if we have seen it on the left, as it will not
+ get its ename assigned to it.)
+
+ To avoid allocating extra SVs, instead of a bitfield we can make
+ bizarre use of immortals:
+
+ &PL_sv_undef: seen on the left (oldstash)
+ &PL_sv_no : seen on the right (stash)
+ &PL_sv_yes : seen on both sides
+
+ */
+
+ if(oldstash) {
+ /* Add to the big list. */
+ struct mro_meta * meta;
+ HE * const entry
+ = (HE *)
+ hv_common(
+ seen_stashes, NULL, (const char *)&oldstash, sizeof(HV *), 0,
+ HV_FETCH_LVALUE|HV_FETCH_EMPTY_HE, NULL, 0
+ );
+ if(HeVAL(entry) == &PL_sv_undef || HeVAL(entry) == &PL_sv_yes) {
+ oldstash = NULL;
+ goto check_stash;
+ }
+ HeVAL(entry)
+ = HeVAL(entry) == &PL_sv_no ? &PL_sv_yes : &PL_sv_undef;
+ meta = HvMROMETA(oldstash);
+ (void)
+ hv_store(
+ stashes, (const char *)&oldstash, sizeof(HV *),
+ meta->isa
+ ? SvREFCNT_inc_simple_NN((SV *)meta->isa)
+ : &PL_sv_yes,
+ 0
+ );
+ CLEAR_LINEAR(meta);
+
+ /* Update the effective name. */
+ if(HvENAME_get(oldstash)) {
+ const HEK * const enamehek = HvENAME_HEK(oldstash);
+ if(SvTYPE(namesv) == SVt_PVAV) {
+ items = AvFILLp((AV *)namesv) + 1;
+ svp = AvARRAY((AV *)namesv);
+ }
+ else {
+ items = 1;
+ svp = &namesv;
+ }
+ while (items--) {
+ const U32 name_utf8 = SvUTF8(*svp);
+ STRLEN len;
+ const char *name = SvPVx_const(*svp, len);
+ if(PL_stashcache) {
+ DEBUG_o(Perl_deb(aTHX_ "mro_gather_and_rename clearing PL_stashcache for '%"SVf"'\n",
+ SVfARG(*svp)));
+ (void)hv_delete(PL_stashcache, name, name_utf8 ? -(I32)len : (I32)len, G_DISCARD);
+ }
+ ++svp;
+ hv_ename_delete(oldstash, name, len, name_utf8);
+
+ if (!fetched_isarev) {
+ /* If the name deletion caused a name change, then we
+ * are not going to call mro_isa_changed_in with this
+ * name (and not at all if it has become anonymous) so
+ * we need to delete old isarev entries here, both
+ * those in the superclasses and this class's own list
+ * of subclasses. We simply delete the latter from
+ * PL_isarev, since we still need it. hv_delete morti-
+ * fies it for us, so sv_2mortal is not necessary. */
+ if(HvENAME_HEK(oldstash) != enamehek) {
+ if(meta->isa && HvARRAY(meta->isa))
+ mro_clean_isarev(meta->isa, name, len, 0, 0,
+ name_utf8 ? HVhek_UTF8 : 0);
+ isarev = (HV *)hv_delete(PL_isarev, name,
+ name_utf8 ? -(I32)len : (I32)len, 0);
+ fetched_isarev=TRUE;
+ }
+ }
+ }
+ }