+=for apidoc mro_package_moved
+
+Call this function to signal to a stash that it has been assigned to
+another spot in the stash hierarchy. C<stash> is the stash that has been
+assigned. C<oldstash> is the stash it replaces, if any. C<gv> is the glob
+that is actually being assigned to.
+
+This can also be called with a null first argument to
+indicate that C<oldstash> has been deleted.
+
+This function invalidates isa caches on the old stash, on all subpackages
+nested inside it, and on the subclasses of all those, including
+non-existent packages that have corresponding entries in C<stash>.
+
+It also sets the effective names (C<HvENAME>) on all the stashes as
+appropriate.
+
+If the C<gv> is present and is not in the symbol table, then this function
+simply returns. This checked will be skipped if C<flags & 1>.
+
+=cut
+*/
+void
+Perl_mro_package_moved(pTHX_ HV * const stash, HV * const oldstash,
+ const GV * const gv, U32 flags)
+{
+ SV *namesv;
+ HEK **namep;
+ I32 name_count;
+ HV *stashes;
+ HE* iter;
+
+ PERL_ARGS_ASSERT_MRO_PACKAGE_MOVED;
+ assert(stash || oldstash);
+
+ /* Determine the name(s) of the location that stash was assigned to
+ * or from which oldstash was removed.
+ *
+ * We cannot reliably use the name in oldstash, because it may have
+ * been deleted from the location in the symbol table that its name
+ * suggests, as in this case:
+ *
+ * $globref = \*foo::bar::;
+ * Symbol::delete_package("foo");
+ * *$globref = \%baz::;
+ * *$globref = *frelp::;
+ * # calls mro_package_moved(%frelp::, %baz::, *$globref, NULL, 0)
+ *
+ * So we get it from the gv. But, since the gv may no longer be in the
+ * symbol table, we check that first. The only reliable way to tell is
+ * to see whether its stash has an effective name and whether the gv
+ * resides in that stash under its name. That effective name may be
+ * different from what gv_fullname4 would use.
+ * If flags & 1, the caller has asked us to skip the check.
+ */
+ if(!(flags & 1)) {
+ SV **svp;
+ if(
+ !GvSTASH(gv) || !HvENAME(GvSTASH(gv)) ||
+ !(svp = hv_fetch(GvSTASH(gv), GvNAME(gv), GvNAMELEN(gv), 0)) ||
+ *svp != (SV *)gv
+ ) return;
+ }
+ assert(SvOOK(GvSTASH(gv)));
+ assert(GvNAMELEN(gv) > 1);
+ assert(GvNAME(gv)[GvNAMELEN(gv) - 1] == ':');
+ assert(GvNAME(gv)[GvNAMELEN(gv) - 2] == ':');
+ name_count = HvAUX(GvSTASH(gv))->xhv_name_count;
+ if (!name_count) {
+ name_count = 1;
+ namep = &HvAUX(GvSTASH(gv))->xhv_name_u.xhvnameu_name;
+ }
+ else {
+ namep = HvAUX(GvSTASH(gv))->xhv_name_u.xhvnameu_names;
+ if (name_count < 0) ++namep, name_count = -name_count - 1;
+ }
+ if (name_count == 1) {
+ if (HEK_LEN(*namep) == 4 && strnEQ(HEK_KEY(*namep), "main", 4)) {
+ namesv = newSVpvs_flags("", SVs_TEMP);
+ }
+ else {
+ namesv = sv_2mortal(newSVhek(*namep));
+ sv_catpvs(namesv, "::");
+ }
+ sv_catpvn(namesv, GvNAME(gv), GvNAMELEN(gv) - 2);
+ /* skip trailing :: */
+ }
+ else {
+ SV *aname;
+ namesv = sv_2mortal((SV *)newAV());
+ while (name_count--) {
+ if(HEK_LEN(*namep) == 4 && strnEQ(HEK_KEY(*namep), "main", 4)){
+ aname = newSVpvs(""); namep++;
+ }
+ else {
+ aname = newSVhek(*namep++);
+ sv_catpvs(aname, "::");
+ }
+ sv_catpvn(aname, GvNAME(gv), GvNAMELEN(gv) - 2);
+ /* skip trailing :: */
+ av_push((AV *)namesv, aname);
+ }
+ }
+
+ /* Get a list of all the affected classes. */
+ /* We cannot simply pass them all to mro_isa_changed_in to avoid
+ the list, as that function assumes that only one package has
+ changed. It does not work with:
+
+ @foo::ISA = qw( B B::B );
+ *B:: = delete $::{"A::"};
+
+ as neither B nor B::B can be updated before the other, since they
+ will reset caches on foo, which will see either B or B::B with the
+ wrong name. The names must be set on *all* affected stashes before
+ we do anything else. (And linearisations must be cleared, too.)
+ */
+ stashes = (HV *) sv_2mortal((SV *)newHV());
+ mro_gather_and_rename(
+ stashes, (HV *) sv_2mortal((SV *)newHV()),
+ stash, oldstash, namesv
+ );
+
+ /* Once the caches have been wiped on all the classes, call
+ mro_isa_changed_in on each. */
+ hv_iterinit(stashes);
+ while((iter = hv_iternext(stashes))) {
+ HV * const stash = *(HV **)HEK_KEY(HeKEY_hek(iter));
+ if(HvENAME(stash)) {
+ /* We have to restore the original meta->isa (that
+ mro_gather_and_rename set aside for us) this way, in case
+ one class in this list is a superclass of a another class
+ that we have already encountered. In such a case, meta->isa
+ will have been overwritten without old entries being deleted
+ from PL_isarev. */
+ struct mro_meta * const meta = HvMROMETA(stash);
+ if(meta->isa != (HV *)HeVAL(iter)){
+ SvREFCNT_dec(meta->isa);
+ meta->isa
+ = HeVAL(iter) == &PL_sv_yes
+ ? NULL
+ : (HV *)HeVAL(iter);
+ HeVAL(iter) = NULL; /* We donated our reference count. */
+ }
+ mro_isa_changed_in(stash);
+ }
+ }
+}
+
+void
+S_mro_gather_and_rename(pTHX_ HV * const stashes, HV * const seen_stashes,
+ HV *stash, HV *oldstash, SV *namesv)
+{
+ register XPVHV* xhv;
+ register 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--) {
+ STRLEN len;
+ const char *name = SvPVx_const(*svp++, len);
+ if(PL_stashcache)
+ (void)hv_delete(PL_stashcache, name, len, G_DISCARD);
+ hv_ename_delete(oldstash, name, len, 0);
+
+ 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, NULL);
+ isarev = (HV *)hv_delete(PL_isarev, name, len, 0);
+ fetched_isarev=TRUE;
+ }
+ }
+ }
+ }
+ }
+ check_stash:
+ if(stash) {
+ if(SvTYPE(namesv) == SVt_PVAV) {
+ items = AvFILLp((AV *)namesv) + 1;
+ svp = AvARRAY((AV *)namesv);
+ }
+ else {
+ items = 1;
+ svp = &namesv;
+ }
+ while (items--) {
+ STRLEN len;
+ const char *name = SvPVx_const(*svp++, len);
+ hv_ename_add(stash, name, len, 0);
+ }
+
+ /* Add it to the big list if it needs
+ * mro_isa_changed_in called on it. That happens if it was
+ * detached from the symbol table (so it had no HvENAME) before
+ * being assigned to the spot named by the ‘name’ variable, because
+ * its cached isa linearisation is now stale (the effective name
+ * having changed), and subclasses will then use that cache when
+ * mro_package_moved calls mro_isa_changed_in. (See
+ * [perl #77358].)
+ *
+ * If it did have a name, then its previous name is still
+ * used in isa caches, and there is no need for
+ * mro_package_moved to call mro_isa_changed_in.
+ */
+
+ entry
+ = (HE *)
+ hv_common(
+ seen_stashes, NULL, (const char *)&stash, sizeof(HV *), 0,
+ HV_FETCH_LVALUE|HV_FETCH_EMPTY_HE, NULL, 0
+ );
+ if(HeVAL(entry) == &PL_sv_yes || HeVAL(entry) == &PL_sv_no)
+ stash = NULL;
+ else {
+ HeVAL(entry)
+ = HeVAL(entry) == &PL_sv_undef ? &PL_sv_yes : &PL_sv_no;
+ if(!stash_had_name)
+ {
+ struct mro_meta * const meta = HvMROMETA(stash);
+ (void)
+ hv_store(
+ stashes, (const char *)&stash, sizeof(HV *),
+ meta->isa
+ ? SvREFCNT_inc_simple_NN((SV *)meta->isa)
+ : &PL_sv_yes,
+ 0
+ );
+ CLEAR_LINEAR(meta);
+ }
+ }
+ }
+
+ if(!stash && !oldstash)
+ /* Both stashes have been encountered already. */
+ return;
+
+ /* Add all the subclasses to the big list. */
+ if(!fetched_isarev) {
+ /* If oldstash is not null, then we can use its HvENAME to look up
+ the isarev hash, since all its subclasses will be listed there.
+ It will always have an HvENAME. It the HvENAME was removed
+ above, then fetch_isarev will be true, and this code will not be
+ reached.
+
+ If oldstash is null, then this is an empty spot with no stash in
+ it, so subclasses could be listed in isarev hashes belonging to
+ any of the names, so we have to check all of them.
+ */
+ assert(!oldstash || HvENAME(oldstash));
+ if (oldstash) {
+ /* Extra variable to avoid a compiler warning */
+ char * const hvename = HvENAME(oldstash);
+ fetched_isarev = TRUE;
+ svp = hv_fetch(PL_isarev, hvename, HvENAMELEN_get(oldstash), 0);
+ if (svp) isarev = MUTABLE_HV(*svp);
+ }
+ else if(SvTYPE(namesv) == SVt_PVAV) {
+ items = AvFILLp((AV *)namesv) + 1;
+ svp = AvARRAY((AV *)namesv);
+ }
+ else {
+ items = 1;
+ svp = &namesv;
+ }
+ }
+ if(
+ isarev || !fetched_isarev
+ ) {
+ while (fetched_isarev || items--) {
+ HE *iter;
+
+ if (!fetched_isarev) {
+ HE * const he = hv_fetch_ent(PL_isarev, *svp++, 0, 0);
+ if (!he || !(isarev = MUTABLE_HV(HeVAL(he)))) continue;
+ }
+
+ hv_iterinit(isarev);
+ while((iter = hv_iternext(isarev))) {
+ I32 len;
+ const char* const revkey = hv_iterkey(iter, &len);
+ HV* revstash = gv_stashpvn(revkey, len, 0);
+ struct mro_meta * meta;
+
+ if(!revstash) continue;
+ meta = HvMROMETA(revstash);
+ (void)
+ hv_store(
+ stashes, (const char *)&revstash, sizeof(HV *),
+ meta->isa
+ ? SvREFCNT_inc_simple_NN((SV *)meta->isa)
+ : &PL_sv_yes,
+ 0
+ );
+ CLEAR_LINEAR(meta);
+ }
+
+ if (fetched_isarev) break;
+ }
+ }
+
+ /* This is partly based on code in hv_iternext_flags. We are not call-
+ ing that here, as we want to avoid resetting the hash iterator. */
+
+ /* Skip the entire loop if the hash is empty. */
+ if(oldstash && HvUSEDKEYS(oldstash)) {
+ xhv = (XPVHV*)SvANY(oldstash);
+ seen = (HV *) sv_2mortal((SV *)newHV());
+
+ /* Iterate through entries in the oldstash, adding them to the
+ list, meanwhile doing the equivalent of $seen{$key} = 1.
+ */
+
+ while (++riter <= (I32)xhv->xhv_max) {
+ entry = (HvARRAY(oldstash))[riter];
+
+ /* Iterate through the entries in this list */
+ for(; entry; entry = HeNEXT(entry)) {
+ const char* key;
+ I32 len;
+
+ /* If this entry is not a glob, ignore it.
+ Try the next. */
+ if (!isGV(HeVAL(entry))) continue;
+
+ key = hv_iterkey(entry, &len);
+ if(len > 1 && key[len-2] == ':' && key[len-1] == ':') {
+ HV * const oldsubstash = GvHV(HeVAL(entry));
+ SV ** const stashentry
+ = stash ? hv_fetch(stash, key, len, 0) : NULL;
+ HV *substash = NULL;
+
+ /* Avoid main::main::main::... */
+ if(oldsubstash == oldstash) continue;
+
+ if(
+ (
+ stashentry && *stashentry
+ && (substash = GvHV(*stashentry))
+ )
+ || (oldsubstash && HvENAME_get(oldsubstash))
+ )
+ {
+ /* Add :: and the key (minus the trailing ::)
+ to each name. */
+ SV *subname;
+ if(SvTYPE(namesv) == SVt_PVAV) {
+ SV *aname;
+ items = AvFILLp((AV *)namesv) + 1;
+ svp = AvARRAY((AV *)namesv);
+ subname = sv_2mortal((SV *)newAV());
+ while (items--) {
+ aname = newSVsv(*svp++);
+ sv_catpvs(aname, "::");
+ sv_catpvn(aname, key, len-2);
+ av_push((AV *)subname, aname);
+ }
+ }
+ else {
+ subname = sv_2mortal(newSVsv(namesv));
+ sv_catpvs(subname, "::");
+ sv_catpvn(subname, key, len-2);
+ }
+ mro_gather_and_rename(
+ stashes, seen_stashes,
+ substash, oldsubstash, subname
+ );
+ }
+
+ (void)hv_store(seen, key, len, &PL_sv_yes, 0);
+ }
+ }
+ }
+ }
+
+ /* Skip the entire loop if the hash is empty. */
+ if (stash && HvUSEDKEYS(stash)) {
+ xhv = (XPVHV*)SvANY(stash);
+ riter = -1;
+
+ /* Iterate through the new stash, skipping $seen{$key} items,
+ calling mro_gather_and_rename(stashes,seen,entry,NULL, ...). */
+ while (++riter <= (I32)xhv->xhv_max) {
+ entry = (HvARRAY(stash))[riter];
+
+ /* Iterate through the entries in this list */
+ for(; entry; entry = HeNEXT(entry)) {
+ const char* key;
+ I32 len;
+
+ /* If this entry is not a glob, ignore it.
+ Try the next. */
+ if (!isGV(HeVAL(entry))) continue;
+
+ key = hv_iterkey(entry, &len);
+ if(len > 1 && key[len-2] == ':' && key[len-1] == ':') {
+ HV *substash;
+
+ /* If this entry was seen when we iterated through the
+ oldstash, skip it. */
+ if(seen && hv_exists(seen, key, len)) continue;
+
+ /* We get here only if this stash has no corresponding
+ entry in the stash being replaced. */
+
+ substash = GvHV(HeVAL(entry));
+ if(substash) {
+ SV *subname;
+
+ /* Avoid checking main::main::main::... */
+ if(substash == stash) continue;
+
+ /* Add :: and the key (minus the trailing ::)
+ to each name. */
+ if(SvTYPE(namesv) == SVt_PVAV) {
+ SV *aname;
+ items = AvFILLp((AV *)namesv) + 1;
+ svp = AvARRAY((AV *)namesv);
+ subname = sv_2mortal((SV *)newAV());
+ while (items--) {
+ aname = newSVsv(*svp++);
+ sv_catpvs(aname, "::");
+ sv_catpvn(aname, key, len-2);
+ av_push((AV *)subname, aname);
+ }
+ }
+ else {
+ subname = sv_2mortal(newSVsv(namesv));
+ sv_catpvs(subname, "::");
+ sv_catpvn(subname, key, len-2);
+ }
+ mro_gather_and_rename(
+ stashes, seen_stashes,
+ substash, NULL, subname
+ );
+ }
+ }
+ }
+ }
+ }
+}
+
+/*