Fix package assignment with nested aliased packages

This commit fixes package assignments like *foo:: = *bar:: when both
foo and bar contain nested stashes that are aliases of each other.

mro_package_moved (actually, its auxiliary routine) need to keep a
list of stashes that have been seen as a separate list from those that
are going to have mro_isa_changed_in called on them. Otherwise, some
stashes will simply not be iterated through.

See the test that this adds and its comments. @ISA = @ISA should never
have any effect visible to Perl (with a capital), but it does in that
test case, prior to this commit.

This also fixes another bug that the test case triggered:
riter was not being reset before the second iteration in
mro_gather_and_rename.

Also, the stashes HV (aka the ‘big list’) now holds refcounts on its
elements, as that makes the code simpler as a result of the changes.

1 files changed, 4 insertions, 3 deletions

diff --git a/proto.h b/proto.h
index 186c2a67c3..4002d67414 100644
--- a/proto.h
+++ b/proto.h
@@ -5671,11 +5671,12 @@ STATIC void	S_mro_clean_isarev(pTHX_ HV * const isa, const char * const name, co
 #define PERL_ARGS_ASSERT_MRO_CLEAN_ISAREV	\
 	assert(isa); assert(name)
 
-STATIC void	S_mro_gather_and_rename(pTHX_ HV * const stashes, HV *stash, HV *oldstash, const char *name, I32 namlen)
+STATIC void	S_mro_gather_and_rename(pTHX_ HV * const stashes, HV * const seen_stashes, HV *stash, HV *oldstash, const char *name, I32 namlen)
 			__attribute__nonnull__(pTHX_1)
-			__attribute__nonnull__(pTHX_4);
+			__attribute__nonnull__(pTHX_2)
+			__attribute__nonnull__(pTHX_5);
 #define PERL_ARGS_ASSERT_MRO_GATHER_AND_RENAME	\
-	assert(stashes); assert(name)
+	assert(stashes); assert(seen_stashes); assert(name)
 
 STATIC AV*	S_mro_get_linear_isa_dfs(pTHX_ HV* stash, U32 level)
 			__attribute__nonnull__(pTHX_1);