Allow mro_isa_changed_in to be called on nonexistent packages

This is necessary for an upcoming bug fix.

(For this bug:

 @left::ISA = 'outer::inner';
 @right::ISA = 'clone::inner';
 *clone:: = \%outer::;
 print left->isa('clone::inner'),"\n";
 print right->isa('outer::inner'),"\n";

)

This commit actually replaces mro_isa_changed_in with
mro_isa_changed_in3. See the docs for it in the diff for mro.c.

6 files changed, 50 insertions, 23 deletions

diff --git a/embed.fnc b/embed.fnc
index d64b268345..b97452df65 100644
--- a/embed.fnc
+++ b/embed.fnc
@@ -2362,7 +2362,8 @@ Apd	|AV*	|mro_get_linear_isa|NN HV* stash
 sd	|AV*	|mro_get_linear_isa_dfs|NN HV* stash|U32 level
 #endif
 : Used in hv.c, mg.c, pp.c, sv.c
-pd	|void   |mro_isa_changed_in|NN HV* stash
+md	|void   |mro_isa_changed_in|NN HV* stash
+pd	|void   |mro_isa_changed_in3|NULLOK HV* stash|NULLOK const char *stashname|STRLEN stashname_len
 Apd	|void	|mro_method_changed_in	|NN HV* stash
 pdx	|void	|mro_package_moved	|NN const HV *stash
 : Only used in perl.c
diff --git a/embed.h b/embed.h
index f4d01f1922..6d15195c44 100644
--- a/embed.h
+++ b/embed.h
@@ -1049,7 +1049,7 @@
 #define magic_wipepack(a,b)	Perl_magic_wipepack(aTHX_ a,b)
 #define mg_localize(a,b,c)	Perl_mg_localize(aTHX_ a,b,c)
 #define mode_from_discipline(a,b)	Perl_mode_from_discipline(aTHX_ a,b)
-#define mro_isa_changed_in(a)	Perl_mro_isa_changed_in(aTHX_ a)
+#define mro_isa_changed_in3(a,b,c)	Perl_mro_isa_changed_in3(aTHX_ a,b,c)
 #define mro_package_moved(a)	Perl_mro_package_moved(aTHX_ a)
 #define munge_qwlist_to_paren_list(a)	Perl_munge_qwlist_to_paren_list(aTHX_ a)
 #define my_attrs(a,b)		Perl_my_attrs(aTHX_ a,b)
diff --git a/hv.h b/hv.h
index 62646b3965..83f90d9a52 100644
--- a/hv.h
+++ b/hv.h
@@ -67,6 +67,7 @@ struct mro_meta {
     (((smeta)->mro_which && (which) == (smeta)->mro_which) \
      ? (smeta)->mro_linear_current			   \
      : Perl_mro_get_private_data(aTHX_ (smeta), (which)))
+#define mro_isa_changed_in(stash) mro_isa_changed_in3(stash, NULL, 0)
 
 /* Subject to change.
    Don't access this directly.
diff --git a/mathoms.c b/mathoms.c
index 78516b3d4b..152a64c089 100644
--- a/mathoms.c
+++ b/mathoms.c
@@ -83,6 +83,7 @@ PERL_CALLCONV I32 Perl_my_lstat(pTHX);
 PERL_CALLCONV I32 Perl_sv_eq(pTHX_ register SV *sv1, register SV *sv2);
 PERL_CALLCONV char * Perl_sv_collxfrm(pTHX_ SV *const sv, STRLEN *const nxp);
 PERL_CALLCONV bool Perl_sv_2bool(pTHX_ register SV *const sv);
+PERL_CALLCONV void Perl_mro_isa_changed_in(HV* stash);
 
 /* ref() is now a macro using Perl_doref;
  * this version provided for binary compatibility only.
@@ -1554,6 +1555,12 @@ Perl_sv_2bool(pTHX_ register SV *const sv)
     return sv_2bool_flags(sv, SV_GMAGIC);
 }
 
+void
+Perl_mro_isa_changed_in(pTHX_ HV* stash)
+{
+    return mro_isa_changed_in3(stash, NULL, 0);
+}
+
 #endif /* NO_MATHOMS */
 
 /*
diff --git a/mro.c b/mro.c
index bd59465eb3..d8ef79c749 100644
--- a/mro.c
+++ b/mro.c
@@ -411,10 +411,22 @@ Takes the necessary steps (cache invalidations, mostly)
 when the @ISA of the given package has changed.  Invoked
 by the C<setisa> magic, should not need to invoke directly.
 
+=for apidoc mro_isa_changed_in3
+
+Takes the necessary steps (cache invalidations, mostly)
+when the @ISA of the given package has changed.  Invoked
+by the C<setisa> magic, should not need to invoke directly.
+
+The stash can be passed as the first argument, or its name and length as
+the second and third (or both). If just the name is passed and the stash
+does not exist, then only the subclasses' method and isa caches will be
+invalidated.
+
 =cut
 */
 void
-Perl_mro_isa_changed_in(pTHX_ HV* stash)
+Perl_mro_isa_changed_in3(pTHX_ HV* stash, const char *stashname,
+                         STRLEN stashname_len)
 {
     dVAR;
     HV* isarev;
@@ -423,35 +435,39 @@ Perl_mro_isa_changed_in(pTHX_ HV* stash)
     SV** svp;
     I32 items;
     bool is_universal;
-    struct mro_meta * meta;
-
-    const char * const stashname = HvNAME_get(stash);
-    const STRLEN stashname_len = HvNAMELEN_get(stash);
+    struct mro_meta * meta = NULL;
 
-    PERL_ARGS_ASSERT_MRO_ISA_CHANGED_IN;
+    if(!stashname && stash) {
+        stashname = HvNAME_get(stash);
+        stashname_len = HvNAMELEN_get(stash);
+    }
+    else if(!stash)
+        stash = gv_stashpvn(stashname, stashname_len, 0 /* don't add */);
 
     if(!stashname)
         Perl_croak(aTHX_ "Can't call mro_isa_changed_in() on anonymous symbol table");
 
-    /* wipe out the cached linearizations for this stash */
-    meta = HvMROMETA(stash);
-    if (meta->mro_linear_all) {
+    if(stash) {
+      /* wipe out the cached linearizations for this stash */
+      meta = HvMROMETA(stash);
+      if (meta->mro_linear_all) {
 	SvREFCNT_dec(MUTABLE_SV(meta->mro_linear_all));
 	meta->mro_linear_all = NULL;
 	/* This is just acting as a shortcut pointer.  */
 	meta->mro_linear_current = NULL;
-    } else if (meta->mro_linear_current) {
+      } else if (meta->mro_linear_current) {
 	/* Only the current MRO is stored, so this owns the data.  */
 	SvREFCNT_dec(meta->mro_linear_current);
 	meta->mro_linear_current = NULL;
-    }
-    if (meta->isa) {
+      }
+      if (meta->isa) {
 	SvREFCNT_dec(meta->isa);
 	meta->isa = NULL;
-    }
+      }
 
-    /* Inc the package generation, since our @ISA changed */
-    meta->pkg_gen++;
+      /* Inc the package generation, since our @ISA changed */
+      meta->pkg_gen++;
+    }
 
     /* Wipe the global method cache if this package
        is UNIVERSAL or one of its parents */
@@ -465,12 +481,12 @@ Perl_mro_isa_changed_in(pTHX_ HV* stash)
         is_universal = TRUE;
     }
     else { /* Wipe the local method cache otherwise */
-        meta->cache_gen++;
+        if(meta) meta->cache_gen++;
 	is_universal = FALSE;
     }
 
     /* wipe next::method cache too */
-    if(meta->mro_nextmethod) hv_clear(meta->mro_nextmethod);
+    if(meta && meta->mro_nextmethod) hv_clear(meta->mro_nextmethod);
 
     /* Iterate the isarev (classes that are our children),
        wiping out their linearization, method and isa caches */
@@ -511,6 +527,9 @@ Perl_mro_isa_changed_in(pTHX_ HV* stash)
          3) Add everything from our isarev to their isarev
     */
 
+    /* This only applies if the stash exists. */
+    if(!stash) return;
+
     /* We're starting at the 2nd element, skipping ourselves here */
     linear_mro = mro_get_linear_isa(stash);
     svp = AvARRAY(linear_mro) + 1;
diff --git a/proto.h b/proto.h
index 48d63608cd..9970d33e73 100644
--- a/proto.h
+++ b/proto.h
@@ -2244,11 +2244,10 @@ PERL_CALLCONV SV*	Perl_mro_get_private_data(pTHX_ struct mro_meta *const smeta,
 #define PERL_ARGS_ASSERT_MRO_GET_PRIVATE_DATA	\
 	assert(smeta); assert(which)
 
-PERL_CALLCONV void	Perl_mro_isa_changed_in(pTHX_ HV* stash)
-			__attribute__nonnull__(pTHX_1);
-#define PERL_ARGS_ASSERT_MRO_ISA_CHANGED_IN	\
-	assert(stash)
+/* PERL_CALLCONV void	mro_isa_changed_in(pTHX_ HV* stash)
+			__attribute__nonnull__(pTHX_1); */
 
+PERL_CALLCONV void	Perl_mro_isa_changed_in3(pTHX_ HV* stash, const char *stashname, STRLEN stashname_len);
 PERL_CALLCONV struct mro_meta*	Perl_mro_meta_init(pTHX_ HV* stash)
 			__attribute__nonnull__(pTHX_1);
 #define PERL_ARGS_ASSERT_MRO_META_INIT	\