Followup to 088225f/[perl #88132]: packages ending with :

Commit 088225f was not sufficient to fix the regression. It still
exists for packages whose names end with a single colon.

I discovered this when trying to determine why RDF::Trine was crashing
with 5.14-to-be.

In trying to write tests for it, I ended up triggering the same crash
that RDF::Trine is having, but in a different way.

In the end, it was easier to fix about three or four bugs (depending
on how you count them), rather than try to fix only the regression
that #88132 deals with (isa caches not updating when packages ending
with colons are aliased), as they are all intertwined.

The changes are as follows:

Concerning the if (!(flags & ~GV_NOADD_MASK)...) statement in
gv_stashpvn: Normally, gv_fetchpvn_flags (which it calls and whose
retval is assigned to tmpgv) returns NULL if it has not been told
to add anything and if the gv requested looks like a stash gv (ends
with ::). If the number of colons is odd (foo:::), that code path is
bypassed, so gv_stashpvn returns a GV without a hash. So gv_stashpvn
tries to used that NULL hash and crashes. It should instead return
NULL, to be consistent with the two-colon case.

Blindly assigning a name to a stash does not work if the stash has
multiple effective names. A call to mro_package_moved is required as
well. So what gv_stashpvn was doing was insufficient.

The parts of the mro code that check for globs or stash elems that
contain stashes by looking for :: at the end of the name now take into
account that the name might consist of a single : instead.

1 files changed, 43 insertions, 18 deletions

diff --git a/mro.c b/mro.c
index 115da8b97f..30be935157 100644
--- a/mro.c
+++ b/mro.c
@@ -738,9 +738,9 @@ Perl_mro_package_moved(pTHX_ HV * const stash, HV * const oldstash,
 	) return;
     }
     assert(SvOOK(GvSTASH(gv)));
-    assert(GvNAMELEN(gv) > 1);
+    assert(GvNAMELEN(gv));
     assert(GvNAME(gv)[GvNAMELEN(gv) - 1] == ':');
-    assert(GvNAME(gv)[GvNAMELEN(gv) - 2] == ':');
+    assert(GvNAMELEN(gv) == 1 || GvNAME(gv)[GvNAMELEN(gv) - 2] == ':');
     name_count = HvAUX(GvSTASH(gv))->xhv_name_count;
     if (!name_count) {
 	name_count = 1;
@@ -752,13 +752,17 @@ Perl_mro_package_moved(pTHX_ HV * const stash, HV * const oldstash,
     }
     if (name_count == 1) {
 	if (HEK_LEN(*namep) == 4 && strnEQ(HEK_KEY(*namep), "main", 4)) {
-	    namesv = newSVpvs_flags("", SVs_TEMP);
+	    namesv = GvNAMELEN(gv) == 1
+		? newSVpvs_flags(":", SVs_TEMP)
+		: newSVpvs_flags("",  SVs_TEMP);
 	}
 	else {
 	    namesv = sv_2mortal(newSVhek(*namep));
-	    sv_catpvs(namesv, "::");
+	    if (GvNAMELEN(gv) == 1) sv_catpvs(namesv, ":");
+	    else                    sv_catpvs(namesv, "::");
 	}
-	sv_catpvn(namesv, GvNAME(gv), GvNAMELEN(gv) - 2);
+	if (GvNAMELEN(gv) != 1)
+	    sv_catpvn(namesv, GvNAME(gv), GvNAMELEN(gv) - 2);
 	                                  /* skip trailing :: */
     }
     else {
@@ -766,13 +770,18 @@ Perl_mro_package_moved(pTHX_ HV * const stash, HV * const oldstash,
 	namesv = sv_2mortal((SV *)newAV());
 	while (name_count--) {
 	    if(HEK_LEN(*namep) == 4 && strnEQ(HEK_KEY(*namep), "main", 4)){
-		aname = newSVpvs(""); namep++;
+		aname = GvNAMELEN(gv) == 1
+		         ? newSVpvs(":")
+		         : newSVpvs("");
+		namep++;
 	    }
 	    else {
 		aname = newSVhek(*namep++);
-		sv_catpvs(aname, "::");
+		if (GvNAMELEN(gv) == 1) sv_catpvs(aname, ":");
+		else                    sv_catpvs(aname, "::");
 	    }
-	    sv_catpvn(aname, GvNAME(gv), GvNAMELEN(gv) - 2);
+	    if (GvNAMELEN(gv) != 1)
+		sv_catpvn(aname, GvNAME(gv), GvNAMELEN(gv) - 2);
 	                                  /* skip trailing :: */
 	    av_push((AV *)namesv, aname);
 	}
@@ -1069,7 +1078,8 @@ S_mro_gather_and_rename(pTHX_ HV * const stashes, HV * const seen_stashes,
 		if (!isGV(HeVAL(entry))) continue;
 
 		key = hv_iterkey(entry, &len);
-		if(len > 1 && key[len-2] == ':' && key[len-1] == ':') {
+		if ((len > 1 && key[len-2] == ':' && key[len-1] == ':')
+		 || (len == 1 && key[0] == ':')) {
 		    HV * const oldsubstash = GvHV(HeVAL(entry));
 		    SV ** const stashentry
 		     = stash ? hv_fetch(stash, key, len, 0) : NULL;
@@ -1096,15 +1106,22 @@ S_mro_gather_and_rename(pTHX_ HV * const stashes, HV * const seen_stashes,
 			    subname = sv_2mortal((SV *)newAV());
 			    while (items--) {
 				aname = newSVsv(*svp++);
-				sv_catpvs(aname, "::");
-				sv_catpvn(aname, key, len-2);
+				if (len == 1)
+				    sv_catpvs(aname, ":");
+				else {
+				    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);
+			    if (len == 1) sv_catpvs(subname, ":");
+			    else {
+				sv_catpvs(subname, "::");
+				sv_catpvn(subname, key, len-2);
+			    }
 			}
 			mro_gather_and_rename(
 			     stashes, seen_stashes,
@@ -1138,7 +1155,8 @@ S_mro_gather_and_rename(pTHX_ HV * const stashes, HV * const seen_stashes,
 		if (!isGV(HeVAL(entry))) continue;
 
 		key = hv_iterkey(entry, &len);
-		if(len > 1 && key[len-2] == ':' && key[len-1] == ':') {
+		if ((len > 1 && key[len-2] == ':' && key[len-1] == ':')
+		 || (len == 1 && key[0] == ':')) {
 		    HV *substash;
 
 		    /* If this entry was seen when we iterated through the
@@ -1164,15 +1182,22 @@ S_mro_gather_and_rename(pTHX_ HV * const stashes, HV * const seen_stashes,
 			    subname = sv_2mortal((SV *)newAV());
 			    while (items--) {
 				aname = newSVsv(*svp++);
-				sv_catpvs(aname, "::");
-				sv_catpvn(aname, key, len-2);
+				if (len == 1)
+				    sv_catpvs(aname, ":");
+				else {
+				    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);
+			    if (len == 1) sv_catpvs(subname, ":");
+			    else {
+				sv_catpvs(subname, "::");
+				sv_catpvn(subname, key, len-2);
+			    }
 			}
 			mro_gather_and_rename(
 			  stashes, seen_stashes,