From e7acdfe976f01ee0d1ba31b3b1db61454a72d6c9 Mon Sep 17 00:00:00 2001
From: David Mitchell <davem@iabyn.com>
Date: Tue, 21 Jun 2016 17:06:52 +0100
Subject: [PATCH] only treat stash entries with  .*:: as sub-stashes
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RT #128238

%: = 0 would cause an assertion failure in Perl_gv_check(), since when
it searched a stash for substashes, it assumed anything ending in ':' was
a substash, whereas substashes end in '::'. So check for a double colon
before recursing.

Signed-off-by: Petr Písař <ppisar@redhat.com>
---
 gv.c         | 5 ++++-
 t/op/stash.t | 9 ++++++++-
 2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/gv.c b/gv.c
index 4df3bce..2b3bdfa 100644
--- a/gv.c
+++ b/gv.c
@@ -2423,7 +2423,10 @@ Perl_gv_check(pTHX_ HV *stash)
 	for (entry = HvARRAY(stash)[i]; entry; entry = HeNEXT(entry)) {
             GV *gv;
             HV *hv;
-	    if (HeKEY(entry)[HeKLEN(entry)-1] == ':' &&
+	    STRLEN keylen = HeKLEN(entry);
+            const char * const key = HeKEY(entry);
+
+	    if (keylen >= 2 && key[keylen-2] == ':'  && key[keylen-1] == ':' &&
 		(gv = MUTABLE_GV(HeVAL(entry))) && isGV(gv) && (hv = GvHV(gv)))
 	    {
 		if (hv != PL_defstash && hv != stash
diff --git a/t/op/stash.t b/t/op/stash.t
index b8e0f34..ec795a9 100644
--- a/t/op/stash.t
+++ b/t/op/stash.t
@@ -7,7 +7,7 @@ BEGIN {
 
 BEGIN { require "./test.pl"; }
 
-plan( tests => 52 );
+plan( tests => 53 );
 
 # Used to segfault (bug #15479)
 fresh_perl_like(
@@ -341,3 +341,10 @@ is runperl(
    ),
    "ok\n",
    '[perl #128086] no crash from assigning hash to *:::::: & deleting it';
+
+is runperl(
+    prog => 'BEGIN { %: = 0; $^W=1}; print qq|ok\n|',
+    stderr => 1,
+   ),
+   "ok\n",
+   "[perl #128238] don't treat %: as a stash (needs 2 colons)"
-- 
2.5.5