From c5333953a555847ef4f1457905bf0f111a79eb72 Mon Sep 17 00:00:00 2001
From: Father Chrysostomos <sprout@cpan.org>
Date: Wed, 18 May 2011 14:35:47 -0700
Subject: [PATCH] =?utf8?q?[perl=20#90160]=20U*=20gives=20=E2=80=98U0=20mod?=
 =?utf8?q?e=20on=20an=20empty=20string=E2=80=99?=
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This is a regression in 5.10 caused by change 23966/08ca2aa38a29,
which added a bit of faulty logic. It was treating U* in the middle of
a pack template as equivalent to U0, if the input string was empty.
---
 pp_pack.c   | 2 +-
 t/op/pack.t | 6 +++++-
 2 files changed, 6 insertions(+), 2 deletions(-)

diff --git a/pp_pack.c b/pp_pack.c
index 5229fc3..c62754f 100644
--- a/pp_pack.c
+++ b/pp_pack.c
@@ -1660,7 +1660,7 @@ S_unpack_rec(pTHX_ tempsym_t* symptr, const char *s, const char *strbeg, const c
 	    break;
 	case 'U':
 	    if (len == 0) {
-                if (explicit_length) {
+                if (explicit_length && howlen != e_star) {
 		    /* Switch to "bytes in UTF-8" mode */
 		    if (symptr->flags & FLAG_DO_UTF8) utf8 = 0;
 		    else
diff --git a/t/op/pack.t b/t/op/pack.t
index 025bb09..43189ab 100644
--- a/t/op/pack.t
+++ b/t/op/pack.t
@@ -12,7 +12,7 @@ my $no_endianness = $] > 5.009 ? '' :
 my $no_signedness = $] > 5.009 ? '' :
   "Signed/unsigned pack modifiers not available on this perl";
 
-plan tests => 14699;
+plan tests => 14700;
 
 use strict;
 use warnings qw(FATAL all);
@@ -1993,3 +1993,7 @@ is(unpack('c'), 65, "one-arg unpack (change #18751)"); # defaulting to $_
     my $y = runperl( prog => 'print split( /,/, unpack(q(%32u*), q(#,3,Q)), qq(\n)), qq(\n)' );
     is($y, "0\n", "split /a/, unpack('%32u*'...) didn't crash");
 }
+
+#90160
+is(eval { () = unpack "C0 U*", ""; "ok" }, "ok",
+  'medial U* on empty string');
-- 
1.8.3.1