From f132ae694cadce5cea5b006969b9b9ad169ecf64 Mon Sep 17 00:00:00 2001
From: Father Chrysostomos <sprout@cpan.org>
Date: Fri, 26 Aug 2011 06:20:01 -0700
Subject: [PATCH] Make *{undef} self-consistent

Commit afd1915d made filehandle vivification work on hash and array
elements, but in doing so it accidentally changed

    *{;undef} = 3;

to do the same thing as

    *{""} = 3;

while leaving

    *{$some_undefined_variable}

an error.

This commit adjusts the if() conditions in S_rv2gv (formerly in
pp_rv2gv) in pp.c to make PL_sv_undef follow the same path as before.

It also removes the uninit tests from lib/warnings/pp, since they
are now errors.  The uninit warning in rv2gv is only triggered now
when it is implicit, as in close().  That is already tested in
lib/warnings/9uninit.
---
 pp.c              |  4 ++--
 t/lib/warnings/pp | 11 -----------
 t/op/gv.t         | 10 +++++++++-
 3 files changed, 11 insertions(+), 14 deletions(-)

diff --git a/pp.c b/pp.c
index ea6eb00..e2427f8 100644
--- a/pp.c
+++ b/pp.c
@@ -176,11 +176,11 @@ S_rv2gv(pTHX_ SV *sv, const bool vivify_sv, const bool strict,
     }
     else {
 	if (!isGV_with_GP(sv)) {
-	    if (!SvOK(sv) && sv != &PL_sv_undef) {
+	    if (!SvOK(sv)) {
 		/* If this is a 'my' scalar and flag is set then vivify
 		 * NI-S 1999/05/07
 		 */
-		if (vivify_sv) {
+		if (vivify_sv && sv != &PL_sv_undef) {
 		    GV *gv;
 		    if (SvREADONLY(sv))
 			Perl_croak_no_modify(aTHX);
diff --git a/t/lib/warnings/pp b/t/lib/warnings/pp
index 2251b94..e6b3802 100644
--- a/t/lib/warnings/pp
+++ b/t/lib/warnings/pp
@@ -6,9 +6,6 @@
   Attempt to use reference as lvalue in substr 
     $a = "ab" ; $b = \$a ;  substr($b, 1,1) = $b
 
-  Use of uninitialized value in ref-to-glob cast	[pp_rv2gv()]
-	*b = *{ undef()}
-
   Use of uninitialized value in scalar dereference	[pp_rv2sv()]
 	my $a = undef ; my $b = $$a
 
@@ -65,14 +62,6 @@ splice() offset past end of array at - line 4.
 splice() offset past end of array at - line 6.
 ########
 # pp.c
-use warnings 'uninitialized' ;
-*x = *{ undef() };
-no warnings 'uninitialized' ;
-*y = *{ undef() };
-EXPECT
-Use of uninitialized value in ref-to-glob cast at - line 3.
-########
-# pp.c
 use warnings 'uninitialized';
 $x = undef; $y = $$x;
 no warnings 'uninitialized' ;
diff --git a/t/op/gv.t b/t/op/gv.t
index c4570e3..2930e12 100644
--- a/t/op/gv.t
+++ b/t/op/gv.t
@@ -12,7 +12,7 @@ BEGIN {
 
 use warnings;
 
-plan( tests => 234 );
+plan( tests => 236 );
 
 # type coersion on assignment
 $foo = 'foo';
@@ -898,6 +898,14 @@ ok eval {
   'no error when gp_free calls a destructor that assigns to the gv';
 }
 
+# *{undef}
+eval { *{my $undef} = 3 };
+like $@, qr/^Can't use an undefined value as a symbol reference at /,
+  '*{ $undef } assignment';
+eval { *{;undef} = 3 };
+like $@, qr/^Can't use an undefined value as a symbol reference at /,
+  '*{ ;undef } assignment';
+
 __END__
 Perl
 Rules
-- 
2.7.4