On Fri, Jan 23, 2009 at 08:21:24PM +0000, Marcin Owsiany wrote:
> The following program dies for me on perl v5.8.8 with:
> Can't call method "foo" without a package or object reference at a line 10.
> 
> -------------------------------------------------------->8---
> package A;
> sub new { bless {}, shift }
> sub foo { }
> sub getref { setpgrp() }
> 
> package main;
> my $o = A->new;
> # my $r = A::getref;
> # $o->foo($r);
> $o->foo(A::getref);
> -------------------------------------------------------->8---
> 
> However just uncomment the commented lines, and comment the last one,
> and it works! :-O

Thanks for the report. 

This bug is still present in bleadperl. The attached patch should fix it.
-- 
Niko Tyni   nt...@debian.org
>From 38bc943b3e930c46bd9043230ab36503f43a657e Mon Sep 17 00:00:00 2001
From: Niko Tyni <nt...@debian.org>
Date: Mon, 26 Jan 2009 14:14:36 +0200
Subject: [PATCH] setpgrp() should extend the stack before modifying it

As reported by Marcin Owsiany in <http://bugs.debian.org/512796>,
invoking setpgrp without any arguments could corrupt the stack.
---
 pp_sys.c            |    1 +
 t/op/setpgrpstack.t |   16 ++++++++++++++++
 2 files changed, 17 insertions(+), 0 deletions(-)
 create mode 100644 t/op/setpgrpstack.t

diff --git a/pp_sys.c b/pp_sys.c
index cfbf918..0d2c970 100644
--- a/pp_sys.c
+++ b/pp_sys.c
@@ -4318,6 +4318,7 @@ PP(pp_setpgrp)
     if (MAXARG < 2) {
 	pgrp = 0;
 	pid = 0;
+	XPUSHi(-1);
     }
     else {
 	pgrp = POPi;
diff --git a/t/op/setpgrpstack.t b/t/op/setpgrpstack.t
new file mode 100644
index 0000000..31f498e
--- /dev/null
+++ b/t/op/setpgrpstack.t
@@ -0,0 +1,16 @@
+#!./perl -w
+
+BEGIN {
+    chdir 't' if -d 't';
+    @INC = '../lib';
+    require './test.pl';
+}
+
+use Config;
+plan tests => 2;
+
+SKIP: {
+    skip "setpgrp() is not available", 2 unless $Config{d_setpgrp};
+    ok(!eval { package A;sub foo { die("got here") }; package main; A->foo(setpgrp())});
+    ok($@ =~ /got here/, "setpgrp() should extend the stack before modifying it");
+}
-- 
1.5.6.5

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