From b5af6498f25dc28766a428c65eb577162d22d69e Mon Sep 17 00:00:00 2001
From: Tony Cook <tony@develop-help.com>
Date: Wed, 12 Jun 2019 15:21:47 +1000
Subject: [PATCH] (perl #133989) scalar() the argument to readline, if any
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C< readline @foo > would treat @foo as array.  If the array was empty
this would push zero items and readline() would then pop one item,
possibly underflowing the stack.

Petr Písař: Ported to 5.28.2 from
a8e0c1fd5ade7c30aa0782f1aea274ef89190f6d.

Signed-off-by: Petr Písař <ppisar@redhat.com>
---
 op.c               | 1 +
 t/lib/croak/pp_sys | 6 ++++++
 2 files changed, 7 insertions(+)

diff --git a/op.c b/op.c
index cf90902..d1458cb 100644
--- a/op.c
+++ b/op.c
@@ -12041,6 +12041,7 @@ Perl_ck_readline(pTHX_ OP *o)
     if (o->op_flags & OPf_KIDS) {
 	 OP *kid = cLISTOPo->op_first;
 	 if (kid->op_type == OP_RV2GV) kid->op_private |= OPpALLOW_FAKE;
+         scalar(kid);
     }
     else {
 	OP * const newop
diff --git a/t/lib/croak/pp_sys b/t/lib/croak/pp_sys
index 8b7dc9d..3fd4a9f 100644
--- a/t/lib/croak/pp_sys
+++ b/t/lib/croak/pp_sys
@@ -73,3 +73,9 @@ open my $ｆｏｏ, "../harness";
 opendir $ｆｏｏ, ".";
 EXPECT
 Cannot open $ｆｏｏ as a dirhandle: it is already open as a filehandle at - line 5.
+########
+# NAME readline() didn't scalar() its argument
+# this would assert rather than failing on the method call
+E{0;readline@0}
+EXPECT
+Can't call method "E" without a package or object reference at - line 2.
-- 
2.20.1