Tests for #85026

Almost all of this is taken verbatim from Ton Hospel’s sample script
for demonstrating the bug.

2 files changed, 68 insertions, 0 deletions

diff --git a/MANIFEST b/MANIFEST
index 7aefe0ecba..b1395489c4 100644
--- a/MANIFEST
+++ b/MANIFEST
@@ -4892,6 +4892,7 @@ t/op/grep.t			See if grep() and map() work
 t/op/groups.t			See if $( works
 t/op/gv.t			See if typeglobs work
 t/op/hashassign.t		See if hash assignments work
+t/op/hash-rt85026.t		See if hash iteration/deletion works
 t/op/hash.t			See if the complexity attackers are repelled
 t/op/hashwarn.t			See if warnings for bad hash assignments work
 t/op/inccode.t			See if coderefs work in @INC
diff --git a/t/op/hash-rt85026.t b/t/op/hash-rt85026.t
new file mode 100644
index 0000000000..61c0fb4c97
--- /dev/null
+++ b/t/op/hash-rt85026.t
@@ -0,0 +1,67 @@
+#!/usr/bin/perl -w
+
+BEGIN {
+  chdir 't';
+  @INC = '../lib';
+  require './test.pl';
+  skip_all_without_dynamic_extension("Devel::Peek");
+}
+
+use strict;
+use Devel::Peek;
+use File::Temp qw(tempdir);
+
+my %hash = map +($_ => 1), ("a".."z");
+
+my $tmp_dir = tempdir(CLEANUP => 1);
+
+sub riter {
+    local *OLDERR;
+    open(OLDERR, ">&STDERR") || die "Can't dup STDERR: $!";
+    open(STDERR, ">", "$tmp_dir/dump") ||
+        die "Could not open '$tmp_dir/dump' for write: $^E";
+    Dump(\%hash);
+    open(STDERR, ">&OLDERR") || die "Can't dup OLDERR: $!";
+    open(my $fh, "<", "$tmp_dir/dump") ||
+        die "Could not open '$tmp_dir/dump' for read: $^E";
+    local $/;
+    my $dump = <$fh>;
+    my ($riter) = $dump =~ /^\s*RITER\s*=\s*(\d+)/m or
+        die "No plain RITER in dump '$dump'";
+    return $riter;
+}
+
+my @riters;
+while (my $key = each %hash) {
+    push @{$riters[riter()]}, $key;
+}
+
+my ($first_key, $second_key);
+my $riter = 0;
+for my $chain (@riters) {
+    if ($chain && @$chain >= 2) {
+        $first_key  = $chain->[0];
+        $second_key = $chain->[1];
+        last;
+    }
+    $riter++;
+}
+$first_key ||
+    skip_all "No 2 element chains; need a different initial HASH";
+$| = 1;
+
+plan(1);
+
+# Ok all preparation is done
+diag <<"EOF"
+Found keys '$first_key' and '$second_key' on chain $riter
+Will now iterato to key '$first_key' then delete '$first_key' and '$second_key'.
+EOF
+;
+1 until $first_key eq each %hash;
+delete $hash{$first_key};
+delete $hash{$second_key};
+
+diag "Now iterating into freed memory\n";
+1 for each %hash;
+ok(1, "Survived!");