Dispatch signals in infinite loops such as 1 while 1;

With the move of PERL_ASYNC_CHECK() out from the runloop to control ops,
infinite loops became truely infinite, as their optree has no control ops.
Hence add a PERL_ASYNC_CHECK() to pp_unstack to ensure signals will be
dispatched.

Bug noticed by Jerry Hedden.

1 files changed, 38 insertions, 0 deletions

diff --git a/t/op/sigdispatch.t b/t/op/sigdispatch.t
new file mode 100755
index 0000000000..5d9908e6ed
--- /dev/null
+++ b/t/op/sigdispatch.t
@@ -0,0 +1,38 @@
+#!perl -w
+
+# We assume that TestInit has been used.
+
+BEGIN {
+      require './test.pl';
+}
+
+use strict;
+
+plan tests => 4;
+
+watchdog(10);
+
+$SIG{ALRM} = sub {
+    die "Alarm!\n";
+};
+
+pass('before the first loop');
+
+alarm 2;
+
+eval {
+    1 while 1;
+};
+
+is($@, "Alarm!\n", 'after the first loop');
+
+pass('before the second loop');
+
+alarm 2;
+
+eval {
+    while (1) {
+    }
+};
+
+is($@, "Alarm!\n", 'after the second loop');