Added tests for SIGCHLD blocking during system()

2 files changed, 64 insertions, 0 deletions

diff --git a/MANIFEST b/MANIFEST
index 99eb9ef0d8..2df1462169 100644
--- a/MANIFEST
+++ b/MANIFEST
@@ -5273,6 +5273,7 @@ t/op/runlevel.t			See if die() works from perl_call_*()
 t/op/select.t			See if 0- and 1-argument select works
 t/op/setpgrpstack.t		See if setpgrp works
 t/op/sigdispatch.t		See if signals are always dispatched
+t/op/sigsystem.t		See if system and SIGCHLD handlers play together nicely
 t/op/sleep.t			See if sleep works
 t/op/smartkve.t			See if smart deref for keys/values/each works
 t/op/smartmatch.t		See if the ~~ operator works
diff --git a/t/op/sigsystem.t b/t/op/sigsystem.t
new file mode 100644
index 0000000000..0197ad9e61
--- /dev/null
+++ b/t/op/sigsystem.t
@@ -0,0 +1,63 @@
+#!perl -w
+
+BEGIN {
+      require './test.pl';
+}
+
+use strict;
+use constant TRUE => ($^X, '-e', 'exit 0');
+use Data::Dumper;
+
+plan tests => 4;
+
+SKIP: {
+    skip 'Platform doesn\'t support SIGCHLD', 3 if is_miniperl() or not exists $SIG{CHLD};
+    require POSIX;
+    require Time::HiRes;
+
+    my $pid = fork // die "Can't fork: $!";
+    unless ($pid) {
+	note("Child PID: $$");
+	Time::HiRes::sleep(0.250);
+	POSIX::_exit(0);
+    }
+
+    test_system('without reaper');
+
+    my @pids;
+    $SIG{CHLD} = sub {
+	while ((my $child = waitpid(-1, POSIX::WNOHANG())) > 0) {
+	    note "Reaped: $child";
+	    push @pids, $child;
+	}
+    };
+
+    test_system('with reaper');
+
+    note("Waiting briefly for SIGCHLD...");
+    Time::HiRes::sleep(0.500);
+
+    ok(@pids == 1, 'Reaped only one process');
+    ok($pids[0] == $pid, "Reaped the right process.") or diag(Dumper(\@pids));
+}
+
+sub test_system {
+    my $subtest = shift;
+
+    my $expected_zeroes = 10;
+    my $got_zeroes      = 0;
+
+    # This test is looking for a race between system()'s waitpid() and a
+    # signal handler.    Looping a few times increases the chances of
+    # catching the error.
+
+    for (1..$expected_zeroes) {
+	$got_zeroes++ unless system(TRUE);
+    }
+
+    is(
+	$got_zeroes, $expected_zeroes,
+	"system() $subtest succeeded $got_zeroes times out of $expected_zeroes"
+    );
+}
+