[PATCH] t/spawn: Find invalid PID to try to join its process group

[Thiago Jung Bauermann <bauermann@kolabnow.com>]

In the container used to build packages of the GNU Guix distribution, PID 1
runs as the same user as the test so this spawn that should fail actually
succeeds.

Fix the problem by going through different PIDs and picking one that
either doesn't exist or we aren't allowed to signal.
---
 t/spawn.t | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

Hello,

First of all, thank you for public-inbox! Mailing list archives are so much
better now for projects that use this project!

I've also been using lei and it's extremely helpful, thank you for this new
tool as well.

I packaged v1.8.0 for the GNU Guix distribution, but its build environment
causes this test to fail. This patch fixes it.

I'm not a Perl developer, so please let me know if there's anything I should
improve in the code.

diff --git a/t/spawn.t b/t/spawn.t
index 6168c1f6171c..4af215809962 100644
--- a/t/spawn.t
+++ b/t/spawn.t
@@ -24,7 +24,17 @@ SKIP: {
 	is(waitpid($pid, 0), $pid, 'waitpid succeeds on spawned process');
 	is($?, 0, 'true exited successfully');
 	pipe(my ($r, $w)) or BAIL_OUT;
-	$pid = eval { spawn(['true'], undef, { pgid => 1, 2 => $w }) };
+
+        # Find invalid PID to try to join its process group.
+        my $wrong_pgid = 1;
+        for (my $i=65534; $i >= 2; $i--) {
+            if (kill(0, $i) == 0) {
+                $wrong_pgid = $i;
+                last;
+            }
+        }
+
+	$pid = eval { spawn(['true'], undef, { pgid => $wrong_pgid, 2 => $w }) };
 	close $w;
 	my $err = do { local $/; <$r> };
 	# diag "$err ($@)";

base-commit: 930d2dc63e04c652e3b64cc7f3b3a7d377637065