test_common: avoid needless fcntl in start_script

POSIX::dup2 does not do anything in addition to dup2(2) and is
thus immune to Perl automatically setting FD_CLOEXEC on FDs it
makes into IO objects/globs.  We only need to account for the
case when both args for dup2 are identical, in which case the
kernel treats it as a no-op and then thus we need to clear
FD_CLOEXEC ourselves.

1 files changed, 8 insertions, 10 deletions

diff --git a/lib/PublicInbox/TestCommon.pm b/lib/PublicInbox/TestCommon.pm
index 888c1f1e..b36c71a6 100644
--- a/lib/PublicInbox/TestCommon.pm
+++ b/lib/PublicInbox/TestCommon.pm
@@ -6,7 +6,7 @@ package PublicInbox::TestCommon;
 use strict;
 use parent qw(Exporter);
 use v5.10.1;
-use Fcntl qw(FD_CLOEXEC F_SETFD F_GETFD :seek);
+use Fcntl qw(F_SETFD :seek);
 use POSIX qw(dup2);
 use IO::Socket::INET;
 use File::Spec;
@@ -479,16 +479,14 @@ sub start_script {
                 # pretend to be systemd (cf. sd_listen_fds(3))
                 # 3 == SD_LISTEN_FDS_START
                 my $fd;
-                for ($fd = 0; 1; $fd++) {
-                        my $s = $opt->{$fd};
-                        last if $fd >= 3 && !defined($s);
-                        next unless $s;
-                        my $fl = fcntl($s, F_GETFD, 0);
-                        if (($fl & FD_CLOEXEC) != FD_CLOEXEC) {
-                                warn "got FD:".fileno($s)." w/o CLOEXEC\n";
+                for ($fd = 0; $fd < 3 || defined($opt->{$fd}); $fd++) {
+                        my $io = $opt->{$fd} // next;
+                        my $old = fileno($io);
+                        if ($old == $fd) {
+                                fcntl($io, F_SETFD, 0) // die "F_SETFD: $!";
+                        } else {
+                                dup2($old, $fd) // die "dup2($old, $fd): $!";
                         }
-                        fcntl($s, F_SETFD, $fl &= ~FD_CLOEXEC);
-                        dup2(fileno($s), $fd) or die "dup2 failed: $!\n";
                 }
                 %ENV = (%ENV, %$env) if $env;
                 my $fds = $fd - 3;