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From: Eric Wong <e@80x24.org>
To: meta@public-inbox.org
Subject: [PATCH 04/19] spawn_pp: die more consistently in child
Date: Sun,  7 Feb 2021 08:51:46 +0000
Message-Id: <20210207085201.13871-5-e@80x24.org>
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The default $SIG{__DIE__} inside a forked child doesn't actually
do what we want it to do.  We don't want it to zip up the stack
the parent used, but instead want to exit the child process
after warning.
---
 lib/PublicInbox/SpawnPP.pm | 20 +++++++++-----------
 1 file changed, 9 insertions(+), 11 deletions(-)

diff --git a/lib/PublicInbox/SpawnPP.pm b/lib/PublicInbox/SpawnPP.pm
index 401cb78d..2c5edef6 100644
--- a/lib/PublicInbox/SpawnPP.pm
+++ b/lib/PublicInbox/SpawnPP.pm
@@ -22,15 +22,15 @@ sub pi_fork_exec ($$$$$$$) {
 		$pid = -1;
 	}
 	if ($pid == 0) {
+		$SIG{__DIE__} = sub { warn @_; _exit 1 };
 		for my $child_fd (0..$#$redir) {
 			my $parent_fd = $redir->[$child_fd];
 			next if $parent_fd == $child_fd;
 			dup2($parent_fd, $child_fd) or
-				die "dup2($parent_fd, $child_fd): $!\n";
+				die "dup2($parent_fd, $child_fd): $!";
 		}
 		if ($pgid >= 0 && !defined(setpgid(0, $pgid))) {
-			warn "setpgid: $!";
-			_exit(1);
+			die "setpgid(0, $pgid): $!";
 		}
 		$SIG{$_} = 'DEFAULT' for keys %SIG;
 		if ($cd ne '') {
@@ -39,20 +39,18 @@ sub pi_fork_exec ($$$$$$$) {
 		while (@$rlim) {
 			my ($r, $soft, $hard) = splice(@$rlim, 0, 3);
 			BSD::Resource::setrlimit($r, $soft, $hard) or
-			  warn "failed to set $r=[$soft,$hard]\n";
+				die "setrlimit($r=[$soft,$hard]: $!)";
 		}
 		$old->delset(POSIX::SIGCHLD) or die "delset SIGCHLD: $!";
 		sigprocmask(SIG_SETMASK, $old) or die "SETMASK: ~SIGCHLD: $!";
+		$cmd->[0] = $f;
 		if ($ENV{MOD_PERL}) {
-			exec which('env'), '-i', @$env, @$cmd;
-			die "exec env -i ... $cmd->[0] failed: $!\n";
+			@$cmd = (which('env'), '-i', @$env, @$cmd);
 		} else {
-			local %ENV = map { split(/=/, $_, 2) } @$env;
-			my @cmd = @$cmd;
-			$cmd[0] = $f;
-			exec @cmd;
-			die "exec $cmd->[0] failed: $!\n";
+			%ENV = map { split(/=/, $_, 2) } @$env;
 		}
+		exec @$cmd;
+		die "exec @$cmd failed: $!";
 	}
 	sigprocmask(SIG_SETMASK, $old) or die "can't unblock signals: $!";
 	$! = $syserr;