From c790a75439f3a1dbbaa2162feca2593de5997bd3 Mon Sep 17 00:00:00 2001
From: Eric Wong <e@80x24.org>
Date: Wed, 31 Mar 2021 23:29:36 +0000
Subject: script/lei: background ourselves on MUA/pager exec

This ought to give the MUA or pager exclusive access to the
controlling terminal.  The downside is we can only exec the
pager or MUA once per invocation, but I can't imagine a valid
case for running those things multiple times, either.

Note: I'm no expert when it comes to terminal control matters,
but this allows Ctrl-Z-ed mutt instance to come back and is
a nice code reduction, as well.
---
 script/lei | 37 +++++++++++++++----------------------
 1 file changed, 15 insertions(+), 22 deletions(-)

diff --git a/script/lei b/script/lei
index cb605e2e..bea8dcde 100755
--- a/script/lei
+++ b/script/lei
@@ -14,36 +14,31 @@ my $send_cmd = PublicInbox::CmdIPC4->can('send_cmd4') // do {
 	PublicInbox::Spawn->can('send_cmd4');
 };
 
-my %pids;
-my $sigchld = sub {
-	my $flags = scalar(@_) ? POSIX::WNOHANG() : 0;
-	for my $pid (keys %pids) {
-		delete($pids{$pid}) if waitpid($pid, $flags) == $pid;
-	}
-};
-
+my @orig_pid;
 my $exec_cmd = sub {
 	my ($fds, $argc, @argv) = @_;
+	die "BUG: already exec-ed\n" if @orig_pid;
+	@orig_pid = ($$);
+	require POSIX; # WNOHANG
 	my @old = (*STDIN{IO}, *STDOUT{IO}, *STDERR{IO});
 	my @rdr;
 	for my $fd (@$fds) {
 		open(my $tmpfh, '+<&=', $fd) or die "open +<&=$fd: $!";
 		push @rdr, shift(@old), $tmpfh;
 	}
-	require POSIX; # WNOHANG
-	$SIG{CHLD} = $sigchld;
 	my $pid = fork // die "fork: $!";
 	if ($pid == 0) {
-		my %env = map { split(/=/, $_, 2) } splice(@argv, $argc);
-		while (my ($old_io, $tmpfh) = splice(@rdr, 0, 2)) {
-			open $old_io, '+<&', $tmpfh or die "open +<&=: $!";
-		}
-		%ENV = (%ENV, %env);
-		exec(@argv);
-		warn "exec: @argv: $!\n";
-		POSIX::_exit(1);
+		POSIX::setsid() > 0 or die "setsid: $!";
+		return; # continue $recv_cmd in background
+	}
+	my %env = map { split(/=/, $_, 2) } splice(@argv, $argc);
+	while (my ($old_io, $tmpfh) = splice(@rdr, 0, 2)) {
+		open $old_io, '+<&', $tmpfh or die "open +<&=: $!";
 	}
-	$pids{$pid} = 1;
+	@ENV{keys %env} = values %env;
+	exec(@argv);
+	warn "exec: @argv: $!\n";
+	POSIX::_exit(1);
 };
 
 if ($send_cmd && eval {
@@ -100,18 +95,16 @@ Falling back to (slow) one-shot mode
 		if ($buf =~ /\Aexec (.+)\z/) {
 			$exec_cmd->(\@fds, split(/\0/, $1));
 		} elsif ($buf eq '-WINCH') {
-			kill($buf, $$); # for MUA
+			kill($buf, @orig_pid); # for MUA
 		} elsif ($buf =~ /\Ax_it ([0-9]+)\z/) {
 			$x_it_code = $1 + 0;
 			last;
 		} elsif ($buf =~ /\Achild_error ([0-9]+)\z/) {
 			$x_it_code = $1 + 0;
 		} else {
-			$sigchld->();
 			die $buf;
 		}
 	}
-	$sigchld->();
 	if (my $sig = ($x_it_code & 127)) {
 		kill $sig, $$;
 		sleep(1) while 1;
-- 
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