From e33faef861e9a43ae401fb0b0014c8c96a69fe51 Mon Sep 17 00:00:00 2001
From: Yorhel <git@yorhel.nl>
Date: Sun, 2 Mar 2025 21:37:54 +0100
Subject: [PATCH] ManUtils: Fix possible deadlock on groff I/O

---
 ManUtils/ManUtils.pm | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/ManUtils/ManUtils.pm b/ManUtils/ManUtils.pm
index 261b274..88280a4 100644
--- a/ManUtils/ManUtils.pm
+++ b/ManUtils/ManUtils.pm
@@ -5,6 +5,7 @@ use IPC::Open3;
 use IO::Poll qw/POLLOUT POLLIN/;
 use Symbol 'gensym';
 use XSLoader;
+use Fcntl qw(F_GETFL F_SETFL O_NONBLOCK);
 XSLoader::load('ManUtils');
 
 sub fmt($input) {
@@ -27,6 +28,10 @@ sub fmt($input) {
 
     my $pid = open3(my $in, my $out, my $err = gensym, @cmd);
 
+    # "POLLOUT" does NOT guarantee that a write will not block, we must set
+    # O_NONBLOCK to tell the kernel that we can handle short writes.
+    fcntl($in, F_SETFL, fcntl($in, F_GETFL, 0) | O_NONBLOCK);
+
     my $inoff = 0;
     my $output = '';
     my $poll = IO::Poll->new;