From 5bcc2912e7d7c16d3052a7ed4f0904f72573255e Mon Sep 17 00:00:00 2001
From: =?utf8?q?P=C3=A1draig=20Brady?= <P@draigBrady.com>
Date: Tue, 28 Feb 2023 13:34:31 +0000
Subject: [PATCH] tail: avoid undefined behavior when polling outputs

* src/tail.c (check_output_alive): Only check the returned
events from poll() when it indicates there are events to check.
---
 src/tail.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/tail.c b/src/tail.c
index e2e7f46909..78022fc4b5 100644
--- a/src/tail.c
+++ b/src/tail.c
@@ -367,9 +367,9 @@ check_output_alive (void)
   struct pollfd pfd;
   pfd.fd = STDOUT_FILENO;
   pfd.events = pfd.revents = 0;
-  pfd.events |= POLLRDBAND; /* Needed for illumos, macos.  */
+  pfd.events |= POLLRDBAND; /* Needed for illumos, macOS.  */
 
-  if (poll (&pfd, 1, 0) >= 0 && (pfd.revents & (POLLERR | POLLHUP)))
+  if (poll (&pfd, 1, 0) > 0 && (pfd.revents & (POLLERR | POLLHUP)))
     die_pipe ();
 #else
   struct timeval delay;
-- 
2.47.2