From 8e0bc2c3a858118fa9f4c2532d43b71b39b0adc1 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?J=C3=B6rg=20Thalheim?= <joerg@thalheim.io>
Date: Fri, 21 Mar 2025 16:23:31 +0100
Subject: [PATCH] `MonitorFdHup`: raise explicit SysError rather unreachable

Syscalls can fail for many reasons and we don't want to loose the errno
and error context.
---
 src/libutil/unix/monitor-fd.hh | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/libutil/unix/monitor-fd.hh b/src/libutil/unix/monitor-fd.hh
index cfbf10d5a..0829c1309 100644
--- a/src/libutil/unix/monitor-fd.hh
+++ b/src/libutil/unix/monitor-fd.hh
@@ -39,8 +39,11 @@ public:
 #endif
                     ;
                 auto count = poll(fds, 1, -1);
-                if (count == -1)
-                    unreachable();
+                if (count == -1) {
+                    if (errno == EINTR || errno == EAGAIN)
+                        continue;
+                    throw SysError("failed to poll() in MonitorFdHup");
+                }
 
                 /* This shouldn't happen, but can on macOS due to a bug.
                    See rdar://37550628.