From 5412d36b4f4576c9ba116883f47d0291d667eeac Mon Sep 17 00:00:00 2001
From: Binbin <binloveplay1314@qq.com>
Date: Mon, 25 Nov 2024 12:16:22 +0800
Subject: [PATCH] Save open's errno when opening temp rdb fails to prevent it
 from being modified

Apparently on Mac, sleep will modify errno to ETIMEDOUT, and then it
prints the misleading message: Operation timed out.

Signed-off-by: Binbin <binloveplay1314@qq.com>
---
 src/replication.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/replication.c b/src/replication.c
index dcf7ee3f8c..7785f3999c 100644
--- a/src/replication.c
+++ b/src/replication.c
@@ -3684,13 +3684,18 @@ void syncWithPrimary(connection *conn) {
 
     /* Prepare a suitable temp file for bulk transfer */
     if (!useDisklessLoad()) {
+        /* We save the errno of open to prevent some systems from modifying it after
+         * the sleep call. For example, sleep in Mac will change errno to ETIMEDOUT. */
+        int saved_errno;
         while (maxtries--) {
             snprintf(tmpfile, 256, "temp-%d.%ld.rdb", (int)server.unixtime, (long int)getpid());
             dfd = open(tmpfile, O_CREAT | O_WRONLY | O_EXCL, 0644);
             if (dfd != -1) break;
+            saved_errno = errno;
             sleep(1);
         }
         if (dfd == -1) {
+            errno = saved_errno;
             serverLog(LL_WARNING, "Opening the temp file needed for PRIMARY <-> REPLICA synchronization: %s",
                       strerror(errno));
             goto error;