From af8a7c13b516c77c1e6092157e23ca26db44b1af Mon Sep 17 00:00:00 2001
From: Takashi Yano <takashi.yano@nifty.ne.jp>
Date: Sat, 12 Mar 2022 06:19:53 +0900
Subject: [PATCH] Cygwin: fsync: Return EINVAL for special files.

- Unlike linux, fsync() calls FlushFileBuffers() even for special
  files. This causes the problem reported in:
    https://cygwin.com/pipermail/cygwin/2022-March/251022.html
  This patch fixes the issue.
---
 winsup/cygwin/fhandler.cc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/winsup/cygwin/fhandler.cc b/winsup/cygwin/fhandler.cc
index 98d7a3b2d..fc7bf0a0e 100644
--- a/winsup/cygwin/fhandler.cc
+++ b/winsup/cygwin/fhandler.cc
@@ -1750,7 +1750,7 @@ fhandler_base::utimens (const struct timespec *tvp)
 int
 fhandler_base::fsync ()
 {
-  if (!get_handle () || nohandle ())
+  if (!get_handle () || nohandle () || pc.isspecial ())
     {
       set_errno (EINVAL);
       return -1;