From f9b9b44f5341b0d8df7b1bb00de6f7231258891b Mon Sep 17 00:00:00 2001
From: Mikael Pettersson <mikpelinux@gmail.com>
Date: Fri, 5 Feb 2021 14:43:52 +0100
Subject: [PATCH] Ensure fileno_unlocked() is visible on Cygwin.

---
 gcc/ada/cstreams.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/gcc/ada/cstreams.c b/gcc/ada/cstreams.c
index 4e00dedbbd6..7d64277110b 100644
--- a/gcc/ada/cstreams.c
+++ b/gcc/ada/cstreams.c
@@ -37,6 +37,11 @@
 #define _FILE_OFFSET_BITS 64
 /* the define above will make off_t a 64bit type on GNU/Linux */
 
+/* tell Cygwin's <stdio.h> to expose fileno_unlocked() */
+#if defined(__CYGWIN__) && !defined(__CYGWIN32__) && !defined(_GNU_SOURCE)
+#define _GNU_SOURCE
+#endif
+
 #include <stdio.h>
 #include <sys/types.h>
 #include <sys/stat.h>
-- 
2.26.2