From 0b2df3511769c9b52481d029bae5bf22cbf02f83 Mon Sep 17 00:00:00 2001
From: david gauchard <gauchard@laas.fr>
Date: Fri, 29 Dec 2017 05:16:41 +0100
Subject: [PATCH] follow arduino API: pure virtual Stream::flush() moved to
 empty virtual Print::flush() (#4029)

re fix #4018
---
 cores/esp8266/Print.h  | 2 ++
 cores/esp8266/Stream.h | 1 -
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/cores/esp8266/Print.h b/cores/esp8266/Print.h
index 69f5ad621..73a955b4d 100644
--- a/cores/esp8266/Print.h
+++ b/cores/esp8266/Print.h
@@ -89,6 +89,8 @@ class Print {
         size_t println(double, int = 2);
         size_t println(const Printable&);
         size_t println(void);
+
+        virtual void flush() { /* Empty implementation for backward compatibility */ }
 };
 
 #endif
diff --git a/cores/esp8266/Stream.h b/cores/esp8266/Stream.h
index 6d2646d77..290971cf4 100644
--- a/cores/esp8266/Stream.h
+++ b/cores/esp8266/Stream.h
@@ -47,7 +47,6 @@ class Stream: public Print {
         virtual int available() = 0;
         virtual int read() = 0;
         virtual int peek() = 0;
-        virtual void flush() = 0;
 
         Stream() {
             _timeout = 1000;