From 63ab79e549bbf63b99cd53688ff1d253bb1a2671 Mon Sep 17 00:00:00 2001
From: "Earle F. Philhower, III" <earlephilhower@yahoo.com>
Date: Wed, 18 Jul 2018 18:36:31 -0700
Subject: [PATCH] Fix overlapping memcpy call in String::trim (#4938)

memcpy() is undefined when source and destination overlap.  String::trim
uses it when shifting the string left to remove left padding.

Replace with memmove() which is always safe, even when overlapped.
---
 cores/esp8266/WString.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/cores/esp8266/WString.cpp b/cores/esp8266/WString.cpp
index 4efba3e7d..e21316379 100644
--- a/cores/esp8266/WString.cpp
+++ b/cores/esp8266/WString.cpp
@@ -753,7 +753,7 @@ void String::trim(void) {
         end--;
     len = end + 1 - begin;
     if(begin > buffer)
-        memcpy(buffer, begin, len);
+        memmove(buffer, begin, len);
     buffer[len] = 0;
 }