Fix overlapping memcpy call in String::trim (esp8266#4938)

earlephilhower · web-flow · commit 63ab79e549bb · 2018-07-18T18:36:31.000-07:00
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.
diff --git 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;
 }
 

Original file line number	Diff line number	Diff line change
`@@ -753,7 +753,7 @@ void String::trim(void) {`
`753`	`753`	`end--;`
`754`	`754`	`len = end + 1 - begin;`
`755`	`755`	`if(begin > buffer)`
`756`		`- memcpy(buffer, begin, len);`
	`756`	`+ memmove(buffer, begin, len);`
`757`	`757`	`buffer[len] = 0;`
`758`	`758`	`}`
`759`	`759`