(memmove): Add prototypes. (MALLOC_MEMMOVE): Define. (chunk_realloc): Use it instead of MALLOC_COPY if source and destination might overlap.

malloc/malloc.c

@@ -415,9 +415,11 @@ extern "C" {
 #if __STD_C
 void* memset(void*, int, size_t);
 void* memcpy(void*, const void*, size_t);
+void* memmove(void*, const void*, size_t);
 #else
 Void_t* memset();
 Void_t* memcpy();
+Void_t* memmove();
 #endif
 #endif
 
@@ -462,6 +464,9 @@ do {                                                                          \
   } else memcpy(dest, src, mcsz);                                             \
 } while(0)
 
+#define MALLOC_MEMMOVE(dest,src,nbytes)                                       \
+  memmove(dest, src, mcsz)
+
 #else /* !USE_MEMCPY */
 
 /* Use Duff's device for good zeroing/copying performance. */