Fix ulib's memmove to handle overlap when src<dst

NTHU-LSALAB · Oct 9, 2019 · f2df0fa · f2df0fa
1 parent 8509784
commit f2df0fa
Showing 1 changed file with 9 additions and 2 deletions.
diff --git a/user/ulib.c b/user/ulib.c
@@ -103,8 +103,15 @@ memmove(void *vdst, const void *vsrc, int n)
 
   dst = vdst;
   src = vsrc;
-  while(n-- > 0)
-    *dst++ = *src++;
+  if (src > dst) {
+    while(n-- > 0)
+      *dst++ = *src++;
+  } else {
+    dst += n;
+    src += n;
+    while(n-- > 0)
+      *--dst = *--src;
+  }
   return vdst;
 }