--- idlc/source/preproc/tokens.c	2010-09-08 13:23:54.000000000 +0100
+++ idlc/source/preproc/tokens.c	2010-09-08 13:24:20.000000000 +0100
@@ -477,7 +477,7 @@
             if (write(1, wbuf, OBS) != OBS)
                 error(ERROR, "short write!");
             if (wbp > &wbuf[OBS])
-                memcpy(wbuf, wbuf + OBS, wbp - &wbuf[OBS]);
+                memmove(wbuf, wbuf + OBS, wbp - &wbuf[OBS]);
             wbp -= OBS;
         }
     }