(Fforward_word): Avoid non-idempotent side-effects in macro arguments.

1 files changed, 4 insertions, 2 deletions

diff --git a/src/syntax.c b/src/syntax.c
index 8bfa62b49fc..fa34c2433c1 100644
--- a/src/syntax.c
+++ b/src/syntax.c
@@ -1295,6 +1295,7 @@ and the function returns nil.  Field boundaries are not noticed if
      (arg)
      Lisp_Object arg;
 {
+  Lisp_Object tmp;
   int orig_val, val;
 
   if (NILP (arg))
@@ -1307,8 +1308,9 @@ and the function returns nil.  Field boundaries are not noticed if
     val = XINT (arg) > 0 ? ZV : BEGV;
 
   /* Avoid jumping out of an input field.  */
-  val = XFASTINT (Fconstrain_to_field (make_number (val), make_number (PT),
-                                       Qt, Qnil, Qnil));
+  tmp = Fconstrain_to_field (make_number (val), make_number (PT),
+                             Qt, Qnil, Qnil);
+  val = XFASTINT (tmp);
 
   SET_PT (val);
   return val == orig_val ? Qt : Qnil;