Fix bad mutation in arg handling.

* args.h (args_atz): Do not zap the car field
of the first list cons; rather, zap the list itself.
The list shouldn't be modified because in apply
calls, it is a data structure belonging to the
caller.

1 files changed, 1 insertions, 2 deletions

diff --git a/args.h b/args.h
index 5735b828..964a8126 100644
--- a/args.h
+++ b/args.h
@@ -164,8 +164,7 @@ INLINE val args_atz(struct args *args, cnum arg_index)
   if (arg_index < args->fill) {
     return z(args->arg[arg_index]);
   } else {
-    loc l = car_l(args->list);
-    return zap(valptr(l));
+    return car(z(args->list));
   }
 }