Error on non-bindable sym in defvar and defparm.

* eval.c (me_def_variable): Check for sym not
being a bindable symbol. Otherwise we might call
mark_special on nil, which triggers an assertion.

1 files changed, 3 insertions, 0 deletions

diff --git a/eval.c b/eval.c
index 36c07890..07d8c5cd 100644
--- a/eval.c
+++ b/eval.c
@@ -2365,6 +2365,9 @@ static val me_def_variable(val form, val menv)
   if (op != defvar_s && length(args) != two)
     eval_error(form, lit("~s: two arguments expected"), op, nao);
 
+  if (!bindable(sym))
+    eval_error(form, lit("~s: ~s is not a bindable symbol"), op, sym, nao);
+
   if (op == defparm_s || op == defvar_s)
     mark_special(sym);