* hash.c (hash_begin): Missing type check added, otherwise

passing in an object that is not a hash results in corruption
or crashing behavior.

* lib.c (class_check): Improved to a one-step check with a clear
message.

1 files changed, 4 insertions, 1 deletions

diff --git a/hash.c b/hash.c
index e03664cd..e8f5bb1b 100644
--- a/hash.c
+++ b/hash.c
@@ -389,7 +389,10 @@ static struct cobj_ops hash_iter_ops = {
 val hash_begin(val hash)
 {
   val hi_obj;
-  struct hash_iter *hi = (struct hash_iter *) chk_malloc(sizeof *hi);
+  struct hash_iter *hi;
+  class_check (hash, hash_s);
+
+  hi = (struct hash_iter *) chk_malloc(sizeof *hi);
   hi->hash = nil;
   hi->chain = -1;
   hi->cons = nil;