From 76bbb0c92c0a9e2cadac9796e55fdd2836424fdb Mon Sep 17 00:00:00 2001
From: Peter Bex <address@hidden>
Date: Sun, 28 May 2017 12:37:44 +0200
Subject: [PATCH] Fix segmentation fault in "length" on improper lists.

This fixes #1375
---
 runtime.c               | 2 +-
 tests/library-tests.scm | 6 ++++++
 3 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/runtime.c b/runtime.c
index 86db413..7a513c2 100644
--- a/runtime.c
+++ b/runtime.c
@@ -5379,7 +5379,7 @@ C_regparm C_word C_fcall C_i_length(C_word lst)
       }
     }
 
-    if(C_immediatep(slow) || C_block_header(lst) != C_PAIR_TAG)
+    if(C_immediatep(slow) || C_block_header(slow) != C_PAIR_TAG)
       barf(C_NOT_A_PROPER_LIST_ERROR, "length", lst);
 
     slow = C_u_i_cdr(slow);
diff --git a/tests/library-tests.scm b/tests/library-tests.scm
index cd2f6e9..9c7cab4 100644
--- a/tests/library-tests.scm
+++ b/tests/library-tests.scm
@@ -693,3 +693,9 @@ A
 (assert (not (member "foo" '("bar"))))
 (assert (not (member "foo" '())))
 (assert-fail (member "foo" "foo"))
+
+
+;; length
+
+(assert-fail (length 1))
+(assert-fail (length '(x . y)))
-- 
2.1.4