From dfe3440e911101399dbd1ba6ae9a5a4d1eaee637 Mon Sep 17 00:00:00 2001
From: Alex Shinn <ashinn@users.noreply.github.com>
Date: Mon, 14 Nov 2011 11:53:28 +0900
Subject: [PATCH] Adding type check to get-output-string.

---
 sexp.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/sexp.c b/sexp.c
index 4cd9a989..bb5c34ee 100644
--- a/sexp.c
+++ b/sexp.c
@@ -1221,7 +1221,9 @@ sexp sexp_make_output_string_port_op (sexp ctx, sexp self, sexp_sint_t n) {
 }
 
 sexp sexp_get_output_string_op (sexp ctx, sexp self, sexp_sint_t n, sexp port) {
-  sexp cookie = sexp_port_cookie(port);
+  sexp cookie;
+  sexp_assert_type(ctx, sexp_oportp, SEXP_OPORT, port);
+  cookie = sexp_port_cookie(port);
   fflush(sexp_port_stream(port));
   return sexp_substring(ctx,
                         sexp_stream_buf(cookie),