From 75b8fc52b85c945e71a6fb6f2e616ee242b07b43 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Daniel=20Ekl=C3=B6f?= <daniel@ekloef.se>
Date: Thu, 23 Jan 2020 17:39:25 +0100
Subject: [PATCH] vt: bug: fix check for error from mbrtowc()

mbrtowc() returns an unsigned. Need to cast to signed before checking
if less than zero.

This fixes an issue where invalid utf-8 sequences where treated as valid.
---
 vt.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/vt.c b/vt.c
index 8eeefda2..4af40789 100644
--- a/vt.c
+++ b/vt.c
@@ -474,7 +474,10 @@ action_utf8_print(struct terminal *term, uint8_t c)
     /* Convert to wchar */
     mbstate_t ps = {0};
     wchar_t wc;
-    if (mbrtowc(&wc, (const char *)term->vt.utf8.data, term->vt.utf8.idx, &ps) < 0)
+    size_t count = mbrtowc(
+        &wc, (const char *)term->vt.utf8.data, term->vt.utf8.idx, &ps);
+
+    if ((ssize_t)count < 0)
         wc = 0;
 
     /* Reset VT utf8 state */