From c19d37adf0bf156fdea7b18bf068e3aea3a1374f Mon Sep 17 00:00:00 2001
From: Xiang Xiao <xiaoxiang@xiaomi.com>
Date: Wed, 1 Jun 2022 01:14:56 +0800
Subject: [PATCH] libc/wchar: Call mbsnrtowcs in mbrtowc to handle the partial
 sequence correctly

Signed-off-by: Xiang Xiao <xiaoxiang@xiaomi.com>
---
 libs/libc/wchar/lib_mbrtowc.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/libs/libc/wchar/lib_mbrtowc.c b/libs/libc/wchar/lib_mbrtowc.c
index 8acf296b62..25862fce05 100644
--- a/libs/libc/wchar/lib_mbrtowc.c
+++ b/libs/libc/wchar/lib_mbrtowc.c
@@ -57,15 +57,19 @@
 size_t mbrtowc(FAR wchar_t *pwc, FAR const char *s,
                size_t n, FAR mbstate_t *ps)
 {
-  int retval = 0;
+  FAR const char *e = s;
+  size_t retval = 0;
 
   if (s == NULL)
     {
-      retval = mbtowc(NULL, "", 1);
+      s = e = "";
+      n = 1;
     }
-  else
+
+  retval = mbsnrtowcs(pwc, &e, 1, n, ps);
+  if (retval == 1)
     {
-      retval = mbtowc(pwc, s, n);
+      retval = e - s;
     }
 
   return retval;