From 359205bcccd8b89f8de5f8e13f69742eee94ce0f Mon Sep 17 00:00:00 2001
From: Eric Kohl <eric.kohl@reactos.org>
Date: Fri, 22 Aug 2025 16:48:06 +0200
Subject: [PATCH] [CRT] wctomb must return 0 if the destination pointer is NULL

This fixes 3 test failures.
---
 sdk/lib/crt/string/wcs.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/sdk/lib/crt/string/wcs.c b/sdk/lib/crt/string/wcs.c
index e056bf593f6..f238a78616d 100644
--- a/sdk/lib/crt/string/wcs.c
+++ b/sdk/lib/crt/string/wcs.c
@@ -246,6 +246,9 @@ INT CDECL wctomb( char *dst, wchar_t ch )
     BOOL error;
     INT size;
 
+    if (!dst)
+        return 0;
+
     size = WideCharToMultiByte(get_locinfo()->lc_codepage, 0, &ch, 1, dst, dst ? 6 : 0, NULL, &error);
     if(!size || error) {
         *_errno() = EINVAL;