[LIBCNTPR] Implement NT version of towupper

sdk/lib/crt/string/ctype.c

@@ -895,6 +895,7 @@ wint_t __cdecl towlower(wint_t c)
    return(c);
 }
 
+#ifndef _LIBCNT_
 /*
  * @implemented
  */
@@ -904,5 +905,6 @@ wint_t __cdecl towupper(wint_t c)
       return (c + upalpha);
    return(c);
 }
+#endif /* _LIBCNT_ */
 
 /* EOF */

sdk/lib/crt/string/string.cmake

@@ -112,6 +112,7 @@ list(APPEND CRT_STRING_ASM_SOURCE
 
 list(APPEND LIBCNTPR_STRING_SOURCE
     string/mbstowcs_nt.c
+    string/towupper_nt.c
     string/wcstombs_nt.c
 )
 

sdk/lib/crt/string/towupper_nt.c

@@ -0,0 +1,20 @@
+/*
+ * PROJECT:     ReactOS NT CRT library
+ * LICENSE:     MIT (https://spdx.org/licenses/MIT)
+ * PURPOSE:     Implementation of towupper
+ * COPYRIGHT:   Copyright 2025 Timo Kreuzer <timo.kreuzer@reactos.org>
+ */
+
+#define WIN32_NO_STATUS
+#include <windef.h>
+#include <ndk/rtlfuncs.h>
+
+_Check_return_
+_CRTIMP
+wint_t
+__cdecl
+towupper(
+    _In_ wint_t _C)
+{
+    return RtlUpcaseUnicodeChar((WCHAR)_C);
+}