hope this fix the issue

Author: shubh@DOE

libc/src/stdio/printf_core/char_converter.h

@@ -40,7 +40,7 @@ LIBC_INLINE int convert_char(Writer<write_mode> *writer,
   }
 
   if (to_conv.length_modifier == LengthModifier::l) {
-    wc = static_cast<wchar_t>(to_conv.conv_val_raw);
+    wc = static_cast<wchar_t>(static_cast<unsigned int>(to_conv.conv_val_raw));
     ret = internal::wcrtomb(mb_str, wc, &internal_mbstate);
     if (ret <= 0) {
       return -1;

libc/test/src/stdio/printf_core/converter_test.cpp

@@ -6,10 +6,10 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "hdr/types/wchar_t.h"
 #include "src/stdio/printf_core/converter.h"
 #include "src/stdio/printf_core/core_structs.h"
 #include "src/stdio/printf_core/writer.h"
-#include "hdr/types/wchar_t.h"
 #include "test/UnitTest/Test.h"
 
 class LlvmLibcPrintfConverterTest : public LIBC_NAMESPACE::testing::Test {