utf8_to_wstrbuf now handles invalid utf8 sequences (#3244)

include/spdlog/details/os-inl.h

@@ -483,12 +483,12 @@ SPDLOG_INLINE void utf8_to_wstrbuf(string_view_t str, wmemory_buf_t &target) {
 
     // find the size to allocate for the result buffer
     int result_size =
-        ::MultiByteToWideChar(CP_UTF8, MB_ERR_INVALID_CHARS, str.data(), str_size, NULL, 0);
+        ::MultiByteToWideChar(CP_UTF8, 0, str.data(), str_size, NULL, 0);
 
     if (result_size > 0) {
         target.resize(result_size);
-        result_size = ::MultiByteToWideChar(CP_UTF8, MB_ERR_INVALID_CHARS, str.data(), str_size,
-                                            target.data(), result_size);
+        result_size = ::MultiByteToWideChar(CP_UTF8, 0, str.data(), str_size, target.data(),
+                                            result_size);
         if (result_size > 0) {
             assert(result_size == target.size());
             return;

tests/includes.h

@@ -26,6 +26,7 @@
 #include "spdlog/spdlog.h"
 #include "spdlog/async.h"
 #include "spdlog/details/fmt_helper.h"
+#include "spdlog/details/os.h"
 
 #ifndef SPDLOG_NO_TLS
     #include "spdlog/mdc.h"

tests/test_misc.cpp

@@ -167,3 +167,21 @@ TEST_CASE("default logger API", "[default logger]") {
     spdlog::drop_all();
     spdlog::set_pattern("%v");
 }
+
+#if (defined(SPDLOG_WCHAR_TO_UTF8_SUPPORT) || defined(SPDLOG_WCHAR_FILENAMES)) && defined(_WIN32)
+TEST_CASE("utf8 to utf16 conversion using windows api", "[windows utf]") {
+    spdlog::wmemory_buf_t buffer;
+
+    spdlog::details::os::utf8_to_wstrbuf("", buffer);
+    REQUIRE(buffer.data() == std::wstring(L""));
+
+    spdlog::details::os::utf8_to_wstrbuf("abc", buffer);
+    REQUIRE(buffer.data() == std::wstring(L"abc"));
+
+    spdlog::details::os::utf8_to_wstrbuf("\xc3\x28", buffer); // Invalid UTF-8 sequence.
+    REQUIRE(buffer.data() == std::wstring(L"\xfffd("));
+
+    spdlog::details::os::utf8_to_wstrbuf("\xe3\x81\xad\xe3\x81\x93", buffer); // "Neko" in hiragana.
+    REQUIRE(buffer.data() == std::wstring(L"\x306d\x3053"));
+}
+#endif