Fix #2318

httplib.h

@@ -2443,16 +2443,20 @@ namespace detail {
 
 #if defined(_WIN32)
 inline std::wstring u8string_to_wstring(const char *s) {
-  std::wstring ws;
+  if (!s) { return std::wstring(); }
+
   auto len = static_cast<int>(strlen(s));
+  if (!len) { return std::wstring(); }
+
   auto wlen = ::MultiByteToWideChar(CP_UTF8, 0, s, len, nullptr, 0);
-  if (wlen > 0) {
-    ws.resize(wlen);
-    wlen = ::MultiByteToWideChar(
-        CP_UTF8, 0, s, len,
-        const_cast<LPWSTR>(reinterpret_cast<LPCWSTR>(ws.data())), wlen);
-    if (wlen != static_cast<int>(ws.size())) { ws.clear(); }
-  }
+  if (!wlen) { return std::wstring(); }
+
+  std::wstring ws;
+  ws.resize(wlen);
+  wlen = ::MultiByteToWideChar(
+      CP_UTF8, 0, s, len,
+      const_cast<LPWSTR>(reinterpret_cast<LPCWSTR>(ws.data())), wlen);
+  if (wlen != static_cast<int>(ws.size())) { ws.clear(); }
   return ws;
 }
 #endif

test/test.cc

@@ -14086,3 +14086,18 @@ TEST_F(SSEIntegrationTest, LastEventIdSentOnReconnect) {
     EXPECT_EQ(received_last_event_ids[1], "event-0");
   }
 }
+
+TEST(Issue2318Test, EmptyHostString) {
+  {
+    httplib::Client cli_empty("", PORT);
+    auto res = cli_empty.Get("/");
+    ASSERT_FALSE(res);
+    EXPECT_EQ(httplib::Error::Connection, res.error());
+  }
+  {
+    httplib::Client cli("   ", PORT);
+    auto res = cli.Get("/");
+    ASSERT_FALSE(res);
+    EXPECT_EQ(httplib::Error::Connection, res.error());
+  }
+}