From 23a1d79a662a17398a3ea2c12bc818eedff24756 Mon Sep 17 00:00:00 2001
From: yhirose <yuji.hirose.bug@gmail.com>
Date: Fri, 2 Jan 2026 20:45:01 -0500
Subject: [PATCH] Fix #2318

---
 httplib.h    | 20 ++++++++++++--------
 test/test.cc | 15 +++++++++++++++
 2 files changed, 27 insertions(+), 8 deletions(-)

diff --git a/httplib.h b/httplib.h
index 5c2c287..e40e7f6 100644
--- a/httplib.h
+++ b/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
diff --git a/test/test.cc b/test/test.cc
index e1fa239..41f072b 100644
--- a/test/test.cc
+++ b/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());
+  }
+}