Fix #2068 (#2080)

* Fix #2068

* Add unit test

httplib.h

@@ -7333,6 +7333,16 @@ inline ClientImpl::ClientImpl(const std::string &host, int port,
       client_cert_path_(client_cert_path), client_key_path_(client_key_path) {}
 
 inline ClientImpl::~ClientImpl() {
+  // Wait until all the requests in flight are handled.
+  size_t retry_count = 10;
+  while (retry_count-- > 0) {
+    {
+      std::lock_guard<std::mutex> guard(socket_mutex_);
+      if (socket_requests_in_flight_ == 0) { break; }
+    }
+    std::this_thread::sleep_for(std::chrono::milliseconds{1});
+  }
+
   std::lock_guard<std::mutex> guard(socket_mutex_);
   shutdown_socket(socket_);
   close_socket(socket_);

test/test.cc

@@ -8351,3 +8351,86 @@ TEST(MaxTimeoutTest, ContentStreamSSL) {
   max_timeout_test(svr, cli, timeout, threshold);
 }
 #endif
+
+class EventDispatcher {
+public:
+  EventDispatcher() {}
+
+  void wait_event(DataSink *sink) {
+    unique_lock<mutex> lk(m_);
+    int id = id_;
+    cv_.wait(lk, [&] { return cid_ == id; });
+    sink->write(message_.data(), message_.size());
+  }
+
+  void send_event(const string &message) {
+    lock_guard<mutex> lk(m_);
+    cid_ = id_++;
+    message_ = message;
+    cv_.notify_all();
+  }
+
+private:
+  mutex m_;
+  condition_variable cv_;
+  atomic_int id_{0};
+  atomic_int cid_{-1};
+  string message_;
+};
+
+TEST(ClientInThreadTest, Issue2068) {
+  EventDispatcher ed;
+
+  Server svr;
+  svr.Get("/event1", [&](const Request & /*req*/, Response &res) {
+    res.set_chunked_content_provider("text/event-stream",
+                                     [&](size_t /*offset*/, DataSink &sink) {
+                                       ed.wait_event(&sink);
+                                       return true;
+                                     });
+  });
+
+  auto listen_thread = std::thread([&svr]() { svr.listen(HOST, PORT); });
+
+  svr.wait_until_ready();
+
+  thread event_thread([&] {
+    int id = 0;
+    while (svr.is_running()) {
+      this_thread::sleep_for(chrono::milliseconds(500));
+
+      std::stringstream ss;
+      ss << "data: " << id << "\n\n";
+      ed.send_event(ss.str());
+      id++;
+    }
+  });
+
+  auto se = detail::scope_exit([&] {
+    svr.stop();
+
+    listen_thread.join();
+    event_thread.join();
+
+    ASSERT_FALSE(svr.is_running());
+  });
+
+  {
+    auto client = detail::make_unique<Client>(HOST, PORT);
+    client->set_read_timeout(std::chrono::minutes(10));
+
+    std::atomic<bool> stop{false};
+
+    std::thread t([&] {
+      client->Get("/event1",
+                  [&](const char *, size_t) -> bool { return !stop; });
+    });
+
+    std::this_thread::sleep_for(std::chrono::seconds(2));
+    stop = true;
+    client->stop();
+    client.reset();
+
+    t.join();
+  }
+}