Fix #2068

httplib.h

@@ -1534,7 +1534,10 @@ class ClientImpl {
   std::recursive_mutex request_mutex_;
 
   // These are all protected under socket_mutex
+public:
   size_t socket_requests_in_flight_ = 0;
+
+protected:
   std::thread::id socket_requests_are_from_thread_ = std::thread::id();
   bool socket_should_be_closed_when_request_is_done_ = false;
 
@@ -7333,6 +7336,16 @@ 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::microseconds{1});
+  }
+
   std::lock_guard<std::mutex> guard(socket_mutex_);
   shutdown_socket(socket_);
   close_socket(socket_);