fix(streaming): make ServerSession::CloseNow idempotent on ue5-dev

CHANGELOG.md

@@ -1,6 +1,7 @@
 =======
 ## LATEST Changes
 
+* Fixed ServerSession::CloseNow double-invocation on ue5-dev by guarding with std::atomic_bool _is_closed so the close path runs exactly once, preventing a dropped client from evicting a still-alive subscriber (port of ue4-dev fix #9740)
 * Added NumPy 2 compatibility to the PythonAPI by upgrading Boost to 1.90.0, which ships the upstream NumPy 2 C ABI fix. LibCarla networking migrated from `boost::asio::deadline_timer` to `boost::asio::steady_timer`, and the deprecated `io_service`, `address::from_string`, `resolver::query`, `buffer_cast`, and `io_context::work` APIs replaced across LibCarla and the CarlaTools plugin.
 * Added `Vehicle.get_telemetry_data()` returning `VehicleTelemetryData` with last-applied control, forward speed, engine RPM, current gear, and per-wheel lateral slip, longitudinal slip, and angular velocity sourced from the Chaos vehicle physics state.
 * Added a GeoProjection engine that parses the OpenDRIVE `geoReference` PROJ string into a typed cartographic projection (Transverse Mercator, UTM, Web Mercator, or Lambert Conformal Conic) and exposes it via `Map.get_geoprojection`. `Map.transform_to_geolocation` and `Map.geolocation_to_transform` now accept an optional projection argument together with the new `carla.GeoProjectionTM`/`GeoProjectionUTM`/`GeoProjectionWebMerc`/`GeoProjectionLCC2SP` and `carla.GeoEllipsoid` types, replacing the previous fixed Mercator conversion.

LibCarla/source/carla/streaming/detail/tcp/ServerSession.cpp

@@ -135,6 +135,7 @@ namespace tcp {
   }
 
   void ServerSession::CloseNow(boost::system::error_code ec) {
+    if (_is_closed.exchange(true)) return;
     _deadline.cancel();
     if (!ec)
     {

LibCarla/source/carla/streaming/detail/tcp/ServerSession.h

@@ -25,6 +25,7 @@
 #  pragma clang diagnostic pop
 #endif
 
+#include <atomic>
 #include <functional>
 #include <memory>
 
@@ -109,6 +110,7 @@ namespace tcp {
     callback_function_type _on_closed;
 
     bool _is_writing = false;
+    std::atomic_bool _is_closed{false};
   };
 
 } // namespace tcp