fix(sim): tolerate webots-controller SIGSEGV on TCP disconnect

webots-controller crashes with SIGSEGV (exit 139) in libController.so
when the remote Webots host closes the TCP connection. Replace the raw
shell action with a subprocess wrapper that treats exit code 139 as
success, since the DCS process itself exits cleanly at that point.

Also replace `return status` with `exit(status)` in main() to bypass
C++ static destructor teardown: ~webots::Robot() calls
wb_robot_cleanup() and ~MqttClient() calls mosquitto_loop_stop(),
both of which crash or block when the Webots connection is already gone.

Author: stefanvogel

lib/MainNative/src/main.cpp

@@ -291,7 +291,12 @@ extern int main(int argc, char** argv)
         }
     }
 
-    return status;
+    /* Use exit() instead of return to skip C++ static destructor teardown.
+     * ~webots::Robot() calls wb_robot_cleanup() and ~MqttClient() calls
+     * mosquitto_loop_stop(), both of which crash or block when Webots has
+     * already closed the connection.
+     */
+    exit(status);
 }
 
 /******************************************************************************

scripts/webots_launcher.py

@@ -85,7 +85,7 @@
     print(f"OS type {OS_PLATFORM_TYPE} not supported.")
     sys.exit(1)
 
-WEBOTS_LAUNCHER_ACTION = WEBOTS_CONTROLLER + ' '\
+WEBOTS_LAUNCHER_CMD = WEBOTS_CONTROLLER + ' '\
     + WEBOTS_CONTROLLER_OPTIONS + ' ' \
     + PROGRAM_PATH + PROGRAM_NAME + ' ' \
     + PROGRAM_OPTIONS
@@ -147,6 +147,21 @@ def check_webots_ready(source, target, env):  # pylint: disable=unused-argument
     _abort_missing_slot(protocol, ip, robot_name)
 
 
+def launch_webots_controller(source, target, env):  # pylint: disable=unused-argument
+    """Run webots-controller, tolerating SIGSEGV (exit 139) on TCP disconnect.
+
+    webots-controller segfaults in libController.so when the remote Webots host
+    closes the TCP connection. The DCS process itself exits cleanly; the crash
+    is inside the launcher binary and is harmless.
+    """
+    import subprocess
+    cmd = env.subst(WEBOTS_LAUNCHER_CMD)
+    print(cmd)
+    result = subprocess.run(cmd, shell=True)
+    if result.returncode not in (0, -11, 139):  # 139 = 128 + SIGSEGV(11)
+        env.Exit(result.returncode)
+
+
 ################################################################################
 # Main
 ################################################################################
@@ -157,7 +172,7 @@ def check_webots_ready(source, target, env):  # pylint: disable=unused-argument
     dependencies=PROGRAM_PATH + PROGRAM_NAME,
     actions=[
         check_webots_ready,
-        WEBOTS_LAUNCHER_ACTION
+        launch_webots_controller,
     ],
     title="Launch",
     description="Launch application with Webots launcher."