AP_HAL_SITL: catch SIGTERM and exit with zero exit status

libraries/AP_HAL_SITL/HAL_SITL_Class.cpp

@@ -122,11 +122,26 @@ static void sig_alrm(int signum)
     execv(new_argv[0], new_argv);
 }
 
+void HAL_SITL::exit_signal_handler(int signum)
+{
+    HALSITL::Scheduler::_should_exit = true;
+}
+
+void HAL_SITL::setup_signal_handlers() const
+{
+    struct sigaction sa = { };
+
+    sa.sa_flags = SA_NOCLDSTOP;
+    sa.sa_handler = HAL_SITL::exit_signal_handler;
+    sigaction(SIGTERM, &sa, NULL);
+}
+
 void HAL_SITL::run(int argc, char * const argv[], Callbacks* callbacks) const
 {
     assert(callbacks);
 
     _sitl_state->init(argc, argv);
+
     scheduler->init();
     uartA->begin(115200);
 
@@ -173,10 +188,15 @@ void HAL_SITL::run(int argc, char * const argv[], Callbacks* callbacks) const
         signal(SIGALRM, sig_alrm);
         alarm(2);
     }
+    setup_signal_handlers();
 
     uint32_t last_watchdog_save = AP_HAL::millis();
 
     while (!HALSITL::Scheduler::_should_reboot) {
+        if (HALSITL::Scheduler::_should_exit) {
+            ::fprintf(stderr, "Exitting\n");
+            exit(0);
+        }
         callbacks->loop();
         HALSITL::Scheduler::_run_io_procs();
 

libraries/AP_HAL_SITL/HAL_SITL_Class.h

@@ -16,6 +16,9 @@ public:
 
 private:
     HALSITL::SITL_State *_sitl_state;
+
+    void setup_signal_handlers() const;
+    static void exit_signal_handler(int);
 };
 
 #endif  // CONFIG_HAL_BOARD == HAL_BOARD_SITL

libraries/AP_HAL_SITL/Scheduler.cpp

@@ -28,6 +28,7 @@ AP_HAL::MemberProc Scheduler::_io_proc[SITL_SCHEDULER_MAX_TIMER_PROCS] = {nullpt
 uint8_t Scheduler::_num_io_procs = 0;
 bool Scheduler::_in_io_proc = false;
 bool Scheduler::_should_reboot = false;
+bool Scheduler::_should_exit = false;
 
 bool Scheduler::_in_semaphore_take_wait = false;
 

libraries/AP_HAL_SITL/Scheduler.h

@@ -50,6 +50,7 @@ public:
 
     static void _run_io_procs();
     static bool _should_reboot;
+    static bool _should_exit;
 
     /*
       create a new thread