Fix event callback on shutdown (closes #2869)

Author: zuckschwerdt

src/r_api.c

@@ -209,9 +209,11 @@ void r_free_cfg(r_cfg_t *cfg)
     if (cfg->dev) {
         sdr_deactivate(cfg->dev);
         sdr_close(cfg->dev);
+        cfg->dev = NULL;
     }
 
     free(cfg->gain_str);
+    cfg->gain_str = NULL;
 
     for (void **iter = cfg->demod->dumper.elems; iter && *iter; ++iter) {
         file_info_t const *dumper = *iter;
@@ -224,8 +226,10 @@ void r_free_cfg(r_cfg_t *cfg)
 
     if (cfg->demod->am_analyze)
         am_analyze_free(cfg->demod->am_analyze);
+    cfg->demod->am_analyze = NULL;
 
     pulse_detect_free(cfg->demod->pulse_detect);
+    cfg->demod->pulse_detect = NULL;
 
     list_free_elems(&cfg->raw_handler, (list_elem_free_fn)raw_output_free);
 
@@ -238,11 +242,14 @@ void r_free_cfg(r_cfg_t *cfg)
     list_free_elems(&cfg->in_files, NULL);
 
     free(cfg->demod);
+    cfg->demod = NULL;
 
     free(cfg->devices);
+    cfg->devices = NULL;
 
     mg_mgr_free(cfg->mgr);
     free(cfg->mgr);
+    cfg->mgr = NULL;
 
     //free(cfg);
 }

src/rtl_433.c

@@ -394,6 +394,11 @@ static void sdr_callback(unsigned char *iq_buf, uint32_t len, void *ctx)
     char time_str[LOCAL_TIME_BUFLEN];
     unsigned long n_samples;
 
+    if (!demod) {
+        // might happen when the demod closed and we get a last data frame
+        return; // ignore the data
+    }
+
     // do this here and not in sdr_handler so realtime replay can use rtl_tcp output
     for (void **iter = cfg->raw_handler.elems; iter && *iter; ++iter) {
         raw_output_t *output = *iter;
@@ -1367,6 +1372,7 @@ static void sighandler(int signum)
 }
 #endif
 
+// NOTE: this handler might be called while already in `r_free_cfg()`.
 static void sdr_handler(struct mg_connection *nc, int ev_type, void *ev_data)
 {
     //fprintf(stderr, "%s: %d, %d, %p, %p\n", __func__, nc->sock, ev_type, nc->user_data, ev_data);
@@ -1441,6 +1447,13 @@ static void acquire_callback(sdr_event_t *ev, void *ctx)
 static int start_sdr(r_cfg_t *cfg)
 {
     int r;
+    if (cfg->dev) {
+        r = sdr_close(cfg->dev);
+        cfg->dev = NULL;
+        if (r < 0) {
+            print_logf(LOG_ERROR, "Input", "Closing SDR failed (%d)", r);
+        }
+    }
     r = sdr_open(&cfg->dev, cfg->dev_query, cfg->verbosity);
     if (r < 0) {
         return -1; // exit(2);