[test] catch ^C correctly and clean up

src/ctxt/ctxt.c

@@ -22,9 +22,11 @@ struct ax_ctxt* ax_new(void)
 
 void ax_free(struct ax_ctxt* ax)
 {
+    if (ax != NULL) {
         ax__ctxt_cleanup(ax);
         rgn_cleanup(ax->init_rgn);
     }
+}
 
 const char* ax_get_error(struct ax_ctxt* ax)
 {

test/main.c

@@ -1,12 +1,30 @@
 #include <stdio.h>
+#include <signal.h>
+#include <stdlib.h>
 #include "../src/ax.h"
 #include "../src/ctxt.h"
 #include "../src/backend.h"
 
+struct ax_ctxt* ax = NULL;
+
+static void cleanup()
+{
+    ax_free(ax);
+    ax = NULL;
+}
+
+static void sigint_handler(int signum)
+{
+    printf("\nCaught interrupt.\n");
+    cleanup();
+    exit(0);
+}
 
 int main(void)
 {
-    struct ax_ctxt* ax = ax_new();
+    signal(SIGINT, sigint_handler);
+
+    ax = ax_new();
     ax_set_logger(ax, 0, false);
 
     int rv = 0;
@@ -22,13 +40,15 @@ int main(void)
 
     ax_log(ax, "Got here\n");
 
+    while (!ax__backend_is_shutdown(ax->bac)) {
         ax__backend_wait_for_event(ax->bac);
         ax__backend_step(ax->bac);
+    }
 
 //cleanup:
     if (rv != 0) {
         printf("error: %s\n", ax_get_error(ax));
     }
-    ax_free(ax);
+    cleanup();
     return rv;
 }