In the plugin registers with the debug framework at open time, the

sudo front-end will now set the default debug instance appropriately
before calling into the plugin.  This means the plugin no longer needs
to do the sudo_debug_set_default_instance() dance.

lib/util/sudo_debug.c

@@ -310,6 +310,10 @@ sudo_debug_register(const char *program, const char *const subsystems[],
 	    SLIST_INSERT_HEAD(&instance->outputs, output, entries);
     }
 
+    /* Set default instance if not already set. */
+    if (sudo_debug_default_instance == -1)
+	sudo_debug_default_instance = idx;
+
     /* Stash the pid string so we only have to format it once. */
     if (sudo_debug_pidlen == 0) {
 	(void)snprintf(sudo_debug_pidstr, sizeof(sudo_debug_pidstr), "[%d] ",