Drop the default logger in atexit callback

spdlog/src/lib.rs

@@ -310,10 +310,10 @@ pub const __EOL: &str = "\n";
 #[doc(hidden)]
 pub const __EOL: &str = "\r\n";
 
-static DEFAULT_LOGGER: OnceCell<ArcSwap<Logger>> = OnceCell::new();
+static DEFAULT_LOGGER: OnceCell<ArcSwapOption<Logger>> = OnceCell::new();
 
 #[must_use]
-fn default_logger_ref() -> &'static ArcSwap<Logger> {
+fn default_logger_ref() -> &'static ArcSwapOption<Logger> {
     DEFAULT_LOGGER.get_or_init(|| {
         let stdout = StdStreamSink::builder()
             .std_stream(StdStream::Stdout)
@@ -329,7 +329,8 @@ fn default_logger_ref() -> &'static ArcSwap<Logger> {
 
         let sinks: [Arc<dyn Sink>; 2] = [Arc::new(stdout), Arc::new(stderr)];
 
-        let res = ArcSwap::from_pointee(Logger::builder().sinks(sinks).build_default().unwrap());
+        let res =
+            ArcSwapOption::from_pointee(Logger::builder().sinks(sinks).build_default().unwrap());
 
         flush_default_logger_at_exit();
         res
@@ -381,7 +382,7 @@ fn default_logger_ref() -> &'static ArcSwap<Logger> {
 /// ```
 #[must_use]
 pub fn default_logger() -> Arc<Logger> {
-    default_logger_ref().load().clone()
+    default_logger_ref().load().clone().unwrap()
 }
 
 /// Sets the given logger as the default logger, and returns the old default
@@ -400,7 +401,7 @@ pub fn default_logger() -> Arc<Logger> {
 /// info!(logger: old_logger, "this log will be handled by `old_logger`");
 /// ```
 pub fn swap_default_logger(logger: Arc<Logger>) -> Arc<Logger> {
-    default_logger_ref().swap(logger)
+    default_logger_ref().swap(Some(logger)).unwrap()
 }
 
 /// Sets the given logger as the default logger.
@@ -658,7 +659,10 @@ fn flush_default_logger_at_exit() {
     extern "C" fn handler() {
         IS_TEARING_DOWN.store(true, Ordering::SeqCst);
         if let Some(default_logger) = DEFAULT_LOGGER.get() {
-            default_logger.load().flush()
+            // Swap with `None` so it will be dropped at the end of this function
+            if let Some(default_logger) = default_logger.swap(None) {
+                default_logger.flush();
+            }
         }
     }