Update error handling

src/memory_manager.rs

@@ -20,6 +20,7 @@ use crate::scheduler::{GCWork, GCWorker};
 use crate::util::alloc::allocators::AllocatorSelector;
 use crate::util::constants::{LOG_BYTES_IN_PAGE, MIN_OBJECT_SIZE};
 use crate::util::heap::layout::vm_layout::vm_layout;
+use crate::util::logger::LoggerError;
 use crate::util::opaque_pointer::*;
 use crate::util::{Address, ObjectReference};
 use crate::vm::slot::MemorySlice;
@@ -38,7 +39,9 @@ use crate::vm::VMBinding;
 ///    supported. Currently we assume a binding will only need one MMTk instance. Note that GC is enabled by default and the binding should
 ///    implement `VMCollection::is_collection_enabled()` if it requires that the GC should be disabled at a particular time.
 ///
-/// Note that this method will attempt to initialize a logger. If the VM would like to use its own logger, it should initialize the logger before calling this method.
+/// This method will attempt to initialize the built-in `env_logger` if the Cargo feature "builtin_env_logger" is enabled (by default).
+/// If the VM would like to use its own logger, it should disable the default feature "builtin_env_logger" in `Cargo.toml`.
+///
 /// Note that, to allow MMTk to do GC properly, `initialize_collection()` needs to be called after this call when
 /// the VM's thread system is ready to spawn GC workers.
 ///
@@ -53,9 +56,11 @@ use crate::vm::VMBinding;
 pub fn mmtk_init<VM: VMBinding>(builder: &MMTKBuilder) -> Box<MMTK<VM>> {
     match crate::util::logger::try_init() {
         Ok(_) => debug!("MMTk initialized the logger."),
-        Err(_) => debug!(
-            "MMTk failed to initialize the logger. Possibly a logger has been initialized by user."
-        ),
+        Err(LoggerError::NoBuiltinLogger) =>
+            debug!("MMTk didn't initialize the built-in env_logger.  The Cargo feature \"builtin_env_logger\" is not enabled."),
+        Err(LoggerError::SetLoggerError(e)) =>
+            // Currently `log::SetLoggerError` can only be raised for one reason: the logger has already been initialized.
+            debug!("MMTk failed to initialize the built-in env_logger: {e}")
     }
     #[cfg(all(feature = "perf_counter", target_os = "linux"))]
     {

src/util/logger.rs

@@ -1,16 +1,24 @@
 use log::SetLoggerError;
 
+/// Failure of setting logger.
+pub(crate) enum LoggerError {
+    /// The user didn't enable the "builtin_env_logger" feature.
+    NoBuiltinLogger,
+    /// Error happened while setting the logger.
+    SetLoggerError(SetLoggerError),
+}
+
 /// Attempt to init a env_logger for MMTk.
 /// Does nothing if the "builtin_env_logger" feature is disabled.
-pub fn try_init() -> Result<(), SetLoggerError> {
+pub fn try_init() -> Result<(), LoggerError> {
     cfg_if::cfg_if! {
         if #[cfg(feature = "builtin_env_logger")] {
             env_logger::try_init_from_env(
                 // By default, use info level logging.
                 env_logger::Env::default().filter_or(env_logger::DEFAULT_FILTER_ENV, "info"),
-            )
+            ).map_err(LoggerError::SetLoggerError)
         } else {
-            Ok(())
+            Err(LoggerError::NoBuiltinLogger)
         }
     }
 }