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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:11:28 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:11:28 +0000 |
commit | 94a0819fe3a0d679c3042a77bfe6a2afc505daea (patch) | |
tree | 2b827afe6a05f3538db3f7803a88c4587fe85648 /vendor/tracing-core/src/dispatcher.rs | |
parent | Adding upstream version 1.64.0+dfsg1. (diff) | |
download | rustc-94a0819fe3a0d679c3042a77bfe6a2afc505daea.tar.xz rustc-94a0819fe3a0d679c3042a77bfe6a2afc505daea.zip |
Adding upstream version 1.66.0+dfsg1.upstream/1.66.0+dfsg1
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'vendor/tracing-core/src/dispatcher.rs')
-rw-r--r-- | vendor/tracing-core/src/dispatcher.rs | 128 |
1 files changed, 119 insertions, 9 deletions
diff --git a/vendor/tracing-core/src/dispatcher.rs b/vendor/tracing-core/src/dispatcher.rs index 041722c36..36b3cfd85 100644 --- a/vendor/tracing-core/src/dispatcher.rs +++ b/vendor/tracing-core/src/dispatcher.rs @@ -134,7 +134,7 @@ use crate::stdlib::{ fmt, sync::{ atomic::{AtomicBool, AtomicUsize, Ordering}, - Arc, + Arc, Weak, }, }; @@ -142,16 +142,50 @@ use crate::stdlib::{ use crate::stdlib::{ cell::{Cell, RefCell, RefMut}, error, - sync::Weak, }; +#[cfg(feature = "alloc")] +use alloc::sync::{Arc, Weak}; + +#[cfg(feature = "alloc")] +use core::ops::Deref; + /// `Dispatch` trace data to a [`Subscriber`]. -/// #[derive(Clone)] pub struct Dispatch { subscriber: Arc<dyn Subscriber + Send + Sync>, } +/// `WeakDispatch` is a version of [`Dispatch`] that holds a non-owning reference +/// to a [`Subscriber`]. +/// +/// The Subscriber` may be accessed by calling [`WeakDispatch::upgrade`], +/// which returns an `Option<Dispatch>`. If all [`Dispatch`] clones that point +/// at the `Subscriber` have been dropped, [`WeakDispatch::upgrade`] will return +/// `None`. Otherwise, it will return `Some(Dispatch)`. +/// +/// A `WeakDispatch` may be created from a [`Dispatch`] by calling the +/// [`Dispatch::downgrade`] method. The primary use for creating a +/// [`WeakDispatch`] is to allow a Subscriber` to hold a cyclical reference to +/// itself without creating a memory leak. See [here] for details. +/// +/// This type is analogous to the [`std::sync::Weak`] type, but for a +/// [`Dispatch`] rather than an [`Arc`]. +/// +/// [`Arc`]: std::sync::Arc +/// [here]: Subscriber#avoiding-memory-leaks +#[derive(Clone)] +pub struct WeakDispatch { + subscriber: Weak<dyn Subscriber + Send + Sync>, +} + +#[cfg(feature = "alloc")] +#[derive(Clone)] +enum Kind<T> { + Global(&'static (dyn Collect + Send + Sync)), + Scoped(T), +} + #[cfg(feature = "std")] thread_local! { static CURRENT_STATE: State = State { @@ -293,14 +327,21 @@ pub fn has_been_set() -> bool { } /// Returned if setting the global dispatcher fails. -#[derive(Debug)] pub struct SetGlobalDefaultError { _no_construct: (), } +impl fmt::Debug for SetGlobalDefaultError { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + f.debug_tuple("SetGlobalDefaultError") + .field(&Self::MESSAGE) + .finish() + } +} + impl fmt::Display for SetGlobalDefaultError { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { - f.pad("a global default trace dispatcher has already been set") + f.pad(Self::MESSAGE) } } @@ -308,6 +349,10 @@ impl fmt::Display for SetGlobalDefaultError { #[cfg_attr(docsrs, doc(cfg(feature = "std")))] impl error::Error for SetGlobalDefaultError {} +impl SetGlobalDefaultError { + const MESSAGE: &'static str = "a global default trace dispatcher has already been set"; +} + /// Executes a closure with a reference to this thread's current [dispatcher]. /// /// Note that calls to `get_default` should not be nested; if this function is @@ -419,8 +464,34 @@ impl Dispatch { Registrar(Arc::downgrade(&self.subscriber)) } - /// Registers a new callsite with this subscriber, returning whether or not - /// the subscriber is interested in being notified about the callsite. + /// Creates a [`WeakDispatch`] from this `Dispatch`. + /// + /// A [`WeakDispatch`] is similar to a [`Dispatch`], but it does not prevent + /// the underlying [`Subscriber`] from being dropped. Instead, it only permits + /// access while other references to the `Subscriber` exist. This is equivalent + /// to the standard library's [`Arc::downgrade`] method, but for `Dispatch` + /// rather than `Arc`. + /// + /// The primary use for creating a [`WeakDispatch`] is to allow a `Subscriber` + /// to hold a cyclical reference to itself without creating a memory leak. + /// See [here] for details. + /// + /// [`Arc::downgrade`]: std::sync::Arc::downgrade + /// [here]: Subscriber#avoiding-memory-leaks + pub fn downgrade(&self) -> WeakDispatch { + WeakDispatch { + subscriber: Arc::downgrade(&self.subscriber), + } + } + + #[inline(always)] + #[cfg(not(feature = "alloc"))] + pub(crate) fn subscriber(&self) -> &(dyn Subscriber + Send + Sync) { + &self.subscriber + } + + /// Registers a new callsite with this collector, returning whether or not + /// the collector is interested in being notified about the callsite. /// /// This calls the [`register_callsite`] function on the [`Subscriber`] /// that this `Dispatch` forwards to. @@ -620,14 +691,14 @@ impl Dispatch { /// `T`. #[inline] pub fn is<T: Any>(&self) -> bool { - <dyn Subscriber>::is::<T>(&*self.subscriber) + <dyn Subscriber>::is::<T>(&self.subscriber) } /// Returns some reference to the `Subscriber` this `Dispatch` forwards to /// if it is of type `T`, or `None` if it isn't. #[inline] pub fn downcast_ref<T: Any>(&self) -> Option<&T> { - <dyn Subscriber>::downcast_ref(&*self.subscriber) + <dyn Subscriber>::downcast_ref(&self.subscriber) } } @@ -656,6 +727,45 @@ where } } +// === impl WeakDispatch === + +impl WeakDispatch { + /// Attempts to upgrade this `WeakDispatch` to a [`Dispatch`]. + /// + /// Returns `None` if the referenced `Dispatch` has already been dropped. + /// + /// ## Examples + /// + /// ``` + /// # use tracing_core::subscriber::NoSubscriber; + /// # use tracing_core::dispatcher::Dispatch; + /// let strong = Dispatch::new(NoSubscriber::default()); + /// let weak = strong.downgrade(); + /// + /// // The strong here keeps it alive, so we can still access the object. + /// assert!(weak.upgrade().is_some()); + /// + /// drop(strong); // But not any more. + /// assert!(weak.upgrade().is_none()); + /// ``` + pub fn upgrade(&self) -> Option<Dispatch> { + self.subscriber + .upgrade() + .map(|subscriber| Dispatch { subscriber }) + } +} + +impl fmt::Debug for WeakDispatch { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + let mut tuple = f.debug_tuple("WeakDispatch"); + match self.subscriber.upgrade() { + Some(subscriber) => tuple.field(&format_args!("Some({:p})", subscriber)), + None => tuple.field(&format_args!("None")), + }; + tuple.finish() + } +} + #[cfg(feature = "std")] impl Registrar { pub(crate) fn upgrade(&self) -> Option<Dispatch> { |