968 lines
33 KiB
Rust
968 lines
33 KiB
Rust
use crate::alloc::Box;
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use crate::backtrace::Backtrace;
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use crate::chain::Chain;
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#[cfg(any(feature = "std", anyhow_no_ptr_addr_of))]
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use crate::ptr::Mut;
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use crate::ptr::{Own, Ref};
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use crate::{Error, StdError};
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use core::any::TypeId;
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use core::fmt::{self, Debug, Display};
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use core::mem::ManuallyDrop;
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#[cfg(not(anyhow_no_ptr_addr_of))]
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use core::ptr;
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use core::ptr::NonNull;
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#[cfg(feature = "std")]
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use core::ops::{Deref, DerefMut};
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impl Error {
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/// Create a new error object from any error type.
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///
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/// The error type must be threadsafe and `'static`, so that the `Error`
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/// will be as well.
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///
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/// If the error type does not provide a backtrace, a backtrace will be
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/// created here to ensure that a backtrace exists.
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#[cfg(feature = "std")]
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#[cfg_attr(doc_cfg, doc(cfg(feature = "std")))]
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#[cold]
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pub fn new<E>(error: E) -> Self
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where
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E: StdError + Send + Sync + 'static,
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{
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let backtrace = backtrace_if_absent!(error);
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Error::from_std(error, backtrace)
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}
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/// Create a new error object from a printable error message.
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///
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/// If the argument implements std::error::Error, prefer `Error::new`
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/// instead which preserves the underlying error's cause chain and
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/// backtrace. If the argument may or may not implement std::error::Error
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/// now or in the future, use `anyhow!(err)` which handles either way
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/// correctly.
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///
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/// `Error::msg("...")` is equivalent to `anyhow!("...")` but occasionally
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/// convenient in places where a function is preferable over a macro, such
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/// as iterator or stream combinators:
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///
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/// ```
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/// # mod ffi {
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/// # pub struct Input;
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/// # pub struct Output;
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/// # pub async fn do_some_work(_: Input) -> Result<Output, &'static str> {
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/// # unimplemented!()
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/// # }
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/// # }
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/// #
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/// # use ffi::{Input, Output};
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/// #
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/// use anyhow::{Error, Result};
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/// use futures::stream::{Stream, StreamExt, TryStreamExt};
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///
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/// async fn demo<S>(stream: S) -> Result<Vec<Output>>
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/// where
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/// S: Stream<Item = Input>,
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/// {
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/// stream
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/// .then(ffi::do_some_work) // returns Result<Output, &str>
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/// .map_err(Error::msg)
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/// .try_collect()
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/// .await
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/// }
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/// ```
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#[cold]
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pub fn msg<M>(message: M) -> Self
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where
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M: Display + Debug + Send + Sync + 'static,
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{
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Error::from_adhoc(message, backtrace!())
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}
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#[cfg(feature = "std")]
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#[cold]
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pub(crate) fn from_std<E>(error: E, backtrace: Option<Backtrace>) -> Self
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where
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E: StdError + Send + Sync + 'static,
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{
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let vtable = &ErrorVTable {
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object_drop: object_drop::<E>,
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object_ref: object_ref::<E>,
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#[cfg(anyhow_no_ptr_addr_of)]
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object_mut: object_mut::<E>,
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object_boxed: object_boxed::<E>,
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object_downcast: object_downcast::<E>,
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#[cfg(anyhow_no_ptr_addr_of)]
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object_downcast_mut: object_downcast_mut::<E>,
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object_drop_rest: object_drop_front::<E>,
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#[cfg(all(not(backtrace), feature = "backtrace"))]
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object_backtrace: no_backtrace,
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};
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// Safety: passing vtable that operates on the right type E.
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unsafe { Error::construct(error, vtable, backtrace) }
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}
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#[cold]
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pub(crate) fn from_adhoc<M>(message: M, backtrace: Option<Backtrace>) -> Self
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where
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M: Display + Debug + Send + Sync + 'static,
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{
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use crate::wrapper::MessageError;
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let error: MessageError<M> = MessageError(message);
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let vtable = &ErrorVTable {
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object_drop: object_drop::<MessageError<M>>,
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object_ref: object_ref::<MessageError<M>>,
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#[cfg(all(feature = "std", anyhow_no_ptr_addr_of))]
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object_mut: object_mut::<MessageError<M>>,
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object_boxed: object_boxed::<MessageError<M>>,
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object_downcast: object_downcast::<M>,
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#[cfg(anyhow_no_ptr_addr_of)]
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object_downcast_mut: object_downcast_mut::<M>,
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object_drop_rest: object_drop_front::<M>,
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#[cfg(all(not(backtrace), feature = "backtrace"))]
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object_backtrace: no_backtrace,
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};
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// Safety: MessageError is repr(transparent) so it is okay for the
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// vtable to allow casting the MessageError<M> to M.
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unsafe { Error::construct(error, vtable, backtrace) }
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}
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#[cold]
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pub(crate) fn from_display<M>(message: M, backtrace: Option<Backtrace>) -> Self
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where
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M: Display + Send + Sync + 'static,
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{
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use crate::wrapper::DisplayError;
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let error: DisplayError<M> = DisplayError(message);
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let vtable = &ErrorVTable {
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object_drop: object_drop::<DisplayError<M>>,
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object_ref: object_ref::<DisplayError<M>>,
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#[cfg(all(feature = "std", anyhow_no_ptr_addr_of))]
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object_mut: object_mut::<DisplayError<M>>,
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object_boxed: object_boxed::<DisplayError<M>>,
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object_downcast: object_downcast::<M>,
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#[cfg(anyhow_no_ptr_addr_of)]
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object_downcast_mut: object_downcast_mut::<M>,
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object_drop_rest: object_drop_front::<M>,
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#[cfg(all(not(backtrace), feature = "backtrace"))]
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object_backtrace: no_backtrace,
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};
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// Safety: DisplayError is repr(transparent) so it is okay for the
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// vtable to allow casting the DisplayError<M> to M.
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unsafe { Error::construct(error, vtable, backtrace) }
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}
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#[cfg(feature = "std")]
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#[cold]
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pub(crate) fn from_context<C, E>(context: C, error: E, backtrace: Option<Backtrace>) -> Self
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where
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C: Display + Send + Sync + 'static,
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E: StdError + Send + Sync + 'static,
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{
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let error: ContextError<C, E> = ContextError { context, error };
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let vtable = &ErrorVTable {
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object_drop: object_drop::<ContextError<C, E>>,
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object_ref: object_ref::<ContextError<C, E>>,
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#[cfg(anyhow_no_ptr_addr_of)]
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object_mut: object_mut::<ContextError<C, E>>,
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object_boxed: object_boxed::<ContextError<C, E>>,
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object_downcast: context_downcast::<C, E>,
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#[cfg(anyhow_no_ptr_addr_of)]
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object_downcast_mut: context_downcast_mut::<C, E>,
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object_drop_rest: context_drop_rest::<C, E>,
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#[cfg(all(not(backtrace), feature = "backtrace"))]
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object_backtrace: no_backtrace,
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};
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// Safety: passing vtable that operates on the right type.
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unsafe { Error::construct(error, vtable, backtrace) }
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}
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#[cfg(feature = "std")]
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#[cold]
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pub(crate) fn from_boxed(
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error: Box<dyn StdError + Send + Sync>,
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backtrace: Option<Backtrace>,
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) -> Self {
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use crate::wrapper::BoxedError;
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let error = BoxedError(error);
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let vtable = &ErrorVTable {
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object_drop: object_drop::<BoxedError>,
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object_ref: object_ref::<BoxedError>,
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#[cfg(anyhow_no_ptr_addr_of)]
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object_mut: object_mut::<BoxedError>,
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object_boxed: object_boxed::<BoxedError>,
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object_downcast: object_downcast::<Box<dyn StdError + Send + Sync>>,
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#[cfg(anyhow_no_ptr_addr_of)]
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object_downcast_mut: object_downcast_mut::<Box<dyn StdError + Send + Sync>>,
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object_drop_rest: object_drop_front::<Box<dyn StdError + Send + Sync>>,
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#[cfg(all(not(backtrace), feature = "backtrace"))]
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object_backtrace: no_backtrace,
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};
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// Safety: BoxedError is repr(transparent) so it is okay for the vtable
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// to allow casting to Box<dyn StdError + Send + Sync>.
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unsafe { Error::construct(error, vtable, backtrace) }
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}
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// Takes backtrace as argument rather than capturing it here so that the
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// user sees one fewer layer of wrapping noise in the backtrace.
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//
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// Unsafe because the given vtable must have sensible behavior on the error
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// value of type E.
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#[cold]
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unsafe fn construct<E>(
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error: E,
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vtable: &'static ErrorVTable,
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backtrace: Option<Backtrace>,
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) -> Self
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where
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E: StdError + Send + Sync + 'static,
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{
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let inner: Box<ErrorImpl<E>> = Box::new(ErrorImpl {
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vtable,
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backtrace,
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_object: error,
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});
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// Erase the concrete type of E from the compile-time type system. This
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// is equivalent to the safe unsize coercion from Box<ErrorImpl<E>> to
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// Box<ErrorImpl<dyn StdError + Send + Sync + 'static>> except that the
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// result is a thin pointer. The necessary behavior for manipulating the
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// underlying ErrorImpl<E> is preserved in the vtable provided by the
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// caller rather than a builtin fat pointer vtable.
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let inner = Own::new(inner).cast::<ErrorImpl>();
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Error { inner }
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}
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/// Wrap the error value with additional context.
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///
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/// For attaching context to a `Result` as it is propagated, the
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/// [`Context`][crate::Context] extension trait may be more convenient than
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/// this function.
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///
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/// The primary reason to use `error.context(...)` instead of
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/// `result.context(...)` via the `Context` trait would be if the context
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/// needs to depend on some data held by the underlying error:
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///
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/// ```
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/// # use std::fmt::{self, Debug, Display};
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/// #
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/// # type T = ();
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/// #
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/// # impl std::error::Error for ParseError {}
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/// # impl Debug for ParseError {
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/// # fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
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/// # unimplemented!()
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/// # }
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/// # }
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/// # impl Display for ParseError {
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/// # fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
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/// # unimplemented!()
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/// # }
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/// # }
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/// #
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/// use anyhow::Result;
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/// use std::fs::File;
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/// use std::path::Path;
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///
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/// struct ParseError {
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/// line: usize,
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/// column: usize,
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/// }
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///
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/// fn parse_impl(file: File) -> Result<T, ParseError> {
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/// # const IGNORE: &str = stringify! {
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/// ...
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/// # };
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/// # unimplemented!()
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/// }
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///
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/// pub fn parse(path: impl AsRef<Path>) -> Result<T> {
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/// let file = File::open(&path)?;
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/// parse_impl(file).map_err(|error| {
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/// let context = format!(
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/// "only the first {} lines of {} are valid",
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/// error.line, path.as_ref().display(),
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/// );
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/// anyhow::Error::new(error).context(context)
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/// })
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/// }
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/// ```
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#[cold]
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pub fn context<C>(self, context: C) -> Self
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where
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C: Display + Send + Sync + 'static,
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{
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let error: ContextError<C, Error> = ContextError {
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context,
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error: self,
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};
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let vtable = &ErrorVTable {
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object_drop: object_drop::<ContextError<C, Error>>,
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object_ref: object_ref::<ContextError<C, Error>>,
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#[cfg(all(feature = "std", anyhow_no_ptr_addr_of))]
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object_mut: object_mut::<ContextError<C, Error>>,
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object_boxed: object_boxed::<ContextError<C, Error>>,
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object_downcast: context_chain_downcast::<C>,
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#[cfg(anyhow_no_ptr_addr_of)]
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object_downcast_mut: context_chain_downcast_mut::<C>,
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object_drop_rest: context_chain_drop_rest::<C>,
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#[cfg(all(not(backtrace), feature = "backtrace"))]
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object_backtrace: context_backtrace::<C>,
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};
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// As the cause is anyhow::Error, we already have a backtrace for it.
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let backtrace = None;
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// Safety: passing vtable that operates on the right type.
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unsafe { Error::construct(error, vtable, backtrace) }
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}
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/// Get the backtrace for this Error.
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///
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/// In order for the backtrace to be meaningful, one of the two environment
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/// variables `RUST_LIB_BACKTRACE=1` or `RUST_BACKTRACE=1` must be defined
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/// and `RUST_LIB_BACKTRACE` must not be `0`. Backtraces are somewhat
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/// expensive to capture in Rust, so we don't necessarily want to be
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/// capturing them all over the place all the time.
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///
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/// - If you want panics and errors to both have backtraces, set
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/// `RUST_BACKTRACE=1`;
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/// - If you want only errors to have backtraces, set
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/// `RUST_LIB_BACKTRACE=1`;
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/// - If you want only panics to have backtraces, set `RUST_BACKTRACE=1` and
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/// `RUST_LIB_BACKTRACE=0`.
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///
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/// # Stability
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///
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/// Standard library backtraces are only available on the nightly channel.
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/// Tracking issue: [rust-lang/rust#53487][tracking].
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///
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/// On stable compilers, this function is only available if the crate's
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/// "backtrace" feature is enabled, and will use the `backtrace` crate as
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/// the underlying backtrace implementation.
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///
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/// ```toml
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/// [dependencies]
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/// anyhow = { version = "1.0", features = ["backtrace"] }
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/// ```
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///
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/// [tracking]: https://github.com/rust-lang/rust/issues/53487
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#[cfg(any(backtrace, feature = "backtrace"))]
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#[cfg_attr(doc_cfg, doc(cfg(any(nightly, feature = "backtrace"))))]
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pub fn backtrace(&self) -> &impl_backtrace!() {
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unsafe { ErrorImpl::backtrace(self.inner.by_ref()) }
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}
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/// An iterator of the chain of source errors contained by this Error.
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///
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/// This iterator will visit every error in the cause chain of this error
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/// object, beginning with the error that this error object was created
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/// from.
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///
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/// # Example
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///
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/// ```
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/// use anyhow::Error;
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/// use std::io;
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///
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/// pub fn underlying_io_error_kind(error: &Error) -> Option<io::ErrorKind> {
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/// for cause in error.chain() {
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/// if let Some(io_error) = cause.downcast_ref::<io::Error>() {
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/// return Some(io_error.kind());
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/// }
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/// }
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/// None
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/// }
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/// ```
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#[cfg(feature = "std")]
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#[cfg_attr(doc_cfg, doc(cfg(feature = "std")))]
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#[cold]
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pub fn chain(&self) -> Chain {
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unsafe { ErrorImpl::chain(self.inner.by_ref()) }
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}
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|
|
/// The lowest level cause of this error — this error's cause's
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/// cause's cause etc.
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///
|
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/// The root cause is the last error in the iterator produced by
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/// [`chain()`][Error::chain].
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#[cfg(feature = "std")]
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#[cfg_attr(doc_cfg, doc(cfg(feature = "std")))]
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pub fn root_cause(&self) -> &(dyn StdError + 'static) {
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self.chain().last().unwrap()
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}
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|
|
|
/// Returns true if `E` is the type held by this error object.
|
|
///
|
|
/// For errors with context, this method returns true if `E` matches the
|
|
/// type of the context `C` **or** the type of the error on which the
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/// context has been attached. For details about the interaction between
|
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/// context and downcasting, [see here].
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///
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/// [see here]: trait.Context.html#effect-on-downcasting
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|
pub fn is<E>(&self) -> bool
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|
where
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E: Display + Debug + Send + Sync + 'static,
|
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{
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self.downcast_ref::<E>().is_some()
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}
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|
|
|
/// Attempt to downcast the error object to a concrete type.
|
|
pub fn downcast<E>(mut self) -> Result<E, Self>
|
|
where
|
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E: Display + Debug + Send + Sync + 'static,
|
|
{
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let target = TypeId::of::<E>();
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let inner = self.inner.by_mut();
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unsafe {
|
|
// Use vtable to find NonNull<()> which points to a value of type E
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|
// somewhere inside the data structure.
|
|
#[cfg(not(anyhow_no_ptr_addr_of))]
|
|
let addr = match (vtable(inner.ptr).object_downcast)(inner.by_ref(), target) {
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|
Some(addr) => addr.by_mut().extend(),
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None => return Err(self),
|
|
};
|
|
#[cfg(anyhow_no_ptr_addr_of)]
|
|
let addr = match (vtable(inner.ptr).object_downcast_mut)(inner, target) {
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Some(addr) => addr.extend(),
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None => return Err(self),
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|
};
|
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|
|
// Prepare to read E out of the data structure. We'll drop the rest
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|
// of the data structure separately so that E is not dropped.
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let outer = ManuallyDrop::new(self);
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|
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// Read E from where the vtable found it.
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let error = addr.cast::<E>().read();
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|
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// Drop rest of the data structure outside of E.
|
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(vtable(outer.inner.ptr).object_drop_rest)(outer.inner, target);
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|
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Ok(error)
|
|
}
|
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}
|
|
|
|
/// Downcast this error object by reference.
|
|
///
|
|
/// # Example
|
|
///
|
|
/// ```
|
|
/// # use anyhow::anyhow;
|
|
/// # use std::fmt::{self, Display};
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|
/// # use std::task::Poll;
|
|
/// #
|
|
/// # #[derive(Debug)]
|
|
/// # enum DataStoreError {
|
|
/// # Censored(()),
|
|
/// # }
|
|
/// #
|
|
/// # impl Display for DataStoreError {
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|
/// # fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
|
|
/// # unimplemented!()
|
|
/// # }
|
|
/// # }
|
|
/// #
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|
/// # impl std::error::Error for DataStoreError {}
|
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/// #
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|
/// # const REDACTED_CONTENT: () = ();
|
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/// #
|
|
/// # let error = anyhow!("...");
|
|
/// # let root_cause = &error;
|
|
/// #
|
|
/// # let ret =
|
|
/// // If the error was caused by redaction, then return a tombstone instead
|
|
/// // of the content.
|
|
/// match root_cause.downcast_ref::<DataStoreError>() {
|
|
/// Some(DataStoreError::Censored(_)) => Ok(Poll::Ready(REDACTED_CONTENT)),
|
|
/// None => Err(error),
|
|
/// }
|
|
/// # ;
|
|
/// ```
|
|
pub fn downcast_ref<E>(&self) -> Option<&E>
|
|
where
|
|
E: Display + Debug + Send + Sync + 'static,
|
|
{
|
|
let target = TypeId::of::<E>();
|
|
unsafe {
|
|
// Use vtable to find NonNull<()> which points to a value of type E
|
|
// somewhere inside the data structure.
|
|
let addr = (vtable(self.inner.ptr).object_downcast)(self.inner.by_ref(), target)?;
|
|
Some(addr.cast::<E>().deref())
|
|
}
|
|
}
|
|
|
|
/// Downcast this error object by mutable reference.
|
|
pub fn downcast_mut<E>(&mut self) -> Option<&mut E>
|
|
where
|
|
E: Display + Debug + Send + Sync + 'static,
|
|
{
|
|
let target = TypeId::of::<E>();
|
|
unsafe {
|
|
// Use vtable to find NonNull<()> which points to a value of type E
|
|
// somewhere inside the data structure.
|
|
|
|
#[cfg(not(anyhow_no_ptr_addr_of))]
|
|
let addr =
|
|
(vtable(self.inner.ptr).object_downcast)(self.inner.by_ref(), target)?.by_mut();
|
|
|
|
#[cfg(anyhow_no_ptr_addr_of)]
|
|
let addr = (vtable(self.inner.ptr).object_downcast_mut)(self.inner.by_mut(), target)?;
|
|
|
|
Some(addr.cast::<E>().deref_mut())
|
|
}
|
|
}
|
|
}
|
|
|
|
#[cfg(feature = "std")]
|
|
#[cfg_attr(doc_cfg, doc(cfg(feature = "std")))]
|
|
impl<E> From<E> for Error
|
|
where
|
|
E: StdError + Send + Sync + 'static,
|
|
{
|
|
#[cold]
|
|
fn from(error: E) -> Self {
|
|
let backtrace = backtrace_if_absent!(error);
|
|
Error::from_std(error, backtrace)
|
|
}
|
|
}
|
|
|
|
#[cfg(feature = "std")]
|
|
#[cfg_attr(doc_cfg, doc(cfg(feature = "std")))]
|
|
impl Deref for Error {
|
|
type Target = dyn StdError + Send + Sync + 'static;
|
|
|
|
fn deref(&self) -> &Self::Target {
|
|
unsafe { ErrorImpl::error(self.inner.by_ref()) }
|
|
}
|
|
}
|
|
|
|
#[cfg(feature = "std")]
|
|
#[cfg_attr(doc_cfg, doc(cfg(feature = "std")))]
|
|
impl DerefMut for Error {
|
|
fn deref_mut(&mut self) -> &mut Self::Target {
|
|
unsafe { ErrorImpl::error_mut(self.inner.by_mut()) }
|
|
}
|
|
}
|
|
|
|
impl Display for Error {
|
|
fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
|
|
unsafe { ErrorImpl::display(self.inner.by_ref(), formatter) }
|
|
}
|
|
}
|
|
|
|
impl Debug for Error {
|
|
fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
|
|
unsafe { ErrorImpl::debug(self.inner.by_ref(), formatter) }
|
|
}
|
|
}
|
|
|
|
impl Drop for Error {
|
|
fn drop(&mut self) {
|
|
unsafe {
|
|
// Invoke the vtable's drop behavior.
|
|
(vtable(self.inner.ptr).object_drop)(self.inner);
|
|
}
|
|
}
|
|
}
|
|
|
|
struct ErrorVTable {
|
|
object_drop: unsafe fn(Own<ErrorImpl>),
|
|
object_ref: unsafe fn(Ref<ErrorImpl>) -> Ref<dyn StdError + Send + Sync + 'static>,
|
|
#[cfg(all(feature = "std", anyhow_no_ptr_addr_of))]
|
|
object_mut: unsafe fn(Mut<ErrorImpl>) -> &mut (dyn StdError + Send + Sync + 'static),
|
|
object_boxed: unsafe fn(Own<ErrorImpl>) -> Box<dyn StdError + Send + Sync + 'static>,
|
|
object_downcast: unsafe fn(Ref<ErrorImpl>, TypeId) -> Option<Ref<()>>,
|
|
#[cfg(anyhow_no_ptr_addr_of)]
|
|
object_downcast_mut: unsafe fn(Mut<ErrorImpl>, TypeId) -> Option<Mut<()>>,
|
|
object_drop_rest: unsafe fn(Own<ErrorImpl>, TypeId),
|
|
#[cfg(all(not(backtrace), feature = "backtrace"))]
|
|
object_backtrace: unsafe fn(Ref<ErrorImpl>) -> Option<&Backtrace>,
|
|
}
|
|
|
|
// Safety: requires layout of *e to match ErrorImpl<E>.
|
|
unsafe fn object_drop<E>(e: Own<ErrorImpl>) {
|
|
// Cast back to ErrorImpl<E> so that the allocator receives the correct
|
|
// Layout to deallocate the Box's memory.
|
|
let unerased = e.cast::<ErrorImpl<E>>().boxed();
|
|
drop(unerased);
|
|
}
|
|
|
|
// Safety: requires layout of *e to match ErrorImpl<E>.
|
|
unsafe fn object_drop_front<E>(e: Own<ErrorImpl>, target: TypeId) {
|
|
// Drop the fields of ErrorImpl other than E as well as the Box allocation,
|
|
// without dropping E itself. This is used by downcast after doing a
|
|
// ptr::read to take ownership of the E.
|
|
let _ = target;
|
|
let unerased = e.cast::<ErrorImpl<ManuallyDrop<E>>>().boxed();
|
|
drop(unerased);
|
|
}
|
|
|
|
// Safety: requires layout of *e to match ErrorImpl<E>.
|
|
unsafe fn object_ref<E>(e: Ref<ErrorImpl>) -> Ref<dyn StdError + Send + Sync + 'static>
|
|
where
|
|
E: StdError + Send + Sync + 'static,
|
|
{
|
|
// Attach E's native StdError vtable onto a pointer to self._object.
|
|
|
|
let unerased = e.cast::<ErrorImpl<E>>();
|
|
|
|
#[cfg(not(anyhow_no_ptr_addr_of))]
|
|
return Ref::from_raw(NonNull::new_unchecked(
|
|
ptr::addr_of!((*unerased.as_ptr())._object) as *mut E,
|
|
));
|
|
|
|
#[cfg(anyhow_no_ptr_addr_of)]
|
|
return Ref::new(&unerased.deref()._object);
|
|
}
|
|
|
|
// Safety: requires layout of *e to match ErrorImpl<E>, and for `e` to be derived
|
|
// from a `&mut`
|
|
#[cfg(all(feature = "std", anyhow_no_ptr_addr_of))]
|
|
unsafe fn object_mut<E>(e: Mut<ErrorImpl>) -> &mut (dyn StdError + Send + Sync + 'static)
|
|
where
|
|
E: StdError + Send + Sync + 'static,
|
|
{
|
|
// Attach E's native StdError vtable onto a pointer to self._object.
|
|
&mut e.cast::<ErrorImpl<E>>().deref_mut()._object
|
|
}
|
|
|
|
// Safety: requires layout of *e to match ErrorImpl<E>.
|
|
unsafe fn object_boxed<E>(e: Own<ErrorImpl>) -> Box<dyn StdError + Send + Sync + 'static>
|
|
where
|
|
E: StdError + Send + Sync + 'static,
|
|
{
|
|
// Attach ErrorImpl<E>'s native StdError vtable. The StdError impl is below.
|
|
e.cast::<ErrorImpl<E>>().boxed()
|
|
}
|
|
|
|
// Safety: requires layout of *e to match ErrorImpl<E>.
|
|
unsafe fn object_downcast<E>(e: Ref<ErrorImpl>, target: TypeId) -> Option<Ref<()>>
|
|
where
|
|
E: 'static,
|
|
{
|
|
if TypeId::of::<E>() == target {
|
|
// Caller is looking for an E pointer and e is ErrorImpl<E>, take a
|
|
// pointer to its E field.
|
|
|
|
let unerased = e.cast::<ErrorImpl<E>>();
|
|
|
|
#[cfg(not(anyhow_no_ptr_addr_of))]
|
|
return Some(
|
|
Ref::from_raw(NonNull::new_unchecked(
|
|
ptr::addr_of!((*unerased.as_ptr())._object) as *mut E,
|
|
))
|
|
.cast::<()>(),
|
|
);
|
|
|
|
#[cfg(anyhow_no_ptr_addr_of)]
|
|
return Some(Ref::new(&unerased.deref()._object).cast::<()>());
|
|
} else {
|
|
None
|
|
}
|
|
}
|
|
|
|
// Safety: requires layout of *e to match ErrorImpl<E>.
|
|
#[cfg(anyhow_no_ptr_addr_of)]
|
|
unsafe fn object_downcast_mut<E>(e: Mut<ErrorImpl>, target: TypeId) -> Option<Mut<()>>
|
|
where
|
|
E: 'static,
|
|
{
|
|
if TypeId::of::<E>() == target {
|
|
// Caller is looking for an E pointer and e is ErrorImpl<E>, take a
|
|
// pointer to its E field.
|
|
let unerased = e.cast::<ErrorImpl<E>>().deref_mut();
|
|
Some(Mut::new(&mut unerased._object).cast::<()>())
|
|
} else {
|
|
None
|
|
}
|
|
}
|
|
|
|
#[cfg(all(not(backtrace), feature = "backtrace"))]
|
|
fn no_backtrace(e: Ref<ErrorImpl>) -> Option<&Backtrace> {
|
|
let _ = e;
|
|
None
|
|
}
|
|
|
|
// Safety: requires layout of *e to match ErrorImpl<ContextError<C, E>>.
|
|
#[cfg(feature = "std")]
|
|
unsafe fn context_downcast<C, E>(e: Ref<ErrorImpl>, target: TypeId) -> Option<Ref<()>>
|
|
where
|
|
C: 'static,
|
|
E: 'static,
|
|
{
|
|
if TypeId::of::<C>() == target {
|
|
let unerased = e.cast::<ErrorImpl<ContextError<C, E>>>().deref();
|
|
Some(Ref::new(&unerased._object.context).cast::<()>())
|
|
} else if TypeId::of::<E>() == target {
|
|
let unerased = e.cast::<ErrorImpl<ContextError<C, E>>>().deref();
|
|
Some(Ref::new(&unerased._object.error).cast::<()>())
|
|
} else {
|
|
None
|
|
}
|
|
}
|
|
|
|
// Safety: requires layout of *e to match ErrorImpl<ContextError<C, E>>.
|
|
#[cfg(all(feature = "std", anyhow_no_ptr_addr_of))]
|
|
unsafe fn context_downcast_mut<C, E>(e: Mut<ErrorImpl>, target: TypeId) -> Option<Mut<()>>
|
|
where
|
|
C: 'static,
|
|
E: 'static,
|
|
{
|
|
if TypeId::of::<C>() == target {
|
|
let unerased = e.cast::<ErrorImpl<ContextError<C, E>>>().deref_mut();
|
|
Some(Mut::new(&mut unerased._object.context).cast::<()>())
|
|
} else if TypeId::of::<E>() == target {
|
|
let unerased = e.cast::<ErrorImpl<ContextError<C, E>>>().deref_mut();
|
|
Some(Mut::new(&mut unerased._object.error).cast::<()>())
|
|
} else {
|
|
None
|
|
}
|
|
}
|
|
|
|
// Safety: requires layout of *e to match ErrorImpl<ContextError<C, E>>.
|
|
#[cfg(feature = "std")]
|
|
unsafe fn context_drop_rest<C, E>(e: Own<ErrorImpl>, target: TypeId)
|
|
where
|
|
C: 'static,
|
|
E: 'static,
|
|
{
|
|
// Called after downcasting by value to either the C or the E and doing a
|
|
// ptr::read to take ownership of that value.
|
|
if TypeId::of::<C>() == target {
|
|
let unerased = e
|
|
.cast::<ErrorImpl<ContextError<ManuallyDrop<C>, E>>>()
|
|
.boxed();
|
|
drop(unerased);
|
|
} else {
|
|
let unerased = e
|
|
.cast::<ErrorImpl<ContextError<C, ManuallyDrop<E>>>>()
|
|
.boxed();
|
|
drop(unerased);
|
|
}
|
|
}
|
|
|
|
// Safety: requires layout of *e to match ErrorImpl<ContextError<C, Error>>.
|
|
unsafe fn context_chain_downcast<C>(e: Ref<ErrorImpl>, target: TypeId) -> Option<Ref<()>>
|
|
where
|
|
C: 'static,
|
|
{
|
|
let unerased = e.cast::<ErrorImpl<ContextError<C, Error>>>().deref();
|
|
if TypeId::of::<C>() == target {
|
|
Some(Ref::new(&unerased._object.context).cast::<()>())
|
|
} else {
|
|
// Recurse down the context chain per the inner error's vtable.
|
|
let source = &unerased._object.error;
|
|
(vtable(source.inner.ptr).object_downcast)(source.inner.by_ref(), target)
|
|
}
|
|
}
|
|
|
|
// Safety: requires layout of *e to match ErrorImpl<ContextError<C, Error>>.
|
|
#[cfg(anyhow_no_ptr_addr_of)]
|
|
unsafe fn context_chain_downcast_mut<C>(e: Mut<ErrorImpl>, target: TypeId) -> Option<Mut<()>>
|
|
where
|
|
C: 'static,
|
|
{
|
|
let unerased = e.cast::<ErrorImpl<ContextError<C, Error>>>().deref_mut();
|
|
if TypeId::of::<C>() == target {
|
|
Some(Mut::new(&mut unerased._object.context).cast::<()>())
|
|
} else {
|
|
// Recurse down the context chain per the inner error's vtable.
|
|
let source = &mut unerased._object.error;
|
|
(vtable(source.inner.ptr).object_downcast_mut)(source.inner.by_mut(), target)
|
|
}
|
|
}
|
|
|
|
// Safety: requires layout of *e to match ErrorImpl<ContextError<C, Error>>.
|
|
unsafe fn context_chain_drop_rest<C>(e: Own<ErrorImpl>, target: TypeId)
|
|
where
|
|
C: 'static,
|
|
{
|
|
// Called after downcasting by value to either the C or one of the causes
|
|
// and doing a ptr::read to take ownership of that value.
|
|
if TypeId::of::<C>() == target {
|
|
let unerased = e
|
|
.cast::<ErrorImpl<ContextError<ManuallyDrop<C>, Error>>>()
|
|
.boxed();
|
|
// Drop the entire rest of the data structure rooted in the next Error.
|
|
drop(unerased);
|
|
} else {
|
|
let unerased = e
|
|
.cast::<ErrorImpl<ContextError<C, ManuallyDrop<Error>>>>()
|
|
.boxed();
|
|
// Read the Own<ErrorImpl> from the next error.
|
|
let inner = unerased._object.error.inner;
|
|
drop(unerased);
|
|
let vtable = vtable(inner.ptr);
|
|
// Recursively drop the next error using the same target typeid.
|
|
(vtable.object_drop_rest)(inner, target);
|
|
}
|
|
}
|
|
|
|
// Safety: requires layout of *e to match ErrorImpl<ContextError<C, Error>>.
|
|
#[cfg(all(not(backtrace), feature = "backtrace"))]
|
|
#[allow(clippy::unnecessary_wraps)]
|
|
unsafe fn context_backtrace<C>(e: Ref<ErrorImpl>) -> Option<&Backtrace>
|
|
where
|
|
C: 'static,
|
|
{
|
|
let unerased = e.cast::<ErrorImpl<ContextError<C, Error>>>().deref();
|
|
let backtrace = ErrorImpl::backtrace(unerased._object.error.inner.by_ref());
|
|
Some(backtrace)
|
|
}
|
|
|
|
// NOTE: If working with `ErrorImpl<()>`, references should be avoided in favor
|
|
// of raw pointers and `NonNull`.
|
|
// repr C to ensure that E remains in the final position.
|
|
#[repr(C)]
|
|
pub(crate) struct ErrorImpl<E = ()> {
|
|
vtable: &'static ErrorVTable,
|
|
backtrace: Option<Backtrace>,
|
|
// NOTE: Don't use directly. Use only through vtable. Erased type may have
|
|
// different alignment.
|
|
_object: E,
|
|
}
|
|
|
|
// Reads the vtable out of `p`. This is the same as `p.as_ref().vtable`, but
|
|
// avoids converting `p` into a reference.
|
|
unsafe fn vtable(p: NonNull<ErrorImpl>) -> &'static ErrorVTable {
|
|
// NOTE: This assumes that `ErrorVTable` is the first field of ErrorImpl.
|
|
*(p.as_ptr() as *const &'static ErrorVTable)
|
|
}
|
|
|
|
// repr C to ensure that ContextError<C, E> has the same layout as
|
|
// ContextError<ManuallyDrop<C>, E> and ContextError<C, ManuallyDrop<E>>.
|
|
#[repr(C)]
|
|
pub(crate) struct ContextError<C, E> {
|
|
pub context: C,
|
|
pub error: E,
|
|
}
|
|
|
|
impl<E> ErrorImpl<E> {
|
|
fn erase(&self) -> Ref<ErrorImpl> {
|
|
// Erase the concrete type of E but preserve the vtable in self.vtable
|
|
// for manipulating the resulting thin pointer. This is analogous to an
|
|
// unsize coercion.
|
|
Ref::new(self).cast::<ErrorImpl>()
|
|
}
|
|
}
|
|
|
|
impl ErrorImpl {
|
|
pub(crate) unsafe fn error(this: Ref<Self>) -> &(dyn StdError + Send + Sync + 'static) {
|
|
// Use vtable to attach E's native StdError vtable for the right
|
|
// original type E.
|
|
(vtable(this.ptr).object_ref)(this).deref()
|
|
}
|
|
|
|
#[cfg(feature = "std")]
|
|
pub(crate) unsafe fn error_mut(this: Mut<Self>) -> &mut (dyn StdError + Send + Sync + 'static) {
|
|
// Use vtable to attach E's native StdError vtable for the right
|
|
// original type E.
|
|
|
|
#[cfg(not(anyhow_no_ptr_addr_of))]
|
|
return (vtable(this.ptr).object_ref)(this.by_ref())
|
|
.by_mut()
|
|
.deref_mut();
|
|
|
|
#[cfg(anyhow_no_ptr_addr_of)]
|
|
return (vtable(this.ptr).object_mut)(this);
|
|
}
|
|
|
|
#[cfg(any(backtrace, feature = "backtrace"))]
|
|
pub(crate) unsafe fn backtrace(this: Ref<Self>) -> &Backtrace {
|
|
// This unwrap can only panic if the underlying error's backtrace method
|
|
// is nondeterministic, which would only happen in maliciously
|
|
// constructed code.
|
|
this.deref()
|
|
.backtrace
|
|
.as_ref()
|
|
.or_else(|| {
|
|
#[cfg(backtrace)]
|
|
return Self::error(this).backtrace();
|
|
#[cfg(all(not(backtrace), feature = "backtrace"))]
|
|
return (vtable(this.ptr).object_backtrace)(this);
|
|
})
|
|
.expect("backtrace capture failed")
|
|
}
|
|
|
|
#[cold]
|
|
pub(crate) unsafe fn chain(this: Ref<Self>) -> Chain {
|
|
Chain::new(Self::error(this))
|
|
}
|
|
}
|
|
|
|
impl<E> StdError for ErrorImpl<E>
|
|
where
|
|
E: StdError,
|
|
{
|
|
#[cfg(backtrace)]
|
|
fn backtrace(&self) -> Option<&Backtrace> {
|
|
Some(unsafe { ErrorImpl::backtrace(self.erase()) })
|
|
}
|
|
|
|
fn source(&self) -> Option<&(dyn StdError + 'static)> {
|
|
unsafe { ErrorImpl::error(self.erase()).source() }
|
|
}
|
|
}
|
|
|
|
impl<E> Debug for ErrorImpl<E>
|
|
where
|
|
E: Debug,
|
|
{
|
|
fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
|
|
unsafe { ErrorImpl::debug(self.erase(), formatter) }
|
|
}
|
|
}
|
|
|
|
impl<E> Display for ErrorImpl<E>
|
|
where
|
|
E: Display,
|
|
{
|
|
fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
|
|
unsafe { Display::fmt(ErrorImpl::error(self.erase()), formatter) }
|
|
}
|
|
}
|
|
|
|
impl From<Error> for Box<dyn StdError + Send + Sync + 'static> {
|
|
#[cold]
|
|
fn from(error: Error) -> Self {
|
|
let outer = ManuallyDrop::new(error);
|
|
unsafe {
|
|
// Use vtable to attach ErrorImpl<E>'s native StdError vtable for
|
|
// the right original type E.
|
|
(vtable(outer.inner.ptr).object_boxed)(outer.inner)
|
|
}
|
|
}
|
|
}
|
|
|
|
impl From<Error> for Box<dyn StdError + Send + 'static> {
|
|
fn from(error: Error) -> Self {
|
|
Box::<dyn StdError + Send + Sync>::from(error)
|
|
}
|
|
}
|
|
|
|
impl From<Error> for Box<dyn StdError + 'static> {
|
|
fn from(error: Error) -> Self {
|
|
Box::<dyn StdError + Send + Sync>::from(error)
|
|
}
|
|
}
|
|
|
|
#[cfg(feature = "std")]
|
|
impl AsRef<dyn StdError + Send + Sync> for Error {
|
|
fn as_ref(&self) -> &(dyn StdError + Send + Sync + 'static) {
|
|
&**self
|
|
}
|
|
}
|
|
|
|
#[cfg(feature = "std")]
|
|
impl AsRef<dyn StdError> for Error {
|
|
fn as_ref(&self) -> &(dyn StdError + 'static) {
|
|
&**self
|
|
}
|
|
}
|