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+use crate::backtrace::Backtrace;
+use crate::chain::Chain;
+#[cfg(any(feature = "std", anyhow_no_ptr_addr_of))]
+use crate::ptr::Mut;
+use crate::ptr::{Own, Ref};
+use crate::{Error, StdError};
+use alloc::boxed::Box;
+use core::any::TypeId;
+use core::fmt::{self, Debug, Display};
+use core::mem::ManuallyDrop;
+#[cfg(not(anyhow_no_ptr_addr_of))]
+use core::ptr;
+use core::ptr::NonNull;
+
+#[cfg(feature = "std")]
+use core::ops::{Deref, DerefMut};
+
+impl Error {
+ /// Create a new error object from any error type.
+ ///
+ /// The error type must be threadsafe and `'static`, so that the `Error`
+ /// will be as well.
+ ///
+ /// If the error type does not provide a backtrace, a backtrace will be
+ /// created here to ensure that a backtrace exists.
+ #[cfg(feature = "std")]
+ #[cfg_attr(doc_cfg, doc(cfg(feature = "std")))]
+ #[cold]
+ #[must_use]
+ pub fn new<E>(error: E) -> Self
+ where
+ E: StdError + Send + Sync + 'static,
+ {
+ let backtrace = backtrace_if_absent!(error);
+ Error::from_std(error, backtrace)
+ }
+
+ /// Create a new error object from a printable error message.
+ ///
+ /// If the argument implements std::error::Error, prefer `Error::new`
+ /// instead which preserves the underlying error's cause chain and
+ /// backtrace. If the argument may or may not implement std::error::Error
+ /// now or in the future, use `anyhow!(err)` which handles either way
+ /// correctly.
+ ///
+ /// `Error::msg("...")` is equivalent to `anyhow!("...")` but occasionally
+ /// convenient in places where a function is preferable over a macro, such
+ /// as iterator or stream combinators:
+ ///
+ /// ```
+ /// # mod ffi {
+ /// # pub struct Input;
+ /// # pub struct Output;
+ /// # pub async fn do_some_work(_: Input) -> Result<Output, &'static str> {
+ /// # unimplemented!()
+ /// # }
+ /// # }
+ /// #
+ /// # use ffi::{Input, Output};
+ /// #
+ /// use anyhow::{Error, Result};
+ /// use futures::stream::{Stream, StreamExt, TryStreamExt};
+ ///
+ /// async fn demo<S>(stream: S) -> Result<Vec<Output>>
+ /// where
+ /// S: Stream<Item = Input>,
+ /// {
+ /// stream
+ /// .then(ffi::do_some_work) // returns Result<Output, &str>
+ /// .map_err(Error::msg)
+ /// .try_collect()
+ /// .await
+ /// }
+ /// ```
+ #[cold]
+ #[must_use]
+ pub fn msg<M>(message: M) -> Self
+ where
+ M: Display + Debug + Send + Sync + 'static,
+ {
+ Error::from_adhoc(message, backtrace!())
+ }
+
+ #[cfg(feature = "std")]
+ #[cold]
+ pub(crate) fn from_std<E>(error: E, backtrace: Option<Backtrace>) -> Self
+ where
+ E: StdError + Send + Sync + 'static,
+ {
+ let vtable = &ErrorVTable {
+ object_drop: object_drop::<E>,
+ object_ref: object_ref::<E>,
+ #[cfg(anyhow_no_ptr_addr_of)]
+ object_mut: object_mut::<E>,
+ object_boxed: object_boxed::<E>,
+ object_downcast: object_downcast::<E>,
+ #[cfg(anyhow_no_ptr_addr_of)]
+ object_downcast_mut: object_downcast_mut::<E>,
+ object_drop_rest: object_drop_front::<E>,
+ #[cfg(all(not(backtrace), feature = "backtrace"))]
+ object_backtrace: no_backtrace,
+ };
+
+ // Safety: passing vtable that operates on the right type E.
+ unsafe { Error::construct(error, vtable, backtrace) }
+ }
+
+ #[cold]
+ pub(crate) fn from_adhoc<M>(message: M, backtrace: Option<Backtrace>) -> Self
+ where
+ M: Display + Debug + Send + Sync + 'static,
+ {
+ use crate::wrapper::MessageError;
+ let error: MessageError<M> = MessageError(message);
+ let vtable = &ErrorVTable {
+ object_drop: object_drop::<MessageError<M>>,
+ object_ref: object_ref::<MessageError<M>>,
+ #[cfg(all(feature = "std", anyhow_no_ptr_addr_of))]
+ object_mut: object_mut::<MessageError<M>>,
+ object_boxed: object_boxed::<MessageError<M>>,
+ object_downcast: object_downcast::<M>,
+ #[cfg(anyhow_no_ptr_addr_of)]
+ object_downcast_mut: object_downcast_mut::<M>,
+ object_drop_rest: object_drop_front::<M>,
+ #[cfg(all(not(backtrace), feature = "backtrace"))]
+ object_backtrace: no_backtrace,
+ };
+
+ // Safety: MessageError is repr(transparent) so it is okay for the
+ // vtable to allow casting the MessageError<M> to M.
+ unsafe { Error::construct(error, vtable, backtrace) }
+ }
+
+ #[cold]
+ pub(crate) fn from_display<M>(message: M, backtrace: Option<Backtrace>) -> Self
+ where
+ M: Display + Send + Sync + 'static,
+ {
+ use crate::wrapper::DisplayError;
+ let error: DisplayError<M> = DisplayError(message);
+ let vtable = &ErrorVTable {
+ object_drop: object_drop::<DisplayError<M>>,
+ object_ref: object_ref::<DisplayError<M>>,
+ #[cfg(all(feature = "std", anyhow_no_ptr_addr_of))]
+ object_mut: object_mut::<DisplayError<M>>,
+ object_boxed: object_boxed::<DisplayError<M>>,
+ object_downcast: object_downcast::<M>,
+ #[cfg(anyhow_no_ptr_addr_of)]
+ object_downcast_mut: object_downcast_mut::<M>,
+ object_drop_rest: object_drop_front::<M>,
+ #[cfg(all(not(backtrace), feature = "backtrace"))]
+ object_backtrace: no_backtrace,
+ };
+
+ // Safety: DisplayError is repr(transparent) so it is okay for the
+ // vtable to allow casting the DisplayError<M> to M.
+ unsafe { Error::construct(error, vtable, backtrace) }
+ }
+
+ #[cfg(feature = "std")]
+ #[cold]
+ pub(crate) fn from_context<C, E>(context: C, error: E, backtrace: Option<Backtrace>) -> Self
+ where
+ C: Display + Send + Sync + 'static,
+ E: StdError + Send + Sync + 'static,
+ {
+ let error: ContextError<C, E> = ContextError { context, error };
+
+ let vtable = &ErrorVTable {
+ object_drop: object_drop::<ContextError<C, E>>,
+ object_ref: object_ref::<ContextError<C, E>>,
+ #[cfg(anyhow_no_ptr_addr_of)]
+ object_mut: object_mut::<ContextError<C, E>>,
+ object_boxed: object_boxed::<ContextError<C, E>>,
+ object_downcast: context_downcast::<C, E>,
+ #[cfg(anyhow_no_ptr_addr_of)]
+ object_downcast_mut: context_downcast_mut::<C, E>,
+ object_drop_rest: context_drop_rest::<C, E>,
+ #[cfg(all(not(backtrace), feature = "backtrace"))]
+ object_backtrace: no_backtrace,
+ };
+
+ // Safety: passing vtable that operates on the right type.
+ unsafe { Error::construct(error, vtable, backtrace) }
+ }
+
+ #[cfg(feature = "std")]
+ #[cold]
+ pub(crate) fn from_boxed(
+ error: Box<dyn StdError + Send + Sync>,
+ backtrace: Option<Backtrace>,
+ ) -> Self {
+ use crate::wrapper::BoxedError;
+ let error = BoxedError(error);
+ let vtable = &ErrorVTable {
+ object_drop: object_drop::<BoxedError>,
+ object_ref: object_ref::<BoxedError>,
+ #[cfg(anyhow_no_ptr_addr_of)]
+ object_mut: object_mut::<BoxedError>,
+ object_boxed: object_boxed::<BoxedError>,
+ object_downcast: object_downcast::<Box<dyn StdError + Send + Sync>>,
+ #[cfg(anyhow_no_ptr_addr_of)]
+ object_downcast_mut: object_downcast_mut::<Box<dyn StdError + Send + Sync>>,
+ object_drop_rest: object_drop_front::<Box<dyn StdError + Send + Sync>>,
+ #[cfg(all(not(backtrace), feature = "backtrace"))]
+ object_backtrace: no_backtrace,
+ };
+
+ // Safety: BoxedError is repr(transparent) so it is okay for the vtable
+ // to allow casting to Box<dyn StdError + Send + Sync>.
+ unsafe { Error::construct(error, vtable, backtrace) }
+ }
+
+ // Takes backtrace as argument rather than capturing it here so that the
+ // user sees one fewer layer of wrapping noise in the backtrace.
+ //
+ // Unsafe because the given vtable must have sensible behavior on the error
+ // value of type E.
+ #[cold]
+ unsafe fn construct<E>(
+ error: E,
+ vtable: &'static ErrorVTable,
+ backtrace: Option<Backtrace>,
+ ) -> Self
+ where
+ E: StdError + Send + Sync + 'static,
+ {
+ let inner: Box<ErrorImpl<E>> = Box::new(ErrorImpl {
+ vtable,
+ backtrace,
+ _object: error,
+ });
+ // Erase the concrete type of E from the compile-time type system. This
+ // is equivalent to the safe unsize coercion from Box<ErrorImpl<E>> to
+ // Box<ErrorImpl<dyn StdError + Send + Sync + 'static>> except that the
+ // result is a thin pointer. The necessary behavior for manipulating the
+ // underlying ErrorImpl<E> is preserved in the vtable provided by the
+ // caller rather than a builtin fat pointer vtable.
+ let inner = Own::new(inner).cast::<ErrorImpl>();
+ Error { inner }
+ }
+
+ /// Wrap the error value with additional context.
+ ///
+ /// For attaching context to a `Result` as it is propagated, the
+ /// [`Context`][crate::Context] extension trait may be more convenient than
+ /// this function.
+ ///
+ /// The primary reason to use `error.context(...)` instead of
+ /// `result.context(...)` via the `Context` trait would be if the context
+ /// needs to depend on some data held by the underlying error:
+ ///
+ /// ```
+ /// # use std::fmt::{self, Debug, Display};
+ /// #
+ /// # type T = ();
+ /// #
+ /// # impl std::error::Error for ParseError {}
+ /// # impl Debug for ParseError {
+ /// # fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+ /// # unimplemented!()
+ /// # }
+ /// # }
+ /// # impl Display for ParseError {
+ /// # fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+ /// # unimplemented!()
+ /// # }
+ /// # }
+ /// #
+ /// use anyhow::Result;
+ /// use std::fs::File;
+ /// use std::path::Path;
+ ///
+ /// struct ParseError {
+ /// line: usize,
+ /// column: usize,
+ /// }
+ ///
+ /// fn parse_impl(file: File) -> Result<T, ParseError> {
+ /// # const IGNORE: &str = stringify! {
+ /// ...
+ /// # };
+ /// # unimplemented!()
+ /// }
+ ///
+ /// pub fn parse(path: impl AsRef<Path>) -> Result<T> {
+ /// let file = File::open(&path)?;
+ /// parse_impl(file).map_err(|error| {
+ /// let context = format!(
+ /// "only the first {} lines of {} are valid",
+ /// error.line, path.as_ref().display(),
+ /// );
+ /// anyhow::Error::new(error).context(context)
+ /// })
+ /// }
+ /// ```
+ #[cold]
+ #[must_use]
+ pub fn context<C>(self, context: C) -> Self
+ where
+ C: Display + Send + Sync + 'static,
+ {
+ let error: ContextError<C, Error> = ContextError {
+ context,
+ error: self,
+ };
+
+ let vtable = &ErrorVTable {
+ object_drop: object_drop::<ContextError<C, Error>>,
+ object_ref: object_ref::<ContextError<C, Error>>,
+ #[cfg(all(feature = "std", anyhow_no_ptr_addr_of))]
+ object_mut: object_mut::<ContextError<C, Error>>,
+ object_boxed: object_boxed::<ContextError<C, Error>>,
+ object_downcast: context_chain_downcast::<C>,
+ #[cfg(anyhow_no_ptr_addr_of)]
+ object_downcast_mut: context_chain_downcast_mut::<C>,
+ object_drop_rest: context_chain_drop_rest::<C>,
+ #[cfg(all(not(backtrace), feature = "backtrace"))]
+ object_backtrace: context_backtrace::<C>,
+ };
+
+ // As the cause is anyhow::Error, we already have a backtrace for it.
+ let backtrace = None;
+
+ // Safety: passing vtable that operates on the right type.
+ unsafe { Error::construct(error, vtable, backtrace) }
+ }
+
+ /// Get the backtrace for this Error.
+ ///
+ /// In order for the backtrace to be meaningful, one of the two environment
+ /// variables `RUST_LIB_BACKTRACE=1` or `RUST_BACKTRACE=1` must be defined
+ /// and `RUST_LIB_BACKTRACE` must not be `0`. Backtraces are somewhat
+ /// expensive to capture in Rust, so we don't necessarily want to be
+ /// capturing them all over the place all the time.
+ ///
+ /// - If you want panics and errors to both have backtraces, set
+ /// `RUST_BACKTRACE=1`;
+ /// - If you want only errors to have backtraces, set
+ /// `RUST_LIB_BACKTRACE=1`;
+ /// - If you want only panics to have backtraces, set `RUST_BACKTRACE=1` and
+ /// `RUST_LIB_BACKTRACE=0`.
+ ///
+ /// # Stability
+ ///
+ /// Standard library backtraces are only available on the nightly channel.
+ /// Tracking issue: [rust-lang/rust#53487][tracking].
+ ///
+ /// On stable compilers, this function is only available if the crate's
+ /// "backtrace" feature is enabled, and will use the `backtrace` crate as
+ /// the underlying backtrace implementation.
+ ///
+ /// ```toml
+ /// [dependencies]
+ /// anyhow = { version = "1.0", features = ["backtrace"] }
+ /// ```
+ ///
+ /// [tracking]: https://github.com/rust-lang/rust/issues/53487
+ #[cfg(any(backtrace, feature = "backtrace"))]
+ #[cfg_attr(doc_cfg, doc(cfg(any(nightly, feature = "backtrace"))))]
+ pub fn backtrace(&self) -> &impl_backtrace!() {
+ unsafe { ErrorImpl::backtrace(self.inner.by_ref()) }
+ }
+
+ /// An iterator of the chain of source errors contained by this Error.
+ ///
+ /// This iterator will visit every error in the cause chain of this error
+ /// object, beginning with the error that this error object was created
+ /// from.
+ ///
+ /// # Example
+ ///
+ /// ```
+ /// use anyhow::Error;
+ /// use std::io;
+ ///
+ /// pub fn underlying_io_error_kind(error: &Error) -> Option<io::ErrorKind> {
+ /// for cause in error.chain() {
+ /// if let Some(io_error) = cause.downcast_ref::<io::Error>() {
+ /// return Some(io_error.kind());
+ /// }
+ /// }
+ /// None
+ /// }
+ /// ```
+ #[cfg(feature = "std")]
+ #[cfg_attr(doc_cfg, doc(cfg(feature = "std")))]
+ #[cold]
+ pub fn chain(&self) -> Chain {
+ unsafe { ErrorImpl::chain(self.inner.by_ref()) }
+ }
+
+ /// The lowest level cause of this error &mdash; this error's cause's
+ /// cause's cause etc.
+ ///
+ /// The root cause is the last error in the iterator produced by
+ /// [`chain()`][Error::chain].
+ #[cfg(feature = "std")]
+ #[cfg_attr(doc_cfg, doc(cfg(feature = "std")))]
+ pub fn root_cause(&self) -> &(dyn StdError + 'static) {
+ self.chain().last().unwrap()
+ }
+
+ /// 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
+ /// context has been attached. For details about the interaction between
+ /// context and downcasting, [see here].
+ ///
+ /// [see here]: trait.Context.html#effect-on-downcasting
+ pub fn is<E>(&self) -> bool
+ where
+ E: Display + Debug + Send + Sync + 'static,
+ {
+ self.downcast_ref::<E>().is_some()
+ }
+
+ /// Attempt to downcast the error object to a concrete type.
+ pub fn downcast<E>(mut self) -> Result<E, Self>
+ where
+ E: Display + Debug + Send + Sync + 'static,
+ {
+ let target = TypeId::of::<E>();
+ let inner = self.inner.by_mut();
+ 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 = match (vtable(inner.ptr).object_downcast)(inner.by_ref(), target) {
+ Some(addr) => addr.by_mut().extend(),
+ None => return Err(self),
+ };
+ #[cfg(anyhow_no_ptr_addr_of)]
+ let addr = match (vtable(inner.ptr).object_downcast_mut)(inner, target) {
+ Some(addr) => addr.extend(),
+ None => return Err(self),
+ };
+
+ // Prepare to read E out of the data structure. We'll drop the rest
+ // of the data structure separately so that E is not dropped.
+ let outer = ManuallyDrop::new(self);
+
+ // Read E from where the vtable found it.
+ let error = addr.cast::<E>().read();
+
+ // Drop rest of the data structure outside of E.
+ (vtable(outer.inner.ptr).object_drop_rest)(outer.inner, target);
+
+ Ok(error)
+ }
+ }
+
+ /// Downcast this error object by reference.
+ ///
+ /// # Example
+ ///
+ /// ```
+ /// # use anyhow::anyhow;
+ /// # use std::fmt::{self, Display};
+ /// # use std::task::Poll;
+ /// #
+ /// # #[derive(Debug)]
+ /// # enum DataStoreError {
+ /// # Censored(()),
+ /// # }
+ /// #
+ /// # impl Display for DataStoreError {
+ /// # fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+ /// # unimplemented!()
+ /// # }
+ /// # }
+ /// #
+ /// # impl std::error::Error for DataStoreError {}
+ /// #
+ /// # const REDACTED_CONTENT: () = ();
+ /// #
+ /// # 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
+ }
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-06-09 08:14:45 +0000