client.rs.html -- source
Description: Source to the Rust file `library/proc_macro/src/bridge/client.rs`.
Keywords: rust, rustlang, rust-lang

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    //! Client-side types.

    use super::*;

    macro_rules! define_handles {
        (
            'owned: $($oty:ident,)*
            'interned: $($ity:ident,)*
        ) => {
            #[repr(C)]
            #[allow(non_snake_case)]
            pub struct HandleCounters {
                $($oty: AtomicUsize,)*
                $($ity: AtomicUsize,)*
            }

            impl HandleCounters {
                // FIXME(eddyb) use a reference to the `static COUNTERS`, instead of
                // a wrapper `fn` pointer, once `const fn` can reference `static`s.
                extern "C" fn get() -> &'static Self {
                    static COUNTERS: HandleCounters = HandleCounters {
                        $($oty: AtomicUsize::new(1),)*
                        $($ity: AtomicUsize::new(1),)*
                    };
                    &COUNTERS
                }
            }

            // FIXME(eddyb) generate the definition of `HandleStore` in `server.rs`.
            #[repr(C)]
            #[allow(non_snake_case)]
            pub(super) struct HandleStore<S: server::Types> {
                $($oty: handle::OwnedStore<S::$oty>,)*
                $($ity: handle::InternedStore<S::$ity>,)*
            }

            impl<S: server::Types> HandleStore<S> {
                pub(super) fn new(handle_counters: &'static HandleCounters) -> Self {
                    HandleStore {
                        $($oty: handle::OwnedStore::new(&handle_counters.$oty),)*
                        $($ity: handle::InternedStore::new(&handle_counters.$ity),)*
                    }
                }
            }

            $(
                #[repr(C)]
                pub(crate) struct $oty(handle::Handle);
                impl !Send for $oty {}
                impl !Sync for $oty {}

                // Forward `Drop::drop` to the inherent `drop` method.
                impl Drop for $oty {
                    fn drop(&mut self) {
                        $oty(self.0).drop();
                    }
                }

                impl<S> Encode<S> for $oty {
                    fn encode(self, w: &mut Writer, s: &mut S) {
                        let handle = self.0;
                        mem::forget(self);
                        handle.encode(w, s);
                    }
                }

                impl<S: server::Types> DecodeMut<'_, '_, HandleStore<server::MarkedTypes<S>>>
                    for Marked<S::$oty, $oty>
                {
                    fn decode(r: &mut Reader<'_>, s: &mut HandleStore<server::MarkedTypes<S>>) -> Self {
                        s.$oty.take(handle::Handle::decode(r, &mut ()))
                    }
                }

                impl<S> Encode<S> for &$oty {
                    fn encode(self, w: &mut Writer, s: &mut S) {
                        self.0.encode(w, s);
                    }
                }

                impl<S: server::Types> Decode<'_, 's, HandleStore<server::MarkedTypes<S>>>
                    for &'s Marked<S::$oty, $oty>
                {
                    fn decode(r: &mut Reader<'_>, s: &'s HandleStore<server::MarkedTypes<S>>) -> Self {
                        &s.$oty[handle::Handle::decode(r, &mut ())]
                    }
                }

                impl<S> Encode<S> for &mut $oty {
                    fn encode(self, w: &mut Writer, s: &mut S) {
                        self.0.encode(w, s);
                    }
                }

                impl<S: server::Types> DecodeMut<'_, 's, HandleStore<server::MarkedTypes<S>>>
                    for &'s mut Marked<S::$oty, $oty>
                {
                    fn decode(
                        r: &mut Reader<'_>,
                        s: &'s mut HandleStore<server::MarkedTypes<S>>
                    ) -> Self {
                        &mut s.$oty[handle::Handle::decode(r, &mut ())]
                    }
                }

                impl<S: server::Types> Encode<HandleStore<server::MarkedTypes<S>>>
                    for Marked<S::$oty, $oty>
                {
                    fn encode(self, w: &mut Writer, s: &mut HandleStore<server::MarkedTypes<S>>) {
                        s.$oty.alloc(self).encode(w, s);
                    }
                }

                impl<S> DecodeMut<'_, '_, S> for $oty {
                    fn decode(r: &mut Reader<'_>, s: &mut S) -> Self {
                        $oty(handle::Handle::decode(r, s))
                    }
                }
            )*

            $(
                #[repr(C)]
                #[derive(Copy, Clone, PartialEq, Eq, Hash)]
                pub(crate) struct $ity(handle::Handle);
                impl !Send for $ity {}
                impl !Sync for $ity {}

                impl<S> Encode<S> for $ity {
                    fn encode(self, w: &mut Writer, s: &mut S) {
                        self.0.encode(w, s);
                    }
                }

                impl<S: server::Types> DecodeMut<'_, '_, HandleStore<server::MarkedTypes<S>>>
                    for Marked<S::$ity, $ity>
                {
                    fn decode(r: &mut Reader<'_>, s: &mut HandleStore<server::MarkedTypes<S>>) -> Self {
                        s.$ity.copy(handle::Handle::decode(r, &mut ()))
                    }
                }

                impl<S: server::Types> Encode<HandleStore<server::MarkedTypes<S>>>
                    for Marked<S::$ity, $ity>
                {
                    fn encode(self, w: &mut Writer, s: &mut HandleStore<server::MarkedTypes<S>>) {
                        s.$ity.alloc(self).encode(w, s);
                    }
                }

                impl<S> DecodeMut<'_, '_, S> for $ity {
                    fn decode(r: &mut Reader<'_>, s: &mut S) -> Self {
                        $ity(handle::Handle::decode(r, s))
                    }
                }
            )*
        }
    }
    define_handles! {
        'owned:
        FreeFunctions,
        TokenStream,
        TokenStreamBuilder,
        TokenStreamIter,
        Group,
        Literal,
        SourceFile,
        MultiSpan,
        Diagnostic,

        'interned:
        Punct,
        Ident,
        Span,
    }

    // FIXME(eddyb) generate these impls by pattern-matching on the
    // names of methods - also could use the presence of `fn drop`
    // to distinguish between 'owned and 'interned, above.
    // Alternatively, special 'modes" could be listed of types in with_api
    // instead of pattern matching on methods, here and in server decl.

    impl Clone for TokenStream {
        fn clone(&self) -> Self {
            self.clone()
        }
    }

    impl Clone for TokenStreamIter {
        fn clone(&self) -> Self {
            self.clone()
        }
    }

    impl Clone for Group {
        fn clone(&self) -> Self {
            self.clone()
        }
    }

    impl Clone for Literal {
        fn clone(&self) -> Self {
            self.clone()
        }
    }

    impl fmt::Debug for Literal {
        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
            f.debug_struct("Literal")
                // format the kind without quotes, as in `kind: Float`
                .field("kind", &format_args!("{}", &self.debug_kind()))
                .field("symbol", &self.symbol())
                // format `Some("...")` on one line even in {:#?} mode
                .field("suffix", &format_args!("{:?}", &self.suffix()))
                .field("span", &self.span())
                .finish()
        }
    }

    impl Clone for SourceFile {
        fn clone(&self) -> Self {
            self.clone()
        }
    }

    impl fmt::Debug for Span {
        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
            f.write_str(&self.debug())
        }
    }

    macro_rules! define_client_side {
        ($($name:ident {
            $(fn $method:ident($($arg:ident: $arg_ty:ty),* $(,)?) $(-> $ret_ty:ty)*;)*
        }),* $(,)?) => {
            $(impl $name {
                $(pub(crate) fn $method($($arg: $arg_ty),*) $(-> $ret_ty)* {
                    Bridge::with(|bridge| {
                        let mut b = bridge.cached_buffer.take();

                        b.clear();
                        api_tags::Method::$name(api_tags::$name::$method).encode(&mut b, &mut ());
                        reverse_encode!(b; $($arg),*);

                        b = bridge.dispatch.call(b);

                        let r = Result::<_, PanicMessage>::decode(&mut &b[..], &mut ());

                        bridge.cached_buffer = b;

                        r.unwrap_or_else(|e| panic::resume_unwind(e.into()))
                    })
                })*
            })*
        }
    }
    with_api!(self, self, define_client_side);

    enum BridgeState<'a> {
        /// No server is currently connected to this client.
        NotConnected,

        /// A server is connected and available for requests.
        Connected(Bridge<'a>),

        /// Access to the bridge is being exclusively acquired
        /// (e.g., during `BridgeState::with`).
        InUse,
    }

    enum BridgeStateL {}

    impl<'a> scoped_cell::ApplyL<'a> for BridgeStateL {
        type Out = BridgeState<'a>;
    }

    thread_local! {
        static BRIDGE_STATE: scoped_cell::ScopedCell<BridgeStateL> =
            scoped_cell::ScopedCell::new(BridgeState::NotConnected);
    }

    impl BridgeState<'_> {
        /// Take exclusive control of the thread-local
        /// `BridgeState`, and pass it to `f`, mutably.
        /// The state will be restored after `f` exits, even
        /// by panic, including modifications made to it by `f`.
        ///
        /// N.B., while `f` is running, the thread-local state
        /// is `BridgeState::InUse`.
        fn with<R>(f: impl FnOnce(&mut BridgeState<'_>) -> R) -> R {
            BRIDGE_STATE.with(|state| {
                state.replace(BridgeState::InUse, |mut state| {
                    // FIXME(#52812) pass `f` directly to `replace` when `RefMutL` is gone
                    f(&mut *state)
                })
            })
        }
    }

    impl Bridge<'_> {
        pub(crate) fn is_available() -> bool {
            BridgeState::with(|state| match state {
                BridgeState::Connected(_) | BridgeState::InUse => true,
                BridgeState::NotConnected => false,
            })
        }

        fn enter<R>(self, f: impl FnOnce() -> R) -> R {
            let force_show_panics = self.force_show_panics;
            // Hide the default panic output within `proc_macro` expansions.
            // NB. the server can't do this because it may use a different libstd.
            static HIDE_PANICS_DURING_EXPANSION: Once = Once::new();
            HIDE_PANICS_DURING_EXPANSION.call_once(|| {
                let prev = panic::take_hook();
                panic::set_hook(Box::new(move |info| {
                    let show = BridgeState::with(|state| match state {
                        BridgeState::NotConnected => true,
                        BridgeState::Connected(_) | BridgeState::InUse => force_show_panics,
                    });
                    if show {
                        prev(info)
                    }
                }));
            });

            BRIDGE_STATE.with(|state| state.set(BridgeState::Connected(self), f))
        }

        fn with<R>(f: impl FnOnce(&mut Bridge<'_>) -> R) -> R {
            BridgeState::with(|state| match state {
                BridgeState::NotConnected => {
                    panic!("procedural macro API is used outside of a procedural macro");
                }
                BridgeState::InUse => {
                    panic!("procedural macro API is used while it's already in use");
                }
                BridgeState::Connected(bridge) => f(bridge),
            })
        }
    }

    /// A client-side "global object" (usually a function pointer),
    /// which may be using a different `proc_macro` from the one
    /// used by the server, but can be interacted with compatibly.
    ///
    /// N.B., `F` must have FFI-friendly memory layout (e.g., a pointer).
    /// The call ABI of function pointers used for `F` doesn't
    /// need to match between server and client, since it's only
    /// passed between them and (eventually) called by the client.
    #[repr(C)]
    #[derive(Copy, Clone)]
    pub struct Client<F> {
        // FIXME(eddyb) use a reference to the `static COUNTERS`, instead of
        // a wrapper `fn` pointer, once `const fn` can reference `static`s.
        pub(super) get_handle_counters: extern "C" fn() -> &'static HandleCounters,
        pub(super) run: extern "C" fn(Bridge<'_>, F) -> Buffer<u8>,
        pub(super) f: F,
    }

    /// Client-side helper for handling client panics, entering the bridge,
    /// deserializing input and serializing output.
    // FIXME(eddyb) maybe replace `Bridge::enter` with this?
    fn run_client<A: for<'a, 's> DecodeMut<'a, 's, ()>, R: Encode<()>>(
        mut bridge: Bridge<'_>,
        f: impl FnOnce(A) -> R,
    ) -> Buffer<u8> {
        // The initial `cached_buffer` contains the input.
        let mut b = bridge.cached_buffer.take();

        panic::catch_unwind(panic::AssertUnwindSafe(|| {
            bridge.enter(|| {
                let reader = &mut &b[..];
                let input = A::decode(reader, &mut ());

                // Put the `cached_buffer` back in the `Bridge`, for requests.
                Bridge::with(|bridge| bridge.cached_buffer = b.take());

                let output = f(input);

                // Take the `cached_buffer` back out, for the output value.
                b = Bridge::with(|bridge| bridge.cached_buffer.take());

                // HACK(eddyb) Separate encoding a success value (`Ok(output)`)
                // from encoding a panic (`Err(e: PanicMessage)`) to avoid
                // having handles outside the `bridge.enter(|| ...)` scope, and
                // to catch panics that could happen while encoding the success.
                //
                // Note that panics should be impossible beyond this point, but
                // this is defensively trying to avoid any accidental panicking
                // reaching the `extern "C"` (which should `abort` but may not
                // at the moment, so this is also potentially preventing UB).
                b.clear();
                Ok::<_, ()>(output).encode(&mut b, &mut ());
            })
        }))
        .map_err(PanicMessage::from)
        .unwrap_or_else(|e| {
            b.clear();
            Err::<(), _>(e).encode(&mut b, &mut ());
        });
        b
    }

    impl Client<fn(crate::TokenStream) -> crate::TokenStream> {
        #[allow_internal_unstable(const_fn)]
        pub const fn expand1(f: fn(crate::TokenStream) -> crate::TokenStream) -> Self {
            extern "C" fn run(
                bridge: Bridge<'_>,
                f: impl FnOnce(crate::TokenStream) -> crate::TokenStream,
            ) -> Buffer<u8> {
                run_client(bridge, |input| f(crate::TokenStream(input)).0)
            }
            Client { get_handle_counters: HandleCounters::get, run, f }
        }
    }

    impl Client<fn(crate::TokenStream, crate::TokenStream) -> crate::TokenStream> {
        #[allow_internal_unstable(const_fn)]
        pub const fn expand2(
            f: fn(crate::TokenStream, crate::TokenStream) -> crate::TokenStream,
        ) -> Self {
            extern "C" fn run(
                bridge: Bridge<'_>,
                f: impl FnOnce(crate::TokenStream, crate::TokenStream) -> crate::TokenStream,
            ) -> Buffer<u8> {
                run_client(bridge, |(input, input2)| {
                    f(crate::TokenStream(input), crate::TokenStream(input2)).0
                })
            }
            Client { get_handle_counters: HandleCounters::get, run, f }
        }
    }

    #[repr(C)]
    #[derive(Copy, Clone)]
    pub enum ProcMacro {
        CustomDerive {
            trait_name: &'static str,
            attributes: &'static [&'static str],
            client: Client<fn(crate::TokenStream) -> crate::TokenStream>,
        },

        Attr {
            name: &'static str,
            client: Client<fn(crate::TokenStream, crate::TokenStream) -> crate::TokenStream>,
        },

        Bang {
            name: &'static str,
            client: Client<fn(crate::TokenStream) -> crate::TokenStream>,
        },
    }

    impl ProcMacro {
        pub fn name(&self) -> &'static str {
            match self {
                ProcMacro::CustomDerive { trait_name, .. } => trait_name,
                ProcMacro::Attr { name, .. } => name,
                ProcMacro::Bang { name, .. } => name,
            }
        }

        #[allow_internal_unstable(const_fn)]
        pub const fn custom_derive(
            trait_name: &'static str,
            attributes: &'static [&'static str],
            expand: fn(crate::TokenStream) -> crate::TokenStream,
        ) -> Self {
            ProcMacro::CustomDerive { trait_name, attributes, client: Client::expand1(expand) }
        }

        #[allow_internal_unstable(const_fn)]
        pub const fn attr(
            name: &'static str,
            expand: fn(crate::TokenStream, crate::TokenStream) -> crate::TokenStream,
        ) -> Self {
            ProcMacro::Attr { name, client: Client::expand2(expand) }
        }

        #[allow_internal_unstable(const_fn)]
        pub const fn bang(
            name: &'static str,
            expand: fn(crate::TokenStream) -> crate::TokenStream,
        ) -> Self {
            ProcMacro::Bang { name, client: Client::expand1(expand) }
        }
    }