library/proc_macro/src/bridge/client.rs

   1 //! Client-side types.
   2
   3 use super::*;
   4
   5 use std::marker::PhantomData;
   6
   7 macro_rules! define_handles {
   8     (
   9         'owned: $($oty:ident,)*
  10         'interned: $($ity:ident,)*
  11     ) => {
  12         #[repr(C)]
  13         #[allow(non_snake_case)]
  14         pub struct HandleCounters {
  15             $($oty: AtomicUsize,)*
  16             $($ity: AtomicUsize,)*
  17         }
  18
  19         impl HandleCounters {
  20             // FIXME(eddyb) use a reference to the `static COUNTERS`, instead of
  21             // a wrapper `fn` pointer, once `const fn` can reference `static`s.
  22             extern "C" fn get() -> &'static Self {
  23                 static COUNTERS: HandleCounters = HandleCounters {
  24                     $($oty: AtomicUsize::new(1),)*
  25                     $($ity: AtomicUsize::new(1),)*
  26                 };
  27                 &COUNTERS
  28             }
  29         }
  30
  31         // FIXME(eddyb) generate the definition of `HandleStore` in `server.rs`.
  32         #[allow(non_snake_case)]
  33         pub(super) struct HandleStore<S: server::Types> {
  34             $($oty: handle::OwnedStore<S::$oty>,)*
  35             $($ity: handle::InternedStore<S::$ity>,)*
  36         }
  37
  38         impl<S: server::Types> HandleStore<S> {
  39             pub(super) fn new(handle_counters: &'static HandleCounters) -> Self {
  40                 HandleStore {
  41                     $($oty: handle::OwnedStore::new(&handle_counters.$oty),)*
  42                     $($ity: handle::InternedStore::new(&handle_counters.$ity),)*
  43                 }
  44             }
  45         }
  46
  47         $(
  48             pub(crate) struct $oty {
  49                 handle: handle::Handle,
  50                 // Prevent Send and Sync impls. `!Send`/`!Sync` is the usual
  51                 // way of doing this, but that requires unstable features.
  52                 // rust-analyzer uses this code and avoids unstable features.
  53                 _marker: PhantomData<*mut ()>,
  54             }
  55
  56             // Forward `Drop::drop` to the inherent `drop` method.
  57             impl Drop for $oty {
  58                 fn drop(&mut self) {
  59                     $oty {
  60                         handle: self.handle,
  61                         _marker: PhantomData,
  62                     }.drop();
  63                 }
  64             }
  65
  66             impl<S> Encode<S> for $oty {
  67                 fn encode(self, w: &mut Writer, s: &mut S) {
  68                     let handle = self.handle;
  69                     mem::forget(self);
  70                     handle.encode(w, s);
  71                 }
  72             }
  73
  74             impl<S: server::Types> DecodeMut<'_, '_, HandleStore<server::MarkedTypes<S>>>
  75                 for Marked<S::$oty, $oty>
  76             {
  77                 fn decode(r: &mut Reader<'_>, s: &mut HandleStore<server::MarkedTypes<S>>) -> Self {
  78                     s.$oty.take(handle::Handle::decode(r, &mut ()))
  79                 }
  80             }
  81
  82             impl<S> Encode<S> for &$oty {
  83                 fn encode(self, w: &mut Writer, s: &mut S) {
  84                     self.handle.encode(w, s);
  85                 }
  86             }
  87
  88             impl<'s, S: server::Types> Decode<'_, 's, HandleStore<server::MarkedTypes<S>>>
  89                 for &'s Marked<S::$oty, $oty>
  90             {
  91                 fn decode(r: &mut Reader<'_>, s: &'s HandleStore<server::MarkedTypes<S>>) -> Self {
  92                     &s.$oty[handle::Handle::decode(r, &mut ())]
  93                 }
  94             }
  95
  96             impl<S> Encode<S> for &mut $oty {
  97                 fn encode(self, w: &mut Writer, s: &mut S) {
  98                     self.handle.encode(w, s);
  99                 }
 100             }
 101
 102             impl<'s, S: server::Types> DecodeMut<'_, 's, HandleStore<server::MarkedTypes<S>>>
 103                 for &'s mut Marked<S::$oty, $oty>
 104             {
 105                 fn decode(
 106                     r: &mut Reader<'_>,
 107                     s: &'s mut HandleStore<server::MarkedTypes<S>>
 108                 ) -> Self {
 109                     &mut s.$oty[handle::Handle::decode(r, &mut ())]
 110                 }
 111             }
 112
 113             impl<S: server::Types> Encode<HandleStore<server::MarkedTypes<S>>>
 114                 for Marked<S::$oty, $oty>
 115             {
 116                 fn encode(self, w: &mut Writer, s: &mut HandleStore<server::MarkedTypes<S>>) {
 117                     s.$oty.alloc(self).encode(w, s);
 118                 }
 119             }
 120
 121             impl<S> DecodeMut<'_, '_, S> for $oty {
 122                 fn decode(r: &mut Reader<'_>, s: &mut S) -> Self {
 123                     $oty {
 124                         handle: handle::Handle::decode(r, s),
 125                         _marker: PhantomData,
 126                     }
 127                 }
 128             }
 129         )*
 130
 131         $(
 132             #[derive(Copy, Clone, PartialEq, Eq, Hash)]
 133             pub(crate) struct $ity {
 134                 handle: handle::Handle,
 135                 // Prevent Send and Sync impls. `!Send`/`!Sync` is the usual
 136                 // way of doing this, but that requires unstable features.
 137                 // rust-analyzer uses this code and avoids unstable features.
 138                 _marker: PhantomData<*mut ()>,
 139             }
 140
 141             impl<S> Encode<S> for $ity {
 142                 fn encode(self, w: &mut Writer, s: &mut S) {
 143                     self.handle.encode(w, s);
 144                 }
 145             }
 146
 147             impl<S: server::Types> DecodeMut<'_, '_, HandleStore<server::MarkedTypes<S>>>
 148                 for Marked<S::$ity, $ity>
 149             {
 150                 fn decode(r: &mut Reader<'_>, s: &mut HandleStore<server::MarkedTypes<S>>) -> Self {
 151                     s.$ity.copy(handle::Handle::decode(r, &mut ()))
 152                 }
 153             }
 154
 155             impl<S: server::Types> Encode<HandleStore<server::MarkedTypes<S>>>
 156                 for Marked<S::$ity, $ity>
 157             {
 158                 fn encode(self, w: &mut Writer, s: &mut HandleStore<server::MarkedTypes<S>>) {
 159                     s.$ity.alloc(self).encode(w, s);
 160                 }
 161             }
 162
 163             impl<S> DecodeMut<'_, '_, S> for $ity {
 164                 fn decode(r: &mut Reader<'_>, s: &mut S) -> Self {
 165                     $ity {
 166                         handle: handle::Handle::decode(r, s),
 167                         _marker: PhantomData,
 168                     }
 169                 }
 170             }
 171         )*
 172     }
 173 }
 174 define_handles! {
 175     'owned:
 176     FreeFunctions,
 177     TokenStream,
 178     SourceFile,
 179
 180     'interned:
 181     Span,
 182 }
 183
 184 // FIXME(eddyb) generate these impls by pattern-matching on the
 185 // names of methods - also could use the presence of `fn drop`
 186 // to distinguish between 'owned and 'interned, above.
 187 // Alternatively, special "modes" could be listed of types in with_api
 188 // instead of pattern matching on methods, here and in server decl.
 189
 190 impl Clone for TokenStream {
 191     fn clone(&self) -> Self {
 192         self.clone()
 193     }
 194 }
 195
 196 impl Clone for SourceFile {
 197     fn clone(&self) -> Self {
 198         self.clone()
 199     }
 200 }
 201
 202 impl Span {
 203     pub(crate) fn def_site() -> Span {
 204         Bridge::with(|bridge| bridge.globals.def_site)
 205     }
 206
 207     pub(crate) fn call_site() -> Span {
 208         Bridge::with(|bridge| bridge.globals.call_site)
 209     }
 210
 211     pub(crate) fn mixed_site() -> Span {
 212         Bridge::with(|bridge| bridge.globals.mixed_site)
 213     }
 214 }
 215
 216 impl fmt::Debug for Span {
 217     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 218         f.write_str(&self.debug())
 219     }
 220 }
 221
 222 pub(crate) use super::symbol::Symbol;
 223
 224 macro_rules! define_client_side {
 225     ($($name:ident {
 226         $(fn $method:ident($($arg:ident: $arg_ty:ty),* $(,)?) $(-> $ret_ty:ty)*;)*
 227     }),* $(,)?) => {
 228         $(impl $name {
 229             $(pub(crate) fn $method($($arg: $arg_ty),*) $(-> $ret_ty)* {
 230                 Bridge::with(|bridge| {
 231                     let mut buf = bridge.cached_buffer.take();
 232
 233                     buf.clear();
 234                     api_tags::Method::$name(api_tags::$name::$method).encode(&mut buf, &mut ());
 235                     reverse_encode!(buf; $($arg),*);
 236
 237                     buf = bridge.dispatch.call(buf);
 238
 239                     let r = Result::<_, PanicMessage>::decode(&mut &buf[..], &mut ());
 240
 241                     bridge.cached_buffer = buf;
 242
 243                     r.unwrap_or_else(|e| panic::resume_unwind(e.into()))
 244                 })
 245             })*
 246         })*
 247     }
 248 }
 249 with_api!(self, self, define_client_side);
 250
 251 struct Bridge<'a> {
 252     /// Reusable buffer (only `clear`-ed, never shrunk), primarily
 253     /// used for making requests.
 254     cached_buffer: Buffer,
 255
 256     /// Server-side function that the client uses to make requests.
 257     dispatch: closure::Closure<'a, Buffer, Buffer>,
 258
 259     /// Provided globals for this macro expansion.
 260     globals: ExpnGlobals<Span>,
 261 }
 262
 263 impl<'a> !Send for Bridge<'a> {}
 264 impl<'a> !Sync for Bridge<'a> {}
 265
 266 enum BridgeState<'a> {
 267     /// No server is currently connected to this client.
 268     NotConnected,
 269
 270     /// A server is connected and available for requests.
 271     Connected(Bridge<'a>),
 272
 273     /// Access to the bridge is being exclusively acquired
 274     /// (e.g., during `BridgeState::with`).
 275     InUse,
 276 }
 277
 278 enum BridgeStateL {}
 279
 280 impl<'a> scoped_cell::ApplyL<'a> for BridgeStateL {
 281     type Out = BridgeState<'a>;
 282 }
 283
 284 thread_local! {
 285     static BRIDGE_STATE: scoped_cell::ScopedCell<BridgeStateL> =
 286         scoped_cell::ScopedCell::new(BridgeState::NotConnected);
 287 }
 288
 289 impl BridgeState<'_> {
 290     /// Take exclusive control of the thread-local
 291     /// `BridgeState`, and pass it to `f`, mutably.
 292     /// The state will be restored after `f` exits, even
 293     /// by panic, including modifications made to it by `f`.
 294     ///
 295     /// N.B., while `f` is running, the thread-local state
 296     /// is `BridgeState::InUse`.
 297     fn with<R>(f: impl FnOnce(&mut BridgeState<'_>) -> R) -> R {
 298         BRIDGE_STATE.with(|state| {
 299             state.replace(BridgeState::InUse, |mut state| {
 300                 // FIXME(#52812) pass `f` directly to `replace` when `RefMutL` is gone
 301                 f(&mut *state)
 302             })
 303         })
 304     }
 305 }
 306
 307 impl Bridge<'_> {
 308     fn with<R>(f: impl FnOnce(&mut Bridge<'_>) -> R) -> R {
 309         BridgeState::with(|state| match state {
 310             BridgeState::NotConnected => {
 311                 panic!("procedural macro API is used outside of a procedural macro");
 312             }
 313             BridgeState::InUse => {
 314                 panic!("procedural macro API is used while it's already in use");
 315             }
 316             BridgeState::Connected(bridge) => f(bridge),
 317         })
 318     }
 319 }
 320
 321 pub(crate) fn is_available() -> bool {
 322     BridgeState::with(|state| match state {
 323         BridgeState::Connected(_) | BridgeState::InUse => true,
 324         BridgeState::NotConnected => false,
 325     })
 326 }
 327
 328 /// A client-side RPC entry-point, which may be using a different `proc_macro`
 329 /// from the one used by the server, but can be invoked compatibly.
 330 ///
 331 /// Note that the (phantom) `I` ("input") and `O` ("output") type parameters
 332 /// decorate the `Client<I, O>` with the RPC "interface" of the entry-point, but
 333 /// do not themselves participate in ABI, at all, only facilitate type-checking.
 334 ///
 335 /// E.g. `Client<TokenStream, TokenStream>` is the common proc macro interface,
 336 /// used for `#[proc_macro] fn foo(input: TokenStream) -> TokenStream`,
 337 /// indicating that the RPC input and output will be serialized token streams,
 338 /// and forcing the use of APIs that take/return `S::TokenStream`, server-side.
 339 #[repr(C)]
 340 pub struct Client<I, O> {
 341     // FIXME(eddyb) use a reference to the `static COUNTERS`, instead of
 342     // a wrapper `fn` pointer, once `const fn` can reference `static`s.
 343     pub(super) get_handle_counters: extern "C" fn() -> &'static HandleCounters,
 344
 345     pub(super) run: extern "C" fn(BridgeConfig<'_>) -> Buffer,
 346
 347     pub(super) _marker: PhantomData<fn(I) -> O>,
 348 }
 349
 350 impl<I, O> Copy for Client<I, O> {}
 351 impl<I, O> Clone for Client<I, O> {
 352     fn clone(&self) -> Self {
 353         *self
 354     }
 355 }
 356
 357 fn maybe_install_panic_hook(force_show_panics: bool) {
 358     // Hide the default panic output within `proc_macro` expansions.
 359     // NB. the server can't do this because it may use a different libstd.
 360     static HIDE_PANICS_DURING_EXPANSION: Once = Once::new();
 361     HIDE_PANICS_DURING_EXPANSION.call_once(|| {
 362         let prev = panic::take_hook();
 363         panic::set_hook(Box::new(move |info| {
 364             let show = BridgeState::with(|state| match state {
 365                 BridgeState::NotConnected => true,
 366                 BridgeState::Connected(_) | BridgeState::InUse => force_show_panics,
 367             });
 368             if show {
 369                 prev(info)
 370             }
 371         }));
 372     });
 373 }
 374
 375 /// Client-side helper for handling client panics, entering the bridge,
 376 /// deserializing input and serializing output.
 377 // FIXME(eddyb) maybe replace `Bridge::enter` with this?
 378 fn run_client<A: for<'a, 's> DecodeMut<'a, 's, ()>, R: Encode<()>>(
 379     config: BridgeConfig<'_>,
 380     f: impl FnOnce(A) -> R,
 381 ) -> Buffer {
 382     let BridgeConfig { input: mut buf, dispatch, force_show_panics, .. } = config;
 383
 384     panic::catch_unwind(panic::AssertUnwindSafe(|| {
 385         maybe_install_panic_hook(force_show_panics);
 386
 387         // Make sure the symbol store is empty before decoding inputs.
 388         Symbol::invalidate_all();
 389
 390         let reader = &mut &buf[..];
 391         let (globals, input) = <(ExpnGlobals<Span>, A)>::decode(reader, &mut ());
 392
 393         // Put the buffer we used for input back in the `Bridge` for requests.
 394         let new_state =
 395             BridgeState::Connected(Bridge { cached_buffer: buf.take(), dispatch, globals });
 396
 397         BRIDGE_STATE.with(|state| {
 398             state.set(new_state, || {
 399                 let output = f(input);
 400
 401                 // Take the `cached_buffer` back out, for the output value.
 402                 buf = Bridge::with(|bridge| bridge.cached_buffer.take());
 403
 404                 // HACK(eddyb) Separate encoding a success value (`Ok(output)`)
 405                 // from encoding a panic (`Err(e: PanicMessage)`) to avoid
 406                 // having handles outside the `bridge.enter(|| ...)` scope, and
 407                 // to catch panics that could happen while encoding the success.
 408                 //
 409                 // Note that panics should be impossible beyond this point, but
 410                 // this is defensively trying to avoid any accidental panicking
 411                 // reaching the `extern "C"` (which should `abort` but might not
 412                 // at the moment, so this is also potentially preventing UB).
 413                 buf.clear();
 414                 Ok::<_, ()>(output).encode(&mut buf, &mut ());
 415             })
 416         })
 417     }))
 418     .map_err(PanicMessage::from)
 419     .unwrap_or_else(|e| {
 420         buf.clear();
 421         Err::<(), _>(e).encode(&mut buf, &mut ());
 422     });
 423
 424     // Now that a response has been serialized, invalidate all symbols
 425     // registered with the interner.
 426     Symbol::invalidate_all();
 427     buf
 428 }
 429
 430 impl Client<crate::TokenStream, crate::TokenStream> {
 431     pub const fn expand1(f: impl Fn(crate::TokenStream) -> crate::TokenStream + Copy) -> Self {
 432         Client {
 433             get_handle_counters: HandleCounters::get,
 434             run: super::selfless_reify::reify_to_extern_c_fn_hrt_bridge(move |bridge| {
 435                 run_client(bridge, |input| f(crate::TokenStream(Some(input))).0)
 436             }),
 437             _marker: PhantomData,
 438         }
 439     }
 440 }
 441
 442 impl Client<(crate::TokenStream, crate::TokenStream), crate::TokenStream> {
 443     pub const fn expand2(
 444         f: impl Fn(crate::TokenStream, crate::TokenStream) -> crate::TokenStream + Copy,
 445     ) -> Self {
 446         Client {
 447             get_handle_counters: HandleCounters::get,
 448             run: super::selfless_reify::reify_to_extern_c_fn_hrt_bridge(move |bridge| {
 449                 run_client(bridge, |(input, input2)| {
 450                     f(crate::TokenStream(Some(input)), crate::TokenStream(Some(input2))).0
 451                 })
 452             }),
 453             _marker: PhantomData,
 454         }
 455     }
 456 }
 457
 458 #[repr(C)]
 459 #[derive(Copy, Clone)]
 460 pub enum ProcMacro {
 461     CustomDerive {
 462         trait_name: &'static str,
 463         attributes: &'static [&'static str],
 464         client: Client<crate::TokenStream, crate::TokenStream>,
 465     },
 466
 467     Attr {
 468         name: &'static str,
 469         client: Client<(crate::TokenStream, crate::TokenStream), crate::TokenStream>,
 470     },
 471
 472     Bang {
 473         name: &'static str,
 474         client: Client<crate::TokenStream, crate::TokenStream>,
 475     },
 476 }
 477
 478 impl ProcMacro {
 479     pub fn name(&self) -> &'static str {
 480         match self {
 481             ProcMacro::CustomDerive { trait_name, .. } => trait_name,
 482             ProcMacro::Attr { name, .. } => name,
 483             ProcMacro::Bang { name, .. } => name,
 484         }
 485     }
 486
 487     pub const fn custom_derive(
 488         trait_name: &'static str,
 489         attributes: &'static [&'static str],
 490         expand: impl Fn(crate::TokenStream) -> crate::TokenStream + Copy,
 491     ) -> Self {
 492         ProcMacro::CustomDerive { trait_name, attributes, client: Client::expand1(expand) }
 493     }
 494
 495     pub const fn attr(
 496         name: &'static str,
 497         expand: impl Fn(crate::TokenStream, crate::TokenStream) -> crate::TokenStream + Copy,
 498     ) -> Self {
 499         ProcMacro::Attr { name, client: Client::expand2(expand) }
 500     }
 501
 502     pub const fn bang(
 503         name: &'static str,
 504         expand: impl Fn(crate::TokenStream) -> crate::TokenStream + Copy,
 505     ) -> Self {
 506         ProcMacro::Bang { name, client: Client::expand1(expand) }
 507     }
 508 }