src/libproc_macro/bridge/client.rs

   1 //! Client-side types.
   2
   3 use super::*;
   4
   5 macro_rules! define_handles {
   6     (
   7         'owned: $($oty:ident,)*
   8         'interned: $($ity:ident,)*
   9     ) => {
  10         #[repr(C)]
  11         #[allow(non_snake_case)]
  12         pub struct HandleCounters {
  13             $($oty: AtomicUsize,)*
  14             $($ity: AtomicUsize,)*
  15         }
  16
  17         impl HandleCounters {
  18             // FIXME(eddyb) use a reference to the `static COUNTERS`, intead of
  19             // a wrapper `fn` pointer, once `const fn` can reference `static`s.
  20             extern "C" fn get() -> &'static Self {
  21                 static COUNTERS: HandleCounters = HandleCounters {
  22                     $($oty: AtomicUsize::new(1),)*
  23                     $($ity: AtomicUsize::new(1),)*
  24                 };
  25                 &COUNTERS
  26             }
  27         }
  28
  29         // FIXME(eddyb) generate the definition of `HandleStore` in `server.rs`.
  30         #[repr(C)]
  31         #[allow(non_snake_case)]
  32         pub(super) struct HandleStore<S: server::Types> {
  33             $($oty: handle::OwnedStore<S::$oty>,)*
  34             $($ity: handle::InternedStore<S::$ity>,)*
  35         }
  36
  37         impl<S: server::Types> HandleStore<S> {
  38             pub(super) fn new(handle_counters: &'static HandleCounters) -> Self {
  39                 HandleStore {
  40                     $($oty: handle::OwnedStore::new(&handle_counters.$oty),)*
  41                     $($ity: handle::InternedStore::new(&handle_counters.$ity),)*
  42                 }
  43             }
  44         }
  45
  46         $(
  47             #[repr(C)]
  48             pub(crate) struct $oty(handle::Handle);
  49             impl !Send for $oty {}
  50             impl !Sync for $oty {}
  51
  52             // Forward `Drop::drop` to the inherent `drop` method.
  53             impl Drop for $oty {
  54                 fn drop(&mut self) {
  55                     $oty(self.0).drop();
  56                 }
  57             }
  58
  59             impl<S> Encode<S> for $oty {
  60                 fn encode(self, w: &mut Writer, s: &mut S) {
  61                     let handle = self.0;
  62                     mem::forget(self);
  63                     handle.encode(w, s);
  64                 }
  65             }
  66
  67             impl<S: server::Types> DecodeMut<'_, '_, HandleStore<server::MarkedTypes<S>>>
  68                 for Marked<S::$oty, $oty>
  69             {
  70                 fn decode(r: &mut Reader<'_>, s: &mut HandleStore<server::MarkedTypes<S>>) -> Self {
  71                     s.$oty.take(handle::Handle::decode(r, &mut ()))
  72                 }
  73             }
  74
  75             impl<S> Encode<S> for &$oty {
  76                 fn encode(self, w: &mut Writer, s: &mut S) {
  77                     self.0.encode(w, s);
  78                 }
  79             }
  80
  81             impl<S: server::Types> Decode<'_, 's, HandleStore<server::MarkedTypes<S>>>
  82                 for &'s Marked<S::$oty, $oty>
  83             {
  84                 fn decode(r: &mut Reader<'_>, s: &'s HandleStore<server::MarkedTypes<S>>) -> Self {
  85                     &s.$oty[handle::Handle::decode(r, &mut ())]
  86                 }
  87             }
  88
  89             impl<S> Encode<S> for &mut $oty {
  90                 fn encode(self, w: &mut Writer, s: &mut S) {
  91                     self.0.encode(w, s);
  92                 }
  93             }
  94
  95             impl<S: server::Types> DecodeMut<'_, 's, HandleStore<server::MarkedTypes<S>>>
  96                 for &'s mut Marked<S::$oty, $oty>
  97             {
  98                 fn decode(
  99                     r: &mut Reader<'_>,
 100                     s: &'s mut HandleStore<server::MarkedTypes<S>>
 101                 ) -> Self {
 102                     &mut s.$oty[handle::Handle::decode(r, &mut ())]
 103                 }
 104             }
 105
 106             impl<S: server::Types> Encode<HandleStore<server::MarkedTypes<S>>>
 107                 for Marked<S::$oty, $oty>
 108             {
 109                 fn encode(self, w: &mut Writer, s: &mut HandleStore<server::MarkedTypes<S>>) {
 110                     s.$oty.alloc(self).encode(w, s);
 111                 }
 112             }
 113
 114             impl<S> DecodeMut<'_, '_, S> for $oty {
 115                 fn decode(r: &mut Reader<'_>, s: &mut S) -> Self {
 116                     $oty(handle::Handle::decode(r, s))
 117                 }
 118             }
 119         )*
 120
 121         $(
 122             #[repr(C)]
 123             #[derive(Copy, Clone, PartialEq, Eq, Hash)]
 124             pub(crate) struct $ity(handle::Handle);
 125             impl !Send for $ity {}
 126             impl !Sync for $ity {}
 127
 128             impl<S> Encode<S> for $ity {
 129                 fn encode(self, w: &mut Writer, s: &mut S) {
 130                     self.0.encode(w, s);
 131                 }
 132             }
 133
 134             impl<S: server::Types> DecodeMut<'_, '_, HandleStore<server::MarkedTypes<S>>>
 135                 for Marked<S::$ity, $ity>
 136             {
 137                 fn decode(r: &mut Reader<'_>, s: &mut HandleStore<server::MarkedTypes<S>>) -> Self {
 138                     s.$ity.copy(handle::Handle::decode(r, &mut ()))
 139                 }
 140             }
 141
 142             impl<S: server::Types> Encode<HandleStore<server::MarkedTypes<S>>>
 143                 for Marked<S::$ity, $ity>
 144             {
 145                 fn encode(self, w: &mut Writer, s: &mut HandleStore<server::MarkedTypes<S>>) {
 146                     s.$ity.alloc(self).encode(w, s);
 147                 }
 148             }
 149
 150             impl<S> DecodeMut<'_, '_, S> for $ity {
 151                 fn decode(r: &mut Reader<'_>, s: &mut S) -> Self {
 152                     $ity(handle::Handle::decode(r, s))
 153                 }
 154             }
 155         )*
 156     }
 157 }
 158 define_handles! {
 159     'owned:
 160     TokenStream,
 161     TokenStreamBuilder,
 162     TokenStreamIter,
 163     Group,
 164     Literal,
 165     SourceFile,
 166     MultiSpan,
 167     Diagnostic,
 168
 169     'interned:
 170     Punct,
 171     Ident,
 172     Span,
 173 }
 174
 175 // FIXME(eddyb) generate these impls by pattern-matching on the
 176 // names of methods - also could use the presence of `fn drop`
 177 // to distinguish between 'owned and 'interned, above.
 178 // Alternatively, special 'modes" could be listed of types in with_api
 179 // instead of pattern matching on methods, here and in server decl.
 180
 181 impl Clone for TokenStream {
 182     fn clone(&self) -> Self {
 183         self.clone()
 184     }
 185 }
 186
 187 impl Clone for TokenStreamIter {
 188     fn clone(&self) -> Self {
 189         self.clone()
 190     }
 191 }
 192
 193 impl Clone for Group {
 194     fn clone(&self) -> Self {
 195         self.clone()
 196     }
 197 }
 198
 199 impl Clone for Literal {
 200     fn clone(&self) -> Self {
 201         self.clone()
 202     }
 203 }
 204
 205 // FIXME(eddyb) `Literal` should not expose internal `Debug` impls.
 206 impl fmt::Debug for Literal {
 207     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 208         f.write_str(&self.debug())
 209     }
 210 }
 211
 212 impl Clone for SourceFile {
 213     fn clone(&self) -> Self {
 214         self.clone()
 215     }
 216 }
 217
 218 impl fmt::Debug for Span {
 219     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 220         f.write_str(&self.debug())
 221     }
 222 }
 223
 224 macro_rules! define_client_side {
 225     ($($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),*) $(-> $ret_ty)* {
 230                 Bridge::with(|bridge| {
 231                     let mut b = bridge.cached_buffer.take();
 232
 233                     b.clear();
 234                     api_tags::Method::$name(api_tags::$name::$method).encode(&mut b, &mut ());
 235                     reverse_encode!(b; $($arg),*);
 236
 237                     b = bridge.dispatch.call(b);
 238
 239                     let r = Result::<_, PanicMessage>::decode(&mut &b[..], &mut ());
 240
 241                     bridge.cached_buffer = b;
 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 enum BridgeState<'a> {
 252     /// No server is currently connected to this client.
 253     NotConnected,
 254
 255     /// A server is connected and available for requests.
 256     Connected(Bridge<'a>),
 257
 258     /// Access to the bridge is being exclusively acquired
 259     /// (e.g., during `BridgeState::with`).
 260     InUse,
 261 }
 262
 263 enum BridgeStateL {}
 264
 265 impl<'a> scoped_cell::ApplyL<'a> for BridgeStateL {
 266     type Out = BridgeState<'a>;
 267 }
 268
 269 thread_local! {
 270     static BRIDGE_STATE: scoped_cell::ScopedCell<BridgeStateL> =
 271         scoped_cell::ScopedCell::new(BridgeState::NotConnected);
 272 }
 273
 274 impl BridgeState<'_> {
 275     /// Take exclusive control of the thread-local
 276     /// `BridgeState`, and pass it to `f`, mutably.
 277     /// The state will be restored after `f` exits, even
 278     /// by panic, including modifications made to it by `f`.
 279     ///
 280     /// N.B., while `f` is running, the thread-local state
 281     /// is `BridgeState::InUse`.
 282     fn with<R>(f: impl FnOnce(&mut BridgeState<'_>) -> R) -> R {
 283         BRIDGE_STATE.with(|state| {
 284             state.replace(BridgeState::InUse, |mut state| {
 285                 // FIXME(#52812) pass `f` directly to `replace` when `RefMutL` is gone
 286                 f(&mut *state)
 287             })
 288         })
 289     }
 290 }
 291
 292 impl Bridge<'_> {
 293     fn enter<R>(self, f: impl FnOnce() -> R) -> R {
 294         // Hide the default panic output within `proc_macro` expansions.
 295         // NB. the server can't do this because it may use a different libstd.
 296         static HIDE_PANICS_DURING_EXPANSION: Once = Once::new();
 297         HIDE_PANICS_DURING_EXPANSION.call_once(|| {
 298             let prev = panic::take_hook();
 299             panic::set_hook(Box::new(move |info| {
 300                 let hide = BridgeState::with(|state| match state {
 301                     BridgeState::NotConnected => false,
 302                     BridgeState::Connected(_) | BridgeState::InUse => true,
 303                 });
 304                 if !hide {
 305                     prev(info)
 306                 }
 307             }));
 308         });
 309
 310         BRIDGE_STATE.with(|state| state.set(BridgeState::Connected(self), f))
 311     }
 312
 313     fn with<R>(f: impl FnOnce(&mut Bridge<'_>) -> R) -> R {
 314         BridgeState::with(|state| match state {
 315             BridgeState::NotConnected => {
 316                 panic!("procedural macro API is used outside of a procedural macro");
 317             }
 318             BridgeState::InUse => {
 319                 panic!("procedural macro API is used while it's already in use");
 320             }
 321             BridgeState::Connected(bridge) => f(bridge),
 322         })
 323     }
 324 }
 325
 326 /// A client-side "global object" (usually a function pointer),
 327 /// which may be using a different `proc_macro` from the one
 328 /// used by the server, but can be interacted with compatibly.
 329 ///
 330 /// N.B., `F` must have FFI-friendly memory layout (e.g., a pointer).
 331 /// The call ABI of function pointers used for `F` doesn't
 332 /// need to match between server and client, since it's only
 333 /// passed between them and (eventually) called by the client.
 334 #[repr(C)]
 335 #[derive(Copy, Clone)]
 336 pub struct Client<F> {
 337     // FIXME(eddyb) use a reference to the `static COUNTERS`, intead of
 338     // a wrapper `fn` pointer, once `const fn` can reference `static`s.
 339     pub(super) get_handle_counters: extern "C" fn() -> &'static HandleCounters,
 340     pub(super) run: extern "C" fn(Bridge<'_>, F) -> Buffer<u8>,
 341     pub(super) f: F,
 342 }
 343
 344 /// Client-side helper for handling client panics, entering the bridge,
 345 /// deserializing input and serializing output.
 346 // FIXME(eddyb) maybe replace `Bridge::enter` with this?
 347 fn run_client<A: for<'a, 's> DecodeMut<'a, 's, ()>, R: Encode<()>>(
 348     mut bridge: Bridge<'_>,
 349     f: impl FnOnce(A) -> R,
 350 ) -> Buffer<u8> {
 351     // The initial `cached_buffer` contains the input.
 352     let mut b = bridge.cached_buffer.take();
 353
 354     panic::catch_unwind(panic::AssertUnwindSafe(|| {
 355         bridge.enter(|| {
 356             let reader = &mut &b[..];
 357             let input = A::decode(reader, &mut ());
 358
 359             // Put the `cached_buffer` back in the `Bridge`, for requests.
 360             Bridge::with(|bridge| bridge.cached_buffer = b.take());
 361
 362             let output = f(input);
 363
 364             // Take the `cached_buffer` back out, for the output value.
 365             b = Bridge::with(|bridge| bridge.cached_buffer.take());
 366
 367             // HACK(eddyb) Separate encoding a success value (`Ok(output)`)
 368             // from encoding a panic (`Err(e: PanicMessage)`) to avoid
 369             // having handles outside the `bridge.enter(|| ...)` scope, and
 370             // to catch panics that could happen while encoding the success.
 371             //
 372             // Note that panics should be impossible beyond this point, but
 373             // this is defensively trying to avoid any accidental panicking
 374             // reaching the `extern "C"` (which should `abort` but may not
 375             // at the moment, so this is also potentially preventing UB).
 376             b.clear();
 377             Ok::<_, ()>(output).encode(&mut b, &mut ());
 378         })
 379     }))
 380     .map_err(PanicMessage::from)
 381     .unwrap_or_else(|e| {
 382         b.clear();
 383         Err::<(), _>(e).encode(&mut b, &mut ());
 384     });
 385     b
 386 }
 387
 388 impl Client<fn(crate::TokenStream) -> crate::TokenStream> {
 389     pub const fn expand1(f: fn(crate::TokenStream) -> crate::TokenStream) -> Self {
 390         extern "C" fn run(
 391             bridge: Bridge<'_>,
 392             f: impl FnOnce(crate::TokenStream) -> crate::TokenStream,
 393         ) -> Buffer<u8> {
 394             run_client(bridge, |input| f(crate::TokenStream(input)).0)
 395         }
 396         Client { get_handle_counters: HandleCounters::get, run, f }
 397     }
 398 }
 399
 400 impl Client<fn(crate::TokenStream, crate::TokenStream) -> crate::TokenStream> {
 401     pub const fn expand2(
 402         f: fn(crate::TokenStream, crate::TokenStream) -> crate::TokenStream,
 403     ) -> Self {
 404         extern "C" fn run(
 405             bridge: Bridge<'_>,
 406             f: impl FnOnce(crate::TokenStream, crate::TokenStream) -> crate::TokenStream,
 407         ) -> Buffer<u8> {
 408             run_client(bridge, |(input, input2)| {
 409                 f(crate::TokenStream(input), crate::TokenStream(input2)).0
 410             })
 411         }
 412         Client { get_handle_counters: HandleCounters::get, run, f }
 413     }
 414 }
 415
 416 #[repr(C)]
 417 #[derive(Copy, Clone)]
 418 pub enum ProcMacro {
 419     CustomDerive {
 420         trait_name: &'static str,
 421         attributes: &'static [&'static str],
 422         client: Client<fn(crate::TokenStream) -> crate::TokenStream>,
 423     },
 424
 425     Attr {
 426         name: &'static str,
 427         client: Client<fn(crate::TokenStream, crate::TokenStream) -> crate::TokenStream>,
 428     },
 429
 430     Bang {
 431         name: &'static str,
 432         client: Client<fn(crate::TokenStream) -> crate::TokenStream>,
 433     },
 434 }
 435
 436 impl ProcMacro {
 437     pub fn name(&self) -> &'static str {
 438         match self {
 439             ProcMacro::CustomDerive { trait_name, .. } => trait_name,
 440             ProcMacro::Attr { name, .. } => name,
 441             ProcMacro::Bang { name, .. } => name,
 442         }
 443     }
 444
 445     pub const fn custom_derive(
 446         trait_name: &'static str,
 447         attributes: &'static [&'static str],
 448         expand: fn(crate::TokenStream) -> crate::TokenStream,
 449     ) -> Self {
 450         ProcMacro::CustomDerive { trait_name, attributes, client: Client::expand1(expand) }
 451     }
 452
 453     pub const fn attr(
 454         name: &'static str,
 455         expand: fn(crate::TokenStream, crate::TokenStream) -> crate::TokenStream,
 456     ) -> Self {
 457         ProcMacro::Attr { name, client: Client::expand2(expand) }
 458     }
 459
 460     pub const fn bang(
 461         name: &'static str,
 462         expand: fn(crate::TokenStream) -> crate::TokenStream,
 463     ) -> Self {
 464         ProcMacro::Bang { name, client: Client::expand1(expand) }
 465     }
 466 }