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proc_macro: clean up bridge::client::__run_expand{1,2} a bit. #65900

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merged 3 commits into from
Oct 29, 2019
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proc_macro: clean up bridge::client::__run_expand{1,2} a bit. #65900

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b3f6494
proc_macro: remove now-unnecessary ICE workarounds from bridge::client.
eddyb Oct 28, 2019
da5965f
proc_macro: consolidate bridge::client::run_expand{1,2} into one helper.
eddyb Oct 28, 2019
b586344
proc_macro: don't use Rust ABI fn pointers in a C ABI fn signature.
eddyb Oct 28, 2019
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82 changes: 28 additions & 54 deletions src/libproc_macro/bridge/client.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -15,8 +15,9 @@ macro_rules! define_handles {
}

impl HandleCounters {
// FIXME(#53451) public to work around `Cannot create local mono-item` ICE.
pub extern "C" fn get() -> &'static Self {
// FIXME(eddyb) use a reference to the `static COUNTERS`, intead 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),)*
Expand Down Expand Up @@ -333,29 +334,32 @@ impl Bridge<'_> {
#[repr(C)]
#[derive(Copy, Clone)]
pub struct Client<F> {
// FIXME(eddyb) use a reference to the `static COUNTERS`, intead 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,
}

// FIXME(#53451) public to work around `Cannot create local mono-item` ICE,
// affecting not only the function itself, but also the `BridgeState` `thread_local!`.
pub extern "C" fn __run_expand1(
/// 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: fn(crate::TokenStream) -> crate::TokenStream,
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 = TokenStream::decode(reader, &mut ());
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(crate::TokenStream(input)).0;
let output = f(input);

// Take the `cached_buffer` back out, for the output value.
b = Bridge::with(|bridge| bridge.cached_buffer.take());
Expand Down Expand Up @@ -383,65 +387,35 @@ pub extern "C" fn __run_expand1(

impl Client<fn(crate::TokenStream) -> crate::TokenStream> {
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: __run_expand1,
run,
f,
}
}
}

// FIXME(#53451) public to work around `Cannot create local mono-item` ICE,
// affecting not only the function itself, but also the `BridgeState` `thread_local!`.
pub extern "C" fn __run_expand2(
mut bridge: Bridge<'_>,
f: fn(crate::TokenStream, crate::TokenStream) -> crate::TokenStream,
) -> 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 = TokenStream::decode(reader, &mut ());
let input2 = TokenStream::decode(reader, &mut ());

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

let output = f(crate::TokenStream(input), crate::TokenStream(input2)).0;

// 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) -> crate::TokenStream> {
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: __run_expand2,
run,
f,
}
}
Expand Down