executor: use WakerHack unconditionally even if nightly feature is enabled. (#3528)

This ensures the executor compiles with all recent nightly versions,
including the stable-but-with-nightly-features-enabled xtensa rustc.

embassy-executor/Cargo.toml

@@ -57,9 +57,6 @@ avr-device = { version = "0.5.3", optional = true }
 critical-section = { version = "1.1", features = ["std"] }
 trybuild = "1.0"
 
-[build-dependencies]
-rustc_version = "0.4.1"
-
 [features]
 
 ## Enable nightly-only features

embassy-executor/build.rs

@@ -96,15 +96,4 @@ fn main() {
 
     let mut rustc_cfgs = common::CfgSet::new();
     common::set_target_cfgs(&mut rustc_cfgs);
-
-    // Waker API changed on 2024-09-06
-    rustc_cfgs.declare("at_least_2024_09_06");
-    let Some(compiler) = common::compiler_info() else {
-        return;
-    };
-    if compiler.channel == rustc_version::Channel::Nightly
-        && compiler.commit_date.map(|d| d >= "2024-09-06").unwrap_or(false)
-    {
-        rustc_cfgs.enable("at_least_2024_09_06");
-    }
 }

embassy-executor/build_common.rs

@@ -124,22 +124,3 @@ impl PartialOrd<&str> for CompilerDate {
         Self::parse(other).map(|other| self.cmp(&other))
     }
 }
-
-pub struct CompilerInfo {
-    #[allow(unused)]
-    pub version: rustc_version::Version,
-    pub channel: rustc_version::Channel,
-    pub commit_date: Option<CompilerDate>,
-}
-
-pub fn compiler_info() -> Option<CompilerInfo> {
-    let Ok(meta) = rustc_version::version_meta() else {
-        return None;
-    };
-
-    Some(CompilerInfo {
-        version: meta.semver,
-        channel: meta.channel,
-        commit_date: meta.commit_date.as_deref().and_then(CompilerDate::parse),
-    })
-}

embassy-executor/src/lib.rs

@@ -1,5 +1,4 @@
 #![cfg_attr(not(any(feature = "arch-std", feature = "arch-wasm")), no_std)]
-#![cfg_attr(all(feature = "nightly", not(at_least_2024_09_06)), feature(waker_getters))]
 #![allow(clippy::new_without_default)]
 #![doc = include_str!("../README.md")]
 #![warn(missing_docs)]

embassy-executor/src/raw/waker.rs

@@ -32,40 +32,20 @@ pub(crate) unsafe fn from_task(p: TaskRef) -> Waker {
 ///
 /// Panics if the waker is not created by the Embassy executor.
 pub fn task_from_waker(waker: &Waker) -> TaskRef {
-    let (vtable, data) = {
+    struct WakerHack {
-        #[cfg(not(feature = "nightly"))]
+        data: *const (),
-        {
+        vtable: &'static RawWakerVTable,
-            struct WakerHack {
+    }
-                data: *const (),
-                vtable: &'static RawWakerVTable,
-            }
 
-            // safety: OK because WakerHack has the same layout as Waker.
+    // safety: OK because WakerHack has the same layout as Waker.
-            // This is not really guaranteed because the structs are `repr(Rust)`, it is
+    // This is not really guaranteed because the structs are `repr(Rust)`, it is
-            // indeed the case in the current implementation.
+    // indeed the case in the current implementation.
-            // TODO use waker_getters when stable. https://github.com/rust-lang/rust/issues/96992
+    // TODO use waker_getters when stable. https://github.com/rust-lang/rust/issues/96992
-            let hack: &WakerHack = unsafe { core::mem::transmute(waker) };
+    let hack: &WakerHack = unsafe { core::mem::transmute(waker) };
-            (hack.vtable, hack.data)
-        }
 
-        #[cfg(feature = "nightly")]
+    if hack.vtable != &VTABLE {
-        {
-            #[cfg(not(at_least_2024_09_06))]
-            {
-                let raw_waker = waker.as_raw();
-                (raw_waker.vtable(), raw_waker.data())
-            }
-
-            #[cfg(at_least_2024_09_06)]
-            {
-                (waker.vtable(), waker.data())
-            }
-        }
-    };
-
-    if vtable != &VTABLE {
         panic!("Found waker not created by the Embassy executor. `embassy_time::Timer` only works with the Embassy executor.")
     }
     // safety: our wakers are always created with `TaskRef::as_ptr`
-    unsafe { TaskRef::from_ptr(data as *const TaskHeader) }
+    unsafe { TaskRef::from_ptr(hack.data as *const TaskHeader) }
 }