fix(maitake): add no_mangle workaround for ICE (#190)

See rust-lang/rust#97708 for
more details

Author: jamesmunns

maitake/Cargo.toml

@@ -16,6 +16,13 @@ categories = [
 edition = "2021"
 rust-version = "1.61.0"
 
+# NOTE! As a workaround for https://github.com/rust-lang/rust/issues/97708,
+# maitake uses some `no_mangle` functions. This will cause linker errors if
+# you attempt to use two versions of maitake in the same binary. Until then,
+# we use the "links" key to prevent two versions of maitake in the same
+# dependency graph
+links = "maitake"
+
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [features]

maitake/build.rs

@@ -0,0 +1,2 @@
+// Part of https://github.com/rust-lang/rust/issues/97708 workaround
+fn main() {}

maitake/src/task.rs

@@ -437,26 +437,32 @@ unsafe impl Sync for TaskRef {}
 
 // === impl Header ===
 
+// See https://github.com/rust-lang/rust/issues/97708 for why
+// this is necessary
+#[no_mangle]
+unsafe fn _maitake_header_nop(_ptr: TaskRef) -> Poll<()> {
+    #[cfg(debug_assertions)]
+    unreachable!("stub task ({_ptr:?}) should never be polled!");
+    #[cfg(not(debug_assertions))]
+    Poll::Pending
+}
+
+// See https://github.com/rust-lang/rust/issues/97708 for why
+// this is necessary
+#[no_mangle]
+unsafe fn _maitake_header_nop_deallocate(ptr: NonNull<Header>) {
+    unreachable!("stub task ({ptr:p}) should never be deallocated!");
+}
+
 impl Header {
     #[cfg(not(loom))]
     pub(crate) const fn new_stub() -> Self {
-        unsafe fn nop(_ptr: TaskRef) -> Poll<()> {
-            #[cfg(debug_assertions)]
-            unreachable!("stub task ({_ptr:?}) should never be polled!");
-            #[cfg(not(debug_assertions))]
-            Poll::Pending
-        }
-
-        unsafe fn nop_deallocate(ptr: NonNull<Header>) {
-            unreachable!("stub task ({ptr:p}) should never be deallocated!");
-        }
-
         Self {
             run_queue: mpsc_queue::Links::new_stub(),
             state: StateCell::new(),
             vtable: &Vtable {
-                poll: nop,
-                deallocate: nop_deallocate,
+                poll: _maitake_header_nop,
+                deallocate: _maitake_header_nop_deallocate,
             },
         }
     }

maitake/tests/static_stub.rs

@@ -0,0 +1,9 @@
+use maitake::scheduler::TaskStub;
+
+/// This test reproduces an internal compiler error:
+/// https://github.com/rust-lang/rust/issues/97708
+#[test]
+fn compiles() {
+    #[allow(dead_code)]
+    static TASK_STUB: TaskStub = TaskStub::new();
+}