stub fixups

Author: nia-e

src/shims/native_lib/trace/stub.rs

@@ -1,8 +1,11 @@
 use rustc_const_eval::interpret::InterpResult;
 
+static SUPERVISOR: std::sync::Mutex<()> = std::sync::Mutex::new(());
+
 pub struct Supervisor;
 
-static SUPERVISOR: std::sync::Mutex<Option<Supervisor>> = std::sync::Mutex::new(None);
+#[derive(Debug)]
+pub struct SvInitError;
 
 impl Supervisor {
     #[inline(always)]
@@ -21,12 +24,8 @@ impl Supervisor {
 }
 
 #[allow(dead_code, clippy::missing_safety_doc)]
-pub unsafe fn init_sv() -> Result<(), !> {
-    let mut sv_guard = SUPERVISOR.lock().unwrap();
-    if sv_guard.is_none() {
-        *sv_guard = Some(Supervisor);
-    }
-    Ok(())
+pub unsafe fn init_sv() -> Result<!, SvInitError> {
+    Err(SvInitError)
 }
 
 #[inline(always)]