Change futex_wait errno from Scalar to IoError

To shift more Scalars to IoErrors, implement this change, allowing
for a few other changes in the Linux and Windows shims. This also
requires introducing a WindowsError variant in the IoError enum
and implementing the VisitProvenance trait for IoErrors.

src/tools/miri/src/concurrency/sync.rs

@@ -696,7 +696,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
         retval_succ: Scalar,
         retval_timeout: Scalar,
         dest: MPlaceTy<'tcx>,
-        errno_timeout: Scalar,
+        errno_timeout: IoError,
     ) {
         let this = self.eval_context_mut();
         let thread = this.active_thread();
@@ -713,7 +713,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                     retval_succ: Scalar,
                     retval_timeout: Scalar,
                     dest: MPlaceTy<'tcx>,
-                    errno_timeout: Scalar,
+                    errno_timeout: IoError,
                 }
                 @unblock = |this| {
                     let futex = this.machine.sync.futexes.get(&addr).unwrap();

src/tools/miri/src/provenance_gc.rs

@@ -89,6 +89,18 @@ impl VisitProvenance for Scalar {
     }
 }
 
+impl VisitProvenance for IoError {
+    fn visit_provenance(&self, visit: &mut VisitWith<'_>) {
+        use crate::shims::io_error::IoError::*;
+        match self {
+            LibcError(_name) => (),
+            WindowsError(_name) => (),
+            HostError(_io_error) => (),
+            Raw(scalar) => scalar.visit_provenance(visit),
+        }
+    }
+}
+
 impl VisitProvenance for Immediate<Provenance> {
     fn visit_provenance(&self, visit: &mut VisitWith<'_>) {
         match self {

src/tools/miri/src/shims/io_error.rs

@@ -7,6 +7,7 @@ use crate::*;
 #[derive(Debug)]
 pub enum IoError {
     LibcError(&'static str),
+    WindowsError(&'static str),
     HostError(io::Error),
     Raw(Scalar),
 }
@@ -113,6 +114,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
         let errno = match err.into() {
             HostError(err) => this.io_error_to_errnum(err)?,
             LibcError(name) => this.eval_libc(name),
+            WindowsError(name) => this.eval_windows("c", name),
             Raw(val) => val,
         };
         let errno_place = this.last_error_place()?;

src/tools/miri/src/shims/unix/linux/sync.rs

@@ -150,7 +150,7 @@ pub fn futex<'tcx>(
                     Scalar::from_target_isize(0, this), // retval_succ
                     Scalar::from_target_isize(-1, this), // retval_timeout
                     dest.clone(),
-                    this.eval_libc("ETIMEDOUT"), // errno_timeout
+                    LibcError("ETIMEDOUT"), // errno_timeout
                 );
             } else {
                 // The futex value doesn't match the expected value, so we return failure

src/tools/miri/src/shims/windows/sync.rs

@@ -202,7 +202,7 @@ pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
                 Scalar::from_i32(1), // retval_succ
                 Scalar::from_i32(0), // retval_timeout
                 dest.clone(),
-                this.eval_windows("c", "ERROR_TIMEOUT"), // errno_timeout
+                IoError::WindowsError("ERROR_TIMEOUT"), // errno_timeout
             );
         }