Auto merge of #3781 - RalfJung:flock, r=RalfJung

flock: a bit of cleanup

Follow-up to https://github.com/rust-lang/miri/pull/3759

src/tools/miri/src/shims/unix/fd.rs

@@ -12,6 +12,13 @@
 use crate::shims::unix::*;
 use crate::*;
 
+#[derive(Debug, Clone, Copy, Eq, PartialEq)]
+pub(crate) enum FlockOp {
+    SharedLock { nonblocking: bool },
+    ExclusiveLock { nonblocking: bool },
+    Unlock,
+}
+
 /// Represents an open file descriptor.
 pub trait FileDescription: std::fmt::Debug + Any {
     fn name(&self) -> &'static str;
@@ -567,10 +574,3 @@ fn write(
         Ok(Scalar::from_target_isize(this.try_unwrap_io_result(result)?, this))
     }
 }
-
-#[derive(Debug, Clone, Copy, Eq, PartialEq)]
-pub(crate) enum FlockOp {
-    SharedLock { nonblocking: bool },
-    ExclusiveLock { nonblocking: bool },
-    Unlock,
-}

src/tools/miri/src/shims/unix/fs.rs

@@ -198,8 +198,8 @@ fn flock<'tcx>(
                     let code: u32 = err.raw_os_error().unwrap().try_into().unwrap();
                     if matches!(code, ERROR_IO_PENDING | ERROR_LOCK_VIOLATION) {
                         if lock_nb {
-                            // Replace error with a custom WouldBlock error, which later will be
-                            // mapped in the `helpers` module
+                            // The io error mapping does not know about these error codes,
+                            // so we translate it to `WouldBlock` manually.
                             let desc = format!("LockFileEx wouldblock error: {err}");
                             err = io::Error::new(io::ErrorKind::WouldBlock, desc);
                         } else {

src/tools/miri/tests/pass-dep/libc/libc-fs-flock.rs

@@ -1,4 +1,3 @@
-// Flock tests are separate since they don't in general work on a Windows host.
 //@ignore-target-windows: File handling is not implemented yet
 //@compile-flags: -Zmiri-disable-isolation