os: refactor to use runtime.Addcleanup

src/os/file_unix.go

@@ -63,6 +63,7 @@ type file struct {
 	nonblock    bool                    // whether we set nonblocking mode
 	stdoutOrErr bool                    // whether this is stdout or stderr
 	appendMode  bool                    // whether file is opened for appending
+	cleanup     runtime.Cleanup
 }
 
 // fd is the Unix implementation of Fd.
@@ -221,7 +222,9 @@ func newFile(fd int, name string, kind newFileKind, nonBlocking bool) *File {
 		}
 	}
 
-	runtime.SetFinalizer(f.file, (*file).close)
+	f.file.cleanup = runtime.AddCleanup(f, func(f *file) {
+		f.close()
+	}, f.file)
 	return f
 }
 
@@ -319,7 +322,7 @@ func (file *file) close() error {
 	}
 
 	// no need for a finalizer anymore
-	runtime.SetFinalizer(file, nil)
+	file.cleanup.Stop()
 	return err
 }
 

src/os/file_windows.go

@@ -29,6 +29,7 @@ type file struct {
 	name       string
 	dirinfo    atomic.Pointer[dirInfo] // nil unless directory being read
 	appendMode bool                    // whether file is opened for appending
+	cleanup    runtime.Cleanup
 }
 
 // fd is the Windows implementation of Fd.
@@ -68,7 +69,9 @@ func newFile(h syscall.Handle, name string, kind string, nonBlocking bool) *File
 		},
 		name: name,
 	}}
-	runtime.SetFinalizer(f.file, (*file).close)
+	f.file.cleanup = runtime.AddCleanup(f, func(f *file) {
+		f.close()
+	}, f.file)
 
 	// Ignore initialization errors.
 	// Assume any problems will show up in later I/O.
@@ -144,7 +147,7 @@ func (file *file) close() error {
 	}
 
 	// no need for a finalizer anymore
-	runtime.SetFinalizer(file, nil)
+	file.cleanup.Stop()
 	return err
 }
 

src/os/root_openat.go

@@ -22,10 +22,11 @@ type root struct {
 	// refs is incremented while an operation is using fd.
 	// closed is set when Close is called.
 	// fd is closed when closed is true and refs is 0.
-	mu     sync.Mutex
-	fd     sysfdType
-	refs   int  // number of active operations
-	closed bool // set when closed
+	mu      sync.Mutex
+	fd      sysfdType
+	refs    int  // number of active operations
+	closed  bool // set when closed
+	cleanup runtime.Cleanup
 }
 
 func (r *root) Close() error {
@@ -35,7 +36,7 @@ func (r *root) Close() error {
 		syscall.Close(r.fd)
 	}
 	r.closed = true
-	runtime.SetFinalizer(r, nil) // no need for a finalizer any more
+	r.cleanup.Stop()
 	return nil
 }
 

src/os/root_unix.go

@@ -56,7 +56,9 @@ func newRoot(fd int, name string) (*Root, error) {
 		fd:   fd,
 		name: name,
 	}}
-	runtime.SetFinalizer(r.root, (*root).Close)
+	r.root.cleanup = runtime.AddCleanup(r.root, func(_ int) {
+		r.root.Close()
+	}, 0)
 	return r, nil
 }