error when sync dest to nonexistant root directory on windows

Support
21 
oops
22 
diff --git a/lib/fs/basicfs_windows.go b/lib/fs/basicfs_windows.go
index c4b56de02..87d146d2b 100644
--- a/lib/fs/basicfs_windows.go
+++ b/lib/fs/basicfs_windows.go
@@ -42,11 +42,11 @@ func (f *BasicFilesystem) MkdirAll(path string, perm FileMode) error {
 		return err
 	}
 
-	return f.mkdirAll(path, os.FileMode(perm))
+	return f.mkdirAll(path, perm)
 }
 
 // Required due to https://github.com/golang/go/issues/10900
-func (f *BasicFilesystem) mkdirAll(path string, perm os.FileMode) error {
+func (f *BasicFilesystem) mkdirAll(path string, perm FileMode) error {
 	// Fast path: if we can tell whether path is a directory or file, stop with success or error.
 	dir, err := os.Stat(path)
 	if err == nil {
@@ -74,8 +74,9 @@ func (f *BasicFilesystem) mkdirAll(path string, perm os.FileMode) error {
 	if j > 1 {
 		// Create parent
 		parent := path[0 : j-1]
+		l.Infoln("Volume name check", parent, filepath.VolumeName(parent))
 		if parent != filepath.VolumeName(parent) {
-			err = os.MkdirAll(parent, perm)
+			err = f.mkdirAll(parent, perm)
 			if err != nil {
 				return err
 			}
@@ -83,7 +84,7 @@ func (f *BasicFilesystem) mkdirAll(path string, perm os.FileMode) error {
 	}
 
 	// Parent now exists; invoke Mkdir and use its result.
-	err = os.Mkdir(path, perm)
+	err = os.Mkdir(path, os.FileMode(perm))
 	if err != nil {
 		// Handle arguments like "foo/." by
 		// double-checking that directory doesn't exist.
23

I patched at home, and on first sight it looks good. Have to enter debug info and test again. Be back later.

24

We should move further discussion to your bug report, as it is now pretty much proven to be a bug :slight_smile: Fails to create folder root directory on Windows · Issue #4762 · syncthing/syncthing · GitHub
I filed a PR to get buildable diffs: lib/fs: Fix MkdirAll failure due to \\?\ by imsodin · Pull Request #4763 · syncthing/syncthing · GitHub

25

Solved. Should be fixed in v0.14.46 .

Thanks!