Make sure `CreateDirectoryW` works for path lengths > 247

2 files changed, 12 insertions, 1 deletions

diff --git a/library/std/src/sys/windows/path.rs b/library/std/src/sys/windows/path.rs
index eea7f3247c0..ad3f44fee8d 100644
--- a/library/std/src/sys/windows/path.rs
+++ b/library/std/src/sys/windows/path.rs
@@ -150,7 +150,11 @@ fn parse_next_component(path: &OsStr, verbatim: bool) -> (&OsStr, &OsStr) {
 ///
 /// This path may or may not have a verbatim prefix.
 pub(crate) fn maybe_verbatim(path: &Path) -> io::Result<Vec<u16>> {
-    const LEGACY_MAX_PATH: usize = 260;
+    // Normally the MAX path is 260 UTF-16 code units (including the NULL).
+    // However, for APIs such as CreateDirectory[1], the limit is 248.
+    //
+    // [1]: https://docs.microsoft.com/en-us/windows/win32/api/fileapi/nf-fileapi-createdirectorya#parameters
+    const LEGACY_MAX_PATH: usize = 248;
     // UTF-16 encoded code points, used in parsing and building UTF-16 paths.
     // All of these are in the ASCII range so they can be cast directly to `u16`.
     const SEP: u16 = b'\\' as _;
diff --git a/library/std/src/sys/windows/path/tests.rs b/library/std/src/sys/windows/path/tests.rs
index 131d27a99fe..c6c84519f41 100644
--- a/library/std/src/sys/windows/path/tests.rs
+++ b/library/std/src/sys/windows/path/tests.rs
@@ -81,6 +81,13 @@ fn verbatim() {
     check(r"\\server\share", r"\\server\share");
     check(r"\\.\COM1", r"\\.\COM1");
 
+    // Check that paths of length 247 are converted to verbatim.
+    // This is necessary for `CreateDirectory`.
+    check(
+        r"C:\aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
+        r"\\?\C:\aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
+    );
+
     // Make sure opening a drive will work.
     check("Z:", "Z:");