fix(windows): don't automatically delete files on open (#344)

We tried doing this to match the behavior on Unix platforms but this
appears to trigger some form of Windows kernel bug at scale. Given that
it's not necessary, we're reverting it. I'm leaving the feature flag in
the `Cargo.toml` for now but will remove it in the near future.

fixes #339

Author: Stebalien

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Changelog
 
+## 3.19.1 [unreleased]
+
+- Don't unlink temporary files immediately on Windows (fixes #339). Unfortunately, this seemed to corrupt the file object (possibly a Windows kernel bug) in rare cases and isn't strictly speaking necessary.
+
 ## 3.19.0
 
 - Remove direct dependency on `cfg-if`. It's still in the tree, but we didn't really need to use it in this crate.

Cargo.toml

@@ -40,6 +40,5 @@ doc-comment = "0.3"
 [features]
 default = ["getrandom"]
 nightly = []
-# Disables immediate deletion of newly opened tempfiles on windows, instead relying on the old
-# "delete on close" behavior. This will hopefully fix #339.
+# DEPRECATED unstable feature, will be removed in the near future.
 unstable-windows-keep-open-tempfile = []

src/file/imp/windows.rs

@@ -8,11 +8,9 @@ use std::{io, iter};
 
 use windows_sys::Win32::Foundation::{HANDLE, INVALID_HANDLE_VALUE};
 use windows_sys::Win32::Storage::FileSystem::{
-    FileDispositionInfoEx, MoveFileExW, ReOpenFile, SetFileAttributesW, SetFileInformationByHandle,
-    FILE_ATTRIBUTE_NORMAL, FILE_ATTRIBUTE_TEMPORARY, FILE_DISPOSITION_FLAG_DELETE,
-    FILE_DISPOSITION_FLAG_POSIX_SEMANTICS, FILE_DISPOSITION_INFO_EX, FILE_FLAG_DELETE_ON_CLOSE,
-    FILE_GENERIC_READ, FILE_GENERIC_WRITE, FILE_SHARE_DELETE, FILE_SHARE_READ, FILE_SHARE_WRITE,
-    MOVEFILE_REPLACE_EXISTING,
+    MoveFileExW, ReOpenFile, SetFileAttributesW, FILE_ATTRIBUTE_NORMAL, FILE_ATTRIBUTE_TEMPORARY,
+    FILE_FLAG_DELETE_ON_CLOSE, FILE_GENERIC_READ, FILE_GENERIC_WRITE, FILE_SHARE_DELETE,
+    FILE_SHARE_READ, FILE_SHARE_WRITE, MOVEFILE_REPLACE_EXISTING,
 };
 
 use crate::util;
@@ -25,25 +23,6 @@ fn not_supported<T>(msg: &str) -> io::Result<T> {
     Err(io::Error::new(io::ErrorKind::Other, msg))
 }
 
-fn delete_open_file(f: &File) -> io::Result<()> {
-    unsafe {
-        let info = FILE_DISPOSITION_INFO_EX {
-            Flags: FILE_DISPOSITION_FLAG_DELETE | FILE_DISPOSITION_FLAG_POSIX_SEMANTICS,
-        };
-        if SetFileInformationByHandle(
-            f.as_raw_handle() as HANDLE,
-            FileDispositionInfoEx,
-            &info as *const _ as *const _,
-            std::mem::size_of::<FILE_DISPOSITION_INFO_EX>() as u32,
-        ) == 0
-        {
-            Err(io::Error::last_os_error())
-        } else {
-            Ok(())
-        }
-    }
-}
-
 pub fn create_named(
     path: &Path,
     open_options: &mut OpenOptions,
@@ -74,10 +53,9 @@ pub fn create(dir: &Path) -> io::Result<File> {
                 .share_mode(0)
                 .custom_flags(FILE_ATTRIBUTE_TEMPORARY | FILE_FLAG_DELETE_ON_CLOSE)
                 .open(path)?;
-            // Attempt to delete the file by-handle. If this fails, do nothing; the file will be
-            // deleted on close anyways.
-            #[cfg(not(feature = "unstable-windows-keep-open-tempfile"))]
-            let _ = delete_open_file(&f);
+            // NOTE: in theory, we could delete the file immediately (we open the file in "unix
+            // semantics" mode) but this seemed to corrupt something in Windows at scale (see #339).
+            // So we just rely on `FILE_FLAG_DELETE_ON_CLOSE`.
             Ok(f)
         },
     )