From b85b2a783b813def53b2a7f0c9b53fed119e2338 Mon Sep 17 00:00:00 2001 From: Alex Crichton Date: Sun, 28 Jan 2024 11:24:27 -0800 Subject: [PATCH] std: Update documentation of seek_write on Windows Currently the documentation of `FileExt::seek_write` on Windows indicates that writes beyond the end of the file leave intermediate bytes uninitialized. This commentary dates back to the original inclusion of these functions in #35704 (wow blast from the past!). At the time the functionality here was implemented using `WriteFile`, but nowadays the `NtWriteFile` method is used instead. The documentation for `NtWriteFile` explicitly states: > If Length and ByteOffset specify a write operation past the current > end-of-file mark, NtWriteFile automatically extends the file and updates > the end-of-file mark; any bytes that are not explicitly written between > such old and new end-of-file marks are defined to be zero. This commentary has had a downstream impact in the `system-interface` crate where it tries to handle this by explicitly writing zeros, but I don't believe that's necessary any more. I'm sending a PR upstream here to avoid future confusion and codify that zeros are written in the intermediate bytes matching what Windows currently provides. --- library/std/src/os/windows/fs.rs | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/library/std/src/os/windows/fs.rs b/library/std/src/os/windows/fs.rs index 1b013d1c154c9..e9d7a13e9d5b2 100644 --- a/library/std/src/os/windows/fs.rs +++ b/library/std/src/os/windows/fs.rs @@ -59,7 +59,7 @@ pub trait FileExt { /// function, it is set to the end of the write. /// /// When writing beyond the end of the file, the file is appropriately - /// extended and the intermediate bytes are left uninitialized. + /// extended and the intermediate bytes are set to zero. /// /// Note that similar to `File::write`, it is not an error to return a /// short write. When returning from such a short write, the file pointer