use offset_of in 1.75

Author: tesuji

.github/workflows/ci.yml

@@ -134,7 +134,7 @@ jobs:
       - run: |
           rustup toolchain install nightly -c clippy
           rustup default nightly
-      - run: cargo clippy --all-targets --all-features -- -Dwarnings
+      - run: cargo clippy --all-targets --all-features -- -Dwarnings -A clippy::assertions-on-constants
 
 
   # Use static analyzer Rudra <https://github.com/sslab-gatech/Rudra>.

Cargo.toml

@@ -18,6 +18,8 @@ description = "library for working with NTFS junctions"
 
 [features]
 default = ["unstable_admin"]
+# Flag for trying out new rust language features
+nightly = []
 # # Unstable flag
 #
 # Enable the SE_BACKUP_NAME and SE_RESTORE_NAME access privileges.

src/internals/c.rs

@@ -1,11 +1,13 @@
 #![allow(non_snake_case)]
 
+// MSRV(1.75): use `offset_of!` when stabilized.
+#[cfg(feature = "nightly")]
+mod nightly;
+
 use std::alloc::Layout;
-use std::mem::size_of;
 use std::os::raw::{c_ulong, c_ushort};
 use std::os::windows::io::RawHandle;
 
-use windows_sys::core::GUID;
 pub use windows_sys::Win32::Foundation::{
     CloseHandle, GetLastError, SetLastError, ERROR_INSUFFICIENT_BUFFER, FALSE, GENERIC_READ, GENERIC_WRITE, HANDLE,
     INVALID_HANDLE_VALUE,
@@ -39,26 +41,18 @@ const _: () = {
 };
 
 // NOTE: to use `size_of` operator, below structs should be packed.
-// TODO: use `offset_of!` when stabilized.
 /// Reparse Data Buffer header size
 pub const REPARSE_DATA_BUFFER_HEADER_SIZE: u16 = 8;
 /// Reparse GUID Data Buffer header size
 pub const REPARSE_GUID_DATA_BUFFER_HEADER_SIZE: u16 = 24;
 /// MountPointReparseBuffer header size
 pub const MOUNT_POINT_REPARSE_BUFFER_HEADER_SIZE: u16 = 8;
 
-// Safety checks for correct header size due to the lacks of `offset_of!`.
-// MSRV(1.57): for const assert!
-#[allow(clippy::no_effect)] // noisy clippy lints
+#[cfg(feature = "nightly")]
 const _: () = {
-    let rdb_header_size = size_of::<c_ulong>() + size_of::<c_ushort>() * 2;
-    [(); 1][!(rdb_header_size == REPARSE_DATA_BUFFER_HEADER_SIZE as _) as usize];
-
-    let mprb_header_size = size_of::<c_ushort>() * 4;
-    [(); 1][!(mprb_header_size == MOUNT_POINT_REPARSE_BUFFER_HEADER_SIZE as _) as usize];
-
-    let rgdb_header_size = size_of::<c_ulong>() + size_of::<c_ushort>() * 2 + size_of::<GUID>();
-    [(); 1][!(rgdb_header_size == REPARSE_GUID_DATA_BUFFER_HEADER_SIZE as _) as usize];
+    assert!(REPARSE_DATA_BUFFER_HEADER_SIZE == nightly::REPARSE_DATA_BUFFER_HEADER_SIZE);
+    assert!(REPARSE_GUID_DATA_BUFFER_HEADER_SIZE == nightly::REPARSE_GUID_DATA_BUFFER_HEADER_SIZE);
+    assert!(MOUNT_POINT_REPARSE_BUFFER_HEADER_SIZE == nightly::MOUNT_POINT_REPARSE_BUFFER_HEADER_SIZE);
 };
 
 type VarLenArr<T> = [T; 1];

src/internals/c/nightly.rs

@@ -0,0 +1,11 @@
+#![allow(unused)]
+
+use std::mem::offset_of;
+
+/// Reparse Data Buffer header size
+pub const REPARSE_DATA_BUFFER_HEADER_SIZE: u16 = offset_of!(super::REPARSE_DATA_BUFFER, ReparseBuffer) as u16;
+/// Reparse GUID Data Buffer header size
+pub const REPARSE_GUID_DATA_BUFFER_HEADER_SIZE: u16 =
+    offset_of!(super::REPARSE_GUID_DATA_BUFFER, GenericReparseBuffer) as u16;
+/// MountPointReparseBuffer header size
+pub const MOUNT_POINT_REPARSE_BUFFER_HEADER_SIZE: u16 = offset_of!(super::MountPointReparseBuffer, PathBuffer) as u16;