fsext.rs: use type inference fsid_t / __fsid_t

Ecordonnier · Ecordonnier · commit 8f17113d61a0 · 2025-03-17T11:05:02.000+01:00
Commit 2a0d58d (part of #3396 which contains a description of the changes) changed this line from libc::fsid_t to nix::sys::statfs::fsid_t. The pull-request description at #3396 indicates that this was done in order to fix the android build, and indeed using a cast to nix::sys::statfs::fsid_t takes advantage of the definition of nix::sys::statfs::fsid_t which abstracts away the different name on Android: ``` /// Identifies a mounted file system #[cfg(target_os = "android")] pub type fsid_t = libc::__fsid_t; /// Identifies a mounted file system #[cfg(not(target_os = "android"))] pub type fsid_t = libc::fsid_t; ``` This cast works as long as the libc version used by nix is the same than the libc version used by coreutils. This cast becomes invalid when using a local libc version for local debugging, and changing Cargo.toml to point to it: ``` -libc = "0.2.153" +libc = { path = "../path/to/libc" } ``` The cast becomes invalid because self.f_fsid is of type libc::fsid_t (local version of libc), whereas nix::sys::statfs::fsid_t still uses the libc version downloaded by cargo from crates.io in this case. I was getting this error: ``` coreutils$ cargo build Compiling libc v0.2.171 (/home/ecordonnier/dev/libc) Compiling uucore v0.0.30 (/home/ecordonnier/dev/coreutils/src/uucore) error[E0606]: casting `&libc::fsid_t` as `*const nix::libc::fsid_t` is invalid --> src/uucore/src/lib/features/fsext.rs:816:25 | 816 | unsafe { &*(&self.f_fsid as *const nix::sys::statfs::fsid_t as *const [u32; 2]) }; | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ For more information about this error, try `rustc --explain E0606`. error: could not compile `uucore` (lib) due to 1 previous error ``` Let's rather use type inference to deal with libc::fsid_t vs libc::__fsid_t. Signed-off-by: Etienne Cordonnier <ecordonnier@snap.com>
diff --git a/src/uucore/src/lib/features/fsext.rs b/src/uucore/src/lib/features/fsext.rs
@@ -812,8 +812,9 @@ impl FsMeta for StatFs {
         target_os = "openbsd"
     ))]
     fn fsid(&self) -> u64 {
-        let f_fsid: &[u32; 2] =
-            unsafe { &*(&self.f_fsid as *const nix::sys::statfs::fsid_t as *const [u32; 2]) };
+        // Use type inference to determine the type of f_fsid
+        // (libc::__fsid_t on Android, libc::fsid_t on other platforms)
+        let f_fsid: &[u32; 2] = unsafe { &*(&self.f_fsid as *const _ as *const [u32; 2]) };
         ((u64::from(f_fsid[0])) << 32) | u64::from(f_fsid[1])
     }
     #[cfg(not(any(
