uefi: Add ptr_meta dependency

The `ptr_meta` crate (https://docs.rs/ptr_meta) is a polyfill for the unstable
[`ptr_metadata`](rust-lang/rust#81513) feature on
stable Rust. This allows us to drop use of an unstable feature with fairly
minimal code changes; mostly just adding a derive for the `Pointee` type on some
DST structs.

Author: nicholasbishop

CHANGELOG.md

@@ -29,6 +29,8 @@
   `impl Iterator` which simplifies usage.
 - `GraphicsOutput::modes()` now returns `ModesIter` instead of `impl Iterator`
    which simplifies usage.
+- Use of the unstable `ptr_metadata` feature has been replaced with a dependency
+  on the [`ptr_meta`](https://docs.rs/ptr_meta) crate.
 
 ### Removed
 

uefi/Cargo.toml

@@ -25,6 +25,7 @@ unstable = []
 [dependencies]
 bitflags = "1.3.1"
 log = { version = "0.4.5", default-features = false }
+ptr_meta = { version = "0.2.0", default-features = false }
 ucs2 = "0.3.2"
 uefi-macros = "0.9.0"
 

uefi/src/lib.rs

@@ -60,7 +60,6 @@
 
 #![feature(abi_efiapi)]
 #![feature(maybe_uninit_slice)]
-#![feature(ptr_metadata)]
 #![cfg_attr(feature = "alloc", feature(vec_into_raw_parts))]
 #![cfg_attr(feature = "unstable", feature(error_in_core))]
 #![cfg_attr(all(feature = "unstable", feature = "alloc"), feature(allocator_api))]

uefi/src/proto/device_path/build.rs

@@ -9,7 +9,6 @@ pub use uefi::proto::device_path::device_path_gen::build::*;
 
 use crate::proto::device_path::{DevicePath, DevicePathNode};
 use core::mem::MaybeUninit;
-use core::ptr;
 
 #[cfg(feature = "alloc")]
 use alloc::vec::Vec;
@@ -139,7 +138,7 @@ impl<'a> DevicePathBuilder<'a> {
         };
 
         let ptr: *const () = data.as_ptr().cast();
-        Ok(unsafe { &*ptr::from_raw_parts(ptr, data.len()) })
+        Ok(unsafe { &*ptr_meta::from_raw_parts(ptr, data.len()) })
     }
 }