Use stablilized addr_of macro

Since Rust 1.51.0, support for macro addr_of!() has been stabilized[1],
and this provides a way to get a raw pointer without potential UB in
some cases.

Memoffset alreadly uses the feature at the pre-stablilized stage (the
macro was named as raw_const then). Therefore, switch to use the
stablilized version (and name) and remove the out-dated version, also
remove the related feature gate.

[1]: rust-lang/rust#72279

Signed-off-by: Boqun Feng <boqun.feng@gmail.com>

Author: fbq

Cargo.toml

@@ -18,4 +18,3 @@ doc-comment = "0.3"
 [features]
 default = []
 unstable_const = []
-unstable_raw = []

README.md

@@ -75,6 +75,5 @@ Your crate root: (`lib.rs`/`main.rs`)
 If you intend to use `offset_of!` inside a `const fn`, also add the `const_fn` compiler feature.
 
 ### Raw references ###
-Recent nightlies support [a way to create raw pointers](https://github.com/rust-lang/rust/issues/73394) that avoids creating intermediate safe references.
-`memoffset` can make use of that feature to avoid what is technically Undefined Behavior.
-Use the `unstable_raw` feature to enable this.
+Since Rust 1.51.0, [a way to create raw pointers](https://github.com/rust-lang/rust/issues/73394) that avoids creating intermediate safe references
+has been stablilized, now `memoffset` makes use of that feature to avoid what is technically Undefined Behavior.

src/lib.rs

@@ -67,7 +67,6 @@
         const_raw_ptr_deref,
     )
 )]
-#![cfg_attr(feature = "unstable_raw", feature(raw_ref_macros))]
 
 #[macro_use]
 #[cfg(doctests)]

src/raw_field.rs

@@ -18,26 +18,6 @@
 // OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 // SOFTWARE.
 
-/// `raw_const!`, or just ref-then-cast when that is not available.
-#[cfg(feature = "unstable_raw")]
-#[macro_export]
-#[doc(hidden)]
-macro_rules! _memoffset__raw_const {
-    ($path:expr) => {{
-        $crate::ptr::raw_const!($path)
-    }};
-}
-#[cfg(not(feature = "unstable_raw"))]
-#[macro_export]
-#[doc(hidden)]
-macro_rules! _memoffset__raw_const {
-    ($path:expr) => {{
-        // This is UB because we create an intermediate reference to uninitialized memory.
-        // Nothing we can do about that without `raw_const!` though.
-        &$path as *const _
-    }};
-}
-
 /// Deref-coercion protection macro.
 #[cfg(allow_clippy)]
 #[macro_export]
@@ -88,7 +68,7 @@ macro_rules! raw_field {
         // of the field check we did above.
         #[allow(unused_unsafe)] // for when the macro is used in an unsafe block
         unsafe {
-            _memoffset__raw_const!((*($base as *const $parent)).$field)
+            $crate::ptr::addr_of!((*($base as *const $parent)).$field)
         }
     }};
 }
@@ -109,7 +89,7 @@ macro_rules! raw_field_tuple {
         // of the field check we did above.
         #[allow(unused_unsafe)] // for when the macro is used in an unsafe block
         unsafe {
-            _memoffset__raw_const!((*($base as *const $parent)).$field)
+            $crate::ptr::addr_of!((*($base as *const $parent)).$field)
         }
     }};
 }