Merge pull request #58 from mkroening/must-use

fix: add `#[must_use]` to volatile types, `read`, and `as_raw_ptr`

Author: phil-opp

src/volatile_ptr/mod.rs

@@ -24,6 +24,7 @@ mod very_unstable;
 /// to `ReadWrite`, which allows all operations.
 ///
 /// The size of this struct is the same as the size of the contained reference.
+#[must_use]
 #[repr(transparent)]
 pub struct VolatilePtr<'a, T, A = ReadWrite>
 where

src/volatile_ptr/operations.rs

@@ -82,6 +82,7 @@ where
     /// };
     /// assert_eq!(pointer.read(), 42);
     /// ```
+    #[must_use]
     pub fn read(self) -> T
     where
         T: Copy,
@@ -154,6 +155,7 @@ where
     ///
     /// assert_eq!(unsafe { *unwrapped }, 50); // non volatile access, be careful!
     /// ```
+    #[must_use]
     pub fn as_raw_ptr(self) -> NonNull<T> {
         self.pointer
     }
@@ -191,10 +193,12 @@ where
     ///
     /// // DON'T DO THIS:
     /// let mut readout = 0;
-    /// unsafe { volatile.map(|value| {
-    ///    readout = *value.as_ptr(); // non-volatile read, might lead to bugs
-    ///    value
-    /// })};
+    /// unsafe {
+    ///     let _ = volatile.map(|value| {
+    ///         readout = *value.as_ptr(); // non-volatile read, might lead to bugs
+    ///         value
+    ///     });
+    /// };
     /// ```
     ///
     /// ## Safety

src/volatile_ptr/tests.rs

@@ -128,7 +128,7 @@ fn test_slice() {
 fn test_bounds_check_1() {
     let val: &mut [u32] = &mut [1, 2, 3];
     let volatile = unsafe { VolatilePtr::new(NonNull::from(val)) };
-    volatile.index(3);
+    let _ = volatile.index(3);
 }
 
 #[cfg(feature = "unstable")]
@@ -138,7 +138,7 @@ fn test_bounds_check_2() {
     let val: &mut [u32] = &mut [1, 2, 3];
     let volatile = unsafe { VolatilePtr::new(NonNull::from(val)) };
     #[allow(clippy::reversed_empty_ranges)]
-    volatile.index(2..1);
+    let _ = volatile.index(2..1);
 }
 
 #[cfg(feature = "unstable")]
@@ -147,7 +147,7 @@ fn test_bounds_check_2() {
 fn test_bounds_check_3() {
     let val: &mut [u32] = &mut [1, 2, 3];
     let volatile = unsafe { VolatilePtr::new(NonNull::from(val)) };
-    volatile.index(4..); // `3..` is is still ok (see next test)
+    let _ = volatile.index(4..); // `3..` is is still ok (see next test)
 }
 
 #[cfg(feature = "unstable")]
@@ -164,7 +164,7 @@ fn test_bounds_check_4() {
 fn test_bounds_check_5() {
     let val: &mut [u32] = &mut [1, 2, 3];
     let volatile = unsafe { VolatilePtr::new(NonNull::from(val)) };
-    volatile.index(..4);
+    let _ = volatile.index(..4);
 }
 
 #[cfg(feature = "unstable")]

src/volatile_ref.rs

@@ -25,6 +25,7 @@ use core::{cmp::Ordering, fmt, hash, marker::PhantomData, ptr::NonNull};
 /// to `ReadWrite`, which allows all operations.
 ///
 /// The size of this struct is the same as the size of the contained reference.
+#[must_use]
 #[repr(transparent)]
 pub struct VolatileRef<'a, T, A = ReadWrite>
 where