diff options
Diffstat (limited to 'src/libcore/ptr/mut_ptr.rs')
| -rw-r--r-- | src/libcore/ptr/mut_ptr.rs | 66 |
1 files changed, 66 insertions, 0 deletions
diff --git a/src/libcore/ptr/mut_ptr.rs b/src/libcore/ptr/mut_ptr.rs index 2bbeb95965e..b86ef5b13b3 100644 --- a/src/libcore/ptr/mut_ptr.rs +++ b/src/libcore/ptr/mut_ptr.rs @@ -273,6 +273,72 @@ impl<T: ?Sized> *mut T { if self.is_null() { None } else { Some(&mut *self) } } + /// Returns whether two pointers are guaranteed to be equal. + /// + /// At runtime this function behaves like `self == other`. + /// However, in some contexts (e.g., compile-time evaluation), + /// it is not always possible to determine equality of two pointers, so this function may + /// spuriously return `false` for pointers that later actually turn out to be equal. + /// But when it returns `true`, the pointers are guaranteed to be equal. + /// + /// This function is the mirror of [`guaranteed_ne`], but not its inverse. There are pointer + /// comparisons for which both functions return `false`. + /// + /// [`guaranteed_ne`]: #method.guaranteed_ne + /// + /// The return value may change depending on the compiler version and unsafe code may not + /// rely on the result of this function for soundness. It is suggested to only use this function + /// for performance optimizations where spurious `false` return values by this function do not + /// affect the outcome, but just the performance. + /// The consequences of using this method to make runtime and compile-time code behave + /// differently have not been explored. This method should not be used to introduce such + /// differences, and it should also not be stabilized before we have a better understanding + /// of this issue. + /// ``` + #[unstable(feature = "const_raw_ptr_comparison", issue = "53020")] + #[rustc_const_unstable(feature = "const_raw_ptr_comparison", issue = "53020")] + #[inline] + #[cfg(not(bootstrap))] + pub const fn guaranteed_eq(self, other: *mut T) -> bool + where + T: Sized, + { + intrinsics::ptr_guaranteed_eq(self as *const _, other as *const _) + } + + /// Returns whether two pointers are guaranteed to be inequal. + /// + /// At runtime this function behaves like `self != other`. + /// However, in some contexts (e.g., compile-time evaluation), + /// it is not always possible to determine the inequality of two pointers, so this function may + /// spuriously return `false` for pointers that later actually turn out to be inequal. + /// But when it returns `true`, the pointers are guaranteed to be inequal. + /// + /// This function is the mirror of [`guaranteed_eq`], but not its inverse. There are pointer + /// comparisons for which both functions return `false`. + /// + /// [`guaranteed_eq`]: #method.guaranteed_eq + /// + /// The return value may change depending on the compiler version and unsafe code may not + /// rely on the result of this function for soundness. It is suggested to only use this function + /// for performance optimizations where spurious `false` return values by this function do not + /// affect the outcome, but just the performance. + /// The consequences of using this method to make runtime and compile-time code behave + /// differently have not been explored. This method should not be used to introduce such + /// differences, and it should also not be stabilized before we have a better understanding + /// of this issue. + /// ``` + #[unstable(feature = "const_raw_ptr_comparison", issue = "53020")] + #[rustc_const_unstable(feature = "const_raw_ptr_comparison", issue = "53020")] + #[inline] + #[cfg(not(bootstrap))] + pub const unsafe fn guaranteed_ne(self, other: *mut T) -> bool + where + T: Sized, + { + intrinsics::ptr_guaranteed_ne(self as *const _, other as *const _) + } + /// Calculates the distance between two pointers. The returned value is in /// units of T: the distance in bytes is divided by `mem::size_of::<T>()`. /// |