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Rollup merge of #103489 - WaffleLapkin:byte_offset_from_you, r=scottmcm

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Make `pointer::byte_offset_from` more generic

As suggested by https://github.com/rust-lang/rust/issues/96283#issuecomment-1288792955 (cc ````@scottmcm),```` make `pointer::byte_offset_from` work on pointers of different types. `byte_offset_from` really doesn't care about pointer types, so this is totally fine and, for example, allows patterns like this:
```rust
ptr::addr_of!(x.b).byte_offset_from(ptr::addr_of!(x))
```

The only possible downside is that this removes the `T` == `U` hint to inference, but I don't think this matter much. I don't think there are a lot of cases where you'd want to use `byte_offset_from` with a pointer of unbounded type (and in such cases you can just specify the type).

````@rustbot```` label +T-libs-api
This commit is contained in:
Matthias Krüger
2022-11-16 08:36:10 +01:00
committed by GitHub
parent 5140bbd102 6279d092c3
commit 91963cc244
2 changed files with 2 additions and 2 deletions
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library/core/src/ptr/const_ptr.rs
+1 -1
View File
@@ -709,7 +709,7 @@ pub fn mask(self, mask: usize) -> *const T {
#[unstable(feature = "pointer_byte_offsets", issue = "96283")]
#[rustc_const_unstable(feature = "const_pointer_byte_offsets", issue = "96283")]
#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
pub const unsafe fn byte_offset_from(self, origin: *const T) -> isize {
pub const unsafe fn byte_offset_from<U: ?Sized>(self, origin: *const U) -> isize {
// SAFETY: the caller must uphold the safety contract for `offset_from`.
unsafe { self.cast::<u8>().offset_from(origin.cast::<u8>()) }
}
library/core/src/ptr/mut_ptr.rs
+1 -1
View File
@@ -889,7 +889,7 @@ pub const fn guaranteed_ne(self, other: *mut T) -> Option<bool>
#[unstable(feature = "pointer_byte_offsets", issue = "96283")]
#[rustc_const_unstable(feature = "const_pointer_byte_offsets", issue = "96283")]
#[cfg_attr(miri, track_caller)] // even without panics, this helps for Miri backtraces
pub const unsafe fn byte_offset_from(self, origin: *const T) -> isize {
pub const unsafe fn byte_offset_from<U: ?Sized>(self, origin: *const U) -> isize {
// SAFETY: the caller must uphold the safety contract for `offset_from`.
unsafe { self.cast::<u8>().offset_from(origin.cast::<u8>()) }
}