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Rollup merge of #67462 - DutchGhost:const_slice_from_raw_parts, r=dtolnay

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Make ptr::slice_from_raw_parts a const fn available under a feature flag

A first step in the direction of https://github.com/rust-lang/rust/issues/67456 .
This makes `ptr::slice_from_raw_parts` and `ptr::slice_from_raw_parts_mut` available as a const fn under a feature flag.
This commit is contained in:
Mazdak Farrokhzad 2019-12-21 15:29:47 +01:00 committed by GitHub
commit f43ced3dbc
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3 changed files with 18 additions and 2 deletions
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6
src/libcore/ptr/mod.rs
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@ -259,7 +259,8 @@ pub(crate) struct FatPtr<T> {
/// ```
#[inline]
#[unstable(feature = "slice_from_raw_parts", reason = "recently added", issue = "36925")]
pub fn slice_from_raw_parts<T>(data: *const T, len: usize) -> *const [T] {
#[rustc_const_unstable(feature = "const_slice_from_raw_parts", issue = "67456")]
pub const fn slice_from_raw_parts<T>(data: *const T, len: usize) -> *const [T] {
unsafe { Repr { raw: FatPtr { data, len } }.rust }
}
@ -275,7 +276,8 @@ pub fn slice_from_raw_parts<T>(data: *const T, len: usize) -> *const [T] {
/// [`from_raw_parts_mut`]: ../../std/slice/fn.from_raw_parts_mut.html
#[inline]
#[unstable(feature = "slice_from_raw_parts", reason = "recently added", issue = "36925")]
pub fn slice_from_raw_parts_mut<T>(data: *mut T, len: usize) -> *mut [T] {
#[rustc_const_unstable(feature = "const_slice_from_raw_parts", issue = "67456")]
pub const fn slice_from_raw_parts_mut<T>(data: *mut T, len: usize) -> *mut [T] {
unsafe { Repr { raw: FatPtr { data, len } }.rust_mut }
}

3
src/libcore/tests/lib.rs
View File

@ -36,6 +36,9 @@
#![feature(iter_is_partitioned)]
#![feature(iter_order_by)]
#![feature(cmp_min_max_by)]
#![feature(slice_from_raw_parts)]
#![feature(const_slice_from_raw_parts)]
#![feature(const_raw_ptr_deref)]
extern crate test;

11
src/libcore/tests/ptr.rs
View File

@ -1,6 +1,17 @@
use core::cell::RefCell;
use core::ptr::*;
#[test]
fn test_const_from_raw_parts() {
const SLICE: &[u8] = &[1, 2, 3, 4];
const FROM_RAW: &[u8] = unsafe { &*slice_from_raw_parts(SLICE.as_ptr(), SLICE.len()) };
assert_eq!(SLICE, FROM_RAW);
let slice = &[1, 2, 3, 4, 5];
let from_raw = unsafe { &*slice_from_raw_parts(slice.as_ptr(), 2) } ;
assert_eq!(&slice[..2], from_raw);
}
#[test]
fn test() {
unsafe {