Rollup merge of #76662 - RalfJung:lib-test-miri, r=Mark-Simulacrum

Fix liballoc test suite for Miri

Mostly, fix the regression introduced by https://github.com/rust-lang/rust/pull/75207 that caused slices (i.e., references) to be created to invalid memory or memory that has aliasing pointers that we want to keep valid. @dylni  this changes the type of `check_range` to only require the length, not the full reference to the slice, which indeed is all the information this function requires.

Also reduce the size of a test introduced in https://github.com/rust-lang/rust/pull/70793 to make it not take 3 minutes in Miri.

This makes https://github.com/RalfJung/miri-test-libstd work again.

4 files changed, 6 insertions, 7 deletions

diff --git a/library/alloc/src/collections/vec_deque.rs b/library/alloc/src/collections/vec_deque.rs
index 253a3e9f2be..65cfe9a9b49 100644
--- a/library/alloc/src/collections/vec_deque.rs
+++ b/library/alloc/src/collections/vec_deque.rs
@@ -1089,11 +1089,7 @@ impl<T> VecDeque<T> {
     where
         R: RangeBounds<usize>,
     {
-        // SAFETY: This buffer is only used to check the range. It might be partially
-        // uninitialized, but `check_range` needs a contiguous slice.
-        // https://github.com/rust-lang/rust/pull/75207#discussion_r471193682
-        let buffer = unsafe { slice::from_raw_parts(self.ptr(), self.len()) };
-        let Range { start, end } = buffer.check_range(range);
+        let Range { start, end } = slice::check_range(self.len(), range);
         let tail = self.wrap_add(self.tail, start);
         let head = self.wrap_add(self.tail, end);
         (tail, head)
diff --git a/library/alloc/src/slice.rs b/library/alloc/src/slice.rs
index 677bfdd2349..55afdd94f44 100644
--- a/library/alloc/src/slice.rs
+++ b/library/alloc/src/slice.rs
@@ -91,6 +91,8 @@ use crate::borrow::ToOwned;
 use crate::boxed::Box;
 use crate::vec::Vec;
 
+#[unstable(feature = "slice_check_range", issue = "76393")]
+pub use core::slice::check_range;
 #[unstable(feature = "array_chunks", issue = "74985")]
 pub use core::slice::ArrayChunks;
 #[unstable(feature = "array_chunks", issue = "74985")]
diff --git a/library/alloc/src/string.rs b/library/alloc/src/string.rs
index e1724bf3c9a..2b0ce5ede56 100644
--- a/library/alloc/src/string.rs
+++ b/library/alloc/src/string.rs
@@ -49,6 +49,7 @@ use core::iter::{FromIterator, FusedIterator};
 use core::ops::Bound::{Excluded, Included, Unbounded};
 use core::ops::{self, Add, AddAssign, Index, IndexMut, Range, RangeBounds};
 use core::ptr;
+use core::slice;
 use core::str::{lossy, pattern::Pattern};
 
 use crate::borrow::{Cow, ToOwned};
@@ -1506,7 +1507,7 @@ impl String {
         // of the vector version. The data is just plain bytes.
         // Because the range removal happens in Drop, if the Drain iterator is leaked,
         // the removal will not happen.
-        let Range { start, end } = self.as_bytes().check_range(range);
+        let Range { start, end } = slice::check_range(self.len(), range);
         assert!(self.is_char_boundary(start));
         assert!(self.is_char_boundary(end));
 
diff --git a/library/alloc/src/vec.rs b/library/alloc/src/vec.rs
index f9ee2034f31..9dbea0dc9e6 100644
--- a/library/alloc/src/vec.rs
+++ b/library/alloc/src/vec.rs
@@ -1312,7 +1312,7 @@ impl<T> Vec<T> {
         // the hole, and the vector length is restored to the new length.
         //
         let len = self.len();
-        let Range { start, end } = self.check_range(range);
+        let Range { start, end } = slice::check_range(len, range);
 
         unsafe {
             // set self.vec length's to start, to be safe in case Drain is leaked