Rollup merge of #130342 - RalfJung:slice-idx-overflow, r=saethlin

interpret, miri: fix dealing with overflow during slice indexing and allocation

This is mostly to fix https://github.com/rust-lang/rust/issues/130284.

I then realized we're using somewhat sketchy arguments for a similar multiplication in `copy`/`copy_nonoverlapping`/`write_bytes`,  so I made them all share the same function that checks exactly the right thing. (The intrinsics would previously fail on allocations larger than `1 << 47` bytes... which are theoretically possible maybe? Anyway it seems conceptually wrong to use any other bound than `isize::MAX` here.)

2 files changed, 22 insertions, 0 deletions

diff --git a/tests/ui/consts/slice-index-overflow-issue-130284.rs b/tests/ui/consts/slice-index-overflow-issue-130284.rs
new file mode 100644
index 00000000000..29900908256
--- /dev/null
+++ b/tests/ui/consts/slice-index-overflow-issue-130284.rs
@@ -0,0 +1,13 @@
+const C: () = {
+    let value = [1, 2];
+    let ptr = value.as_ptr().wrapping_add(2);
+    let fat = std::ptr::slice_from_raw_parts(ptr, usize::MAX);
+    unsafe {
+        // This used to ICE, but it should just report UB.
+        let _ice = (*fat)[usize::MAX - 1];
+        //~^ERROR: constant value failed
+        //~| overflow
+    }
+};
+
+fn main() {}
diff --git a/tests/ui/consts/slice-index-overflow-issue-130284.stderr b/tests/ui/consts/slice-index-overflow-issue-130284.stderr
new file mode 100644
index 00000000000..e3e676c8949
--- /dev/null
+++ b/tests/ui/consts/slice-index-overflow-issue-130284.stderr
@@ -0,0 +1,9 @@
+error[E0080]: evaluation of constant value failed
+  --> $DIR/slice-index-overflow-issue-130284.rs:7:20
+   |
+LL |         let _ice = (*fat)[usize::MAX - 1];
+   |                    ^^^^^^^^^^^^^^^^^^^^^^ overflowing pointer arithmetic: the total offset in bytes does not fit in an `isize`
+
+error: aborting due to 1 previous error
+
+For more information about this error, try `rustc --explain E0080`.