rustup

Author: RalfJung

rust-version

@@ -1 +1 @@
-20ffea6938b5839c390252e07940b99e3b6a889a
+75b7e52e92c3b00fc891b47f5b2efdff0a2be55a

src/lib.rs

@@ -116,4 +116,5 @@ pub const MIRI_DEFAULT_ARGS: &[&str] = &[
     "-Zmir-opt-level=0",
     "--cfg=miri",
     "-Cdebug-assertions=on",
+    "-Zextra-const-ub-checks",
 ];

tests/fail/const-ub-checks.rs

@@ -0,0 +1,11 @@
+#![feature(const_ptr_read)]
+
+const UNALIGNED_READ: () = unsafe {
+    let x = &[0u8; 4];
+    let ptr = x.as_ptr().cast::<u32>();
+    ptr.read(); //~ERROR: evaluation of constant value failed
+};
+
+fn main() {
+    let _x = UNALIGNED_READ;
+}

tests/fail/const-ub-checks.stderr

@@ -0,0 +1,9 @@
+error[E0080]: evaluation of constant value failed
+  --> $DIR/const-ub-checks.rs:LL:CC
+   |
+LL |     ptr.read();
+   |     ^^^^^^^^^^ accessing memory with alignment ALIGN, but alignment ALIGN is required
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0080`.