add test for printing per-byte provenance

src/tools/miri/tests/fail/uninit_buffer_with_provenance.rs

@@ -0,0 +1,32 @@
+//@error-pattern: memory is uninitialized at [0x4..0x8]
+//@normalize-stderr-test: "a[0-9]+" -> "ALLOC"
+#![feature(strict_provenance)]
+
+// Test printing allocations that contain single-byte provenance.
+
+use std::alloc::{alloc, dealloc, Layout};
+use std::mem::{self, MaybeUninit};
+use std::slice::from_raw_parts;
+
+fn byte_with_provenance<T>(val: u8, prov: *const T) -> MaybeUninit<u8> {
+    let ptr = prov.with_addr(val as usize);
+    let bytes: [MaybeUninit<u8>; mem::size_of::<*const ()>()] = unsafe { mem::transmute(ptr) };
+    let lsb = if cfg!(target_endian = "little") { 0 } else { bytes.len() - 1 };
+    bytes[lsb]
+}
+
+fn main() {
+    let layout = Layout::from_size_align(16, 8).unwrap();
+    unsafe {
+        let ptr = alloc(layout);
+        let ptr_raw = ptr.cast::<MaybeUninit<u8>>();
+        *ptr_raw.add(0) = byte_with_provenance(0x42, &42u8);
+        *ptr.add(1) = 0x12;
+        *ptr.add(2) = 0x13;
+        *ptr_raw.add(3) = byte_with_provenance(0x43, &0u8);
+        let slice1 = from_raw_parts(ptr, 8);
+        let slice2 = from_raw_parts(ptr.add(8), 8);
+        drop(slice1.cmp(slice2));
+        dealloc(ptr, layout);
+    }
+}

src/tools/miri/tests/fail/uninit_buffer_with_provenance.stderr

@@ -0,0 +1,32 @@
+error: Undefined Behavior: reading memory at ALLOC[0x0..0x8], but memory is uninitialized at [0x4..0x8], and this operation requires initialized memory
+  --> RUSTLIB/core/src/slice/cmp.rs:LL:CC
+   |
+LL |         let mut order = unsafe { memcmp(left.as_ptr(), right.as_ptr(), len) as isize };
+   |                                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ reading memory at ALLOC[0x0..0x8], but memory is uninitialized at [0x4..0x8], and this operation requires initialized memory
+   |
+   = help: this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior
+   = help: see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information
+   = note: BACKTRACE:
+   = note: inside `<u8 as core::slice::cmp::SliceOrd>::compare` at RUSTLIB/core/src/slice/cmp.rs:LL:CC
+   = note: inside `core::slice::cmp::<impl std::cmp::Ord for [u8]>::cmp` at RUSTLIB/core/src/slice/cmp.rs:LL:CC
+note: inside `main` at $DIR/uninit_buffer_with_provenance.rs:LL:CC
+  --> $DIR/uninit_buffer_with_provenance.rs:LL:CC
+   |
+LL |         drop(slice1.cmp(slice2));
+   |              ^^^^^^^^^^^^^^^^^^
+
+note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
+
+Uninitialized memory occurred at ALLOC[0x4..0x8], in this allocation:
+ALLOC (Rust heap, size: 16, align: 8) {
+    ╾42[ALLOC]<TAG> (1 ptr byte)╼ 12 13 ╾43[ALLOC]<TAG> (1 ptr byte)╼ __ __ __ __ __ __ __ __ __ __ __ __ │ ━..━░░░░░░░░░░░░
+}
+ALLOC (global (static or const), size: 1, align: 1) {
+    2a                                              │ *
+}
+ALLOC (global (static or const), size: 1, align: 1) {
+    00                                              │ .
+}
+
+error: aborting due to previous error
+