Report the range of uninit bytes in CTFE errors

oli-obk · oli-obk · commit 98f175b0a8f8 · 2025-07-17T20:00:51.000Z
diff --git a/tests/fail-dep/concurrency/libc_pthread_cond_double_destroy.rs b/tests/fail-dep/concurrency/libc_pthread_cond_double_destroy.rs
@@ -15,6 +15,6 @@ fn main() {
         libc::pthread_cond_destroy(cond.as_mut_ptr());
 
         libc::pthread_cond_destroy(cond.as_mut_ptr());
-        //~^ ERROR: Undefined Behavior: using uninitialized data, but this operation requires initialized memory
+        //~^ ERROR: /Undefined Behavior: reading memory .*, but memory is uninitialized/
     }
 }
diff --git a/tests/fail-dep/concurrency/libc_pthread_cond_double_destroy.stderr b/tests/fail-dep/concurrency/libc_pthread_cond_double_destroy.stderr
@@ -1,4 +1,4 @@
-error: Undefined Behavior: using uninitialized data, but this operation requires initialized memory
+error: Undefined Behavior: reading memory at ALLOC[0x0..0x4], but memory is uninitialized at [0x0..0x4], and this operation requires initialized memory
   --> tests/fail-dep/concurrency/libc_pthread_cond_double_destroy.rs:LL:CC
    |
 LL |         libc::pthread_cond_destroy(cond.as_mut_ptr());
@@ -9,6 +9,13 @@ LL |         libc::pthread_cond_destroy(cond.as_mut_ptr());
    = note: BACKTRACE:
    = note: inside `main` at tests/fail-dep/concurrency/libc_pthread_cond_double_destroy.rs:LL:CC
 
+Uninitialized memory occurred at ALLOC[0x0..0x4], in this allocation:
+ALLOC (stack variable, size: 48, align: 8) {
+    0x00 │ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ │ ░░░░░░░░░░░░░░░░
+    0x10 │ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ │ ░░░░░░░░░░░░░░░░
+    0x20 │ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ │ ░░░░░░░░░░░░░░░░
+}
+
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
 
 error: aborting due to 1 previous error
diff --git a/tests/fail-dep/concurrency/libc_pthread_condattr_double_destroy.rs b/tests/fail-dep/concurrency/libc_pthread_condattr_double_destroy.rs
@@ -13,6 +13,6 @@ fn main() {
         libc::pthread_condattr_destroy(attr.as_mut_ptr());
 
         libc::pthread_condattr_destroy(attr.as_mut_ptr());
-        //~^ ERROR: Undefined Behavior: using uninitialized data, but this operation requires initialized memory
+        //~^ ERROR: /Undefined Behavior: reading memory .*, but memory is uninitialized/
     }
 }
diff --git a/tests/fail-dep/concurrency/libc_pthread_condattr_double_destroy.stderr b/tests/fail-dep/concurrency/libc_pthread_condattr_double_destroy.stderr
@@ -1,4 +1,4 @@
-error: Undefined Behavior: using uninitialized data, but this operation requires initialized memory
+error: Undefined Behavior: reading memory at ALLOC[0x0..0x4], but memory is uninitialized at [0x0..0x4], and this operation requires initialized memory
   --> tests/fail-dep/concurrency/libc_pthread_condattr_double_destroy.rs:LL:CC
    |
 LL |         libc::pthread_condattr_destroy(attr.as_mut_ptr());
@@ -9,6 +9,11 @@ LL |         libc::pthread_condattr_destroy(attr.as_mut_ptr());
    = note: BACKTRACE:
    = note: inside `main` at tests/fail-dep/concurrency/libc_pthread_condattr_double_destroy.rs:LL:CC
 
+Uninitialized memory occurred at ALLOC[0x0..0x4], in this allocation:
+ALLOC (stack variable, size: 4, align: 4) {
+    __ __ __ __                                     │ ░░░░
+}
+
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
 
 error: aborting due to 1 previous error
diff --git a/tests/fail-dep/concurrency/libc_pthread_mutex_double_destroy.rs b/tests/fail-dep/concurrency/libc_pthread_mutex_double_destroy.rs
@@ -16,6 +16,6 @@ fn main() {
         libc::pthread_mutex_destroy(mutex.as_mut_ptr());
 
         libc::pthread_mutex_destroy(mutex.as_mut_ptr());
-        //~^ ERROR: Undefined Behavior: using uninitialized data, but this operation requires initialized memory
+        //~^ ERROR: /Undefined Behavior: reading memory .*, but memory is uninitialized/
     }
 }
diff --git a/tests/fail-dep/concurrency/libc_pthread_mutex_double_destroy.stderr b/tests/fail-dep/concurrency/libc_pthread_mutex_double_destroy.stderr
@@ -1,4 +1,4 @@
-error: Undefined Behavior: using uninitialized data, but this operation requires initialized memory
+error: Undefined Behavior: reading memory at ALLOC[0x0..0x4], but memory is uninitialized at [0x0..0x4], and this operation requires initialized memory
   --> tests/fail-dep/concurrency/libc_pthread_mutex_double_destroy.rs:LL:CC
    |
 LL |         libc::pthread_mutex_destroy(mutex.as_mut_ptr());
@@ -9,6 +9,13 @@ LL |         libc::pthread_mutex_destroy(mutex.as_mut_ptr());
    = note: BACKTRACE:
    = note: inside `main` at tests/fail-dep/concurrency/libc_pthread_mutex_double_destroy.rs:LL:CC
 
+Uninitialized memory occurred at ALLOC[0x0..0x4], in this allocation:
+ALLOC (stack variable, size: 40, align: 8) {
+    0x00 │ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ │ ░░░░░░░░░░░░░░░░
+    0x10 │ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ │ ░░░░░░░░░░░░░░░░
+    0x20 │ __ __ __ __ __ __ __ __                         │ ░░░░░░░░
+}
+
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
 
 error: aborting due to 1 previous error
diff --git a/tests/fail-dep/concurrency/libc_pthread_mutexattr_double_destroy.rs b/tests/fail-dep/concurrency/libc_pthread_mutexattr_double_destroy.rs
@@ -12,6 +12,6 @@ fn main() {
         libc::pthread_mutexattr_destroy(attr.as_mut_ptr());
 
         libc::pthread_mutexattr_destroy(attr.as_mut_ptr());
-        //~^ ERROR: Undefined Behavior: using uninitialized data, but this operation requires initialized memory
+        //~^ ERROR: /Undefined Behavior: reading memory .*, but memory is uninitialized/
     }
 }
diff --git a/tests/fail-dep/concurrency/libc_pthread_mutexattr_double_destroy.stderr b/tests/fail-dep/concurrency/libc_pthread_mutexattr_double_destroy.stderr
@@ -1,4 +1,4 @@
-error: Undefined Behavior: using uninitialized data, but this operation requires initialized memory
+error: Undefined Behavior: reading memory at ALLOC[0x0..0x4], but memory is uninitialized at [0x0..0x4], and this operation requires initialized memory
   --> tests/fail-dep/concurrency/libc_pthread_mutexattr_double_destroy.rs:LL:CC
    |
 LL |         libc::pthread_mutexattr_destroy(attr.as_mut_ptr());
@@ -9,6 +9,11 @@ LL |         libc::pthread_mutexattr_destroy(attr.as_mut_ptr());
    = note: BACKTRACE:
    = note: inside `main` at tests/fail-dep/concurrency/libc_pthread_mutexattr_double_destroy.rs:LL:CC
 
+Uninitialized memory occurred at ALLOC[0x0..0x4], in this allocation:
+ALLOC (stack variable, size: 4, align: 4) {
+    __ __ __ __                                     │ ░░░░
+}
+
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
 
 error: aborting due to 1 previous error
diff --git a/tests/fail-dep/concurrency/libc_pthread_rwlock_double_destroy.rs b/tests/fail-dep/concurrency/libc_pthread_rwlock_double_destroy.rs
@@ -9,6 +9,6 @@ fn main() {
         libc::pthread_rwlock_destroy(&mut lock);
 
         libc::pthread_rwlock_destroy(&mut lock);
-        //~^ ERROR: Undefined Behavior: using uninitialized data, but this operation requires initialized memory
+        //~^ ERROR: /Undefined Behavior: reading memory .*, but memory is uninitialized/
     }
 }
diff --git a/tests/fail-dep/concurrency/libc_pthread_rwlock_double_destroy.stderr b/tests/fail-dep/concurrency/libc_pthread_rwlock_double_destroy.stderr
@@ -1,4 +1,4 @@
-error: Undefined Behavior: using uninitialized data, but this operation requires initialized memory
+error: Undefined Behavior: reading memory at ALLOC[0x0..0x4], but memory is uninitialized at [0x0..0x4], and this operation requires initialized memory
   --> tests/fail-dep/concurrency/libc_pthread_rwlock_double_destroy.rs:LL:CC
    |
 LL |         libc::pthread_rwlock_destroy(&mut lock);
@@ -9,6 +9,14 @@ LL |         libc::pthread_rwlock_destroy(&mut lock);
    = note: BACKTRACE:
    = note: inside `main` at tests/fail-dep/concurrency/libc_pthread_rwlock_double_destroy.rs:LL:CC
 
+Uninitialized memory occurred at ALLOC[0x0..0x4], in this allocation:
+ALLOC (stack variable, size: 56, align: 8) {
+    0x00 │ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ │ ░░░░░░░░░░░░░░░░
+    0x10 │ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ │ ░░░░░░░░░░░░░░░░
+    0x20 │ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ │ ░░░░░░░░░░░░░░░░
+    0x30 │ __ __ __ __ __ __ __ __                         │ ░░░░░░░░
+}
+
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
 
 error: aborting due to 1 previous error
diff --git a/tests/fail/function_calls/arg_inplace_observe_after.stderr b/tests/fail/function_calls/arg_inplace_observe_after.stderr
@@ -1,4 +1,4 @@
-error: Undefined Behavior: using uninitialized data, but this operation requires initialized memory
+error: Undefined Behavior: reading memory at ALLOC[0x0..0x4], but memory is uninitialized at [0x0..0x4], and this operation requires initialized memory
   --> tests/fail/function_calls/arg_inplace_observe_after.rs:LL:CC
    |
 LL |             _observe = non_copy.0;
@@ -9,6 +9,11 @@ LL |             _observe = non_copy.0;
    = note: BACKTRACE:
    = note: inside `main` at tests/fail/function_calls/arg_inplace_observe_after.rs:LL:CC
 
+Uninitialized memory occurred at ALLOC[0x0..0x4], in this allocation:
+ALLOC (stack variable, size: 4, align: 4) {
+    __ __ __ __                                     │ ░░░░
+}
+
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
 
 error: aborting due to 1 previous error
diff --git a/tests/fail/function_calls/arg_inplace_observe_during.none.stderr b/tests/fail/function_calls/arg_inplace_observe_during.none.stderr
@@ -1,4 +1,4 @@
-error: Undefined Behavior: using uninitialized data, but this operation requires initialized memory
+error: Undefined Behavior: reading memory at ALLOC[0x0..0x4], but memory is uninitialized at [0x0..0x4], and this operation requires initialized memory
   --> tests/fail/function_calls/arg_inplace_observe_during.rs:LL:CC
    |
 LL |     unsafe { ptr.read() };
@@ -14,6 +14,11 @@ note: inside `main`
 LL |             Call(_unit = change_arg(Move(*ptr), ptr), ReturnTo(after_call), UnwindContinue())
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
+Uninitialized memory occurred at ALLOC[0x0..0x4], in this allocation:
+ALLOC (stack variable, size: 4, align: 4) {
+    __ __ __ __                                     │ ░░░░
+}
+
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
 
 error: aborting due to 1 previous error
diff --git a/tests/fail/function_calls/return_pointer_aliasing_read.none.stderr b/tests/fail/function_calls/return_pointer_aliasing_read.none.stderr
@@ -1,4 +1,4 @@
-error: Undefined Behavior: using uninitialized data, but this operation requires initialized memory
+error: Undefined Behavior: reading memory at ALLOC[0x0..0x4], but memory is uninitialized at [0x0..0x4], and this operation requires initialized memory
   --> tests/fail/function_calls/return_pointer_aliasing_read.rs:LL:CC
    |
 LL |     unsafe { ptr.read() };
@@ -14,6 +14,11 @@ note: inside `main`
 LL |             Call(*ptr = myfun(ptr), ReturnTo(after_call), UnwindContinue())
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
+Uninitialized memory occurred at ALLOC[0x0..0x4], in this allocation:
+ALLOC (stack variable, size: 4, align: 4) {
+    __ __ __ __                                     │ ░░░░
+}
+
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
 
 error: aborting due to 1 previous error
diff --git a/tests/fail/function_calls/return_pointer_on_unwind.stderr b/tests/fail/function_calls/return_pointer_on_unwind.stderr
@@ -3,7 +3,7 @@ thread 'main' panicked at tests/fail/function_calls/return_pointer_on_unwind.rs:
 explicit panic
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
 note: in Miri, you may have to set `MIRIFLAGS=-Zmiri-env-forward=RUST_BACKTRACE` for the environment variable to have an effect
-error: Undefined Behavior: using uninitialized data, but this operation requires initialized memory
+error: Undefined Behavior: reading memory at ALLOC[0x0..0x4], but memory is uninitialized at [0x0..0x4], and this operation requires initialized memory
   --> tests/fail/function_calls/return_pointer_on_unwind.rs:LL:CC
    |
 LL |     dbg!(x.0);
@@ -15,6 +15,19 @@ LL |     dbg!(x.0);
    = note: inside `main` at RUSTLIB/std/src/macros.rs:LL:CC
    = note: this error originates in the macro `dbg` (in Nightly builds, run with -Z macro-backtrace for more info)
 
+Uninitialized memory occurred at ALLOC[0x0..0x4], in this allocation:
+ALLOC (stack variable, size: 132, align: 4) {
+    0x00 │ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ │ ░░░░░░░░░░░░░░░░
+    0x10 │ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ │ ░░░░░░░░░░░░░░░░
+    0x20 │ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ │ ░░░░░░░░░░░░░░░░
+    0x30 │ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ │ ░░░░░░░░░░░░░░░░
+    0x40 │ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ │ ░░░░░░░░░░░░░░░░
+    0x50 │ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ │ ░░░░░░░░░░░░░░░░
+    0x60 │ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ │ ░░░░░░░░░░░░░░░░
+    0x70 │ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ │ ░░░░░░░░░░░░░░░░
+    0x80 │ __ __ __ __                                     │ ░░░░
+}
+
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
 
 error: aborting due to 1 previous error
diff --git a/tests/fail/intrinsics/ptr_metadata_uninit_slice_data.rs b/tests/fail/intrinsics/ptr_metadata_uninit_slice_data.rs
@@ -9,7 +9,7 @@ use std::intrinsics::mir::*;
 pub unsafe fn deref_meta(p: *const *const [i32]) -> usize {
     mir! {
         {
-            RET = PtrMetadata(*p); //~ ERROR: Undefined Behavior: using uninitialized data
+            RET = PtrMetadata(*p); //~ ERROR: /Undefined Behavior: .*, but memory is uninitialized/
             Return()
         }
     }
diff --git a/tests/fail/intrinsics/ptr_metadata_uninit_slice_data.stderr b/tests/fail/intrinsics/ptr_metadata_uninit_slice_data.stderr
@@ -1,4 +1,4 @@
-error: Undefined Behavior: using uninitialized data, but this operation requires initialized memory
+error: Undefined Behavior: reading memory at ALLOC[0x0..0x8], but memory is uninitialized at [0x0..0x8], and this operation requires initialized memory
   --> tests/fail/intrinsics/ptr_metadata_uninit_slice_data.rs:LL:CC
    |
 LL |             RET = PtrMetadata(*p);
@@ -14,6 +14,11 @@ note: inside `main`
 LL |         let _meta = deref_meta(p.as_ptr().cast());
    |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
+Uninitialized memory occurred at ALLOC[0x0..0x8], in this allocation:
+ALLOC (stack variable, size: 16, align: 8) {
+    __ __ __ __ __ __ __ __ 04 00 00 00 00 00 00 00 │ ░░░░░░░░........
+}
+
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
 
 error: aborting due to 1 previous error
diff --git a/tests/fail/intrinsics/ptr_metadata_uninit_slice_len.rs b/tests/fail/intrinsics/ptr_metadata_uninit_slice_len.rs
@@ -9,7 +9,7 @@ use std::intrinsics::mir::*;
 pub unsafe fn deref_meta(p: *const *const [i32]) -> usize {
     mir! {
         {
-            RET = PtrMetadata(*p); //~ ERROR: Undefined Behavior: using uninitialized data
+            RET = PtrMetadata(*p); //~ ERROR: /Undefined Behavior: .*, but memory is uninitialized/
             Return()
         }
     }
diff --git a/tests/fail/intrinsics/ptr_metadata_uninit_slice_len.stderr b/tests/fail/intrinsics/ptr_metadata_uninit_slice_len.stderr
@@ -12,7 +12,7 @@ LL |         (*p.as_mut_ptr().cast::<[*const i32; 2]>())[0] = 4 as *const i32;
    = note: BACKTRACE:
    = note: inside `main` at tests/fail/intrinsics/ptr_metadata_uninit_slice_len.rs:LL:CC
 
-error: Undefined Behavior: using uninitialized data, but this operation requires initialized memory
+error: Undefined Behavior: reading memory at ALLOC[0x8..0x10], but memory is uninitialized at [0x8..0x10], and this operation requires initialized memory
   --> tests/fail/intrinsics/ptr_metadata_uninit_slice_len.rs:LL:CC
    |
 LL |             RET = PtrMetadata(*p);
@@ -28,6 +28,11 @@ note: inside `main`
 LL |         let _meta = deref_meta(p.as_ptr().cast());
    |                     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
+Uninitialized memory occurred at ALLOC[0x8..0x10], in this allocation:
+ALLOC (stack variable, size: 16, align: 8) {
+    ╾────0x4[wildcard]────╼ __ __ __ __ __ __ __ __ │ ╾──────╼░░░░░░░░
+}
+
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
 
 error: aborting due to 1 previous error; 1 warning emitted
diff --git a/tests/fail/intrinsics/ptr_metadata_uninit_thin.rs b/tests/fail/intrinsics/ptr_metadata_uninit_thin.rs
@@ -9,7 +9,7 @@ use std::intrinsics::mir::*;
 pub unsafe fn deref_meta(p: *const *const i32) -> () {
     mir! {
         {
-            RET = PtrMetadata(*p); //~ ERROR: Undefined Behavior: using uninitialized data
+            RET = PtrMetadata(*p); //~ ERROR: /Undefined Behavior: .*, but memory is uninitialized/
             Return()
         }
     }
diff --git a/tests/fail/intrinsics/ptr_metadata_uninit_thin.stderr b/tests/fail/intrinsics/ptr_metadata_uninit_thin.stderr
@@ -1,4 +1,4 @@
-error: Undefined Behavior: using uninitialized data, but this operation requires initialized memory
+error: Undefined Behavior: reading memory at ALLOC[0x0..0x8], but memory is uninitialized at [0x0..0x8], and this operation requires initialized memory
   --> tests/fail/intrinsics/ptr_metadata_uninit_thin.rs:LL:CC
    |
 LL |             RET = PtrMetadata(*p);
@@ -14,6 +14,11 @@ note: inside `main`
 LL |         let _meta = deref_meta(p.as_ptr());
    |                     ^^^^^^^^^^^^^^^^^^^^^^
 
+Uninitialized memory occurred at ALLOC[0x0..0x8], in this allocation:
+ALLOC (stack variable, size: 8, align: 8) {
+    __ __ __ __ __ __ __ __                         │ ░░░░░░░░
+}
+
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
 
 error: aborting due to 1 previous error
diff --git a/tests/fail/read_from_trivial_switch.rs b/tests/fail/read_from_trivial_switch.rs
@@ -10,5 +10,5 @@ fn main() {
     let uninit: MaybeUninit<i32> = MaybeUninit::uninit();
     let bad_ref: &i32 = unsafe { uninit.assume_init_ref() };
     let &(0 | _) = bad_ref;
-    //~^ ERROR: Undefined Behavior: using uninitialized data, but this operation requires initialized memory
+    //~^ ERROR: /Undefined Behavior: .*, but memory is uninitialized .* requires initialized memory/
 }
diff --git a/tests/fail/read_from_trivial_switch.stderr b/tests/fail/read_from_trivial_switch.stderr
@@ -1,4 +1,4 @@
-error: Undefined Behavior: using uninitialized data, but this operation requires initialized memory
+error: Undefined Behavior: reading memory at ALLOC[0x0..0x4], but memory is uninitialized at [0x0..0x4], and this operation requires initialized memory
   --> tests/fail/read_from_trivial_switch.rs:LL:CC
    |
 LL |     let &(0 | _) = bad_ref;
@@ -9,6 +9,11 @@ LL |     let &(0 | _) = bad_ref;
    = note: BACKTRACE:
    = note: inside `main` at tests/fail/read_from_trivial_switch.rs:LL:CC
 
+Uninitialized memory occurred at ALLOC[0x0..0x4], in this allocation:
+ALLOC (stack variable, size: 4, align: 4) {
+    __ __ __ __                                     │ ░░░░
+}
+
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
 
 error: aborting due to 1 previous error
diff --git a/tests/fail/uninit/padding-enum.stderr b/tests/fail/uninit/padding-enum.stderr
@@ -1,4 +1,4 @@
-error: Undefined Behavior: using uninitialized data, but this operation requires initialized memory
+error: Undefined Behavior: reading memory at ALLOC[0x8..0x9], but memory is uninitialized at [0x8..0x9], and this operation requires initialized memory
   --> tests/fail/uninit/padding-enum.rs:LL:CC
    |
 LL |         let _val = *c.add(padding_offset);
@@ -9,6 +9,12 @@ LL |         let _val = *c.add(padding_offset);
    = note: BACKTRACE:
    = note: inside `main` at tests/fail/uninit/padding-enum.rs:LL:CC
 
+Uninitialized memory occurred at ALLOC[0x8..0x9], in this allocation:
+ALLOC (stack variable, size: 24, align: 8) {
+    0x00 │ 00 00 00 00 00 00 00 00 __ __ __ __ __ __ __ __ │ ........░░░░░░░░
+    0x10 │ __ __ __ __ __ __ __ __                         │ ░░░░░░░░
+}
+
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
 
 error: aborting due to 1 previous error
diff --git a/tests/fail/uninit/padding-pair.stderr b/tests/fail/uninit/padding-pair.stderr
@@ -1,4 +1,4 @@
-error: Undefined Behavior: using uninitialized data, but this operation requires initialized memory
+error: Undefined Behavior: reading memory at ALLOC[0x9..0xa], but memory is uninitialized at [0x9..0xa], and this operation requires initialized memory
   --> tests/fail/uninit/padding-pair.rs:LL:CC
    |
 LL |     let v = unsafe { *z.offset(first_undef) };
@@ -9,6 +9,11 @@ LL |     let v = unsafe { *z.offset(first_undef) };
    = note: BACKTRACE:
    = note: inside `main` at tests/fail/uninit/padding-pair.rs:LL:CC
 
+Uninitialized memory occurred at ALLOC[0x9..0xa], in this allocation:
+ALLOC (stack variable, size: 16, align: 8) {
+    00 00 00 00 00 00 00 00 00 __ __ __ __ __ __ __ │ .........░░░░░░░
+}
+
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
 
 error: aborting due to 1 previous error
diff --git a/tests/fail/uninit/padding-struct.stderr b/tests/fail/uninit/padding-struct.stderr
@@ -1,4 +1,4 @@
-error: Undefined Behavior: using uninitialized data, but this operation requires initialized memory
+error: Undefined Behavior: reading memory at ALLOC[0x1..0x2], but memory is uninitialized at [0x1..0x2], and this operation requires initialized memory
   --> tests/fail/uninit/padding-struct.rs:LL:CC
    |
 LL |         let _val = *c.add(1);
@@ -9,6 +9,11 @@ LL |         let _val = *c.add(1);
    = note: BACKTRACE:
    = note: inside `main` at tests/fail/uninit/padding-struct.rs:LL:CC
 
+Uninitialized memory occurred at ALLOC[0x1..0x2], in this allocation:
+ALLOC (stack variable, size: 4, align: 2) {
+    00 __ 00 00                                     │ .░..
+}
+
 note: some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace
 
 error: aborting due to 1 previous error
diff --git a/tests/fail/uninit/padding-wide-ptr.stderr b/tests/fail/uninit/padding-wide-ptr.stderr
diff --git a/tests/fail/uninit/transmute-pair-uninit.stderr b/tests/fail/uninit/transmute-pair-uninit.stderr
diff --git a/tests/fail/uninit/uninit_byte_read.stderr b/tests/fail/uninit/uninit_byte_read.stderr
diff --git a/tests/fail/validity/invalid_int_op.stderr b/tests/fail/validity/invalid_int_op.stderr

Original file line number	Diff line number	Diff line change
`@@ -15,6 +15,6 @@ fn main() {`
`15`	`15`	`libc::pthread_cond_destroy(cond.as_mut_ptr());`
`16`	`16`
`17`	`17`	`libc::pthread_cond_destroy(cond.as_mut_ptr());`
`18`		`- //~^ ERROR: Undefined Behavior: using uninitialized data, but this operation requires initialized memory`
	`18`	`+ //~^ ERROR: /Undefined Behavior: reading memory .*, but memory is uninitialized/`
`19`	`19`	`}`
`20`	`20`	`}`
Original file line number	Diff line number	Diff line change
`@@ -13,6 +13,6 @@ fn main() {`
`13`	`13`	`libc::pthread_condattr_destroy(attr.as_mut_ptr());`
`14`	`14`
`15`	`15`	`libc::pthread_condattr_destroy(attr.as_mut_ptr());`
`16`		`- //~^ ERROR: Undefined Behavior: using uninitialized data, but this operation requires initialized memory`
	`16`	`+ //~^ ERROR: /Undefined Behavior: reading memory .*, but memory is uninitialized/`
`17`	`17`	`}`
`18`	`18`	`}`
Original file line number	Diff line number	Diff line change
`@@ -16,6 +16,6 @@ fn main() {`
`16`	`16`	`libc::pthread_mutex_destroy(mutex.as_mut_ptr());`
`17`	`17`
`18`	`18`	`libc::pthread_mutex_destroy(mutex.as_mut_ptr());`
`19`		`- //~^ ERROR: Undefined Behavior: using uninitialized data, but this operation requires initialized memory`
	`19`	`+ //~^ ERROR: /Undefined Behavior: reading memory .*, but memory is uninitialized/`
`20`	`20`	`}`
`21`	`21`	`}`
Original file line number	Diff line number	Diff line change
`@@ -12,6 +12,6 @@ fn main() {`
`12`	`12`	`libc::pthread_mutexattr_destroy(attr.as_mut_ptr());`
`13`	`13`
`14`	`14`	`libc::pthread_mutexattr_destroy(attr.as_mut_ptr());`
`15`		`- //~^ ERROR: Undefined Behavior: using uninitialized data, but this operation requires initialized memory`
	`15`	`+ //~^ ERROR: /Undefined Behavior: reading memory .*, but memory is uninitialized/`
`16`	`16`	`}`
`17`	`17`	`}`
Original file line number	Diff line number	Diff line change
`@@ -9,6 +9,6 @@ fn main() {`
`9`	`9`	`libc::pthread_rwlock_destroy(&mut lock);`
`10`	`10`
`11`	`11`	`libc::pthread_rwlock_destroy(&mut lock);`
`12`		`- //~^ ERROR: Undefined Behavior: using uninitialized data, but this operation requires initialized memory`
	`12`	`+ //~^ ERROR: /Undefined Behavior: reading memory .*, but memory is uninitialized/`
`13`	`13`	`}`
`14`	`14`	`}`