fix error reporting in validation

diff --git a/src/librustc_mir/interpret/validity.rs b/src/librustc_mir/interpret/validity.rs
index 5eb32cd7eac774ef20269dc5c5c6a04fb5b7c109..8f0e8196605412446a01b4bd3bbb9f92de2e3fa9 100644 (file)
--- a/src/librustc_mir/interpret/validity.rs
+++ b/src/librustc_mir/interpret/validity.rs
@@ -5,7 +5,7 @@
 use rustc::ty::{self, Ty};
 use rustc_data_structures::fx::FxHashSet;
 use rustc::mir::interpret::{
-    Scalar, AllocType, EvalResult, ScalarMaybeUndef,
+    Scalar, AllocType, EvalResult, ScalarMaybeUndef, EvalErrorKind
 };
 
 use super::{
@@ -285,15 +285,22 @@ pub fn validate_mplace(
                     // This is a fat pointer.
                     let ptr = match self.ref_to_mplace(self.read_value(dest.into())?) {
                         Ok(ptr) => ptr,
-                        Err(ReadPointerAsBytes) =>
-                            return validation_failure!("fat pointer length is not a valid integer", path),
-                        Err(ReadBytesAsPointer) =>
-                            return validation_failure!("fat pointer vtable is not a valid pointer", path),
-                        Err(err) => return Err(err),
+                        Err(err) => match err.kind {
+                            EvalErrorKind::ReadPointerAsBytes =>
+                                return validation_failure!(
+                                    "fat pointer length is not a valid integer", path
+                                ),
+                            EvalErrorKind::ReadBytesAsPointer =>
+                                return validation_failure!(
+                                    "fat pointer vtable is not a valid pointer", path
+                                ),
+                            _ => return Err(err),
+                        }
                     };
                     let unpacked_ptr = self.unpack_unsized_mplace(ptr)?;
                     // for safe ptrs, recursively check it
                     if !dest.layout.ty.is_unsafe_ptr() {
+                        trace!("Recursing below fat ptr {:?} (unpacked: {:?})", ptr, unpacked_ptr);
                         if seen.insert(unpacked_ptr) {
                             todo.push((unpacked_ptr, path_clone_and_deref(path)));
                         }

diff --git a/src/test/ui/union-ub-fat-ptr.stderr b/src/test/ui/union-ub-fat-ptr.stderr
index 85a514ea99ea01fa4908439b0ca1931d6f33d94a..cc22422304d68ca92d5bd0e5d86fef9a336e8a4a 100644 (file)
--- a/src/test/ui/union-ub-fat-ptr.stderr
+++ b/src/test/ui/union-ub-fat-ptr.stderr
@@ -58,7 +58,7 @@ error[E0080]: this constant likely exhibits undefined behavior
   --> $DIR/union-ub-fat-ptr.rs:104:1
    |
 LL | const F: &Trait = unsafe { DynTransmute { bad: BadDynRepr { ptr: &92, vtable: 3 } }.rust};
-   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered fat pointer length is not a valid integer
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered fat pointer vtable is not a valid pointer
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rust compiler repository if you believe it should not be considered undefined behavior