Report the range of uninit bytes in CTFE errors

Author: oli-obk

compiler/rustc_const_eval/src/interpret/operand.rs

@@ -7,7 +7,7 @@ use either::{Either, Left, Right};
 use rustc_abi as abi;
 use rustc_abi::{BackendRepr, HasDataLayout, Size};
 use rustc_hir::def::Namespace;
-use rustc_middle::mir::interpret::ScalarSizeMismatch;
+use rustc_middle::mir::interpret::{BadBytesAccess, ScalarSizeMismatch};
 use rustc_middle::ty::layout::{HasTyCtxt, HasTypingEnv, LayoutOf, TyAndLayout};
 use rustc_middle::ty::print::{FmtPrinter, PrettyPrinter};
 use rustc_middle::ty::{ConstInt, ScalarInt, Ty, TyCtxt};
@@ -663,7 +663,15 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
         }
         let imm = self.read_immediate_raw(op)?.right().unwrap();
         if matches!(*imm, Immediate::Uninit) {
-            throw_ub!(InvalidUninitBytes(None));
+            throw_ub!(InvalidUninitBytes(match op.to_op(self)?.as_mplace_or_imm() {
+                Left(mplace) => mplace.ptr().provenance.and_then(|prov| {
+                    let start = mplace.ptr().into_parts().1;
+                    let size = op.layout().size;
+                    let range = alloc_range(start, size);
+                    Some((prov.get_alloc_id()?, BadBytesAccess { access: range, bad: range }))
+                }),
+                Right(_) => None,
+            }))
         }
         interp_ok(imm)
     }

compiler/rustc_const_eval/src/interpret/validity.rs

@@ -396,7 +396,7 @@ impl<'rt, 'tcx, M: Machine<'tcx>> ValidityVisitor<'rt, 'tcx, M> {
         interp_ok(try_validation!(
             self.ecx.read_immediate(val),
             self.path,
-            Ub(InvalidUninitBytes(None)) =>
+            Ub(InvalidUninitBytes(_)) =>
                 Uninit { expected },
             // The `Unsup` cases can only occur during CTFE
             Unsup(ReadPointerAsInt(_)) =>

compiler/rustc_middle/src/mir/interpret/allocation.rs

@@ -700,8 +700,11 @@ impl<Prov: Provenance, Extra, Bytes: AllocBytes> Allocation<Prov, Extra, Bytes>
         read_provenance: bool,
     ) -> AllocResult<Scalar<Prov>> {
         // First and foremost, if anything is uninit, bail.
-        if self.init_mask.is_range_initialized(range).is_err() {
-            return Err(AllocError::InvalidUninitBytes(None));
+        if let Err(bad) = self.init_mask.is_range_initialized(range) {
+            return Err(AllocError::InvalidUninitBytes(Some(BadBytesAccess {
+                access: range,
+                bad,
+            })));
         }
 
         // Get the integer part of the result. We HAVE TO check provenance before returning this!

tests/ui/const-generics/min_const_generics/invalid-patterns.32bit.stderr

@@ -1,4 +1,4 @@
-error[E0080]: using uninitialized data, but this operation requires initialized memory
+error[E0080]: reading memory at ALLOC0[0x0..0x4], but memory is uninitialized at [0x1..0x4], and this operation requires initialized memory
   --> $DIR/invalid-patterns.rs:40:32
    |
 LL |   get_flag::<false, { unsafe { char_raw.character } }>();
@@ -26,7 +26,7 @@ LL |   get_flag::<{ unsafe { bool_raw.boolean } }, { unsafe { char_raw.character
                42                                              │ B
            }
 
-error[E0080]: using uninitialized data, but this operation requires initialized memory
+error[E0080]: reading memory at ALLOC1[0x0..0x4], but memory is uninitialized at [0x1..0x4], and this operation requires initialized memory
   --> $DIR/invalid-patterns.rs:44:58
    |
 LL |   get_flag::<{ unsafe { bool_raw.boolean } }, { unsafe { char_raw.character } }>();

tests/ui/const-generics/min_const_generics/invalid-patterns.64bit.stderr

@@ -1,4 +1,4 @@
-error[E0080]: using uninitialized data, but this operation requires initialized memory
+error[E0080]: reading memory at ALLOC0[0x0..0x4], but memory is uninitialized at [0x1..0x4], and this operation requires initialized memory
   --> $DIR/invalid-patterns.rs:40:32
    |
 LL |   get_flag::<false, { unsafe { char_raw.character } }>();
@@ -26,7 +26,7 @@ LL |   get_flag::<{ unsafe { bool_raw.boolean } }, { unsafe { char_raw.character
                42                                              │ B
            }
 
-error[E0080]: using uninitialized data, but this operation requires initialized memory
+error[E0080]: reading memory at ALLOC1[0x0..0x4], but memory is uninitialized at [0x1..0x4], and this operation requires initialized memory
   --> $DIR/invalid-patterns.rs:44:58
    |
 LL |   get_flag::<{ unsafe { bool_raw.boolean } }, { unsafe { char_raw.character } }>();

tests/ui/consts/const-err-enum-discriminant.stderr

@@ -1,4 +1,4 @@
-error[E0080]: using uninitialized data, but this operation requires initialized memory
+error[E0080]: reading memory at ALLOC0[0x0..0x4], but memory is uninitialized at [0x0..0x4], and this operation requires initialized memory
   --> $DIR/const-err-enum-discriminant.rs:8:21
    |
 LL |     Boo = [unsafe { Foo { b: () }.a }; 4][3],

tests/ui/consts/const-eval/const-pointer-values-in-various-types.64bit.stderr

@@ -43,7 +43,7 @@ LL |     const I32_REF_U64_UNION: u64 = unsafe { Nonsense { int_32_ref: &3 }.uin
    = help: this code performed an operation that depends on the underlying bytes representing a pointer
    = help: the absolute address of a pointer is not known at compile-time, so such operations are not supported
 
-error[E0080]: using uninitialized data, but this operation requires initialized memory
+error[E0080]: reading memory at ALLOC0[0x0..0x10], but memory is uninitialized at [0x8..0x10], and this operation requires initialized memory
   --> $DIR/const-pointer-values-in-various-types.rs:42:47
    |
 LL |     const I32_REF_U128_UNION: u128 = unsafe { Nonsense { int_32_ref: &3 }.uint_128 };
@@ -85,7 +85,7 @@ LL |     const I32_REF_I64_UNION: i64 = unsafe { Nonsense { int_32_ref: &3 }.int
    = help: this code performed an operation that depends on the underlying bytes representing a pointer
    = help: the absolute address of a pointer is not known at compile-time, so such operations are not supported
 
-error[E0080]: using uninitialized data, but this operation requires initialized memory
+error[E0080]: reading memory at ALLOC1[0x0..0x10], but memory is uninitialized at [0x8..0x10], and this operation requires initialized memory
   --> $DIR/const-pointer-values-in-various-types.rs:57:47
    |
 LL |     const I32_REF_I128_UNION: i128 = unsafe { Nonsense { int_32_ref: &3 }.int_128 };

tests/ui/consts/const-eval/ub-enum-overwrite.stderr

@@ -1,4 +1,4 @@
-error[E0080]: using uninitialized data, but this operation requires initialized memory
+error[E0080]: reading memory at ALLOC0[0x1..0x2], but memory is uninitialized at [0x1..0x2], and this operation requires initialized memory
   --> $DIR/ub-enum-overwrite.rs:11:14
    |
 LL |     unsafe { *p }

tests/ui/consts/const-eval/ub-enum.stderr

@@ -56,7 +56,7 @@ LL | const BAD_ENUM2_WRAPPED: Wrap<Enum2> = unsafe { mem::transmute(&0) };
    = help: this code performed an operation that depends on the underlying bytes representing a pointer
    = help: the absolute address of a pointer is not known at compile-time, so such operations are not supported
 
-error[E0080]: using uninitialized data, but this operation requires initialized memory
+error[E0080]: reading memory at ALLOC0[0x0..0x4], but memory is uninitialized at [0x0..0x4], and this operation requires initialized memory
   --> $DIR/ub-enum.rs:61:41
    |
 LL | const BAD_ENUM2_UNDEF: Enum2 = unsafe { MaybeUninit { uninit: () }.init };

tests/ui/consts/const-eval/ub-nonnull.stderr

@@ -37,7 +37,7 @@ LL | const NULL_USIZE: NonZero<usize> = unsafe { mem::transmute(0usize) };
                HEX_DUMP
            }
 
-error[E0080]: using uninitialized data, but this operation requires initialized memory
+error[E0080]: reading memory at ALLOC2[0x0..0x1], but memory is uninitialized at [0x0..0x1], and this operation requires initialized memory
   --> $DIR/ub-nonnull.rs:36:38
    |
 LL | const UNINIT: NonZero<u8> = unsafe { MaybeUninit { uninit: () }.init };