Rollup merge of #76881 - hameerabbasi:issue-53325, r=oli-obk

Add allocation information to undefined behaviour errors.

So far I'm looking on information on whether the error messages are suitable.

Fixes #53325.

Author: Dylan-DPC

compiler/rustc_mir/src/const_eval/eval_queries.rs

@@ -6,6 +6,7 @@ use crate::interpret::{
     ScalarMaybeUninit, StackPopCleanup,
 };
 
+use crate::util::pretty::display_allocation;
 use rustc_hir::def::DefKind;
 use rustc_middle::mir;
 use rustc_middle::mir::interpret::ErrorHandled;
@@ -192,7 +193,7 @@ fn validate_and_turn_into_const<'tcx>(
     let is_static = tcx.is_static(def_id);
     let ecx = mk_eval_cx(tcx, tcx.def_span(key.value.instance.def_id()), key.param_env, is_static);
     let val = (|| {
-        let mplace = ecx.raw_const_to_mplace(constant)?;
+        let mplace = ecx.raw_const_to_mplace(&constant)?;
 
         // FIXME do not validate promoteds until a decision on
         // https://github.com/rust-lang/rust/issues/67465 is made
@@ -225,6 +226,13 @@ fn validate_and_turn_into_const<'tcx>(
         let err = ConstEvalErr::new(&ecx, error, None);
         err.struct_error(ecx.tcx, "it is undefined behavior to use this value", |mut diag| {
             diag.note(note_on_undefined_behavior_error());
+            diag.note(&format!(
+                "the raw bytes of the constant ({}",
+                display_allocation(
+                    *ecx.tcx,
+                    ecx.tcx.global_alloc(constant.alloc_id).unwrap_memory()
+                )
+            ));
             diag.emit();
         })
     })

compiler/rustc_mir/src/interpret/eval_context.rs

@@ -922,7 +922,7 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
         // that problem, but we never run validation to show an error. Can we ensure
         // this does not happen?
         let val = self.tcx.const_eval_raw(param_env.and(gid))?;
-        self.raw_const_to_mplace(val)
+        self.raw_const_to_mplace(&val)
     }
 
     #[must_use]

compiler/rustc_mir/src/interpret/place.rs

@@ -1120,7 +1120,7 @@ where
 
     pub fn raw_const_to_mplace(
         &self,
-        raw: RawConst<'tcx>,
+        raw: &RawConst<'tcx>,
     ) -> InterpResult<'tcx, MPlaceTy<'tcx, M::PointerTag>> {
         // This must be an allocation in `tcx`
         let _ = self.tcx.global_alloc(raw.alloc_id);

src/test/ui/consts/const-err4.stderr

@@ -5,6 +5,9 @@ LL |     Boo = [unsafe { Foo { b: () }.a }; 4][3],
    |           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered uninitialized bytes, but expected initialized plain (non-pointer) bytes
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
+   = note: the raw bytes of the constant (size: 8, align: 8) {
+               __ __ __ __ __ __ __ __                         │ ░░░░░░░░
+           }
 
 error: aborting due to previous error
 

src/test/ui/consts/const-eval/const-pointer-values-in-various-types.stderr

@@ -5,6 +5,9 @@ LL |     const I32_REF_USIZE_UNION: usize = unsafe { Nonsense { int_32_ref: &3 }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered pointer to alloc2, but expected initialized plain (non-pointer) bytes
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
+   = note: the raw bytes of the constant (size: 8, align: 8) {
+               ╾───────alloc2────────╼                         │ ╾──────╼
+           }
 
 error: any use of this value will cause an error
   --> $DIR/const-pointer-values-in-various-types.rs:28:43
@@ -39,6 +42,9 @@ LL |     const I32_REF_U64_UNION: u64 = unsafe { Nonsense { int_32_ref: &3 }.uin
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered pointer to alloc22, but expected initialized plain (non-pointer) bytes
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
+   = note: the raw bytes of the constant (size: 8, align: 8) {
+               ╾───────alloc22───────╼                         │ ╾──────╼
+           }
 
 error[E0080]: it is undefined behavior to use this value
   --> $DIR/const-pointer-values-in-various-types.rs:40:5
@@ -47,6 +53,9 @@ LL |     const I32_REF_U128_UNION: u128 = unsafe { Nonsense { int_32_ref: &3 }.u
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered uninitialized bytes, but expected initialized plain (non-pointer) bytes
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
+   = note: the raw bytes of the constant (size: 16, align: 8) {
+               __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ │ ░░░░░░░░░░░░░░░░
+           }
 
 error: any use of this value will cause an error
   --> $DIR/const-pointer-values-in-various-types.rs:43:43
@@ -79,6 +88,9 @@ LL |     const I32_REF_I64_UNION: i64 = unsafe { Nonsense { int_32_ref: &3 }.int
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered pointer to alloc47, but expected initialized plain (non-pointer) bytes
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
+   = note: the raw bytes of the constant (size: 8, align: 8) {
+               ╾───────alloc47───────╼                         │ ╾──────╼
+           }
 
 error[E0080]: it is undefined behavior to use this value
   --> $DIR/const-pointer-values-in-various-types.rs:55:5
@@ -87,6 +99,9 @@ LL |     const I32_REF_I128_UNION: i128 = unsafe { Nonsense { int_32_ref: &3 }.i
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered uninitialized bytes, but expected initialized plain (non-pointer) bytes
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
+   = note: the raw bytes of the constant (size: 16, align: 8) {
+               __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ __ │ ░░░░░░░░░░░░░░░░
+           }
 
 error: any use of this value will cause an error
   --> $DIR/const-pointer-values-in-various-types.rs:58:45
@@ -103,6 +118,9 @@ LL |     const I32_REF_F64_UNION: f64 = unsafe { Nonsense { int_32_ref: &3 }.flo
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered pointer to alloc62, but expected initialized plain (non-pointer) bytes
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
+   = note: the raw bytes of the constant (size: 8, align: 8) {
+               ╾───────alloc62───────╼                         │ ╾──────╼
+           }
 
 error: any use of this value will cause an error
   --> $DIR/const-pointer-values-in-various-types.rs:64:47
@@ -151,6 +169,9 @@ LL |     const STR_U64_UNION: u64 = unsafe { Nonsense { stringy: "3" }.uint_64 }
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered pointer to alloc86, but expected initialized plain (non-pointer) bytes
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
+   = note: the raw bytes of the constant (size: 8, align: 8) {
+               ╾───────alloc86───────╼                         │ ╾──────╼
+           }
 
 error: any use of this value will cause an error
   --> $DIR/const-pointer-values-in-various-types.rs:82:43
@@ -191,6 +212,9 @@ LL |     const STR_I64_UNION: i64 = unsafe { Nonsense { stringy: "3" }.int_64 };
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered pointer to alloc101, but expected initialized plain (non-pointer) bytes
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
+   = note: the raw bytes of the constant (size: 8, align: 8) {
+               ╾──────alloc101───────╼                         │ ╾──────╼
+           }
 
 error: any use of this value will cause an error
   --> $DIR/const-pointer-values-in-various-types.rs:97:43
@@ -215,6 +239,9 @@ LL |     const STR_F64_UNION: f64 = unsafe { Nonsense { stringy: "3" }.float_64
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered pointer to alloc110, but expected initialized plain (non-pointer) bytes
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
+   = note: the raw bytes of the constant (size: 8, align: 8) {
+               ╾──────alloc110───────╼                         │ ╾──────╼
+           }
 
 error: any use of this value will cause an error
   --> $DIR/const-pointer-values-in-various-types.rs:106:43

src/test/ui/consts/const-eval/double_check2.stderr

@@ -8,6 +8,9 @@ LL | | )};
    | |___^ type validation failed: encountered 0x05 at .1.<deref>.<enum-tag>, but expected a valid enum tag
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
+   = note: the raw bytes of the constant (size: 16, align: 8) {
+               ╾───────alloc4────────╼ ╾───────alloc4────────╼ │ ╾──────╼╾──────╼
+           }
 
 error[E0080]: it is undefined behavior to use this value
   --> $DIR/double_check2.rs:20:1
@@ -16,6 +19,9 @@ LL | static FOO2: (&Foo, &Bar) = unsafe {(std::mem::transmute(&BAR), std::mem::t
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 0x05 at .1.<deref>.<enum-tag>, but expected a valid enum tag
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
+   = note: the raw bytes of the constant (size: 16, align: 8) {
+               ╾───────alloc4────────╼ ╾───────alloc4────────╼ │ ╾──────╼╾──────╼
+           }
 
 error: aborting due to 2 previous errors
 

src/test/ui/consts/const-eval/ref_to_int_match.stderr

@@ -5,6 +5,9 @@ LL | const BAR: Int = unsafe { Foo { r: &42 }.f };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered pointer to alloc2, but expected initialized plain (non-pointer) bytes
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
+   = note: the raw bytes of the constant (size: 8, align: 8) {
+               ╾───────alloc2────────╼                         │ ╾──────╼
+           }
 
 error: could not evaluate constant pattern
   --> $DIR/ref_to_int_match.rs:7:14

src/test/ui/consts/const-eval/transmute-const.stderr

@@ -5,6 +5,9 @@ LL | static FOO: bool = unsafe { mem::transmute(3u8) };
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ type validation failed: encountered 0x03, but expected a boolean
    |
    = note: The rules on what exactly is undefined behavior aren't clear, so this check might be overzealous. Please open an issue on the rustc repository if you believe it should not be considered undefined behavior.
+   = note: the raw bytes of the constant (size: 1, align: 1) {
+               03                                              │ .
+           }
 
 error: aborting due to previous error