Rollup merge of #142673 - oli-obk:uninit-read-mem, r=RalfJung

Show the offset, length and memory of uninit read errors

r? ``@RalfJung``

I want to improve memory dumps in general. Not sure yet how to do so best within rust diagnostics, but in a perfect world I could generate a dummy in-memory file (that contains the rendered memory dump) that we then can then provide regular rustc `Span`s to. So we'd basically report normal diagnostics for them with squiggly lines and everything.

3 files changed, 23 insertions, 8 deletions

diff --git a/compiler/rustc_const_eval/src/const_eval/error.rs b/compiler/rustc_const_eval/src/const_eval/error.rs
index 3e880d02001..e00fb2c1eaf 100644
--- a/compiler/rustc_const_eval/src/const_eval/error.rs
+++ b/compiler/rustc_const_eval/src/const_eval/error.rs
@@ -2,17 +2,17 @@ use std::mem;
 
 use rustc_errors::{Diag, DiagArgName, DiagArgValue, DiagMessage, IntoDiagArg};
 use rustc_middle::mir::AssertKind;
-use rustc_middle::mir::interpret::{AllocId, Provenance, ReportedErrorInfo};
+use rustc_middle::mir::interpret::{AllocId, Provenance, ReportedErrorInfo, UndefinedBehaviorInfo};
 use rustc_middle::query::TyCtxtAt;
+use rustc_middle::ty::ConstInt;
 use rustc_middle::ty::layout::LayoutError;
-use rustc_middle::ty::{ConstInt, TyCtxt};
 use rustc_span::{Span, Symbol};
 
 use super::CompileTimeMachine;
 use crate::errors::{self, FrameNote, ReportErrorExt};
 use crate::interpret::{
-    CtfeProvenance, ErrorHandled, Frame, InterpErrorInfo, InterpErrorKind, MachineStopType,
-    Pointer, err_inval, err_machine_stop,
+    CtfeProvenance, ErrorHandled, Frame, InterpCx, InterpErrorInfo, InterpErrorKind,
+    MachineStopType, Pointer, err_inval, err_machine_stop,
 };
 
 /// The CTFE machine has some custom error kinds.
@@ -163,7 +163,7 @@ pub fn get_span_and_frames<'tcx>(
 /// You can use it to add a stacktrace of current execution according to
 /// `get_span_and_frames` or just give context on where the const eval error happened.
 pub(super) fn report<'tcx, C, F>(
-    tcx: TyCtxt<'tcx>,
+    ecx: &InterpCx<'tcx, CompileTimeMachine<'tcx>>,
     error: InterpErrorKind<'tcx>,
     span: Span,
     get_span_and_frames: C,
@@ -173,6 +173,7 @@ where
     C: FnOnce() -> (Span, Vec<FrameNote>),
     F: FnOnce(&mut Diag<'_>, Span, Vec<FrameNote>),
 {
+    let tcx = ecx.tcx.tcx;
     // Special handling for certain errors
     match error {
         // Don't emit a new diagnostic for these errors, they are already reported elsewhere or
@@ -198,6 +199,20 @@ where
                 InterpErrorKind::ResourceExhaustion(_) | InterpErrorKind::InvalidProgram(_)
             );
 
+            if let InterpErrorKind::UndefinedBehavior(UndefinedBehaviorInfo::InvalidUninitBytes(
+                Some((alloc_id, _access)),
+            )) = error
+            {
+                let bytes = ecx.print_alloc_bytes_for_diagnostics(alloc_id);
+                let info = ecx.get_alloc_info(alloc_id);
+                let raw_bytes = errors::RawBytesNote {
+                    size: info.size.bytes(),
+                    align: info.align.bytes(),
+                    bytes,
+                };
+                err.subdiagnostic(raw_bytes);
+            }
+
             error.add_args(&mut err);
 
             mk(&mut err, span, frames);
diff --git a/compiler/rustc_const_eval/src/const_eval/eval_queries.rs b/compiler/rustc_const_eval/src/const_eval/eval_queries.rs
index ce72d59b8b0..f584f6c948e 100644
--- a/compiler/rustc_const_eval/src/const_eval/eval_queries.rs
+++ b/compiler/rustc_const_eval/src/const_eval/eval_queries.rs
@@ -411,7 +411,7 @@ fn report_eval_error<'tcx>(
     let instance = with_no_trimmed_paths!(cid.instance.to_string());
 
     super::report(
-        *ecx.tcx,
+        ecx,
         error,
         DUMMY_SP,
         || super::get_span_and_frames(ecx.tcx, ecx.stack()),
@@ -451,7 +451,7 @@ fn report_validation_error<'tcx>(
         errors::RawBytesNote { size: info.size.bytes(), align: info.align.bytes(), bytes };
 
     crate::const_eval::report(
-        *ecx.tcx,
+        ecx,
         error,
         DUMMY_SP,
         || crate::const_eval::get_span_and_frames(ecx.tcx, ecx.stack()),
diff --git a/compiler/rustc_const_eval/src/interpret/validity.rs b/compiler/rustc_const_eval/src/interpret/validity.rs
index 62f591ceaa9..693b3782960 100644
--- a/compiler/rustc_const_eval/src/interpret/validity.rs
+++ b/compiler/rustc_const_eval/src/interpret/validity.rs
@@ -394,7 +394,7 @@ 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(_)) =>