From cbb89578357d4628a7bdb3fde8d6417bcaadcdd1 Mon Sep 17 00:00:00 2001
From: Ralf Jung <post@ralfj.de>
Date: Tue, 4 Oct 2022 13:15:32 +0200
Subject: [PATCH] more details on stacked borrows tracking

---
 src/diagnostics.rs         | 22 ++++++++++++++--------
 src/stacked_borrows/mod.rs | 21 +++++++++++++++++++--
 2 files changed, 33 insertions(+), 10 deletions(-)

diff --git a/src/diagnostics.rs b/src/diagnostics.rs
index 868c85c04a88d..ecfe0cd3f8a65 100644
--- a/src/diagnostics.rs
+++ b/src/diagnostics.rs
@@ -60,7 +60,10 @@ impl MachineStopType for TerminationInfo {}
 
 /// Miri specific diagnostics
 pub enum NonHaltingDiagnostic {
-    CreatedPointerTag(NonZeroU64, Option<(AllocId, AllocRange)>),
+    /// (new_tag, new_kind, (alloc_id, base_offset, orig_tag))
+    ///
+    /// new_kind is `None` for base tags.
+    CreatedPointerTag(NonZeroU64, Option<String>, Option<(AllocId, AllocRange, ProvenanceExtra)>),
     /// This `Item` was popped from the borrow stack, either due to an access with the given tag or
     /// a deallocation when the second argument is `None`.
     PoppedPointerTag(Item, Option<(ProvenanceExtra, AccessKind)>),
@@ -376,7 +379,7 @@ impl<'mir, 'tcx> MiriMachine<'mir, 'tcx> {
             MiriInterpCx::generate_stacktrace_from_stack(self.threads.active_thread_stack());
         let (stacktrace, _was_pruned) = prune_stacktrace(stacktrace, self);
 
-        let (title, diag_level) = match e {
+        let (title, diag_level) = match &e {
             RejectedIsolatedOp(_) => ("operation rejected by isolation", DiagLevel::Warning),
             Int2Ptr { .. } => ("integer-to-pointer cast", DiagLevel::Warning),
             CreatedPointerTag(..)
@@ -388,10 +391,13 @@ impl<'mir, 'tcx> MiriMachine<'mir, 'tcx> {
             | WeakMemoryOutdatedLoad => ("tracking was triggered", DiagLevel::Note),
         };
 
-        let msg = match e {
-            CreatedPointerTag(tag, None) => format!("created tag {tag:?}"),
-            CreatedPointerTag(tag, Some((alloc_id, range))) =>
-                format!("created tag {tag:?} at {alloc_id:?}{range:?}"),
+        let msg = match &e {
+            CreatedPointerTag(tag, None, _) => format!("created base tag {tag:?}"),
+            CreatedPointerTag(tag, Some(kind), None) => format!("created {tag:?} for {kind}"),
+            CreatedPointerTag(tag, Some(kind), Some((alloc_id, range, orig_tag))) =>
+                format!(
+                    "created tag {tag:?} for {kind} at {alloc_id:?}{range:?} derived from {orig_tag:?}"
+                ),
             PoppedPointerTag(item, tag) =>
                 match tag {
                     None => format!("popped tracked tag for item {item:?} due to deallocation",),
@@ -418,7 +424,7 @@ impl<'mir, 'tcx> MiriMachine<'mir, 'tcx> {
                 format!("weak memory emulation: outdated value returned from load"),
         };
 
-        let notes = match e {
+        let notes = match &e {
             ProgressReport { block_count } => {
                 // It is important that each progress report is slightly different, since
                 // identical diagnostics are being deduplicated.
@@ -427,7 +433,7 @@ impl<'mir, 'tcx> MiriMachine<'mir, 'tcx> {
             _ => vec![],
         };
 
-        let helps = match e {
+        let helps = match &e {
             Int2Ptr { details: true } =>
                 vec![
                     (
diff --git a/src/stacked_borrows/mod.rs b/src/stacked_borrows/mod.rs
index f7f4b1357f106..429c6eb8ef555 100644
--- a/src/stacked_borrows/mod.rs
+++ b/src/stacked_borrows/mod.rs
@@ -5,6 +5,7 @@ use log::trace;
 use std::cell::RefCell;
 use std::cmp;
 use std::fmt;
+use std::fmt::Write;
 use std::num::NonZeroU64;
 
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
@@ -203,7 +204,7 @@ impl GlobalStateInner {
         self.base_ptr_tags.get(&id).copied().unwrap_or_else(|| {
             let tag = self.new_ptr();
             if self.tracked_pointer_tags.contains(&tag) {
-                machine.emit_diagnostic(NonHaltingDiagnostic::CreatedPointerTag(tag.0, None));
+                machine.emit_diagnostic(NonHaltingDiagnostic::CreatedPointerTag(tag.0, None, None));
             }
             trace!("New allocation {:?} has base tag {:?}", id, tag);
             self.base_ptr_tags.try_insert(id, tag).unwrap();
@@ -674,10 +675,26 @@ trait EvalContextPrivExt<'mir: 'ecx, 'tcx: 'mir, 'ecx>: crate::MiriInterpCxExt<'
                             loc: Option<(AllocId, Size, ProvenanceExtra)>| // alloc_id, base_offset, orig_tag
          -> InterpResult<'tcx> {
             let global = this.machine.stacked_borrows.as_ref().unwrap().borrow();
+            let ty = place.layout.ty;
             if global.tracked_pointer_tags.contains(&new_tag) {
+                let mut kind_str = format!("{kind}");
+                match kind {
+                    RefKind::Unique { two_phase: false }
+                        if !ty.is_unpin(this.tcx.at(DUMMY_SP), this.param_env()) =>
+                    {
+                        write!(kind_str, " (!Unpin pointee type {ty})").unwrap()
+                    },
+                    RefKind::Shared
+                        if !ty.is_freeze(this.tcx.at(DUMMY_SP), this.param_env()) =>
+                    {
+                        write!(kind_str, " (!Freeze pointee type {ty})").unwrap()
+                    },
+                    _ => write!(kind_str, " (pointee type {ty})").unwrap(),
+                };
                 this.emit_diagnostic(NonHaltingDiagnostic::CreatedPointerTag(
                     new_tag.0,
-                    loc.map(|(alloc_id, base_offset, _)| (alloc_id, alloc_range(base_offset, size))),
+                    Some(kind_str),
+                    loc.map(|(alloc_id, base_offset, orig_tag)| (alloc_id, alloc_range(base_offset, size), orig_tag)),
                 ));
             }
             drop(global); // don't hold that reference any longer than we have to