Move SB diagnostics to a module

Author: saethlin

src/diagnostics.rs

@@ -8,7 +8,7 @@ use rustc_middle::ty;
 use rustc_span::{source_map::DUMMY_SP, Span, SpanData, Symbol};
 
 use crate::helpers::HexRange;
-use crate::stacked_borrows::{AccessKind, SbTag, TagHistory};
+use crate::stacked_borrows::{diagnostics::TagHistory, AccessKind, SbTag};
 use crate::*;
 
 /// Details of premature program termination.

src/eval.rs

@@ -15,8 +15,8 @@ use rustc_target::spec::abi::Abi;
 
 use rustc_session::config::EntryFnType;
 
-use std::collections::HashSet;
 use rustc_span::DUMMY_SP;
+use std::collections::HashSet;
 
 use crate::*;
 

src/machine.rs

@@ -776,6 +776,7 @@ impl<'mir, 'tcx> Machine<'mir, 'tcx> for Evaluator<'mir, 'tcx> {
 
 // This is potentially a performance hazard.
 // Factoring it into its own function lets us keep an eye on how much it shows up in a profile.
+///
 fn set_current_span<'mir, 'tcx: 'mir>(machine: &Evaluator<'mir, 'tcx>) {
     if let Some(sb) = machine.stacked_borrows.as_ref() {
         if sb.borrow().current_span != DUMMY_SP {

src/stacked_borrows.rs

@@ -14,14 +14,18 @@ use rustc_middle::ty::{
     self,
     layout::{HasParamEnv, LayoutOf},
 };
+use rustc_span::Span;
 use rustc_span::DUMMY_SP;
-use rustc_span::{Span, SpanData};
 use rustc_target::abi::Size;
 use std::collections::HashSet;
 
-use crate::helpers::HexRange;
 use crate::*;
 
+pub mod diagnostics;
+use diagnostics::{AllocHistory, GlobalStateExt, StackExt};
+
+use diagnostics::TagHistory;
+
 pub type PtrId = NonZeroU64;
 pub type CallId = NonZeroU64;
 pub type AllocExtra = Stacks;
@@ -120,47 +124,6 @@ pub struct GlobalStateInner {
     pub(crate) current_span: Span,
 }
 
-#[derive(Debug, Default)]
-struct AllocHistory {
-    // The time tags can be compressed down to one bit per event, by just storing a Vec<u8>
-    // where each bit is set to indicate if the event was a creation or a retag
-    current_time: usize,
-    creations: smallvec::SmallVec<[Event; 2]>,
-    invalidations: smallvec::SmallVec<[Event; 1]>,
-    protectors: smallvec::SmallVec<[Protection; 1]>,
-}
-
-#[derive(Debug)]
-struct Protection {
-    orig_tag: SbTag,
-    tag: SbTag,
-    span: Span,
-}
-
-#[derive(Debug)]
-struct Event {
-    time: usize,
-    parent: Option<SbTag>,
-    tag: SbTag,
-    range: AllocRange,
-    span: Span,
-}
-
-pub enum TagHistory {
-    Tagged {
-        tag: SbTag,
-        created: (AllocRange, SpanData),
-        invalidated: Option<(AllocRange, SpanData)>,
-        protected: Option<(SbTag, SpanData, SpanData)>,
-    },
-    Untagged {
-        recently_created: Option<(AllocRange, SpanData)>,
-        recently_invalidated: Option<(AllocRange, SpanData)>,
-        matching_created: Option<(AllocRange, SpanData)>,
-        protected: Option<(SbTag, SpanData, SpanData)>,
-    },
-}
-
 /// We need interior mutable access to the global state.
 pub type GlobalState = RefCell<GlobalStateInner>;
 
@@ -269,144 +232,10 @@ impl GlobalStateInner {
         self.base_ptr_ids.try_insert(id, tag).unwrap();
         tag
     }
-
-    fn add_creation(
-        &mut self,
-        parent: Option<SbTag>,
-        tag: SbTag,
-        alloc: AllocId,
-        range: AllocRange,
-    ) {
-        let extras = self.extras.entry(alloc).or_default();
-        extras.creations.push(Event {
-            parent,
-            tag,
-            range,
-            span: self.current_span,
-            time: extras.current_time,
-        });
-        extras.current_time += 1;
-    }
-
-    fn add_invalidation(&mut self, tag: SbTag, alloc: AllocId, range: AllocRange) {
-        let extras = self.extras.entry(alloc).or_default();
-        extras.invalidations.push(Event {
-            parent: None,
-            tag,
-            range,
-            span: self.current_span,
-            time: extras.current_time,
-        });
-        extras.current_time += 1;
-    }
-
-    fn add_protector(&mut self, orig_tag: SbTag, tag: SbTag, alloc: AllocId) {
-        let extras = self.extras.entry(alloc).or_default();
-        extras.protectors.push(Protection { orig_tag, tag, span: self.current_span });
-        extras.current_time += 1;
-    }
-
-    fn get_stack_history(
-        &self,
-        tag: SbTag,
-        alloc: AllocId,
-        alloc_range: AllocRange,
-        offset: Size,
-        protector_tag: Option<SbTag>,
-    ) -> Option<TagHistory> {
-        let extras = self.extras.get(&alloc)?;
-        let protected = protector_tag
-            .and_then(|protector| {
-                extras.protectors.iter().find_map(|protection| {
-                    if protection.tag == protector {
-                        Some((protection.orig_tag, protection.span.data()))
-                    } else {
-                        None
-                    }
-                })
-            })
-            .and_then(|(tag, call_span)| {
-                extras.creations.iter().rev().find_map(|event| {
-                    if event.tag == tag {
-                        Some((event.parent?, event.span.data(), call_span))
-                    } else {
-                        None
-                    }
-                })
-            });
-        if let SbTag::Tagged(_) = tag {
-            let get_matching = |events: &[Event]| {
-                events.iter().rev().find_map(|event| {
-                    if event.tag == tag { Some((event.range, event.span.data())) } else { None }
-                })
-            };
-            Some(TagHistory::Tagged {
-                tag,
-                created: get_matching(&extras.creations)?,
-                invalidated: get_matching(&extras.invalidations),
-                protected,
-            })
-        } else {
-            let mut created_time = 0;
-            // Find the most recently created tag that satsfies this offset
-            let recently_created = extras.creations.iter().rev().find_map(|event| {
-                if event.tag == tag && offset >= event.range.start && offset < event.range.end() {
-                    created_time = event.time;
-                    Some((event.range, event.span.data()))
-                } else {
-                    None
-                }
-            });
-
-            // Find a different recently created tag that satisfies this whole operation, predates
-            // the recently created tag, and has a different span.
-            // We're trying to make a guess at which span the user wanted to provide the tag that
-            // they're using.
-            let matching_created = if let Some((_created_range, created_span)) = recently_created {
-                extras.creations.iter().rev().find_map(|event| {
-                    if event.tag == tag
-                        && alloc_range.start >= event.range.start
-                        && alloc_range.end() <= event.range.end()
-                        && event.span.data() != created_span
-                        && event.time != created_time
-                    {
-                        Some((event.range, event.span.data()))
-                    } else {
-                        None
-                    }
-                })
-            } else {
-                None
-            };
-
-            let recently_invalidated = if recently_created.is_some() {
-                // Find the most recent invalidation of this tag which post-dates the creation
-                let mut found = None;
-                for event in extras.invalidations.iter().rev() {
-                    if event.time < created_time {
-                        break;
-                    }
-                    if event.tag == tag && offset >= event.range.start && offset < event.range.end()
-                    {
-                        found = Some((event.range, event.span.data()))
-                    }
-                }
-                found
-            } else {
-                None
-            };
-            Some(TagHistory::Untagged {
-                recently_created,
-                matching_created,
-                recently_invalidated,
-                protected,
-            })
-        }
-    }
 }
 
 /// Error reporting
-fn err_sb_ub(
+pub fn err_sb_ub(
     msg: String,
     help: Option<String>,
     history: Option<TagHistory>,
@@ -498,7 +327,7 @@ impl<'tcx> Stack {
     /// `None` during a deallocation.
     fn check_protector(
         item: &Item,
-        provoking_access: Option<(SbTag, AllocId, AllocRange, Size)>, // just for debug printing amd error messages
+        provoking_access: Option<(SbTag, AllocId, AllocRange, Size)>, // just for debug printing and error messages
         global: &GlobalStateInner,
     ) -> InterpResult<'tcx> {
         if let SbTag::Tagged(id) = item.tag {
@@ -600,7 +429,7 @@ impl<'tcx> Stack {
     fn dealloc(
         &mut self,
         tag: SbTag,
-        (alloc_id, alloc_range, offset): (AllocId, AllocRange, Size), // just for debug printing amd error messages
+        (alloc_id, alloc_range, offset): (AllocId, AllocRange, Size), // just for debug printing and error messages
         global: &GlobalStateInner,
     ) -> InterpResult<'tcx> {
         // Step 1: Find granting item.
@@ -681,75 +510,6 @@ impl<'tcx> Stack {
 
         Ok(())
     }
-
-    /// Report a descriptive error when `new` could not be granted from `derived_from`.
-    fn grant_error(
-        &self,
-        derived_from: SbTag,
-        new: Item,
-        alloc_id: AllocId,
-        alloc_range: AllocRange,
-        error_offset: Size,
-        global: &GlobalStateInner,
-    ) -> InterpError<'static> {
-        let action = format!(
-            "trying to reborrow {:?} for {:?} permission at {}[{:#x}]",
-            derived_from,
-            new.perm,
-            alloc_id,
-            error_offset.bytes(),
-        );
-        err_sb_ub(
-            format!("{}{}", action, self.error_cause(derived_from)),
-            Some(Self::operation_summary("a reborrow", alloc_id, alloc_range)),
-            global.get_stack_history(derived_from, alloc_id, alloc_range, error_offset, None),
-        )
-    }
-
-    /// Report a descriptive error when `access` is not permitted based on `tag`.
-    fn access_error(
-        &self,
-        access: AccessKind,
-        tag: SbTag,
-        alloc_id: AllocId,
-        alloc_range: AllocRange,
-        error_offset: Size,
-        global: &GlobalStateInner,
-    ) -> InterpError<'static> {
-        let action = format!(
-            "attempting a {} using {:?} at {}[{:#x}]",
-            access,
-            tag,
-            alloc_id,
-            error_offset.bytes(),
-        );
-        err_sb_ub(
-            format!("{}{}", action, self.error_cause(tag)),
-            Some(Self::operation_summary("an access", alloc_id, alloc_range)),
-            global.get_stack_history(tag, alloc_id, alloc_range, error_offset, None),
-        )
-    }
-
-    fn operation_summary(
-        operation: &'static str,
-        alloc_id: AllocId,
-        alloc_range: AllocRange,
-    ) -> String {
-        format!(
-            "this error occurs as part of {} at {:?}{}",
-            operation,
-            alloc_id,
-            HexRange(alloc_range)
-        )
-    }
-
-    fn error_cause(&self, tag: SbTag) -> &'static str {
-        if self.borrows.iter().any(|item| item.tag == tag && item.perm != Permission::Disabled) {
-            ", but that tag only grants SharedReadOnly permission for this location"
-        } else {
-            ", but that tag does not exist in the borrow stack for this location"
-        }
-    }
 }
 // # Stacked Borrows Core End