miri/
diagnostics.rs

1use std::fmt::{self, Write};
2use std::num::NonZero;
3use std::sync::Mutex;
4
5use rustc_abi::{Align, Size};
6use rustc_data_structures::fx::{FxBuildHasher, FxHashSet};
7use rustc_errors::{Diag, DiagMessage, Level};
8use rustc_span::{DUMMY_SP, Span, SpanData, Symbol};
9
10use crate::borrow_tracker::stacked_borrows::diagnostics::TagHistory;
11use crate::borrow_tracker::tree_borrows::diagnostics as tree_diagnostics;
12use crate::*;
13
14/// Details of premature program termination.
15pub enum TerminationInfo {
16    Exit {
17        code: i32,
18        leak_check: bool,
19    },
20    Abort(String),
21    /// Miri was interrupted by a Ctrl+C from the user
22    Interrupted,
23    UnsupportedInIsolation(String),
24    StackedBorrowsUb {
25        msg: String,
26        help: Vec<String>,
27        history: Option<TagHistory>,
28    },
29    TreeBorrowsUb {
30        title: String,
31        details: Vec<String>,
32        history: tree_diagnostics::HistoryData,
33    },
34    Int2PtrWithStrictProvenance,
35    /// All threads are blocked.
36    GlobalDeadlock,
37    /// Some thread discovered a deadlock condition (e.g. in a mutex with reentrancy checking).
38    LocalDeadlock,
39    MultipleSymbolDefinitions {
40        link_name: Symbol,
41        first: SpanData,
42        first_crate: Symbol,
43        second: SpanData,
44        second_crate: Symbol,
45    },
46    SymbolShimClashing {
47        link_name: Symbol,
48        span: SpanData,
49    },
50    DataRace {
51        involves_non_atomic: bool,
52        ptr: interpret::Pointer<AllocId>,
53        op1: RacingOp,
54        op2: RacingOp,
55        extra: Option<&'static str>,
56        retag_explain: bool,
57    },
58    UnsupportedForeignItem(String),
59}
60
61pub struct RacingOp {
62    pub action: String,
63    pub thread_info: String,
64    pub span: SpanData,
65}
66
67impl fmt::Display for TerminationInfo {
68    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
69        use TerminationInfo::*;
70        match self {
71            Exit { code, .. } => write!(f, "the evaluated program completed with exit code {code}"),
72            Abort(msg) => write!(f, "{msg}"),
73            Interrupted => write!(f, "interpretation was interrupted"),
74            UnsupportedInIsolation(msg) => write!(f, "{msg}"),
75            Int2PtrWithStrictProvenance =>
76                write!(
77                    f,
78                    "integer-to-pointer casts and `ptr::with_exposed_provenance` are not supported with `-Zmiri-strict-provenance`"
79                ),
80            StackedBorrowsUb { msg, .. } => write!(f, "{msg}"),
81            TreeBorrowsUb { title, .. } => write!(f, "{title}"),
82            GlobalDeadlock => write!(f, "the evaluated program deadlocked"),
83            LocalDeadlock => write!(f, "a thread deadlocked"),
84            MultipleSymbolDefinitions { link_name, .. } =>
85                write!(f, "multiple definitions of symbol `{link_name}`"),
86            SymbolShimClashing { link_name, .. } =>
87                write!(f, "found `{link_name}` symbol definition that clashes with a built-in shim",),
88            DataRace { involves_non_atomic, ptr, op1, op2, .. } =>
89                write!(
90                    f,
91                    "{} detected between (1) {} on {} and (2) {} on {} at {ptr:?}",
92                    if *involves_non_atomic { "Data race" } else { "Race condition" },
93                    op1.action,
94                    op1.thread_info,
95                    op2.action,
96                    op2.thread_info
97                ),
98            UnsupportedForeignItem(msg) => write!(f, "{msg}"),
99        }
100    }
101}
102
103impl fmt::Debug for TerminationInfo {
104    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
105        write!(f, "{self}")
106    }
107}
108
109impl MachineStopType for TerminationInfo {
110    fn diagnostic_message(&self) -> DiagMessage {
111        self.to_string().into()
112    }
113    fn add_args(
114        self: Box<Self>,
115        _: &mut dyn FnMut(std::borrow::Cow<'static, str>, rustc_errors::DiagArgValue),
116    ) {
117    }
118}
119
120/// Miri specific diagnostics
121pub enum NonHaltingDiagnostic {
122    /// (new_tag, new_perm, (alloc_id, base_offset, orig_tag))
123    ///
124    /// new_perm is `None` for base tags.
125    CreatedPointerTag(NonZero<u64>, Option<String>, Option<(AllocId, AllocRange, ProvenanceExtra)>),
126    /// This `Item` was popped from the borrow stack. The string explains the reason.
127    PoppedPointerTag(Item, String),
128    TrackingAlloc(AllocId, Size, Align),
129    FreedAlloc(AllocId),
130    AccessedAlloc(AllocId, AllocRange, borrow_tracker::AccessKind),
131    RejectedIsolatedOp(String),
132    ProgressReport {
133        block_count: u64, // how many basic blocks have been run so far
134    },
135    Int2Ptr {
136        details: bool,
137    },
138    NativeCallSharedMem {
139        tracing: bool,
140    },
141    WeakMemoryOutdatedLoad {
142        ptr: Pointer,
143    },
144    ExternTypeReborrow,
145    GenmcCompareExchangeWeak,
146    GenmcCompareExchangeOrderingMismatch {
147        success_ordering: AtomicRwOrd,
148        upgraded_success_ordering: AtomicRwOrd,
149        failure_ordering: AtomicReadOrd,
150        effective_failure_ordering: AtomicReadOrd,
151    },
152}
153
154/// Level of Miri specific diagnostics
155pub enum DiagLevel {
156    Error,
157    Warning,
158    Note,
159}
160
161/// Generate a note/help text without a span.
162macro_rules! note {
163    ($($tt:tt)*) => { (None, format!($($tt)*)) };
164}
165/// Generate a note/help text with a span.
166macro_rules! note_span {
167    ($span:expr, $($tt:tt)*) => { (Some($span), format!($($tt)*)) };
168}
169
170/// Attempts to prune a stacktrace to omit the Rust runtime, and returns a bool indicating if any
171/// frames were pruned. If the stacktrace does not have any local frames, we conclude that it must
172/// be pointing to a problem in the Rust runtime itself, and do not prune it at all.
173pub fn prune_stacktrace<'tcx>(
174    mut stacktrace: Vec<FrameInfo<'tcx>>,
175    machine: &MiriMachine<'tcx>,
176) -> (Vec<FrameInfo<'tcx>>, bool) {
177    match machine.backtrace_style {
178        BacktraceStyle::Off => {
179            // Remove all frames marked with `caller_location` -- that attribute indicates we
180            // usually want to point at the caller, not them.
181            stacktrace.retain(|frame| !frame.instance.def.requires_caller_location(machine.tcx));
182            // Retain one frame so that we can print a span for the error itself
183            stacktrace.truncate(1);
184            (stacktrace, false)
185        }
186        BacktraceStyle::Short => {
187            let original_len = stacktrace.len();
188            // Remove all frames marked with `caller_location` -- that attribute indicates we
189            // usually want to point at the caller, not them.
190            stacktrace.retain(|frame| !frame.instance.def.requires_caller_location(machine.tcx));
191            // Only prune further frames if there is at least one local frame. This check ensures
192            // that if we get a backtrace that never makes it to the user code because it has
193            // detected a bug in the Rust runtime, we don't prune away every frame.
194            let has_local_frame = stacktrace.iter().any(|frame| machine.is_local(frame.instance));
195            if has_local_frame {
196                // This is part of the logic that `std` uses to select the relevant part of a
197                // backtrace. But here, we only look for __rust_begin_short_backtrace, not
198                // __rust_end_short_backtrace because the end symbol comes from a call to the default
199                // panic handler.
200                stacktrace = stacktrace
201                    .into_iter()
202                    .take_while(|frame| {
203                        let def_id = frame.instance.def_id();
204                        let path = machine.tcx.def_path_str(def_id);
205                        !path.contains("__rust_begin_short_backtrace")
206                    })
207                    .collect::<Vec<_>>();
208
209                // After we prune frames from the bottom, there are a few left that are part of the
210                // Rust runtime. So we remove frames until we get to a local symbol, which should be
211                // main or a test.
212                // This len check ensures that we don't somehow remove every frame, as doing so breaks
213                // the primary error message.
214                while stacktrace.len() > 1
215                    && stacktrace.last().is_some_and(|frame| !machine.is_local(frame.instance))
216                {
217                    stacktrace.pop();
218                }
219            }
220            let was_pruned = stacktrace.len() != original_len;
221            (stacktrace, was_pruned)
222        }
223        BacktraceStyle::Full => (stacktrace, false),
224    }
225}
226
227/// Report the result of a Miri execution.
228///
229/// Returns `Some` if this was regular program termination with a given exit code and a `bool`
230/// indicating whether a leak check should happen; `None` otherwise.
231pub fn report_result<'tcx>(
232    ecx: &InterpCx<'tcx, MiriMachine<'tcx>>,
233    res: InterpErrorInfo<'tcx>,
234) -> Option<(i32, bool)> {
235    use InterpErrorKind::*;
236    use UndefinedBehaviorInfo::*;
237
238    let mut labels = vec![];
239
240    let (title, helps) = if let MachineStop(info) = res.kind() {
241        let info = info.downcast_ref::<TerminationInfo>().expect("invalid MachineStop payload");
242        use TerminationInfo::*;
243        let title = match info {
244            &Exit { code, leak_check } => return Some((code, leak_check)),
245            Abort(_) => Some("abnormal termination"),
246            Interrupted => None,
247            UnsupportedInIsolation(_) | Int2PtrWithStrictProvenance | UnsupportedForeignItem(_) =>
248                Some("unsupported operation"),
249            StackedBorrowsUb { .. } | TreeBorrowsUb { .. } | DataRace { .. } =>
250                Some("Undefined Behavior"),
251            LocalDeadlock => {
252                labels.push(format!("thread got stuck here"));
253                None
254            }
255            GlobalDeadlock => {
256                // Global deadlocks are reported differently: just show all blocked threads.
257                // The "active" thread might actually be terminated, so we ignore it.
258                let mut any_pruned = false;
259                for (thread, stack) in ecx.machine.threads.all_blocked_stacks() {
260                    let stacktrace = Frame::generate_stacktrace_from_stack(stack, *ecx.tcx);
261                    let (stacktrace, was_pruned) = prune_stacktrace(stacktrace, &ecx.machine);
262                    any_pruned |= was_pruned;
263                    report_msg(
264                        DiagLevel::Error,
265                        format!("the evaluated program deadlocked"),
266                        vec![format!("thread got stuck here")],
267                        vec![],
268                        vec![],
269                        &stacktrace,
270                        Some(thread),
271                        &ecx.machine,
272                    )
273                }
274                if any_pruned {
275                    ecx.tcx.dcx().note(
276                        "some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace"
277                    );
278                }
279                return None;
280            }
281            MultipleSymbolDefinitions { .. } | SymbolShimClashing { .. } => None,
282        };
283        #[rustfmt::skip]
284        let helps = match info {
285            UnsupportedInIsolation(_) =>
286                vec![
287                    note!("set `MIRIFLAGS=-Zmiri-disable-isolation` to disable isolation;"),
288                    note!("or set `MIRIFLAGS=-Zmiri-isolation-error=warn` to make Miri return an error code from isolated operations (if supported for that operation) and continue with a warning"),
289                ],
290            UnsupportedForeignItem(_) => {
291                vec![
292                    note!("this means the program tried to do something Miri does not support; it does not indicate a bug in the program"),
293                ]
294            }
295            StackedBorrowsUb { help, history, .. } => {
296                labels.extend(help.clone());
297                let mut helps = vec![
298                    note!("this indicates a potential bug in the program: it performed an invalid operation, but the Stacked Borrows rules it violated are still experimental"),
299                    note!("see https://github.com/rust-lang/unsafe-code-guidelines/blob/master/wip/stacked-borrows.md for further information"),
300                ];
301                if let Some(TagHistory {created, invalidated, protected}) = history.clone() {
302                    helps.push((Some(created.1), created.0));
303                    if let Some((msg, span)) = invalidated {
304                        helps.push(note_span!(span, "{msg}"));
305                    }
306                    if let Some((protector_msg, protector_span)) = protected {
307                        helps.push(note_span!(protector_span, "{protector_msg}"));
308                    }
309                }
310                helps
311            },
312            TreeBorrowsUb { title: _, details, history } => {
313                let mut helps = vec![
314                    note!("this indicates a potential bug in the program: it performed an invalid operation, but the Tree Borrows rules it violated are still experimental"),
315                    note!("see https://github.com/rust-lang/unsafe-code-guidelines/blob/master/wip/tree-borrows.md for further information"),
316                ];
317                for m in details {
318                    helps.push(note!("{m}"));
319                }
320                for event in history.events.clone() {
321                    helps.push(event);
322                }
323                helps
324            }
325            MultipleSymbolDefinitions { first, first_crate, second, second_crate, .. } =>
326                vec![
327                    note_span!(*first, "it's first defined here, in crate `{first_crate}`"),
328                    note_span!(*second, "then it's defined here again, in crate `{second_crate}`"),
329                ],
330            SymbolShimClashing { link_name, span } =>
331                vec![note_span!(*span, "the `{link_name}` symbol is defined here")],
332            Int2PtrWithStrictProvenance =>
333                vec![note!("use Strict Provenance APIs (https://doc.rust-lang.org/nightly/std/ptr/index.html#strict-provenance, https://crates.io/crates/sptr) instead")],
334            DataRace { op1, extra, retag_explain, .. } => {
335                labels.push(format!("(2) just happened here"));
336                let mut helps = vec![note_span!(op1.span, "and (1) occurred earlier here")];
337                if let Some(extra) = extra {
338                    helps.push(note!("{extra}"));
339                    helps.push(note!("see https://doc.rust-lang.org/nightly/std/sync/atomic/index.html#memory-model-for-atomic-accesses for more information about the Rust memory model"));
340                }
341                if *retag_explain {
342                    helps.push(note!("retags occur on all (re)borrows and as well as when references are copied or moved"));
343                    helps.push(note!("retags permit optimizations that insert speculative reads or writes"));
344                    helps.push(note!("therefore from the perspective of data races, a retag has the same implications as a read or write"));
345                }
346                helps.push(note!("this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior"));
347                helps.push(note!("see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information"));
348                helps
349            }
350                ,
351            _ => vec![],
352        };
353        (title, helps)
354    } else {
355        let title = match res.kind() {
356            UndefinedBehavior(ValidationError(validation_err))
357                if matches!(
358                    validation_err.kind,
359                    ValidationErrorKind::PointerAsInt { .. } | ValidationErrorKind::PartialPointer
360                ) =>
361            {
362                ecx.handle_ice(); // print interpreter backtrace (this is outside the eval `catch_unwind`)
363                bug!(
364                    "This validation error should be impossible in Miri: {}",
365                    format_interp_error(ecx.tcx.dcx(), res)
366                );
367            }
368            UndefinedBehavior(_) => "Undefined Behavior",
369            ResourceExhaustion(_) => "resource exhaustion",
370            Unsupported(
371                // We list only the ones that can actually happen.
372                UnsupportedOpInfo::Unsupported(_)
373                | UnsupportedOpInfo::UnsizedLocal
374                | UnsupportedOpInfo::ExternTypeField,
375            ) => "unsupported operation",
376            InvalidProgram(
377                // We list only the ones that can actually happen.
378                InvalidProgramInfo::AlreadyReported(_) | InvalidProgramInfo::Layout(..),
379            ) => "post-monomorphization error",
380            _ => {
381                ecx.handle_ice(); // print interpreter backtrace (this is outside the eval `catch_unwind`)
382                bug!(
383                    "This error should be impossible in Miri: {}",
384                    format_interp_error(ecx.tcx.dcx(), res)
385                );
386            }
387        };
388        #[rustfmt::skip]
389        let helps = match res.kind() {
390            Unsupported(_) =>
391                vec![
392                    note!("this is likely not a bug in the program; it indicates that the program performed an operation that Miri does not support"),
393                ],
394            ResourceExhaustion(ResourceExhaustionInfo::AddressSpaceFull) if ecx.machine.data_race.as_genmc_ref().is_some() =>
395                vec![
396                    note!("in GenMC mode, the address space is limited to 4GB per thread, and addresses cannot be reused")
397                ],
398            UndefinedBehavior(AlignmentCheckFailed { .. })
399                if ecx.machine.check_alignment == AlignmentCheck::Symbolic
400            =>
401                vec![
402                    note!("this usually indicates that your program performed an invalid operation and caused Undefined Behavior"),
403                    note!("but due to `-Zmiri-symbolic-alignment-check`, alignment errors can also be false positives"),
404                ],
405            UndefinedBehavior(info) => {
406                let mut helps = vec![
407                    note!("this indicates a bug in the program: it performed an invalid operation, and caused Undefined Behavior"),
408                    note!("see https://doc.rust-lang.org/nightly/reference/behavior-considered-undefined.html for further information"),
409                ];
410                match info {
411                    PointerUseAfterFree(alloc_id, _) | PointerOutOfBounds { alloc_id, .. } => {
412                        if let Some(span) = ecx.machine.allocated_span(*alloc_id) {
413                            helps.push(note_span!(span, "{:?} was allocated here:", alloc_id));
414                        }
415                        if let Some(span) = ecx.machine.deallocated_span(*alloc_id) {
416                            helps.push(note_span!(span, "{:?} was deallocated here:", alloc_id));
417                        }
418                    }
419                    AbiMismatchArgument { .. } | AbiMismatchReturn { .. } => {
420                        helps.push(note!("this means these two types are not *guaranteed* to be ABI-compatible across all targets"));
421                        helps.push(note!("if you think this code should be accepted anyway, please report an issue with Miri"));
422                    }
423                    _ => {},
424                }
425                helps
426            }
427            InvalidProgram(
428                InvalidProgramInfo::AlreadyReported(_)
429            ) => {
430                // This got already reported. No point in reporting it again.
431                return None;
432            }
433            _ =>
434                vec![],
435        };
436        (Some(title), helps)
437    };
438
439    let stacktrace = ecx.generate_stacktrace();
440    let (stacktrace, pruned) = prune_stacktrace(stacktrace, &ecx.machine);
441
442    // We want to dump the allocation if this is `InvalidUninitBytes`.
443    // Since `format_interp_error` consumes `e`, we compute the outut early.
444    let mut extra = String::new();
445    match res.kind() {
446        UndefinedBehavior(InvalidUninitBytes(Some((alloc_id, access)))) => {
447            writeln!(
448                extra,
449                "Uninitialized memory occurred at {alloc_id:?}{range:?}, in this allocation:",
450                range = access.bad,
451            )
452            .unwrap();
453            writeln!(extra, "{:?}", ecx.dump_alloc(*alloc_id)).unwrap();
454        }
455        _ => {}
456    }
457
458    let mut primary_msg = String::new();
459    if let Some(title) = title {
460        write!(primary_msg, "{title}: ").unwrap();
461    }
462    write!(primary_msg, "{}", format_interp_error(ecx.tcx.dcx(), res)).unwrap();
463
464    if labels.is_empty() {
465        labels.push(format!(
466            "{} occurred {}",
467            title.unwrap_or("error"),
468            if stacktrace.is_empty() { "due to this code" } else { "here" }
469        ));
470    }
471
472    report_msg(
473        DiagLevel::Error,
474        primary_msg,
475        labels,
476        vec![],
477        helps,
478        &stacktrace,
479        Some(ecx.active_thread()),
480        &ecx.machine,
481    );
482
483    eprint!("{extra}"); // newlines are already in the string
484
485    // Include a note like `std` does when we omit frames from a backtrace
486    if pruned {
487        ecx.tcx.dcx().note(
488            "some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace",
489        );
490    }
491
492    // Debug-dump all locals.
493    for (i, frame) in ecx.active_thread_stack().iter().enumerate() {
494        trace!("-------------------");
495        trace!("Frame {}", i);
496        trace!("    return: {:?}", frame.return_place());
497        for (i, local) in frame.locals.iter().enumerate() {
498            trace!("    local {}: {:?}", i, local);
499        }
500    }
501
502    None
503}
504
505pub fn report_leaks<'tcx>(
506    ecx: &InterpCx<'tcx, MiriMachine<'tcx>>,
507    leaks: Vec<(AllocId, MemoryKind, Allocation<Provenance, AllocExtra<'tcx>, MiriAllocBytes>)>,
508) {
509    let mut any_pruned = false;
510    for (id, kind, alloc) in leaks {
511        let mut title = format!(
512            "memory leaked: {id:?} ({}, size: {:?}, align: {:?})",
513            kind,
514            alloc.size().bytes(),
515            alloc.align.bytes()
516        );
517        let Some(backtrace) = alloc.extra.backtrace else {
518            ecx.tcx.dcx().err(title);
519            continue;
520        };
521        title.push_str(", allocated here:");
522        let (backtrace, pruned) = prune_stacktrace(backtrace, &ecx.machine);
523        any_pruned |= pruned;
524        report_msg(
525            DiagLevel::Error,
526            title,
527            vec![],
528            vec![],
529            vec![],
530            &backtrace,
531            None, // we don't know the thread this is from
532            &ecx.machine,
533        );
534    }
535    if any_pruned {
536        ecx.tcx.dcx().note(
537            "some details are omitted, run with `MIRIFLAGS=-Zmiri-backtrace=full` for a verbose backtrace",
538        );
539    }
540}
541
542/// Report an error or note (depending on the `error` argument) with the given stacktrace.
543/// Also emits a full stacktrace of the interpreter stack.
544/// We want to present a multi-line span message for some errors. Diagnostics do not support this
545/// directly, so we pass the lines as a `Vec<String>` and display each line after the first with an
546/// additional `span_label` or `note` call.
547fn report_msg<'tcx>(
548    diag_level: DiagLevel,
549    title: String,
550    span_msg: Vec<String>,
551    notes: Vec<(Option<SpanData>, String)>,
552    helps: Vec<(Option<SpanData>, String)>,
553    stacktrace: &[FrameInfo<'tcx>],
554    thread: Option<ThreadId>,
555    machine: &MiriMachine<'tcx>,
556) {
557    let origin_span = thread.map(|t| machine.threads.thread_ref(t).origin_span).unwrap_or(DUMMY_SP);
558    let span = stacktrace.first().map(|fi| fi.span).unwrap_or(origin_span);
559    // The only time we do not have an origin span is for `main`, and there we check the signature
560    // upfront. So we should always have a span here.
561    assert!(!span.is_dummy());
562
563    let tcx = machine.tcx;
564    let level = match diag_level {
565        DiagLevel::Error => Level::Error,
566        DiagLevel::Warning => Level::Warning,
567        DiagLevel::Note => Level::Note,
568    };
569    let mut err = Diag::<()>::new(tcx.sess.dcx(), level, title);
570    err.span(span);
571
572    // Show main message.
573    for line in span_msg {
574        err.span_label(span, line);
575    }
576
577    // Show note and help messages.
578    for (span_data, note) in notes {
579        if let Some(span_data) = span_data {
580            err.span_note(span_data.span(), note);
581        } else {
582            err.note(note);
583        }
584    }
585    for (span_data, help) in helps {
586        if let Some(span_data) = span_data {
587            err.span_help(span_data.span(), help);
588        } else {
589            err.help(help);
590        }
591    }
592    // Only print thread name if there are multiple threads.
593    if let Some(thread) = thread
594        && machine.threads.get_total_thread_count() > 1
595    {
596        err.note(format!(
597            "this is on thread `{}`",
598            machine.threads.get_thread_display_name(thread)
599        ));
600    }
601
602    // Add backtrace
603    if stacktrace.len() > 0 {
604        // Skip it if we'd only shpw the span we have already shown
605        if stacktrace.len() > 1 {
606            let sm = tcx.sess.source_map();
607            let mut out = format!("stack backtrace:");
608            for (idx, frame_info) in stacktrace.iter().enumerate() {
609                let span = sm.span_to_diagnostic_string(frame_info.span);
610                write!(out, "\n{idx}: {}", frame_info.instance).unwrap();
611                write!(out, "\n    at {span}").unwrap();
612            }
613            err.note(out);
614        }
615        // For TLS dtors and non-main threads, show the "origin"
616        if !origin_span.is_dummy() {
617            let what = if stacktrace.len() > 1 {
618                "the last function in that backtrace"
619            } else {
620                "the current function"
621            };
622            err.span_note(origin_span, format!("{what} got called indirectly due to this code"));
623        }
624    } else if !span.is_dummy() {
625        err.note(format!("this {level} occurred while pushing a call frame onto an empty stack"));
626        err.note("the span indicates which code caused the function to be called, but may not be the literal call site");
627    }
628
629    err.emit();
630}
631
632impl<'tcx> MiriMachine<'tcx> {
633    pub fn emit_diagnostic(&self, e: NonHaltingDiagnostic) {
634        use NonHaltingDiagnostic::*;
635
636        let stacktrace =
637            Frame::generate_stacktrace_from_stack(self.threads.active_thread_stack(), self.tcx);
638        let (stacktrace, _was_pruned) = prune_stacktrace(stacktrace, self);
639
640        let (label, diag_level) = match &e {
641            RejectedIsolatedOp(_) =>
642                ("operation rejected by isolation".to_string(), DiagLevel::Warning),
643            Int2Ptr { .. } => ("integer-to-pointer cast".to_string(), DiagLevel::Warning),
644            NativeCallSharedMem { .. } =>
645                ("sharing memory with a native function".to_string(), DiagLevel::Warning),
646            ExternTypeReborrow =>
647                ("reborrow of reference to `extern type`".to_string(), DiagLevel::Warning),
648            GenmcCompareExchangeWeak | GenmcCompareExchangeOrderingMismatch { .. } =>
649                ("GenMC might miss possible behaviors of this code".to_string(), DiagLevel::Warning),
650            CreatedPointerTag(..)
651            | PoppedPointerTag(..)
652            | TrackingAlloc(..)
653            | AccessedAlloc(..)
654            | FreedAlloc(..)
655            | ProgressReport { .. }
656            | WeakMemoryOutdatedLoad { .. } =>
657                ("tracking was triggered here".to_string(), DiagLevel::Note),
658        };
659
660        let title = match &e {
661            CreatedPointerTag(tag, None, _) => format!("created base tag {tag:?}"),
662            CreatedPointerTag(tag, Some(perm), None) =>
663                format!("created {tag:?} with {perm} derived from unknown tag"),
664            CreatedPointerTag(tag, Some(perm), Some((alloc_id, range, orig_tag))) =>
665                format!(
666                    "created tag {tag:?} with {perm} at {alloc_id:?}{range:?} derived from {orig_tag:?}"
667                ),
668            PoppedPointerTag(item, cause) => format!("popped tracked tag for item {item:?}{cause}"),
669            TrackingAlloc(id, size, align) =>
670                format!(
671                    "now tracking allocation {id:?} of {size} bytes (alignment {align} bytes)",
672                    size = size.bytes(),
673                    align = align.bytes(),
674                ),
675            AccessedAlloc(id, range, access_kind) =>
676                format!("{access_kind} at {id:?}[{}..{}]", range.start.bytes(), range.end().bytes()),
677            FreedAlloc(id) => format!("freed allocation {id:?}"),
678            RejectedIsolatedOp(op) => format!("{op} was made to return an error due to isolation"),
679            ProgressReport { .. } =>
680                format!("progress report: current operation being executed is here"),
681            Int2Ptr { .. } => format!("integer-to-pointer cast"),
682            NativeCallSharedMem { .. } =>
683                format!("sharing memory with a native function called via FFI"),
684            WeakMemoryOutdatedLoad { ptr } =>
685                format!("weak memory emulation: outdated value returned from load at {ptr}"),
686            ExternTypeReborrow =>
687                format!("reborrow of a reference to `extern type` is not properly supported"),
688            GenmcCompareExchangeWeak =>
689                "GenMC currently does not model spurious failures of `compare_exchange_weak`. Miri with GenMC might miss bugs related to spurious failures."
690                    .to_string(),
691            GenmcCompareExchangeOrderingMismatch {
692                success_ordering,
693                upgraded_success_ordering,
694                failure_ordering,
695                effective_failure_ordering,
696            } => {
697                let was_upgraded_msg = if success_ordering != upgraded_success_ordering {
698                    format!("Success ordering '{success_ordering:?}' was upgraded to '{upgraded_success_ordering:?}' to match failure ordering '{failure_ordering:?}'")
699                } else {
700                    assert_ne!(failure_ordering, effective_failure_ordering);
701                    format!("Due to success ordering '{success_ordering:?}', the failure ordering '{failure_ordering:?}' is treated like '{effective_failure_ordering:?}'")
702                };
703                format!("GenMC currently does not model the failure ordering for `compare_exchange`. {was_upgraded_msg}. Miri with GenMC might miss bugs related to this memory access.")
704            }
705        };
706
707        let notes = match &e {
708            ProgressReport { block_count } => {
709                vec![note!("so far, {block_count} basic blocks have been executed")]
710            }
711            _ => vec![],
712        };
713
714        let helps = match &e {
715            Int2Ptr { details: true } => {
716                let mut v = vec![
717                    note!(
718                        "this program is using integer-to-pointer casts or (equivalently) `ptr::with_exposed_provenance`, which means that Miri might miss pointer bugs in this program"
719                    ),
720                    note!(
721                        "see https://doc.rust-lang.org/nightly/std/ptr/fn.with_exposed_provenance.html for more details on that operation"
722                    ),
723                    note!(
724                        "to ensure that Miri does not miss bugs in your program, use Strict Provenance APIs (https://doc.rust-lang.org/nightly/std/ptr/index.html#strict-provenance, https://crates.io/crates/sptr) instead"
725                    ),
726                    note!(
727                        "you can then set `MIRIFLAGS=-Zmiri-strict-provenance` to ensure you are not relying on `with_exposed_provenance` semantics"
728                    ),
729                ];
730                if self.borrow_tracker.as_ref().is_some_and(|b| {
731                    matches!(
732                        b.borrow().borrow_tracker_method(),
733                        BorrowTrackerMethod::TreeBorrows { .. }
734                    )
735                }) {
736                    v.push(
737                        note!("Tree Borrows does not support integer-to-pointer casts, so the program is likely to go wrong when this pointer gets used")
738                    );
739                } else {
740                    v.push(
741                        note!("alternatively, `MIRIFLAGS=-Zmiri-permissive-provenance` disables this warning")
742                    );
743                }
744                v
745            }
746            NativeCallSharedMem { tracing } =>
747                if *tracing {
748                    vec![
749                        note!(
750                            "when memory is shared with a native function call, Miri can only track initialisation and provenance on a best-effort basis"
751                        ),
752                        note!(
753                            "in particular, Miri assumes that the native call initializes all memory it has written to"
754                        ),
755                        note!(
756                            "Miri also assumes that any part of this memory may be a pointer that is permitted to point to arbitrary exposed memory"
757                        ),
758                        note!(
759                            "what this means is that Miri will easily miss Undefined Behavior related to incorrect usage of this shared memory, so you should not take a clean Miri run as a signal that your FFI code is UB-free"
760                        ),
761                        note!(
762                            "tracing memory accesses in native code is not yet fully implemented, so there can be further imprecisions beyond what is documented here"
763                        ),
764                    ]
765                } else {
766                    vec![
767                        note!(
768                            "when memory is shared with a native function call, Miri stops tracking initialization and provenance for that memory"
769                        ),
770                        note!(
771                            "in particular, Miri assumes that the native call initializes all memory it has access to"
772                        ),
773                        note!(
774                            "Miri also assumes that any part of this memory may be a pointer that is permitted to point to arbitrary exposed memory"
775                        ),
776                        note!(
777                            "what this means is that Miri will easily miss Undefined Behavior related to incorrect usage of this shared memory, so you should not take a clean Miri run as a signal that your FFI code is UB-free"
778                        ),
779                    ]
780                },
781            ExternTypeReborrow => {
782                assert!(self.borrow_tracker.as_ref().is_some_and(|b| {
783                    matches!(
784                        b.borrow().borrow_tracker_method(),
785                        BorrowTrackerMethod::StackedBorrows
786                    )
787                }));
788                vec![
789                    note!(
790                        "`extern type` are not compatible with the Stacked Borrows aliasing model implemented by Miri; Miri may miss bugs in this code"
791                    ),
792                    note!(
793                        "try running with `MIRIFLAGS=-Zmiri-tree-borrows` to use the more permissive but also even more experimental Tree Borrows aliasing checks instead"
794                    ),
795                ]
796            }
797            _ => vec![],
798        };
799
800        report_msg(
801            diag_level,
802            title,
803            vec![label],
804            notes,
805            helps,
806            &stacktrace,
807            Some(self.threads.active_thread()),
808            self,
809        );
810    }
811}
812
813impl<'tcx> EvalContextExt<'tcx> for crate::MiriInterpCx<'tcx> {}
814pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
815    fn emit_diagnostic(&self, e: NonHaltingDiagnostic) {
816        let this = self.eval_context_ref();
817        this.machine.emit_diagnostic(e);
818    }
819
820    /// We had a panic in Miri itself, try to print something useful.
821    fn handle_ice(&self) {
822        eprintln!();
823        eprintln!(
824            "Miri caused an ICE during evaluation. Here's the interpreter backtrace at the time of the panic:"
825        );
826        let this = self.eval_context_ref();
827        let stacktrace = this.generate_stacktrace();
828        report_msg(
829            DiagLevel::Note,
830            "the place in the program where the ICE was triggered".to_string(),
831            vec![],
832            vec![],
833            vec![],
834            &stacktrace,
835            Some(this.active_thread()),
836            &this.machine,
837        );
838    }
839
840    /// Call `f` only if this is the first time we are seeing this span.
841    /// The `first` parameter indicates whether this is the first time *ever* that this diagnostic
842    /// is emitted.
843    fn dedup_diagnostic(
844        &self,
845        dedup: &SpanDedupDiagnostic,
846        f: impl FnOnce(/*first*/ bool) -> NonHaltingDiagnostic,
847    ) {
848        let this = self.eval_context_ref();
849        // We want to deduplicate both based on where the error seems to be located "from the user
850        // perspective", and the location of the actual operation (to avoid warning about the same
851        // operation called from different places in the local code).
852        let span1 = this.machine.current_user_relevant_span();
853        // For the "location of the operation", we still skip `track_caller` frames, to match the
854        // span that the diagnostic will point at.
855        let span2 = this
856            .active_thread_stack()
857            .iter()
858            .rev()
859            .find(|frame| !frame.instance().def.requires_caller_location(*this.tcx))
860            .map(|frame| frame.current_span())
861            .unwrap_or(span1);
862
863        let mut lock = dedup.0.lock().unwrap();
864        let first = lock.is_empty();
865        // Avoid mutating the hashset unless both spans are new.
866        if !lock.contains(&span2) && lock.insert(span1) && (span1 == span2 || lock.insert(span2)) {
867            // Both of the two spans were newly inserted.
868            this.emit_diagnostic(f(first));
869        }
870    }
871}
872
873/// Helps deduplicate a diagnostic to ensure it is only shown once per span.
874pub struct SpanDedupDiagnostic(Mutex<FxHashSet<Span>>);
875
876impl SpanDedupDiagnostic {
877    pub const fn new() -> Self {
878        Self(Mutex::new(FxHashSet::with_hasher(FxBuildHasher)))
879    }
880}
miri/diagnostics.rs

miri/
diagnostics.rs
