1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
use super::{AllocId, AllocRange, ConstAllocation, Pointer, Scalar};

use crate::error;
use crate::mir::{ConstAlloc, ConstValue};
use crate::ty::{layout, tls, Ty, TyCtxt, ValTree};

use rustc_ast_ir::Mutability;
use rustc_data_structures::sync::Lock;
use rustc_errors::{DiagArgName, DiagArgValue, DiagMessage, ErrorGuaranteed, IntoDiagArg};
use rustc_macros::HashStable;
use rustc_session::CtfeBacktrace;
use rustc_span::{def_id::DefId, Span, DUMMY_SP};
use rustc_target::abi::{call, Align, Size, VariantIdx, WrappingRange};

use std::borrow::Cow;
use std::{any::Any, backtrace::Backtrace, fmt};

#[derive(Debug, Copy, Clone, PartialEq, Eq, HashStable, TyEncodable, TyDecodable)]
pub enum ErrorHandled {
    /// Already reported an error for this evaluation, and the compilation is
    /// *guaranteed* to fail. Warnings/lints *must not* produce `Reported`.
    Reported(ReportedErrorInfo, Span),
    /// Don't emit an error, the evaluation failed because the MIR was generic
    /// and the args didn't fully monomorphize it.
    TooGeneric(Span),
}

impl From<ErrorGuaranteed> for ErrorHandled {
    #[inline]
    fn from(error: ErrorGuaranteed) -> ErrorHandled {
        ErrorHandled::Reported(error.into(), DUMMY_SP)
    }
}

impl ErrorHandled {
    pub fn with_span(self, span: Span) -> Self {
        match self {
            ErrorHandled::Reported(err, _span) => ErrorHandled::Reported(err, span),
            ErrorHandled::TooGeneric(_span) => ErrorHandled::TooGeneric(span),
        }
    }

    pub fn emit_note(&self, tcx: TyCtxt<'_>) {
        match self {
            &ErrorHandled::Reported(err, span) => {
                if !err.is_tainted_by_errors && !span.is_dummy() {
                    tcx.dcx().emit_note(error::ErroneousConstant { span });
                }
            }
            &ErrorHandled::TooGeneric(_) => {}
        }
    }
}

#[derive(Debug, Copy, Clone, PartialEq, Eq, HashStable, TyEncodable, TyDecodable)]
pub struct ReportedErrorInfo {
    error: ErrorGuaranteed,
    is_tainted_by_errors: bool,
}

impl ReportedErrorInfo {
    #[inline]
    pub fn tainted_by_errors(error: ErrorGuaranteed) -> ReportedErrorInfo {
        ReportedErrorInfo { is_tainted_by_errors: true, error }
    }
}

impl From<ErrorGuaranteed> for ReportedErrorInfo {
    #[inline]
    fn from(error: ErrorGuaranteed) -> ReportedErrorInfo {
        ReportedErrorInfo { is_tainted_by_errors: false, error }
    }
}

impl Into<ErrorGuaranteed> for ReportedErrorInfo {
    #[inline]
    fn into(self) -> ErrorGuaranteed {
        self.error
    }
}

TrivialTypeTraversalImpls! { ErrorHandled }

pub type EvalToAllocationRawResult<'tcx> = Result<ConstAlloc<'tcx>, ErrorHandled>;
pub type EvalStaticInitializerRawResult<'tcx> = Result<ConstAllocation<'tcx>, ErrorHandled>;
pub type EvalToConstValueResult<'tcx> = Result<ConstValue<'tcx>, ErrorHandled>;
/// `Ok(None)` indicates the constant was fine, but the valtree couldn't be constructed.
/// This is needed in `thir::pattern::lower_inline_const`.
pub type EvalToValTreeResult<'tcx> = Result<Option<ValTree<'tcx>>, ErrorHandled>;

#[cfg(all(target_arch = "x86_64", target_pointer_width = "64"))]
static_assert_size!(InterpErrorInfo<'_>, 8);

/// Packages the kind of error we got from the const code interpreter
/// up with a Rust-level backtrace of where the error occurred.
/// These should always be constructed by calling `.into()` on
/// an `InterpError`. In `rustc_mir::interpret`, we have `throw_err_*`
/// macros for this.
#[derive(Debug)]
pub struct InterpErrorInfo<'tcx>(Box<InterpErrorInfoInner<'tcx>>);

#[derive(Debug)]
struct InterpErrorInfoInner<'tcx> {
    kind: InterpError<'tcx>,
    backtrace: InterpErrorBacktrace,
}

#[derive(Debug)]
pub struct InterpErrorBacktrace {
    backtrace: Option<Box<Backtrace>>,
}

impl InterpErrorBacktrace {
    pub fn new() -> InterpErrorBacktrace {
        let capture_backtrace = tls::with_opt(|tcx| {
            if let Some(tcx) = tcx {
                *Lock::borrow(&tcx.sess.ctfe_backtrace)
            } else {
                CtfeBacktrace::Disabled
            }
        });

        let backtrace = match capture_backtrace {
            CtfeBacktrace::Disabled => None,
            CtfeBacktrace::Capture => Some(Box::new(Backtrace::force_capture())),
            CtfeBacktrace::Immediate => {
                // Print it now.
                let backtrace = Backtrace::force_capture();
                print_backtrace(&backtrace);
                None
            }
        };

        InterpErrorBacktrace { backtrace }
    }

    pub fn print_backtrace(&self) {
        if let Some(backtrace) = self.backtrace.as_ref() {
            print_backtrace(backtrace);
        }
    }
}

impl<'tcx> InterpErrorInfo<'tcx> {
    pub fn into_parts(self) -> (InterpError<'tcx>, InterpErrorBacktrace) {
        let InterpErrorInfo(box InterpErrorInfoInner { kind, backtrace }) = self;
        (kind, backtrace)
    }

    pub fn into_kind(self) -> InterpError<'tcx> {
        let InterpErrorInfo(box InterpErrorInfoInner { kind, .. }) = self;
        kind
    }

    #[inline]
    pub fn kind(&self) -> &InterpError<'tcx> {
        &self.0.kind
    }
}

fn print_backtrace(backtrace: &Backtrace) {
    eprintln!("\n\nAn error occurred in the MIR interpreter:\n{backtrace}");
}

impl From<ErrorGuaranteed> for InterpErrorInfo<'_> {
    fn from(err: ErrorGuaranteed) -> Self {
        InterpError::InvalidProgram(InvalidProgramInfo::AlreadyReported(err.into())).into()
    }
}

impl From<ErrorHandled> for InterpErrorInfo<'_> {
    fn from(err: ErrorHandled) -> Self {
        InterpError::InvalidProgram(match err {
            ErrorHandled::Reported(r, _span) => InvalidProgramInfo::AlreadyReported(r),
            ErrorHandled::TooGeneric(_span) => InvalidProgramInfo::TooGeneric,
        })
        .into()
    }
}

impl<'tcx> From<InterpError<'tcx>> for InterpErrorInfo<'tcx> {
    fn from(kind: InterpError<'tcx>) -> Self {
        InterpErrorInfo(Box::new(InterpErrorInfoInner {
            kind,
            backtrace: InterpErrorBacktrace::new(),
        }))
    }
}

/// Error information for when the program we executed turned out not to actually be a valid
/// program. This cannot happen in stand-alone Miri, but it can happen during CTFE/ConstProp
/// where we work on generic code or execution does not have all information available.
#[derive(Debug)]
pub enum InvalidProgramInfo<'tcx> {
    /// Resolution can fail if we are in a too generic context.
    TooGeneric,
    /// Abort in case errors are already reported.
    AlreadyReported(ReportedErrorInfo),
    /// An error occurred during layout computation.
    Layout(layout::LayoutError<'tcx>),
    /// An error occurred during FnAbi computation: the passed --target lacks FFI support
    /// (which unfortunately typeck does not reject).
    /// Not using `FnAbiError` as that contains a nested `LayoutError`.
    FnAbiAdjustForForeignAbi(call::AdjustForForeignAbiError),
}

/// Details of why a pointer had to be in-bounds.
#[derive(Debug, Copy, Clone)]
pub enum CheckInAllocMsg {
    /// We are access memory.
    MemoryAccessTest,
    /// We are doing pointer arithmetic.
    PointerArithmeticTest,
    /// We are doing pointer offset_from.
    OffsetFromTest,
    /// None of the above -- generic/unspecific inbounds test.
    InboundsTest,
}

/// Details of which pointer is not aligned.
#[derive(Debug, Copy, Clone)]
pub enum CheckAlignMsg {
    /// The accessed pointer did not have proper alignment.
    AccessedPtr,
    /// The access ocurred with a place that was based on a misaligned pointer.
    BasedOn,
}

#[derive(Debug, Copy, Clone)]
pub enum InvalidMetaKind {
    /// Size of a `[T]` is too big
    SliceTooBig,
    /// Size of a DST is too big
    TooBig,
}

impl IntoDiagArg for InvalidMetaKind {
    fn into_diag_arg(self) -> DiagArgValue {
        DiagArgValue::Str(Cow::Borrowed(match self {
            InvalidMetaKind::SliceTooBig => "slice_too_big",
            InvalidMetaKind::TooBig => "too_big",
        }))
    }
}

/// Details of an access to uninitialized bytes / bad pointer bytes where it is not allowed.
#[derive(Debug, Clone, Copy)]
pub struct BadBytesAccess {
    /// Range of the original memory access.
    pub access: AllocRange,
    /// Range of the bad memory that was encountered. (Might not be maximal.)
    pub bad: AllocRange,
}

/// Information about a size mismatch.
#[derive(Debug)]
pub struct ScalarSizeMismatch {
    pub target_size: u64,
    pub data_size: u64,
}

/// Information about a misaligned pointer.
#[derive(Copy, Clone, Hash, PartialEq, Eq, Debug)]
pub struct Misalignment {
    pub has: Align,
    pub required: Align,
}

macro_rules! impl_into_diag_arg_through_debug {
    ($($ty:ty),*$(,)?) => {$(
        impl IntoDiagArg for $ty {
            fn into_diag_arg(self) -> DiagArgValue {
                DiagArgValue::Str(Cow::Owned(format!("{self:?}")))
            }
        }
    )*}
}

// These types have nice `Debug` output so we can just use them in diagnostics.
impl_into_diag_arg_through_debug! {
    AllocId,
    Pointer<AllocId>,
    AllocRange,
}

/// Error information for when the program caused Undefined Behavior.
#[derive(Debug)]
pub enum UndefinedBehaviorInfo<'tcx> {
    /// Free-form case. Only for errors that are never caught! Used by miri
    Ub(String),
    // FIXME(fee1-dead) these should all be actual variants of the enum instead of dynamically
    // dispatched
    /// A custom (free-form) fluent-translated error, created by `err_ub_custom!`.
    Custom(crate::error::CustomSubdiagnostic<'tcx>),
    /// Validation error.
    ValidationError(ValidationErrorInfo<'tcx>),

    /// Unreachable code was executed.
    Unreachable,
    /// A slice/array index projection went out-of-bounds.
    BoundsCheckFailed { len: u64, index: u64 },
    /// Something was divided by 0 (x / 0).
    DivisionByZero,
    /// Something was "remainded" by 0 (x % 0).
    RemainderByZero,
    /// Signed division overflowed (INT_MIN / -1).
    DivisionOverflow,
    /// Signed remainder overflowed (INT_MIN % -1).
    RemainderOverflow,
    /// Overflowing inbounds pointer arithmetic.
    PointerArithOverflow,
    /// Invalid metadata in a wide pointer
    InvalidMeta(InvalidMetaKind),
    /// Reading a C string that does not end within its allocation.
    UnterminatedCString(Pointer<AllocId>),
    /// Using a pointer after it got freed.
    PointerUseAfterFree(AllocId, CheckInAllocMsg),
    /// Used a pointer outside the bounds it is valid for.
    /// (If `ptr_size > 0`, determines the size of the memory range that was expected to be in-bounds.)
    PointerOutOfBounds {
        alloc_id: AllocId,
        alloc_size: Size,
        ptr_offset: i64,
        ptr_size: Size,
        msg: CheckInAllocMsg,
    },
    /// Using an integer as a pointer in the wrong way.
    DanglingIntPointer(u64, CheckInAllocMsg),
    /// Used a pointer with bad alignment.
    AlignmentCheckFailed(Misalignment, CheckAlignMsg),
    /// Writing to read-only memory.
    WriteToReadOnly(AllocId),
    /// Trying to access the data behind a function pointer.
    DerefFunctionPointer(AllocId),
    /// Trying to access the data behind a vtable pointer.
    DerefVTablePointer(AllocId),
    /// Using a non-boolean `u8` as bool.
    InvalidBool(u8),
    /// Using a non-character `u32` as character.
    InvalidChar(u32),
    /// The tag of an enum does not encode an actual discriminant.
    InvalidTag(Scalar<AllocId>),
    /// Using a pointer-not-to-a-function as function pointer.
    InvalidFunctionPointer(Pointer<AllocId>),
    /// Using a pointer-not-to-a-vtable as vtable pointer.
    InvalidVTablePointer(Pointer<AllocId>),
    /// Using a string that is not valid UTF-8,
    InvalidStr(std::str::Utf8Error),
    /// Using uninitialized data where it is not allowed.
    InvalidUninitBytes(Option<(AllocId, BadBytesAccess)>),
    /// Working with a local that is not currently live.
    DeadLocal,
    /// Data size is not equal to target size.
    ScalarSizeMismatch(ScalarSizeMismatch),
    /// A discriminant of an uninhabited enum variant is written.
    UninhabitedEnumVariantWritten(VariantIdx),
    /// An uninhabited enum variant is projected.
    UninhabitedEnumVariantRead(VariantIdx),
    /// Trying to set discriminant to the niched variant, but the value does not match.
    InvalidNichedEnumVariantWritten { enum_ty: Ty<'tcx> },
    /// ABI-incompatible argument types.
    AbiMismatchArgument { caller_ty: Ty<'tcx>, callee_ty: Ty<'tcx> },
    /// ABI-incompatible return types.
    AbiMismatchReturn { caller_ty: Ty<'tcx>, callee_ty: Ty<'tcx> },
}

#[derive(Debug, Clone, Copy)]
pub enum PointerKind {
    Ref(Mutability),
    Box,
}

impl IntoDiagArg for PointerKind {
    fn into_diag_arg(self) -> DiagArgValue {
        DiagArgValue::Str(
            match self {
                Self::Ref(_) => "ref",
                Self::Box => "box",
            }
            .into(),
        )
    }
}

#[derive(Debug)]
pub struct ValidationErrorInfo<'tcx> {
    pub path: Option<String>,
    pub kind: ValidationErrorKind<'tcx>,
}

#[derive(Debug)]
pub enum ExpectedKind {
    Reference,
    Box,
    RawPtr,
    InitScalar,
    Bool,
    Char,
    Float,
    Int,
    FnPtr,
    EnumTag,
    Str,
}

impl From<PointerKind> for ExpectedKind {
    fn from(x: PointerKind) -> ExpectedKind {
        match x {
            PointerKind::Box => ExpectedKind::Box,
            PointerKind::Ref(_) => ExpectedKind::Reference,
        }
    }
}

#[derive(Debug)]
pub enum ValidationErrorKind<'tcx> {
    PointerAsInt { expected: ExpectedKind },
    PartialPointer,
    PtrToUninhabited { ptr_kind: PointerKind, ty: Ty<'tcx> },
    PtrToStatic { ptr_kind: PointerKind },
    ConstRefToMutable,
    ConstRefToExtern,
    MutableRefToImmutable,
    UnsafeCellInImmutable,
    NullFnPtr,
    NeverVal,
    NullablePtrOutOfRange { range: WrappingRange, max_value: u128 },
    PtrOutOfRange { range: WrappingRange, max_value: u128 },
    OutOfRange { value: String, range: WrappingRange, max_value: u128 },
    UninhabitedVal { ty: Ty<'tcx> },
    InvalidEnumTag { value: String },
    UninhabitedEnumVariant,
    Uninit { expected: ExpectedKind },
    InvalidVTablePtr { value: String },
    InvalidMetaSliceTooLarge { ptr_kind: PointerKind },
    InvalidMetaTooLarge { ptr_kind: PointerKind },
    UnalignedPtr { ptr_kind: PointerKind, required_bytes: u64, found_bytes: u64 },
    NullPtr { ptr_kind: PointerKind },
    DanglingPtrNoProvenance { ptr_kind: PointerKind, pointer: String },
    DanglingPtrOutOfBounds { ptr_kind: PointerKind },
    DanglingPtrUseAfterFree { ptr_kind: PointerKind },
    InvalidBool { value: String },
    InvalidChar { value: String },
    InvalidFnPtr { value: String },
}

/// Error information for when the program did something that might (or might not) be correct
/// to do according to the Rust spec, but due to limitations in the interpreter, the
/// operation could not be carried out. These limitations can differ between CTFE and the
/// Miri engine, e.g., CTFE does not support dereferencing pointers at integral addresses.
#[derive(Debug)]
pub enum UnsupportedOpInfo {
    /// Free-form case. Only for errors that are never caught!
    // FIXME still use translatable diagnostics
    Unsupported(String),
    /// Unsized local variables.
    UnsizedLocal,
    //
    // The variants below are only reachable from CTFE/const prop, miri will never emit them.
    //
    /// Overwriting parts of a pointer; without knowing absolute addresses, the resulting state
    /// cannot be represented by the CTFE interpreter.
    OverwritePartialPointer(Pointer<AllocId>),
    /// Attempting to read or copy parts of a pointer to somewhere else; without knowing absolute
    /// addresses, the resulting state cannot be represented by the CTFE interpreter.
    ReadPartialPointer(Pointer<AllocId>),
    /// Encountered a pointer where we needed an integer.
    ReadPointerAsInt(Option<(AllocId, BadBytesAccess)>),
    /// Accessing thread local statics
    ThreadLocalStatic(DefId),
    /// Accessing an unsupported extern static.
    ExternStatic(DefId),
}

/// Error information for when the program exhausted the resources granted to it
/// by the interpreter.
#[derive(Debug)]
pub enum ResourceExhaustionInfo {
    /// The stack grew too big.
    StackFrameLimitReached,
    /// There is not enough memory (on the host) to perform an allocation.
    MemoryExhausted,
    /// The address space (of the target) is full.
    AddressSpaceFull,
}

/// A trait for machine-specific errors (or other "machine stop" conditions).
pub trait MachineStopType: Any + fmt::Debug + Send {
    /// The diagnostic message for this error
    fn diagnostic_message(&self) -> DiagMessage;
    /// Add diagnostic arguments by passing name and value pairs to `adder`, which are passed to
    /// fluent for formatting the translated diagnostic message.
    fn add_args(self: Box<Self>, adder: &mut dyn FnMut(DiagArgName, DiagArgValue));
}

impl dyn MachineStopType {
    #[inline(always)]
    pub fn downcast_ref<T: Any>(&self) -> Option<&T> {
        let x: &dyn Any = self;
        x.downcast_ref()
    }
}

#[derive(Debug)]
pub enum InterpError<'tcx> {
    /// The program caused undefined behavior.
    UndefinedBehavior(UndefinedBehaviorInfo<'tcx>),
    /// The program did something the interpreter does not support (some of these *might* be UB
    /// but the interpreter is not sure).
    Unsupported(UnsupportedOpInfo),
    /// The program was invalid (ill-typed, bad MIR, not sufficiently monomorphized, ...).
    InvalidProgram(InvalidProgramInfo<'tcx>),
    /// The program exhausted the interpreter's resources (stack/heap too big,
    /// execution takes too long, ...).
    ResourceExhaustion(ResourceExhaustionInfo),
    /// Stop execution for a machine-controlled reason. This is never raised by
    /// the core engine itself.
    MachineStop(Box<dyn MachineStopType>),
}

pub type InterpResult<'tcx, T = ()> = Result<T, InterpErrorInfo<'tcx>>;

impl InterpError<'_> {
    /// Some errors do string formatting even if the error is never printed.
    /// To avoid performance issues, there are places where we want to be sure to never raise these formatting errors,
    /// so this method lets us detect them and `bug!` on unexpected errors.
    pub fn formatted_string(&self) -> bool {
        matches!(
            self,
            InterpError::Unsupported(UnsupportedOpInfo::Unsupported(_))
                | InterpError::UndefinedBehavior(UndefinedBehaviorInfo::ValidationError { .. })
                | InterpError::UndefinedBehavior(UndefinedBehaviorInfo::Ub(_))
        )
    }
}