1 //! An interpreter for MIR used in CTFE and by miri.
4 macro_rules! err_unsup {
6 $crate::mir::interpret::InterpError::Unsupported(
7 $crate::mir::interpret::UnsupportedOpInfo::$($tt)*
13 macro_rules! err_unsup_format {
14 ($($tt:tt)*) => { err_unsup!(Unsupported(format!($($tt)*))) };
18 macro_rules! err_inval {
20 $crate::mir::interpret::InterpError::InvalidProgram(
21 $crate::mir::interpret::InvalidProgramInfo::$($tt)*
29 $crate::mir::interpret::InterpError::UndefinedBehavior(
30 $crate::mir::interpret::UndefinedBehaviorInfo::$($tt)*
36 macro_rules! err_ub_format {
37 ($($tt:tt)*) => { err_ub!(Ub(format!($($tt)*))) };
41 macro_rules! err_exhaust {
43 $crate::mir::interpret::InterpError::ResourceExhaustion(
44 $crate::mir::interpret::ResourceExhaustionInfo::$($tt)*
50 macro_rules! err_machine_stop {
52 $crate::mir::interpret::InterpError::MachineStop(Box::new($($tt)*))
56 // In the `throw_*` macros, avoid `return` to make them work with `try {}`.
58 macro_rules! throw_unsup {
59 ($($tt:tt)*) => { Err::<!, _>(err_unsup!($($tt)*))? };
63 macro_rules! throw_unsup_format {
64 ($($tt:tt)*) => { throw_unsup!(Unsupported(format!($($tt)*))) };
68 macro_rules! throw_inval {
69 ($($tt:tt)*) => { Err::<!, _>(err_inval!($($tt)*))? };
73 macro_rules! throw_ub {
74 ($($tt:tt)*) => { Err::<!, _>(err_ub!($($tt)*))? };
78 macro_rules! throw_ub_format {
79 ($($tt:tt)*) => { throw_ub!(Ub(format!($($tt)*))) };
83 macro_rules! throw_exhaust {
84 ($($tt:tt)*) => { Err::<!, _>(err_exhaust!($($tt)*))? };
88 macro_rules! throw_machine_stop {
89 ($($tt:tt)*) => { Err::<!, _>(err_machine_stop!($($tt)*))? };
98 use std::convert::TryFrom;
101 use std::io::{Read, Write};
102 use std::num::{NonZeroU32, NonZeroU64};
103 use std::sync::atomic::{AtomicU32, Ordering};
105 use rustc_ast::LitKind;
106 use rustc_data_structures::fx::FxHashMap;
107 use rustc_data_structures::sync::{HashMapExt, Lock};
108 use rustc_data_structures::tiny_list::TinyList;
109 use rustc_hir::def_id::DefId;
110 use rustc_macros::HashStable;
111 use rustc_middle::ty::print::with_no_trimmed_paths;
112 use rustc_serialize::{Decodable, Encodable};
113 use rustc_target::abi::Endian;
116 use crate::ty::codec::{TyDecoder, TyEncoder};
117 use crate::ty::subst::GenericArgKind;
118 use crate::ty::{self, Instance, Ty, TyCtxt};
120 pub use self::error::{
121 struct_error, CheckInAllocMsg, ErrorHandled, EvalToAllocationRawResult, EvalToConstValueResult,
122 EvalToValTreeResult, InterpError, InterpErrorInfo, InterpResult, InvalidProgramInfo,
123 MachineStopType, ResourceExhaustionInfo, ScalarSizeMismatch, UndefinedBehaviorInfo,
124 UninitBytesAccess, UnsupportedOpInfo,
127 pub use self::value::{get_slice_bytes, ConstAlloc, ConstValue, Scalar, ScalarMaybeUninit};
129 pub use self::allocation::{
130 alloc_range, AllocRange, Allocation, ConstAllocation, InitChunk, InitChunkIter, InitMask,
134 pub use self::pointer::{Pointer, PointerArithmetic, Provenance};
136 /// Uniquely identifies one of the following:
139 #[derive(Copy, Clone, Debug, Eq, PartialEq, Hash, TyEncodable, TyDecodable)]
140 #[derive(HashStable, Lift)]
141 pub struct GlobalId<'tcx> {
142 /// For a constant or static, the `Instance` of the item itself.
143 /// For a promoted global, the `Instance` of the function they belong to.
144 pub instance: ty::Instance<'tcx>,
146 /// The index for promoted globals within their function's `mir::Body`.
147 pub promoted: Option<mir::Promoted>,
150 impl<'tcx> GlobalId<'tcx> {
151 pub fn display(self, tcx: TyCtxt<'tcx>) -> String {
152 let instance_name = with_no_trimmed_paths!(tcx.def_path_str(self.instance.def.def_id()));
153 if let Some(promoted) = self.promoted {
154 format!("{}::{:?}", instance_name, promoted)
161 /// Input argument for `tcx.lit_to_const`.
162 #[derive(Copy, Clone, Debug, Eq, PartialEq, Hash, HashStable)]
163 pub struct LitToConstInput<'tcx> {
164 /// The absolute value of the resultant constant.
165 pub lit: &'tcx LitKind,
166 /// The type of the constant.
168 /// If the constant is negative.
172 /// Error type for `tcx.lit_to_const`.
173 #[derive(Copy, Clone, Debug, Eq, PartialEq, HashStable)]
174 pub enum LitToConstError {
175 /// The literal's inferred type did not match the expected `ty` in the input.
176 /// This is used for graceful error handling (`delay_span_bug`) in
177 /// type checking (`Const::from_anon_const`).
182 #[derive(Copy, Clone, Eq, Hash, Ord, PartialEq, PartialOrd)]
183 pub struct AllocId(pub NonZeroU64);
185 // We want the `Debug` output to be readable as it is used by `derive(Debug)` for
186 // all the Miri types.
187 impl fmt::Debug for AllocId {
188 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
189 if f.alternate() { write!(f, "a{}", self.0) } else { write!(f, "alloc{}", self.0) }
193 impl fmt::Display for AllocId {
194 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
195 fmt::Debug::fmt(self, f)
199 #[derive(TyDecodable, TyEncodable)]
200 enum AllocDiscriminant {
206 pub fn specialized_encode_alloc_id<'tcx, E: TyEncoder<'tcx>>(
210 ) -> Result<(), E::Error> {
211 match tcx.global_alloc(alloc_id) {
212 GlobalAlloc::Memory(alloc) => {
213 trace!("encoding {:?} with {:#?}", alloc_id, alloc);
214 AllocDiscriminant::Alloc.encode(encoder)?;
215 alloc.encode(encoder)?;
217 GlobalAlloc::Function(fn_instance) => {
218 trace!("encoding {:?} with {:#?}", alloc_id, fn_instance);
219 AllocDiscriminant::Fn.encode(encoder)?;
220 fn_instance.encode(encoder)?;
222 GlobalAlloc::Static(did) => {
223 assert!(!tcx.is_thread_local_static(did));
224 // References to statics doesn't need to know about their allocations,
225 // just about its `DefId`.
226 AllocDiscriminant::Static.encode(encoder)?;
227 did.encode(encoder)?;
233 // Used to avoid infinite recursion when decoding cyclic allocations.
234 type DecodingSessionId = NonZeroU32;
239 InProgressNonAlloc(TinyList<DecodingSessionId>),
240 InProgress(TinyList<DecodingSessionId>, AllocId),
244 pub struct AllocDecodingState {
245 // For each `AllocId`, we keep track of which decoding state it's currently in.
246 decoding_state: Vec<Lock<State>>,
247 // The offsets of each allocation in the data stream.
248 data_offsets: Vec<u32>,
251 impl AllocDecodingState {
253 pub fn new_decoding_session(&self) -> AllocDecodingSession<'_> {
254 static DECODER_SESSION_ID: AtomicU32 = AtomicU32::new(0);
255 let counter = DECODER_SESSION_ID.fetch_add(1, Ordering::SeqCst);
257 // Make sure this is never zero.
258 let session_id = DecodingSessionId::new((counter & 0x7FFFFFFF) + 1).unwrap();
260 AllocDecodingSession { state: self, session_id }
263 pub fn new(data_offsets: Vec<u32>) -> Self {
264 let decoding_state = vec![Lock::new(State::Empty); data_offsets.len()];
266 Self { decoding_state, data_offsets }
270 #[derive(Copy, Clone)]
271 pub struct AllocDecodingSession<'s> {
272 state: &'s AllocDecodingState,
273 session_id: DecodingSessionId,
276 impl<'s> AllocDecodingSession<'s> {
277 /// Decodes an `AllocId` in a thread-safe way.
278 pub fn decode_alloc_id<'tcx, D>(&self, decoder: &mut D) -> AllocId
282 // Read the index of the allocation.
283 let idx = usize::try_from(decoder.read_u32()).unwrap();
284 let pos = usize::try_from(self.state.data_offsets[idx]).unwrap();
286 // Decode the `AllocDiscriminant` now so that we know if we have to reserve an
288 let (alloc_kind, pos) = decoder.with_position(pos, |decoder| {
289 let alloc_kind = AllocDiscriminant::decode(decoder);
290 (alloc_kind, decoder.position())
293 // Check the decoding state to see if it's already decoded or if we should
296 let mut entry = self.state.decoding_state[idx].lock();
299 State::Done(alloc_id) => {
302 ref mut entry @ State::Empty => {
303 // We are allowed to decode.
305 AllocDiscriminant::Alloc => {
306 // If this is an allocation, we need to reserve an
307 // `AllocId` so we can decode cyclic graphs.
308 let alloc_id = decoder.tcx().reserve_alloc_id();
310 State::InProgress(TinyList::new_single(self.session_id), alloc_id);
313 AllocDiscriminant::Fn | AllocDiscriminant::Static => {
314 // Fns and statics cannot be cyclic, and their `AllocId`
315 // is determined later by interning.
317 State::InProgressNonAlloc(TinyList::new_single(self.session_id));
322 State::InProgressNonAlloc(ref mut sessions) => {
323 if sessions.contains(&self.session_id) {
324 bug!("this should be unreachable");
326 // Start decoding concurrently.
327 sessions.insert(self.session_id);
331 State::InProgress(ref mut sessions, alloc_id) => {
332 if sessions.contains(&self.session_id) {
336 // Start decoding concurrently.
337 sessions.insert(self.session_id);
344 // Now decode the actual data.
345 let alloc_id = decoder.with_position(pos, |decoder| {
347 AllocDiscriminant::Alloc => {
348 let alloc = <ConstAllocation<'tcx> as Decodable<_>>::decode(decoder);
349 // We already have a reserved `AllocId`.
350 let alloc_id = alloc_id.unwrap();
351 trace!("decoded alloc {:?}: {:#?}", alloc_id, alloc);
352 decoder.tcx().set_alloc_id_same_memory(alloc_id, alloc);
355 AllocDiscriminant::Fn => {
356 assert!(alloc_id.is_none());
357 trace!("creating fn alloc ID");
358 let instance = ty::Instance::decode(decoder);
359 trace!("decoded fn alloc instance: {:?}", instance);
360 let alloc_id = decoder.tcx().create_fn_alloc(instance);
363 AllocDiscriminant::Static => {
364 assert!(alloc_id.is_none());
365 trace!("creating extern static alloc ID");
366 let did = <DefId as Decodable<D>>::decode(decoder);
367 trace!("decoded static def-ID: {:?}", did);
368 let alloc_id = decoder.tcx().create_static_alloc(did);
374 self.state.decoding_state[idx].with_lock(|entry| {
375 *entry = State::Done(alloc_id);
382 /// An allocation in the global (tcx-managed) memory can be either a function pointer,
383 /// a static, or a "real" allocation with some data in it.
384 #[derive(Debug, Clone, Eq, PartialEq, Hash, TyDecodable, TyEncodable, HashStable)]
385 pub enum GlobalAlloc<'tcx> {
386 /// The alloc ID is used as a function pointer.
387 Function(Instance<'tcx>),
388 /// The alloc ID points to a "lazy" static variable that did not get computed (yet).
389 /// This is also used to break the cycle in recursive statics.
391 /// The alloc ID points to memory.
392 Memory(ConstAllocation<'tcx>),
395 impl<'tcx> GlobalAlloc<'tcx> {
396 /// Panics if the `GlobalAlloc` does not refer to an `GlobalAlloc::Memory`
399 pub fn unwrap_memory(&self) -> ConstAllocation<'tcx> {
401 GlobalAlloc::Memory(mem) => mem,
402 _ => bug!("expected memory, got {:?}", self),
406 /// Panics if the `GlobalAlloc` is not `GlobalAlloc::Function`
409 pub fn unwrap_fn(&self) -> Instance<'tcx> {
411 GlobalAlloc::Function(instance) => instance,
412 _ => bug!("expected function, got {:?}", self),
417 pub(crate) struct AllocMap<'tcx> {
418 /// Maps `AllocId`s to their corresponding allocations.
419 alloc_map: FxHashMap<AllocId, GlobalAlloc<'tcx>>,
421 /// Used to ensure that statics and functions only get one associated `AllocId`.
422 /// Should never contain a `GlobalAlloc::Memory`!
424 // FIXME: Should we just have two separate dedup maps for statics and functions each?
425 dedup: FxHashMap<GlobalAlloc<'tcx>, AllocId>,
427 /// The `AllocId` to assign to the next requested ID.
428 /// Always incremented; never gets smaller.
432 impl<'tcx> AllocMap<'tcx> {
433 pub(crate) fn new() -> Self {
435 alloc_map: Default::default(),
436 dedup: Default::default(),
437 next_id: AllocId(NonZeroU64::new(1).unwrap()),
440 fn reserve(&mut self) -> AllocId {
441 let next = self.next_id;
442 self.next_id.0 = self.next_id.0.checked_add(1).expect(
443 "You overflowed a u64 by incrementing by 1... \
444 You've just earned yourself a free drink if we ever meet. \
445 Seriously, how did you do that?!",
451 impl<'tcx> TyCtxt<'tcx> {
452 /// Obtains a new allocation ID that can be referenced but does not
453 /// yet have an allocation backing it.
455 /// Make sure to call `set_alloc_id_memory` or `set_alloc_id_same_memory` before returning such
456 /// an `AllocId` from a query.
457 pub fn reserve_alloc_id(self) -> AllocId {
458 self.alloc_map.lock().reserve()
461 /// Reserves a new ID *if* this allocation has not been dedup-reserved before.
462 /// Should only be used for function pointers and statics, we don't want
463 /// to dedup IDs for "real" memory!
464 fn reserve_and_set_dedup(self, alloc: GlobalAlloc<'tcx>) -> AllocId {
465 let mut alloc_map = self.alloc_map.lock();
467 GlobalAlloc::Function(..) | GlobalAlloc::Static(..) => {}
468 GlobalAlloc::Memory(..) => bug!("Trying to dedup-reserve memory with real data!"),
470 if let Some(&alloc_id) = alloc_map.dedup.get(&alloc) {
473 let id = alloc_map.reserve();
474 debug!("creating alloc {:?} with id {}", alloc, id);
475 alloc_map.alloc_map.insert(id, alloc.clone());
476 alloc_map.dedup.insert(alloc, id);
480 /// Generates an `AllocId` for a static or return a cached one in case this function has been
481 /// called on the same static before.
482 pub fn create_static_alloc(self, static_id: DefId) -> AllocId {
483 self.reserve_and_set_dedup(GlobalAlloc::Static(static_id))
486 /// Generates an `AllocId` for a function. Depending on the function type,
487 /// this might get deduplicated or assigned a new ID each time.
488 pub fn create_fn_alloc(self, instance: Instance<'tcx>) -> AllocId {
489 // Functions cannot be identified by pointers, as asm-equal functions can get deduplicated
490 // by the linker (we set the "unnamed_addr" attribute for LLVM) and functions can be
491 // duplicated across crates.
492 // We thus generate a new `AllocId` for every mention of a function. This means that
493 // `main as fn() == main as fn()` is false, while `let x = main as fn(); x == x` is true.
494 // However, formatting code relies on function identity (see #58320), so we only do
495 // this for generic functions. Lifetime parameters are ignored.
496 let is_generic = instance
499 .any(|kind| !matches!(kind.unpack(), GenericArgKind::Lifetime(_)));
502 let mut alloc_map = self.alloc_map.lock();
503 let id = alloc_map.reserve();
504 alloc_map.alloc_map.insert(id, GlobalAlloc::Function(instance));
508 self.reserve_and_set_dedup(GlobalAlloc::Function(instance))
512 /// Interns the `Allocation` and return a new `AllocId`, even if there's already an identical
513 /// `Allocation` with a different `AllocId`.
514 /// Statics with identical content will still point to the same `Allocation`, i.e.,
515 /// their data will be deduplicated through `Allocation` interning -- but they
516 /// are different places in memory and as such need different IDs.
517 pub fn create_memory_alloc(self, mem: ConstAllocation<'tcx>) -> AllocId {
518 let id = self.reserve_alloc_id();
519 self.set_alloc_id_memory(id, mem);
523 /// Returns `None` in case the `AllocId` is dangling. An `InterpretCx` can still have a
524 /// local `Allocation` for that `AllocId`, but having such an `AllocId` in a constant is
525 /// illegal and will likely ICE.
526 /// This function exists to allow const eval to detect the difference between evaluation-
527 /// local dangling pointers and allocations in constants/statics.
529 pub fn get_global_alloc(self, id: AllocId) -> Option<GlobalAlloc<'tcx>> {
530 self.alloc_map.lock().alloc_map.get(&id).cloned()
535 /// Panics in case the `AllocId` is dangling. Since that is impossible for `AllocId`s in
536 /// constants (as all constants must pass interning and validation that check for dangling
537 /// ids), this function is frequently used throughout rustc, but should not be used within
539 pub fn global_alloc(self, id: AllocId) -> GlobalAlloc<'tcx> {
540 match self.get_global_alloc(id) {
541 Some(alloc) => alloc,
542 None => bug!("could not find allocation for {}", id),
546 /// Freezes an `AllocId` created with `reserve` by pointing it at an `Allocation`. Trying to
547 /// call this function twice, even with the same `Allocation` will ICE the compiler.
548 pub fn set_alloc_id_memory(self, id: AllocId, mem: ConstAllocation<'tcx>) {
549 if let Some(old) = self.alloc_map.lock().alloc_map.insert(id, GlobalAlloc::Memory(mem)) {
550 bug!("tried to set allocation ID {}, but it was already existing as {:#?}", id, old);
554 /// Freezes an `AllocId` created with `reserve` by pointing it at an `Allocation`. May be called
555 /// twice for the same `(AllocId, Allocation)` pair.
556 fn set_alloc_id_same_memory(self, id: AllocId, mem: ConstAllocation<'tcx>) {
557 self.alloc_map.lock().alloc_map.insert_same(id, GlobalAlloc::Memory(mem));
561 ////////////////////////////////////////////////////////////////////////////////
562 // Methods to access integers in the target endianness
563 ////////////////////////////////////////////////////////////////////////////////
566 pub fn write_target_uint(
568 mut target: &mut [u8],
570 ) -> Result<(), io::Error> {
571 // This u128 holds an "any-size uint" (since smaller uints can fits in it)
572 // So we do not write all bytes of the u128, just the "payload".
574 Endian::Little => target.write(&data.to_le_bytes())?,
575 Endian::Big => target.write(&data.to_be_bytes()[16 - target.len()..])?,
577 debug_assert!(target.len() == 0); // We should have filled the target buffer.
582 pub fn read_target_uint(endianness: Endian, mut source: &[u8]) -> Result<u128, io::Error> {
583 // This u128 holds an "any-size uint" (since smaller uints can fits in it)
584 let mut buf = [0u8; std::mem::size_of::<u128>()];
585 // So we do not read exactly 16 bytes into the u128, just the "payload".
586 let uint = match endianness {
588 source.read(&mut buf)?;
589 Ok(u128::from_le_bytes(buf))
592 source.read(&mut buf[16 - source.len()..])?;
593 Ok(u128::from_be_bytes(buf))
596 debug_assert!(source.len() == 0); // We should have consumed the source buffer.