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 InterpError, InterpErrorInfo, InterpResult, InvalidProgramInfo, MachineStopType,
123 ResourceExhaustionInfo, UndefinedBehaviorInfo, UninitBytesAccess, UnsupportedOpInfo,
126 pub use self::value::{get_slice_bytes, ConstAlloc, ConstValue, Scalar, ScalarMaybeUninit};
128 pub use self::allocation::{
129 alloc_range, AllocRange, Allocation, InitChunk, InitChunkIter, InitMask, Relocations,
132 pub use self::pointer::{Pointer, PointerArithmetic, Provenance};
134 /// Uniquely identifies one of the following:
137 #[derive(Copy, Clone, Debug, Eq, PartialEq, Hash, TyEncodable, TyDecodable)]
138 #[derive(HashStable, Lift)]
139 pub struct GlobalId<'tcx> {
140 /// For a constant or static, the `Instance` of the item itself.
141 /// For a promoted global, the `Instance` of the function they belong to.
142 pub instance: ty::Instance<'tcx>,
144 /// The index for promoted globals within their function's `mir::Body`.
145 pub promoted: Option<mir::Promoted>,
148 impl<'tcx> GlobalId<'tcx> {
149 pub fn display(self, tcx: TyCtxt<'tcx>) -> String {
150 let instance_name = with_no_trimmed_paths(|| tcx.def_path_str(self.instance.def.def_id()));
151 if let Some(promoted) = self.promoted {
152 format!("{}::{:?}", instance_name, promoted)
159 /// Input argument for `tcx.lit_to_const`.
160 #[derive(Copy, Clone, Debug, Eq, PartialEq, Hash, HashStable)]
161 pub struct LitToConstInput<'tcx> {
162 /// The absolute value of the resultant constant.
163 pub lit: &'tcx LitKind,
164 /// The type of the constant.
166 /// If the constant is negative.
170 /// Error type for `tcx.lit_to_const`.
171 #[derive(Copy, Clone, Debug, Eq, PartialEq, HashStable)]
172 pub enum LitToConstError {
173 /// The literal's inferred type did not match the expected `ty` in the input.
174 /// This is used for graceful error handling (`delay_span_bug`) in
175 /// type checking (`Const::from_anon_const`).
180 #[derive(Copy, Clone, Eq, Hash, Ord, PartialEq, PartialOrd)]
181 pub struct AllocId(pub NonZeroU64);
183 // We want the `Debug` output to be readable as it is used by `derive(Debug)` for
184 // all the Miri types.
185 impl fmt::Debug for AllocId {
186 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
187 if f.alternate() { write!(f, "a{}", self.0) } else { write!(f, "alloc{}", self.0) }
191 impl fmt::Display for AllocId {
192 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
193 fmt::Debug::fmt(self, f)
197 #[derive(TyDecodable, TyEncodable)]
198 enum AllocDiscriminant {
204 pub fn specialized_encode_alloc_id<'tcx, E: TyEncoder<'tcx>>(
208 ) -> Result<(), E::Error> {
209 match tcx.global_alloc(alloc_id) {
210 GlobalAlloc::Memory(alloc) => {
211 trace!("encoding {:?} with {:#?}", alloc_id, alloc);
212 AllocDiscriminant::Alloc.encode(encoder)?;
213 alloc.encode(encoder)?;
215 GlobalAlloc::Function(fn_instance) => {
216 trace!("encoding {:?} with {:#?}", alloc_id, fn_instance);
217 AllocDiscriminant::Fn.encode(encoder)?;
218 fn_instance.encode(encoder)?;
220 GlobalAlloc::Static(did) => {
221 assert!(!tcx.is_thread_local_static(did));
222 // References to statics doesn't need to know about their allocations,
223 // just about its `DefId`.
224 AllocDiscriminant::Static.encode(encoder)?;
225 did.encode(encoder)?;
231 // Used to avoid infinite recursion when decoding cyclic allocations.
232 type DecodingSessionId = NonZeroU32;
237 InProgressNonAlloc(TinyList<DecodingSessionId>),
238 InProgress(TinyList<DecodingSessionId>, AllocId),
242 pub struct AllocDecodingState {
243 // For each `AllocId`, we keep track of which decoding state it's currently in.
244 decoding_state: Vec<Lock<State>>,
245 // The offsets of each allocation in the data stream.
246 data_offsets: Vec<u32>,
249 impl AllocDecodingState {
251 pub fn new_decoding_session(&self) -> AllocDecodingSession<'_> {
252 static DECODER_SESSION_ID: AtomicU32 = AtomicU32::new(0);
253 let counter = DECODER_SESSION_ID.fetch_add(1, Ordering::SeqCst);
255 // Make sure this is never zero.
256 let session_id = DecodingSessionId::new((counter & 0x7FFFFFFF) + 1).unwrap();
258 AllocDecodingSession { state: self, session_id }
261 pub fn new(data_offsets: Vec<u32>) -> Self {
262 let decoding_state = vec![Lock::new(State::Empty); data_offsets.len()];
264 Self { decoding_state, data_offsets }
268 #[derive(Copy, Clone)]
269 pub struct AllocDecodingSession<'s> {
270 state: &'s AllocDecodingState,
271 session_id: DecodingSessionId,
274 impl<'s> AllocDecodingSession<'s> {
275 /// Decodes an `AllocId` in a thread-safe way.
276 pub fn decode_alloc_id<'tcx, D>(&self, decoder: &mut D) -> Result<AllocId, D::Error>
280 // Read the index of the allocation.
281 let idx = usize::try_from(decoder.read_u32()?).unwrap();
282 let pos = usize::try_from(self.state.data_offsets[idx]).unwrap();
284 // Decode the `AllocDiscriminant` now so that we know if we have to reserve an
286 let (alloc_kind, pos) = decoder.with_position(pos, |decoder| {
287 let alloc_kind = AllocDiscriminant::decode(decoder)?;
288 Ok((alloc_kind, decoder.position()))
291 // Check the decoding state to see if it's already decoded or if we should
294 let mut entry = self.state.decoding_state[idx].lock();
297 State::Done(alloc_id) => {
300 ref mut entry @ State::Empty => {
301 // We are allowed to decode.
303 AllocDiscriminant::Alloc => {
304 // If this is an allocation, we need to reserve an
305 // `AllocId` so we can decode cyclic graphs.
306 let alloc_id = decoder.tcx().reserve_alloc_id();
308 State::InProgress(TinyList::new_single(self.session_id), alloc_id);
311 AllocDiscriminant::Fn | AllocDiscriminant::Static => {
312 // Fns and statics cannot be cyclic, and their `AllocId`
313 // is determined later by interning.
315 State::InProgressNonAlloc(TinyList::new_single(self.session_id));
320 State::InProgressNonAlloc(ref mut sessions) => {
321 if sessions.contains(&self.session_id) {
322 bug!("this should be unreachable");
324 // Start decoding concurrently.
325 sessions.insert(self.session_id);
329 State::InProgress(ref mut sessions, alloc_id) => {
330 if sessions.contains(&self.session_id) {
334 // Start decoding concurrently.
335 sessions.insert(self.session_id);
342 // Now decode the actual data.
343 let alloc_id = decoder.with_position(pos, |decoder| {
345 AllocDiscriminant::Alloc => {
346 let alloc = <&'tcx Allocation as Decodable<_>>::decode(decoder)?;
347 // We already have a reserved `AllocId`.
348 let alloc_id = alloc_id.unwrap();
349 trace!("decoded alloc {:?}: {:#?}", alloc_id, alloc);
350 decoder.tcx().set_alloc_id_same_memory(alloc_id, alloc);
353 AllocDiscriminant::Fn => {
354 assert!(alloc_id.is_none());
355 trace!("creating fn alloc ID");
356 let instance = ty::Instance::decode(decoder)?;
357 trace!("decoded fn alloc instance: {:?}", instance);
358 let alloc_id = decoder.tcx().create_fn_alloc(instance);
361 AllocDiscriminant::Static => {
362 assert!(alloc_id.is_none());
363 trace!("creating extern static alloc ID");
364 let did = <DefId as Decodable<D>>::decode(decoder)?;
365 trace!("decoded static def-ID: {:?}", did);
366 let alloc_id = decoder.tcx().create_static_alloc(did);
372 self.state.decoding_state[idx].with_lock(|entry| {
373 *entry = State::Done(alloc_id);
380 /// An allocation in the global (tcx-managed) memory can be either a function pointer,
381 /// a static, or a "real" allocation with some data in it.
382 #[derive(Debug, Clone, Eq, PartialEq, Hash, TyDecodable, TyEncodable, HashStable)]
383 pub enum GlobalAlloc<'tcx> {
384 /// The alloc ID is used as a function pointer.
385 Function(Instance<'tcx>),
386 /// The alloc ID points to a "lazy" static variable that did not get computed (yet).
387 /// This is also used to break the cycle in recursive statics.
389 /// The alloc ID points to memory.
390 Memory(&'tcx Allocation),
393 impl<'tcx> GlobalAlloc<'tcx> {
394 /// Panics if the `GlobalAlloc` does not refer to an `GlobalAlloc::Memory`
397 pub fn unwrap_memory(&self) -> &'tcx Allocation {
399 GlobalAlloc::Memory(mem) => mem,
400 _ => bug!("expected memory, got {:?}", self),
404 /// Panics if the `GlobalAlloc` is not `GlobalAlloc::Function`
407 pub fn unwrap_fn(&self) -> Instance<'tcx> {
409 GlobalAlloc::Function(instance) => instance,
410 _ => bug!("expected function, got {:?}", self),
415 crate struct AllocMap<'tcx> {
416 /// Maps `AllocId`s to their corresponding allocations.
417 alloc_map: FxHashMap<AllocId, GlobalAlloc<'tcx>>,
419 /// Used to ensure that statics and functions only get one associated `AllocId`.
420 /// Should never contain a `GlobalAlloc::Memory`!
422 // FIXME: Should we just have two separate dedup maps for statics and functions each?
423 dedup: FxHashMap<GlobalAlloc<'tcx>, AllocId>,
425 /// The `AllocId` to assign to the next requested ID.
426 /// Always incremented; never gets smaller.
430 impl<'tcx> AllocMap<'tcx> {
431 crate fn new() -> Self {
433 alloc_map: Default::default(),
434 dedup: Default::default(),
435 next_id: AllocId(NonZeroU64::new(1).unwrap()),
438 fn reserve(&mut self) -> AllocId {
439 let next = self.next_id;
440 self.next_id.0 = self.next_id.0.checked_add(1).expect(
441 "You overflowed a u64 by incrementing by 1... \
442 You've just earned yourself a free drink if we ever meet. \
443 Seriously, how did you do that?!",
449 impl<'tcx> TyCtxt<'tcx> {
450 /// Obtains a new allocation ID that can be referenced but does not
451 /// yet have an allocation backing it.
453 /// Make sure to call `set_alloc_id_memory` or `set_alloc_id_same_memory` before returning such
454 /// an `AllocId` from a query.
455 pub fn reserve_alloc_id(self) -> AllocId {
456 self.alloc_map.lock().reserve()
459 /// Reserves a new ID *if* this allocation has not been dedup-reserved before.
460 /// Should only be used for function pointers and statics, we don't want
461 /// to dedup IDs for "real" memory!
462 fn reserve_and_set_dedup(self, alloc: GlobalAlloc<'tcx>) -> AllocId {
463 let mut alloc_map = self.alloc_map.lock();
465 GlobalAlloc::Function(..) | GlobalAlloc::Static(..) => {}
466 GlobalAlloc::Memory(..) => bug!("Trying to dedup-reserve memory with real data!"),
468 if let Some(&alloc_id) = alloc_map.dedup.get(&alloc) {
471 let id = alloc_map.reserve();
472 debug!("creating alloc {:?} with id {}", alloc, id);
473 alloc_map.alloc_map.insert(id, alloc.clone());
474 alloc_map.dedup.insert(alloc, id);
478 /// Generates an `AllocId` for a static or return a cached one in case this function has been
479 /// called on the same static before.
480 pub fn create_static_alloc(self, static_id: DefId) -> AllocId {
481 self.reserve_and_set_dedup(GlobalAlloc::Static(static_id))
484 /// Generates an `AllocId` for a function. Depending on the function type,
485 /// this might get deduplicated or assigned a new ID each time.
486 pub fn create_fn_alloc(self, instance: Instance<'tcx>) -> AllocId {
487 // Functions cannot be identified by pointers, as asm-equal functions can get deduplicated
488 // by the linker (we set the "unnamed_addr" attribute for LLVM) and functions can be
489 // duplicated across crates.
490 // We thus generate a new `AllocId` for every mention of a function. This means that
491 // `main as fn() == main as fn()` is false, while `let x = main as fn(); x == x` is true.
492 // However, formatting code relies on function identity (see #58320), so we only do
493 // this for generic functions. Lifetime parameters are ignored.
494 let is_generic = instance
497 .any(|kind| !matches!(kind.unpack(), GenericArgKind::Lifetime(_)));
500 let mut alloc_map = self.alloc_map.lock();
501 let id = alloc_map.reserve();
502 alloc_map.alloc_map.insert(id, GlobalAlloc::Function(instance));
506 self.reserve_and_set_dedup(GlobalAlloc::Function(instance))
510 /// Interns the `Allocation` and return a new `AllocId`, even if there's already an identical
511 /// `Allocation` with a different `AllocId`.
512 /// Statics with identical content will still point to the same `Allocation`, i.e.,
513 /// their data will be deduplicated through `Allocation` interning -- but they
514 /// are different places in memory and as such need different IDs.
515 pub fn create_memory_alloc(self, mem: &'tcx Allocation) -> AllocId {
516 let id = self.reserve_alloc_id();
517 self.set_alloc_id_memory(id, mem);
521 /// Returns `None` in case the `AllocId` is dangling. An `InterpretCx` can still have a
522 /// local `Allocation` for that `AllocId`, but having such an `AllocId` in a constant is
523 /// illegal and will likely ICE.
524 /// This function exists to allow const eval to detect the difference between evaluation-
525 /// local dangling pointers and allocations in constants/statics.
527 pub fn get_global_alloc(self, id: AllocId) -> Option<GlobalAlloc<'tcx>> {
528 self.alloc_map.lock().alloc_map.get(&id).cloned()
533 /// Panics in case the `AllocId` is dangling. Since that is impossible for `AllocId`s in
534 /// constants (as all constants must pass interning and validation that check for dangling
535 /// ids), this function is frequently used throughout rustc, but should not be used within
537 pub fn global_alloc(self, id: AllocId) -> GlobalAlloc<'tcx> {
538 match self.get_global_alloc(id) {
539 Some(alloc) => alloc,
540 None => bug!("could not find allocation for {}", id),
544 /// Freezes an `AllocId` created with `reserve` by pointing it at an `Allocation`. Trying to
545 /// call this function twice, even with the same `Allocation` will ICE the compiler.
546 pub fn set_alloc_id_memory(self, id: AllocId, mem: &'tcx Allocation) {
547 if let Some(old) = self.alloc_map.lock().alloc_map.insert(id, GlobalAlloc::Memory(mem)) {
548 bug!("tried to set allocation ID {}, but it was already existing as {:#?}", id, old);
552 /// Freezes an `AllocId` created with `reserve` by pointing it at an `Allocation`. May be called
553 /// twice for the same `(AllocId, Allocation)` pair.
554 fn set_alloc_id_same_memory(self, id: AllocId, mem: &'tcx Allocation) {
555 self.alloc_map.lock().alloc_map.insert_same(id, GlobalAlloc::Memory(mem));
559 ////////////////////////////////////////////////////////////////////////////////
560 // Methods to access integers in the target endianness
561 ////////////////////////////////////////////////////////////////////////////////
564 pub fn write_target_uint(
566 mut target: &mut [u8],
568 ) -> Result<(), io::Error> {
569 // This u128 holds an "any-size uint" (since smaller uints can fits in it)
570 // So we do not write all bytes of the u128, just the "payload".
572 Endian::Little => target.write(&data.to_le_bytes())?,
573 Endian::Big => target.write(&data.to_be_bytes()[16 - target.len()..])?,
575 debug_assert!(target.len() == 0); // We should have filled the target buffer.
580 pub fn read_target_uint(endianness: Endian, mut source: &[u8]) -> Result<u128, io::Error> {
581 // This u128 holds an "any-size uint" (since smaller uints can fits in it)
582 let mut buf = [0u8; std::mem::size_of::<u128>()];
583 // So we do not read exactly 16 bytes into the u128, just the "payload".
584 let uint = match endianness {
586 source.read(&mut buf)?;
587 Ok(u128::from_le_bytes(buf))
590 source.read(&mut buf[16 - source.len()..])?;
591 Ok(u128::from_be_bytes(buf))
594 debug_assert!(source.len() == 0); // We should have consumed the source buffer.