2 use rustc_middle::ty::{self, Ty};
3 use std::borrow::Borrow;
4 use std::collections::hash_map::Entry;
7 use rustc_data_structures::fx::FxHashMap;
10 use rustc_ast::Mutability;
11 use rustc_hir::def_id::DefId;
12 use rustc_middle::mir::AssertMessage;
13 use rustc_session::Limit;
14 use rustc_span::symbol::{sym, Symbol};
15 use rustc_target::abi::{Align, Size};
16 use rustc_target::spec::abi::Abi;
18 use crate::interpret::{
19 self, compile_time_machine, AllocId, Allocation, Frame, ImmTy, InterpCx, InterpResult, Memory,
20 OpTy, PlaceTy, Pointer, Scalar, StackPopUnwind,
25 impl<'mir, 'tcx> InterpCx<'mir, 'tcx, CompileTimeInterpreter<'mir, 'tcx>> {
26 /// "Intercept" a function call to a panic-related function
27 /// because we have something special to do for it.
28 /// If this returns successfully (`Ok`), the function should just be evaluated normally.
31 instance: ty::Instance<'tcx>,
33 ) -> InterpResult<'tcx> {
34 let def_id = instance.def_id();
35 if Some(def_id) == self.tcx.lang_items().panic_fn()
36 || Some(def_id) == self.tcx.lang_items().panic_str()
37 || Some(def_id) == self.tcx.lang_items().begin_panic_fn()
40 assert!(args.len() == 1);
42 let msg_place = self.deref_operand(&args[0])?;
43 let msg = Symbol::intern(self.read_str(&msg_place)?);
44 let span = self.find_closest_untracked_caller_location();
45 let (file, line, col) = self.location_triple_for_span(span);
46 Err(ConstEvalErrKind::Panic { msg, file, line, col }.into())
53 /// Extra machine state for CTFE, and the Machine instance
54 pub struct CompileTimeInterpreter<'mir, 'tcx> {
55 /// For now, the number of terminators that can be evaluated before we throw a resource
58 /// Setting this to `0` disables the limit and allows the interpreter to run forever.
59 pub steps_remaining: usize,
61 /// The virtual call stack.
62 pub(crate) stack: Vec<Frame<'mir, 'tcx, (), ()>>,
65 #[derive(Copy, Clone, Debug)]
66 pub struct MemoryExtra {
67 /// We need to make sure consts never point to anything mutable, even recursively. That is
68 /// relied on for pattern matching on consts with references.
69 /// To achieve this, two pieces have to work together:
70 /// * Interning makes everything outside of statics immutable.
71 /// * Pointers to allocations inside of statics can never leak outside, to a non-static global.
72 /// This boolean here controls the second part.
73 pub(super) can_access_statics: bool,
76 impl<'mir, 'tcx> CompileTimeInterpreter<'mir, 'tcx> {
77 pub(super) fn new(const_eval_limit: Limit) -> Self {
78 CompileTimeInterpreter { steps_remaining: const_eval_limit.0, stack: Vec::new() }
82 impl<K: Hash + Eq, V> interpret::AllocMap<K, V> for FxHashMap<K, V> {
84 fn contains_key<Q: ?Sized + Hash + Eq>(&mut self, k: &Q) -> bool
88 FxHashMap::contains_key(self, k)
92 fn insert(&mut self, k: K, v: V) -> Option<V> {
93 FxHashMap::insert(self, k, v)
97 fn remove<Q: ?Sized + Hash + Eq>(&mut self, k: &Q) -> Option<V>
101 FxHashMap::remove(self, k)
105 fn filter_map_collect<T>(&self, mut f: impl FnMut(&K, &V) -> Option<T>) -> Vec<T> {
106 self.iter().filter_map(move |(k, v)| f(k, &*v)).collect()
110 fn get_or<E>(&self, k: K, vacant: impl FnOnce() -> Result<V, E>) -> Result<&V, E> {
115 bug!("The CTFE machine shouldn't ever need to extend the alloc_map when reading")
121 fn get_mut_or<E>(&mut self, k: K, vacant: impl FnOnce() -> Result<V, E>) -> Result<&mut V, E> {
122 match self.entry(k) {
123 Entry::Occupied(e) => Ok(e.into_mut()),
124 Entry::Vacant(e) => {
132 crate type CompileTimeEvalContext<'mir, 'tcx> =
133 InterpCx<'mir, 'tcx, CompileTimeInterpreter<'mir, 'tcx>>;
135 #[derive(Debug, PartialEq, Eq, Copy, Clone)]
136 pub enum MemoryKind {
140 impl fmt::Display for MemoryKind {
141 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
143 MemoryKind::Heap => write!(f, "heap allocation"),
148 impl interpret::MayLeak for MemoryKind {
150 fn may_leak(self) -> bool {
152 MemoryKind::Heap => false,
157 impl interpret::MayLeak for ! {
159 fn may_leak(self) -> bool {
160 // `self` is uninhabited
165 impl<'mir, 'tcx: 'mir> CompileTimeEvalContext<'mir, 'tcx> {
166 fn guaranteed_eq(&mut self, a: Scalar, b: Scalar) -> bool {
168 // Comparisons between integers are always known.
169 (Scalar::Int { .. }, Scalar::Int { .. }) => a == b,
170 // Equality with integers can never be known for sure.
171 (Scalar::Int { .. }, Scalar::Ptr(_)) | (Scalar::Ptr(_), Scalar::Int { .. }) => false,
172 // FIXME: return `true` for when both sides are the same pointer, *except* that
173 // some things (like functions and vtables) do not have stable addresses
174 // so we need to be careful around them (see e.g. #73722).
175 (Scalar::Ptr(_), Scalar::Ptr(_)) => false,
179 fn guaranteed_ne(&mut self, a: Scalar, b: Scalar) -> bool {
181 // Comparisons between integers are always known.
182 (Scalar::Int(_), Scalar::Int(_)) => a != b,
183 // Comparisons of abstract pointers with null pointers are known if the pointer
184 // is in bounds, because if they are in bounds, the pointer can't be null.
185 // Inequality with integers other than null can never be known for sure.
186 (Scalar::Int(int), Scalar::Ptr(ptr)) | (Scalar::Ptr(ptr), Scalar::Int(int)) => {
187 int.is_null() && !self.memory.ptr_may_be_null(ptr)
189 // FIXME: return `true` for at least some comparisons where we can reliably
190 // determine the result of runtime inequality tests at compile-time.
191 // Examples include comparison of addresses in different static items.
192 (Scalar::Ptr(_), Scalar::Ptr(_)) => false,
197 impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter<'mir, 'tcx> {
198 compile_time_machine!(<'mir, 'tcx>);
200 type MemoryKind = MemoryKind;
202 type MemoryExtra = MemoryExtra;
204 const PANIC_ON_ALLOC_FAIL: bool = false; // will be raised as a proper error
207 ecx: &InterpCx<'mir, 'tcx, Self>,
208 instance: ty::InstanceDef<'tcx>,
209 ) -> InterpResult<'tcx, &'tcx mir::Body<'tcx>> {
211 ty::InstanceDef::Item(def) => {
212 if ecx.tcx.is_ctfe_mir_available(def.did) {
213 Ok(ecx.tcx.mir_for_ctfe_opt_const_arg(def))
215 throw_unsup!(NoMirFor(def.did))
218 _ => Ok(ecx.tcx.instance_mir(instance)),
222 fn find_mir_or_eval_fn(
223 ecx: &mut InterpCx<'mir, 'tcx, Self>,
224 instance: ty::Instance<'tcx>,
227 _ret: Option<(&PlaceTy<'tcx>, mir::BasicBlock)>,
228 _unwind: StackPopUnwind, // unwinding is not supported in consts
229 ) -> InterpResult<'tcx, Option<&'mir mir::Body<'tcx>>> {
230 debug!("find_mir_or_eval_fn: {:?}", instance);
232 // Only check non-glue functions
233 if let ty::InstanceDef::Item(def) = instance.def {
234 // Execution might have wandered off into other crates, so we cannot do a stability-
235 // sensitive check here. But we can at least rule out functions that are not const
237 if !ecx.tcx.is_const_fn_raw(def.did) {
238 // Some functions we support even if they are non-const -- but avoid testing
239 // that for const fn!
240 ecx.hook_panic_fn(instance, args)?;
241 // We certainly do *not* want to actually call the fn
242 // though, so be sure we return here.
243 throw_unsup_format!("calling non-const function `{}`", instance)
246 // This is a const fn. Call it.
247 Ok(Some(match ecx.load_mir(instance.def, None) {
250 if let err_unsup!(NoMirFor(did)) = err.kind() {
251 let path = ecx.tcx.def_path_str(*did);
252 return Err(ConstEvalErrKind::NeedsRfc(format!(
253 "calling extern function `{}`",
264 ecx: &mut InterpCx<'mir, 'tcx, Self>,
265 instance: ty::Instance<'tcx>,
267 ret: Option<(&PlaceTy<'tcx>, mir::BasicBlock)>,
268 _unwind: StackPopUnwind,
269 ) -> InterpResult<'tcx> {
270 // Shared intrinsics.
271 if ecx.emulate_intrinsic(instance, args, ret)? {
274 let intrinsic_name = ecx.tcx.item_name(instance.def_id());
276 // CTFE-specific intrinsics.
277 let (dest, ret) = match ret {
279 return Err(ConstEvalErrKind::NeedsRfc(format!(
280 "calling intrinsic `{}`",
287 match intrinsic_name {
288 sym::ptr_guaranteed_eq | sym::ptr_guaranteed_ne => {
289 let a = ecx.read_immediate(&args[0])?.to_scalar()?;
290 let b = ecx.read_immediate(&args[1])?.to_scalar()?;
291 let cmp = if intrinsic_name == sym::ptr_guaranteed_eq {
292 ecx.guaranteed_eq(a, b)
294 ecx.guaranteed_ne(a, b)
296 ecx.write_scalar(Scalar::from_bool(cmp), dest)?;
298 sym::const_allocate => {
299 let size = ecx.read_scalar(&args[0])?.to_machine_usize(ecx)?;
300 let align = ecx.read_scalar(&args[1])?.to_machine_usize(ecx)?;
302 let align = match Align::from_bytes(align) {
304 Err(err) => throw_ub_format!("align has to be a power of 2, {}", err),
307 let ptr = ecx.memory.allocate(
308 Size::from_bytes(size as u64),
310 interpret::MemoryKind::Machine(MemoryKind::Heap),
312 ecx.write_scalar(Scalar::Ptr(ptr), dest)?;
315 return Err(ConstEvalErrKind::NeedsRfc(format!(
316 "calling intrinsic `{}`",
323 ecx.go_to_block(ret);
328 ecx: &mut InterpCx<'mir, 'tcx, Self>,
329 msg: &AssertMessage<'tcx>,
330 _unwind: Option<mir::BasicBlock>,
331 ) -> InterpResult<'tcx> {
332 use rustc_middle::mir::AssertKind::*;
333 // Convert `AssertKind<Operand>` to `AssertKind<Scalar>`.
335 |op| ecx.read_immediate(&ecx.eval_operand(op, None)?).map(|x| x.to_const_int());
336 let err = match msg {
337 BoundsCheck { ref len, ref index } => {
338 let len = eval_to_int(len)?;
339 let index = eval_to_int(index)?;
340 BoundsCheck { len, index }
342 Overflow(op, l, r) => Overflow(*op, eval_to_int(l)?, eval_to_int(r)?),
343 OverflowNeg(op) => OverflowNeg(eval_to_int(op)?),
344 DivisionByZero(op) => DivisionByZero(eval_to_int(op)?),
345 RemainderByZero(op) => RemainderByZero(eval_to_int(op)?),
346 ResumedAfterReturn(generator_kind) => ResumedAfterReturn(*generator_kind),
347 ResumedAfterPanic(generator_kind) => ResumedAfterPanic(*generator_kind),
349 Err(ConstEvalErrKind::AssertFailure(err).into())
352 fn abort(_ecx: &mut InterpCx<'mir, 'tcx, Self>, msg: String) -> InterpResult<'tcx, !> {
353 Err(ConstEvalErrKind::Abort(msg).into())
356 fn ptr_to_int(_mem: &Memory<'mir, 'tcx, Self>, _ptr: Pointer) -> InterpResult<'tcx, u64> {
357 Err(ConstEvalErrKind::PtrToIntCast.into())
361 _ecx: &InterpCx<'mir, 'tcx, Self>,
364 _right: &ImmTy<'tcx>,
365 ) -> InterpResult<'tcx, (Scalar, bool, Ty<'tcx>)> {
366 Err(ConstEvalErrKind::NeedsRfc("pointer arithmetic or comparison".to_string()).into())
370 _ecx: &mut InterpCx<'mir, 'tcx, Self>,
371 _dest: &PlaceTy<'tcx>,
372 ) -> InterpResult<'tcx> {
373 Err(ConstEvalErrKind::NeedsRfc("heap allocations via `box` keyword".to_string()).into())
376 fn before_terminator(ecx: &mut InterpCx<'mir, 'tcx, Self>) -> InterpResult<'tcx> {
377 // The step limit has already been hit in a previous call to `before_terminator`.
378 if ecx.machine.steps_remaining == 0 {
382 ecx.machine.steps_remaining -= 1;
383 if ecx.machine.steps_remaining == 0 {
384 throw_exhaust!(StepLimitReached)
392 ecx: &mut InterpCx<'mir, 'tcx, Self>,
393 frame: Frame<'mir, 'tcx>,
394 ) -> InterpResult<'tcx, Frame<'mir, 'tcx>> {
395 // Enforce stack size limit. Add 1 because this is run before the new frame is pushed.
396 if !ecx.recursion_limit.value_within_limit(ecx.stack().len() + 1) {
397 throw_exhaust!(StackFrameLimitReached)
405 ecx: &'a InterpCx<'mir, 'tcx, Self>,
406 ) -> &'a [Frame<'mir, 'tcx, Self::PointerTag, Self::FrameExtra>] {
412 ecx: &'a mut InterpCx<'mir, 'tcx, Self>,
413 ) -> &'a mut Vec<Frame<'mir, 'tcx, Self::PointerTag, Self::FrameExtra>> {
414 &mut ecx.machine.stack
417 fn before_access_global(
418 memory_extra: &MemoryExtra,
420 allocation: &Allocation,
421 static_def_id: Option<DefId>,
423 ) -> InterpResult<'tcx> {
425 // Write access. These are never allowed, but we give a targeted error message.
426 if allocation.mutability == Mutability::Not {
427 Err(err_ub!(WriteToReadOnly(alloc_id)).into())
429 Err(ConstEvalErrKind::ModifiedGlobal.into())
432 // Read access. These are usually allowed, with some exceptions.
433 if memory_extra.can_access_statics {
434 // Machine configuration allows us read from anything (e.g., `static` initializer).
436 } else if static_def_id.is_some() {
437 // Machine configuration does not allow us to read statics
438 // (e.g., `const` initializer).
439 // See const_eval::machine::MemoryExtra::can_access_statics for why
440 // this check is so important: if we could read statics, we could read pointers
441 // to mutable allocations *inside* statics. These allocations are not themselves
442 // statics, so pointers to them can get around the check in `validity.rs`.
443 Err(ConstEvalErrKind::ConstAccessesStatic.into())
445 // Immutable global, this read is fine.
446 // But make sure we never accept a read from something mutable, that would be
447 // unsound. The reason is that as the content of this allocation may be different
448 // now and at run-time, so if we permit reading now we might return the wrong value.
449 assert_eq!(allocation.mutability, Mutability::Not);
456 // Please do not add any code below the above `Machine` trait impl. I (oli-obk) plan more cleanups
457 // so we can end up having a file with just that impl, but for now, let's keep the impl discoverable
458 // at the bottom of this file.