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, OpTy,
20 PlaceTy, 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.
29 fn hook_special_const_fn(
31 instance: ty::Instance<'tcx>,
33 ) -> InterpResult<'tcx, Option<ty::Instance<'tcx>>> {
34 // All `#[rustc_do_not_const_check]` functions should be hooked here.
35 let def_id = instance.def_id();
37 if Some(def_id) == self.tcx.lang_items().const_eval_select() {
38 // redirect to const_eval_select_ct
39 if let Some(const_eval_select) = self.tcx.lang_items().const_eval_select_ct() {
41 ty::Instance::resolve(
43 ty::ParamEnv::reveal_all(),
51 } else if Some(def_id) == self.tcx.lang_items().panic_display()
52 || Some(def_id) == self.tcx.lang_items().begin_panic_fn()
55 assert!(args.len() == 1);
57 let mut msg_place = self.deref_operand(&args[0])?;
58 while msg_place.layout.ty.is_ref() {
59 msg_place = self.deref_operand(&msg_place.into())?;
62 let msg = Symbol::intern(self.read_str(&msg_place)?);
63 let span = self.find_closest_untracked_caller_location();
64 let (file, line, col) = self.location_triple_for_span(span);
65 return Err(ConstEvalErrKind::Panic { msg, file, line, col }.into());
66 } else if Some(def_id) == self.tcx.lang_items().panic_fmt() {
67 // For panic_fmt, call const_panic_fmt instead.
68 if let Some(const_panic_fmt) = self.tcx.lang_items().const_panic_fmt() {
70 ty::Instance::resolve(
72 ty::ParamEnv::reveal_all(),
74 self.tcx.intern_substs(&[]),
85 /// Extra machine state for CTFE, and the Machine instance
86 pub struct CompileTimeInterpreter<'mir, 'tcx> {
87 /// For now, the number of terminators that can be evaluated before we throw a resource
90 /// Setting this to `0` disables the limit and allows the interpreter to run forever.
91 pub steps_remaining: usize,
93 /// The virtual call stack.
94 pub(crate) stack: Vec<Frame<'mir, 'tcx, AllocId, ()>>,
97 #[derive(Copy, Clone, Debug)]
98 pub struct MemoryExtra {
99 /// We need to make sure consts never point to anything mutable, even recursively. That is
100 /// relied on for pattern matching on consts with references.
101 /// To achieve this, two pieces have to work together:
102 /// * Interning makes everything outside of statics immutable.
103 /// * Pointers to allocations inside of statics can never leak outside, to a non-static global.
104 /// This boolean here controls the second part.
105 pub(super) can_access_statics: bool,
108 impl<'mir, 'tcx> CompileTimeInterpreter<'mir, 'tcx> {
109 pub(super) fn new(const_eval_limit: Limit) -> Self {
110 CompileTimeInterpreter { steps_remaining: const_eval_limit.0, stack: Vec::new() }
114 impl<K: Hash + Eq, V> interpret::AllocMap<K, V> for FxHashMap<K, V> {
116 fn contains_key<Q: ?Sized + Hash + Eq>(&mut self, k: &Q) -> bool
120 FxHashMap::contains_key(self, k)
124 fn insert(&mut self, k: K, v: V) -> Option<V> {
125 FxHashMap::insert(self, k, v)
129 fn remove<Q: ?Sized + Hash + Eq>(&mut self, k: &Q) -> Option<V>
133 FxHashMap::remove(self, k)
137 fn filter_map_collect<T>(&self, mut f: impl FnMut(&K, &V) -> Option<T>) -> Vec<T> {
138 self.iter().filter_map(move |(k, v)| f(k, &*v)).collect()
142 fn get_or<E>(&self, k: K, vacant: impl FnOnce() -> Result<V, E>) -> Result<&V, E> {
147 bug!("The CTFE machine shouldn't ever need to extend the alloc_map when reading")
153 fn get_mut_or<E>(&mut self, k: K, vacant: impl FnOnce() -> Result<V, E>) -> Result<&mut V, E> {
154 match self.entry(k) {
155 Entry::Occupied(e) => Ok(e.into_mut()),
156 Entry::Vacant(e) => {
164 crate type CompileTimeEvalContext<'mir, 'tcx> =
165 InterpCx<'mir, 'tcx, CompileTimeInterpreter<'mir, 'tcx>>;
167 #[derive(Debug, PartialEq, Eq, Copy, Clone)]
168 pub enum MemoryKind {
172 impl fmt::Display for MemoryKind {
173 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
175 MemoryKind::Heap => write!(f, "heap allocation"),
180 impl interpret::MayLeak for MemoryKind {
182 fn may_leak(self) -> bool {
184 MemoryKind::Heap => false,
189 impl interpret::MayLeak for ! {
191 fn may_leak(self) -> bool {
192 // `self` is uninhabited
197 impl<'mir, 'tcx: 'mir> CompileTimeEvalContext<'mir, 'tcx> {
198 fn guaranteed_eq(&mut self, a: Scalar, b: Scalar) -> bool {
200 // Comparisons between integers are always known.
201 (Scalar::Int { .. }, Scalar::Int { .. }) => a == b,
202 // Equality with integers can never be known for sure.
203 (Scalar::Int { .. }, Scalar::Ptr(..)) | (Scalar::Ptr(..), Scalar::Int { .. }) => false,
204 // FIXME: return `true` for when both sides are the same pointer, *except* that
205 // some things (like functions and vtables) do not have stable addresses
206 // so we need to be careful around them (see e.g. #73722).
207 (Scalar::Ptr(..), Scalar::Ptr(..)) => false,
211 fn guaranteed_ne(&mut self, a: Scalar, b: Scalar) -> bool {
213 // Comparisons between integers are always known.
214 (Scalar::Int(_), Scalar::Int(_)) => a != b,
215 // Comparisons of abstract pointers with null pointers are known if the pointer
216 // is in bounds, because if they are in bounds, the pointer can't be null.
217 // Inequality with integers other than null can never be known for sure.
218 (Scalar::Int(int), Scalar::Ptr(ptr, _)) | (Scalar::Ptr(ptr, _), Scalar::Int(int)) => {
219 int.is_null() && !self.memory.ptr_may_be_null(ptr.into())
221 // FIXME: return `true` for at least some comparisons where we can reliably
222 // determine the result of runtime inequality tests at compile-time.
223 // Examples include comparison of addresses in different static items.
224 (Scalar::Ptr(..), Scalar::Ptr(..)) => false,
229 impl<'mir, 'tcx> interpret::Machine<'mir, 'tcx> for CompileTimeInterpreter<'mir, 'tcx> {
230 compile_time_machine!(<'mir, 'tcx>);
232 type MemoryKind = MemoryKind;
234 type MemoryExtra = MemoryExtra;
236 const PANIC_ON_ALLOC_FAIL: bool = false; // will be raised as a proper error
239 ecx: &InterpCx<'mir, 'tcx, Self>,
240 instance: ty::InstanceDef<'tcx>,
241 ) -> InterpResult<'tcx, &'tcx mir::Body<'tcx>> {
243 ty::InstanceDef::Item(def) => {
244 if ecx.tcx.is_ctfe_mir_available(def.did) {
245 Ok(ecx.tcx.mir_for_ctfe_opt_const_arg(def))
247 let path = ecx.tcx.def_path_str(def.did);
248 Err(ConstEvalErrKind::NeedsRfc(format!("calling extern function `{}`", path))
252 _ => Ok(ecx.tcx.instance_mir(instance)),
256 fn find_mir_or_eval_fn(
257 ecx: &mut InterpCx<'mir, 'tcx, Self>,
258 instance: ty::Instance<'tcx>,
261 _ret: Option<(&PlaceTy<'tcx>, mir::BasicBlock)>,
262 _unwind: StackPopUnwind, // unwinding is not supported in consts
263 ) -> InterpResult<'tcx, Option<&'mir mir::Body<'tcx>>> {
264 debug!("find_mir_or_eval_fn: {:?}", instance);
266 // Only check non-glue functions
267 if let ty::InstanceDef::Item(def) = instance.def {
268 // Execution might have wandered off into other crates, so we cannot do a stability-
269 // sensitive check here. But we can at least rule out functions that are not const
271 if !ecx.tcx.is_const_fn_raw(def.did) {
272 // allow calling functions marked with #[default_method_body_is_const].
273 if !ecx.tcx.has_attr(def.did, sym::default_method_body_is_const) {
274 // We certainly do *not* want to actually call the fn
275 // though, so be sure we return here.
276 throw_unsup_format!("calling non-const function `{}`", instance)
280 if let Some(new_instance) = ecx.hook_special_const_fn(instance, args)? {
281 // We call another const fn instead.
282 return Self::find_mir_or_eval_fn(ecx, new_instance, _abi, args, _ret, _unwind);
285 // This is a const fn. Call it.
286 Ok(Some(ecx.load_mir(instance.def, None)?))
290 ecx: &mut InterpCx<'mir, 'tcx, Self>,
291 instance: ty::Instance<'tcx>,
293 ret: Option<(&PlaceTy<'tcx>, mir::BasicBlock)>,
294 _unwind: StackPopUnwind,
295 ) -> InterpResult<'tcx> {
296 // Shared intrinsics.
297 if ecx.emulate_intrinsic(instance, args, ret)? {
300 let intrinsic_name = ecx.tcx.item_name(instance.def_id());
302 // CTFE-specific intrinsics.
303 let (dest, ret) = match ret {
305 return Err(ConstEvalErrKind::NeedsRfc(format!(
306 "calling intrinsic `{}`",
313 match intrinsic_name {
314 sym::ptr_guaranteed_eq | sym::ptr_guaranteed_ne => {
315 let a = ecx.read_immediate(&args[0])?.to_scalar()?;
316 let b = ecx.read_immediate(&args[1])?.to_scalar()?;
317 let cmp = if intrinsic_name == sym::ptr_guaranteed_eq {
318 ecx.guaranteed_eq(a, b)
320 ecx.guaranteed_ne(a, b)
322 ecx.write_scalar(Scalar::from_bool(cmp), dest)?;
324 sym::const_allocate => {
325 let size = ecx.read_scalar(&args[0])?.to_machine_usize(ecx)?;
326 let align = ecx.read_scalar(&args[1])?.to_machine_usize(ecx)?;
328 let align = match Align::from_bytes(align) {
330 Err(err) => throw_ub_format!("align has to be a power of 2, {}", err),
333 let ptr = ecx.memory.allocate(
334 Size::from_bytes(size as u64),
336 interpret::MemoryKind::Machine(MemoryKind::Heap),
338 ecx.write_pointer(ptr, dest)?;
341 return Err(ConstEvalErrKind::NeedsRfc(format!(
342 "calling intrinsic `{}`",
349 ecx.go_to_block(ret);
354 ecx: &mut InterpCx<'mir, 'tcx, Self>,
355 msg: &AssertMessage<'tcx>,
356 _unwind: Option<mir::BasicBlock>,
357 ) -> InterpResult<'tcx> {
358 use rustc_middle::mir::AssertKind::*;
359 // Convert `AssertKind<Operand>` to `AssertKind<Scalar>`.
361 |op| ecx.read_immediate(&ecx.eval_operand(op, None)?).map(|x| x.to_const_int());
362 let err = match msg {
363 BoundsCheck { ref len, ref index } => {
364 let len = eval_to_int(len)?;
365 let index = eval_to_int(index)?;
366 BoundsCheck { len, index }
368 Overflow(op, l, r) => Overflow(*op, eval_to_int(l)?, eval_to_int(r)?),
369 OverflowNeg(op) => OverflowNeg(eval_to_int(op)?),
370 DivisionByZero(op) => DivisionByZero(eval_to_int(op)?),
371 RemainderByZero(op) => RemainderByZero(eval_to_int(op)?),
372 ResumedAfterReturn(generator_kind) => ResumedAfterReturn(*generator_kind),
373 ResumedAfterPanic(generator_kind) => ResumedAfterPanic(*generator_kind),
375 Err(ConstEvalErrKind::AssertFailure(err).into())
378 fn abort(_ecx: &mut InterpCx<'mir, 'tcx, Self>, msg: String) -> InterpResult<'tcx, !> {
379 Err(ConstEvalErrKind::Abort(msg).into())
383 _ecx: &InterpCx<'mir, 'tcx, Self>,
386 _right: &ImmTy<'tcx>,
387 ) -> InterpResult<'tcx, (Scalar, bool, Ty<'tcx>)> {
388 Err(ConstEvalErrKind::NeedsRfc("pointer arithmetic or comparison".to_string()).into())
392 _ecx: &mut InterpCx<'mir, 'tcx, Self>,
393 _dest: &PlaceTy<'tcx>,
394 ) -> InterpResult<'tcx> {
395 Err(ConstEvalErrKind::NeedsRfc("heap allocations via `box` keyword".to_string()).into())
398 fn before_terminator(ecx: &mut InterpCx<'mir, 'tcx, Self>) -> InterpResult<'tcx> {
399 // The step limit has already been hit in a previous call to `before_terminator`.
400 if ecx.machine.steps_remaining == 0 {
404 ecx.machine.steps_remaining -= 1;
405 if ecx.machine.steps_remaining == 0 {
406 throw_exhaust!(StepLimitReached)
414 ecx: &mut InterpCx<'mir, 'tcx, Self>,
415 frame: Frame<'mir, 'tcx>,
416 ) -> InterpResult<'tcx, Frame<'mir, 'tcx>> {
417 // Enforce stack size limit. Add 1 because this is run before the new frame is pushed.
418 if !ecx.recursion_limit.value_within_limit(ecx.stack().len() + 1) {
419 throw_exhaust!(StackFrameLimitReached)
427 ecx: &'a InterpCx<'mir, 'tcx, Self>,
428 ) -> &'a [Frame<'mir, 'tcx, Self::PointerTag, Self::FrameExtra>] {
434 ecx: &'a mut InterpCx<'mir, 'tcx, Self>,
435 ) -> &'a mut Vec<Frame<'mir, 'tcx, Self::PointerTag, Self::FrameExtra>> {
436 &mut ecx.machine.stack
439 fn before_access_global(
440 memory_extra: &MemoryExtra,
442 allocation: &Allocation,
443 static_def_id: Option<DefId>,
445 ) -> InterpResult<'tcx> {
447 // Write access. These are never allowed, but we give a targeted error message.
448 if allocation.mutability == Mutability::Not {
449 Err(err_ub!(WriteToReadOnly(alloc_id)).into())
451 Err(ConstEvalErrKind::ModifiedGlobal.into())
454 // Read access. These are usually allowed, with some exceptions.
455 if memory_extra.can_access_statics {
456 // Machine configuration allows us read from anything (e.g., `static` initializer).
458 } else if static_def_id.is_some() {
459 // Machine configuration does not allow us to read statics
460 // (e.g., `const` initializer).
461 // See const_eval::machine::MemoryExtra::can_access_statics for why
462 // this check is so important: if we could read statics, we could read pointers
463 // to mutable allocations *inside* statics. These allocations are not themselves
464 // statics, so pointers to them can get around the check in `validity.rs`.
465 Err(ConstEvalErrKind::ConstAccessesStatic.into())
467 // Immutable global, this read is fine.
468 // But make sure we never accept a read from something mutable, that would be
469 // unsound. The reason is that as the content of this allocation may be different
470 // now and at run-time, so if we permit reading now we might return the wrong value.
471 assert_eq!(allocation.mutability, Mutability::Not);
478 // Please do not add any code below the above `Machine` trait impl. I (oli-obk) plan more cleanups
479 // so we can end up having a file with just that impl, but for now, let's keep the impl discoverable
480 // at the bottom of this file.