miri/
helpers.rs

1use std::num::NonZero;
2use std::time::Duration;
3use std::{cmp, iter};
4
5use rand::RngCore;
6use rustc_abi::{Align, ExternAbi, FieldIdx, FieldsShape, Size, Variants};
7use rustc_apfloat::Float;
8use rustc_apfloat::ieee::{Double, Half, Quad, Single};
9use rustc_hir::Safety;
10use rustc_hir::def::{DefKind, Namespace};
11use rustc_hir::def_id::{CRATE_DEF_INDEX, CrateNum, DefId, LOCAL_CRATE};
12use rustc_index::IndexVec;
13use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
14use rustc_middle::middle::dependency_format::Linkage;
15use rustc_middle::middle::exported_symbols::ExportedSymbol;
16use rustc_middle::ty::layout::{FnAbiOf, LayoutOf, MaybeResult, TyAndLayout};
17use rustc_middle::ty::{self, Binder, FloatTy, FnSig, IntTy, Ty, TyCtxt, UintTy};
18use rustc_session::config::CrateType;
19use rustc_span::{Span, Symbol};
20use rustc_symbol_mangling::mangle_internal_symbol;
21use rustc_target::callconv::{Conv, FnAbi};
22
23use crate::*;
24
25/// Indicates which kind of access is being performed.
26#[derive(Copy, Clone, Hash, PartialEq, Eq, Debug)]
27pub enum AccessKind {
28    Read,
29    Write,
30}
31
32/// Gets an instance for a path.
33///
34/// A `None` namespace indicates we are looking for a module.
35fn try_resolve_did(tcx: TyCtxt<'_>, path: &[&str], namespace: Option<Namespace>) -> Option<DefId> {
36    /// Yield all children of the given item, that have the given name.
37    fn find_children<'tcx: 'a, 'a>(
38        tcx: TyCtxt<'tcx>,
39        item: DefId,
40        name: &'a str,
41    ) -> impl Iterator<Item = DefId> + 'a {
42        let name = Symbol::intern(name);
43        tcx.module_children(item)
44            .iter()
45            .filter(move |item| item.ident.name == name)
46            .map(move |item| item.res.def_id())
47    }
48
49    // Take apart the path: leading crate, a sequence of modules, and potentially a final item.
50    let (&crate_name, path) = path.split_first().expect("paths must have at least one segment");
51    let (modules, item) = if let Some(namespace) = namespace {
52        let (&item_name, modules) =
53            path.split_last().expect("non-module paths must have at least 2 segments");
54        (modules, Some((item_name, namespace)))
55    } else {
56        (path, None)
57    };
58
59    // There may be more than one crate with this name. We try them all.
60    // (This is particularly relevant when running `std` tests as then there are two `std` crates:
61    // the one in the sysroot and the one locally built by `cargo test`.)
62    // FIXME: can we prefer the one from the sysroot?
63    'crates: for krate in
64        tcx.crates(()).iter().filter(|&&krate| tcx.crate_name(krate).as_str() == crate_name)
65    {
66        let mut cur_item = DefId { krate: *krate, index: CRATE_DEF_INDEX };
67        // Go over the modules.
68        for &segment in modules {
69            let Some(next_item) = find_children(tcx, cur_item, segment)
70                .find(|item| tcx.def_kind(item) == DefKind::Mod)
71            else {
72                continue 'crates;
73            };
74            cur_item = next_item;
75        }
76        // Finally, look up the desired item in this module, if any.
77        match item {
78            Some((item_name, namespace)) => {
79                let Some(item) = find_children(tcx, cur_item, item_name)
80                    .find(|item| tcx.def_kind(item).ns() == Some(namespace))
81                else {
82                    continue 'crates;
83                };
84                return Some(item);
85            }
86            None => {
87                // Just return the module.
88                return Some(cur_item);
89            }
90        }
91    }
92    // Item not found in any of the crates with the right name.
93    None
94}
95
96/// Gets an instance for a path; fails gracefully if the path does not exist.
97pub fn try_resolve_path<'tcx>(
98    tcx: TyCtxt<'tcx>,
99    path: &[&str],
100    namespace: Namespace,
101) -> Option<ty::Instance<'tcx>> {
102    let did = try_resolve_did(tcx, path, Some(namespace))?;
103    Some(ty::Instance::mono(tcx, did))
104}
105
106/// Gets an instance for a path.
107#[track_caller]
108pub fn resolve_path<'tcx>(
109    tcx: TyCtxt<'tcx>,
110    path: &[&str],
111    namespace: Namespace,
112) -> ty::Instance<'tcx> {
113    try_resolve_path(tcx, path, namespace)
114        .unwrap_or_else(|| panic!("failed to find required Rust item: {path:?}"))
115}
116
117/// Gets the layout of a type at a path.
118#[track_caller]
119pub fn path_ty_layout<'tcx>(cx: &impl LayoutOf<'tcx>, path: &[&str]) -> TyAndLayout<'tcx> {
120    let ty = resolve_path(cx.tcx(), path, Namespace::TypeNS).ty(cx.tcx(), cx.typing_env());
121    cx.layout_of(ty).to_result().ok().unwrap()
122}
123
124/// Call `f` for each exported symbol.
125pub fn iter_exported_symbols<'tcx>(
126    tcx: TyCtxt<'tcx>,
127    mut f: impl FnMut(CrateNum, DefId) -> InterpResult<'tcx>,
128) -> InterpResult<'tcx> {
129    // First, the symbols in the local crate. We can't use `exported_symbols` here as that
130    // skips `#[used]` statics (since `reachable_set` skips them in binary crates).
131    // So we walk all HIR items ourselves instead.
132    let crate_items = tcx.hir_crate_items(());
133    for def_id in crate_items.definitions() {
134        let exported = tcx.def_kind(def_id).has_codegen_attrs() && {
135            let codegen_attrs = tcx.codegen_fn_attrs(def_id);
136            codegen_attrs.contains_extern_indicator()
137                || codegen_attrs.flags.contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL)
138                || codegen_attrs.flags.contains(CodegenFnAttrFlags::USED)
139                || codegen_attrs.flags.contains(CodegenFnAttrFlags::USED_LINKER)
140        };
141        if exported {
142            f(LOCAL_CRATE, def_id.into())?;
143        }
144    }
145
146    // Next, all our dependencies.
147    // `dependency_formats` includes all the transitive informations needed to link a crate,
148    // which is what we need here since we need to dig out `exported_symbols` from all transitive
149    // dependencies.
150    let dependency_formats = tcx.dependency_formats(());
151    // Find the dependencies of the executable we are running.
152    let dependency_format = dependency_formats
153        .get(&CrateType::Executable)
154        .expect("interpreting a non-executable crate");
155    for cnum in dependency_format
156        .iter_enumerated()
157        .filter_map(|(num, &linkage)| (linkage != Linkage::NotLinked).then_some(num))
158    {
159        if cnum == LOCAL_CRATE {
160            continue; // Already handled above
161        }
162
163        // We can ignore `_export_info` here: we are a Rust crate, and everything is exported
164        // from a Rust crate.
165        for &(symbol, _export_info) in tcx.exported_symbols(cnum) {
166            if let ExportedSymbol::NonGeneric(def_id) = symbol {
167                f(cnum, def_id)?;
168            }
169        }
170    }
171    interp_ok(())
172}
173
174/// Convert a softfloat type to its corresponding hostfloat type.
175pub trait ToHost {
176    type HostFloat;
177    fn to_host(self) -> Self::HostFloat;
178}
179
180/// Convert a hostfloat type to its corresponding softfloat type.
181pub trait ToSoft {
182    type SoftFloat;
183    fn to_soft(self) -> Self::SoftFloat;
184}
185
186impl ToHost for rustc_apfloat::ieee::Double {
187    type HostFloat = f64;
188
189    fn to_host(self) -> Self::HostFloat {
190        f64::from_bits(self.to_bits().try_into().unwrap())
191    }
192}
193
194impl ToSoft for f64 {
195    type SoftFloat = rustc_apfloat::ieee::Double;
196
197    fn to_soft(self) -> Self::SoftFloat {
198        Float::from_bits(self.to_bits().into())
199    }
200}
201
202impl ToHost for rustc_apfloat::ieee::Single {
203    type HostFloat = f32;
204
205    fn to_host(self) -> Self::HostFloat {
206        f32::from_bits(self.to_bits().try_into().unwrap())
207    }
208}
209
210impl ToSoft for f32 {
211    type SoftFloat = rustc_apfloat::ieee::Single;
212
213    fn to_soft(self) -> Self::SoftFloat {
214        Float::from_bits(self.to_bits().into())
215    }
216}
217
218impl<'tcx> EvalContextExt<'tcx> for crate::MiriInterpCx<'tcx> {}
219pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
220    /// Checks if the given crate/module exists.
221    fn have_module(&self, path: &[&str]) -> bool {
222        try_resolve_did(*self.eval_context_ref().tcx, path, None).is_some()
223    }
224
225    /// Evaluates the scalar at the specified path.
226    fn eval_path(&self, path: &[&str]) -> MPlaceTy<'tcx> {
227        let this = self.eval_context_ref();
228        let instance = resolve_path(*this.tcx, path, Namespace::ValueNS);
229        // We don't give a span -- this isn't actually used directly by the program anyway.
230        this.eval_global(instance).unwrap_or_else(|err| {
231            panic!("failed to evaluate required Rust item: {path:?}\n{err:?}")
232        })
233    }
234    fn eval_path_scalar(&self, path: &[&str]) -> Scalar {
235        let this = self.eval_context_ref();
236        let val = this.eval_path(path);
237        this.read_scalar(&val)
238            .unwrap_or_else(|err| panic!("failed to read required Rust item: {path:?}\n{err:?}"))
239    }
240
241    /// Helper function to get a `libc` constant as a `Scalar`.
242    fn eval_libc(&self, name: &str) -> Scalar {
243        if self.eval_context_ref().tcx.sess.target.os == "windows" {
244            panic!(
245                "`libc` crate is not reliably available on Windows targets; Miri should not use it there"
246            );
247        }
248        self.eval_path_scalar(&["libc", name])
249    }
250
251    /// Helper function to get a `libc` constant as an `i32`.
252    fn eval_libc_i32(&self, name: &str) -> i32 {
253        // TODO: Cache the result.
254        self.eval_libc(name).to_i32().unwrap_or_else(|_err| {
255            panic!("required libc item has unexpected type (not `i32`): {name}")
256        })
257    }
258
259    /// Helper function to get a `libc` constant as an `u32`.
260    fn eval_libc_u32(&self, name: &str) -> u32 {
261        // TODO: Cache the result.
262        self.eval_libc(name).to_u32().unwrap_or_else(|_err| {
263            panic!("required libc item has unexpected type (not `u32`): {name}")
264        })
265    }
266
267    /// Helper function to get a `libc` constant as an `u64`.
268    fn eval_libc_u64(&self, name: &str) -> u64 {
269        // TODO: Cache the result.
270        self.eval_libc(name).to_u64().unwrap_or_else(|_err| {
271            panic!("required libc item has unexpected type (not `u64`): {name}")
272        })
273    }
274
275    /// Helper function to get a `windows` constant as a `Scalar`.
276    fn eval_windows(&self, module: &str, name: &str) -> Scalar {
277        self.eval_context_ref().eval_path_scalar(&["std", "sys", "pal", "windows", module, name])
278    }
279
280    /// Helper function to get a `windows` constant as a `u32`.
281    fn eval_windows_u32(&self, module: &str, name: &str) -> u32 {
282        // TODO: Cache the result.
283        self.eval_windows(module, name).to_u32().unwrap_or_else(|_err| {
284            panic!("required Windows item has unexpected type (not `u32`): {module}::{name}")
285        })
286    }
287
288    /// Helper function to get a `windows` constant as a `u64`.
289    fn eval_windows_u64(&self, module: &str, name: &str) -> u64 {
290        // TODO: Cache the result.
291        self.eval_windows(module, name).to_u64().unwrap_or_else(|_err| {
292            panic!("required Windows item has unexpected type (not `u64`): {module}::{name}")
293        })
294    }
295
296    /// Helper function to get the `TyAndLayout` of a `libc` type
297    fn libc_ty_layout(&self, name: &str) -> TyAndLayout<'tcx> {
298        let this = self.eval_context_ref();
299        if this.tcx.sess.target.os == "windows" {
300            panic!(
301                "`libc` crate is not reliably available on Windows targets; Miri should not use it there"
302            );
303        }
304        path_ty_layout(this, &["libc", name])
305    }
306
307    /// Helper function to get the `TyAndLayout` of a `windows` type
308    fn windows_ty_layout(&self, name: &str) -> TyAndLayout<'tcx> {
309        let this = self.eval_context_ref();
310        path_ty_layout(this, &["std", "sys", "pal", "windows", "c", name])
311    }
312
313    /// Helper function to get `TyAndLayout` of an array that consists of `libc` type.
314    fn libc_array_ty_layout(&self, name: &str, size: u64) -> TyAndLayout<'tcx> {
315        let this = self.eval_context_ref();
316        let elem_ty_layout = this.libc_ty_layout(name);
317        let array_ty = Ty::new_array(*this.tcx, elem_ty_layout.ty, size);
318        this.layout_of(array_ty).unwrap()
319    }
320
321    /// Project to the given *named* field (which must be a struct or union type).
322    fn try_project_field_named<P: Projectable<'tcx, Provenance>>(
323        &self,
324        base: &P,
325        name: &str,
326    ) -> InterpResult<'tcx, Option<P>> {
327        let this = self.eval_context_ref();
328        let adt = base.layout().ty.ty_adt_def().unwrap();
329        for (idx, field) in adt.non_enum_variant().fields.iter().enumerate() {
330            if field.name.as_str() == name {
331                return interp_ok(Some(this.project_field(base, idx)?));
332            }
333        }
334        interp_ok(None)
335    }
336
337    /// Project to the given *named* field (which must be a struct or union type).
338    fn project_field_named<P: Projectable<'tcx, Provenance>>(
339        &self,
340        base: &P,
341        name: &str,
342    ) -> InterpResult<'tcx, P> {
343        interp_ok(
344            self.try_project_field_named(base, name)?
345                .unwrap_or_else(|| bug!("no field named {} in type {}", name, base.layout().ty)),
346        )
347    }
348
349    /// Write an int of the appropriate size to `dest`. The target type may be signed or unsigned,
350    /// we try to do the right thing anyway. `i128` can fit all integer types except for `u128` so
351    /// this method is fine for almost all integer types.
352    fn write_int(
353        &mut self,
354        i: impl Into<i128>,
355        dest: &impl Writeable<'tcx, Provenance>,
356    ) -> InterpResult<'tcx> {
357        assert!(
358            dest.layout().backend_repr.is_scalar(),
359            "write_int on non-scalar type {}",
360            dest.layout().ty
361        );
362        let val = if dest.layout().backend_repr.is_signed() {
363            Scalar::from_int(i, dest.layout().size)
364        } else {
365            // `unwrap` can only fail here if `i` is negative
366            Scalar::from_uint(u128::try_from(i.into()).unwrap(), dest.layout().size)
367        };
368        self.eval_context_mut().write_scalar(val, dest)
369    }
370
371    /// Write the first N fields of the given place.
372    fn write_int_fields(
373        &mut self,
374        values: &[i128],
375        dest: &impl Writeable<'tcx, Provenance>,
376    ) -> InterpResult<'tcx> {
377        let this = self.eval_context_mut();
378        for (idx, &val) in values.iter().enumerate() {
379            let field = this.project_field(dest, idx)?;
380            this.write_int(val, &field)?;
381        }
382        interp_ok(())
383    }
384
385    /// Write the given fields of the given place.
386    fn write_int_fields_named(
387        &mut self,
388        values: &[(&str, i128)],
389        dest: &impl Writeable<'tcx, Provenance>,
390    ) -> InterpResult<'tcx> {
391        let this = self.eval_context_mut();
392        for &(name, val) in values.iter() {
393            let field = this.project_field_named(dest, name)?;
394            this.write_int(val, &field)?;
395        }
396        interp_ok(())
397    }
398
399    /// Write a 0 of the appropriate size to `dest`.
400    fn write_null(&mut self, dest: &impl Writeable<'tcx, Provenance>) -> InterpResult<'tcx> {
401        self.write_int(0, dest)
402    }
403
404    /// Test if this pointer equals 0.
405    fn ptr_is_null(&self, ptr: Pointer) -> InterpResult<'tcx, bool> {
406        interp_ok(ptr.addr().bytes() == 0)
407    }
408
409    /// Generate some random bytes, and write them to `dest`.
410    fn gen_random(&mut self, ptr: Pointer, len: u64) -> InterpResult<'tcx> {
411        // Some programs pass in a null pointer and a length of 0
412        // to their platform's random-generation function (e.g. getrandom())
413        // on Linux. For compatibility with these programs, we don't perform
414        // any additional checks - it's okay if the pointer is invalid,
415        // since we wouldn't actually be writing to it.
416        if len == 0 {
417            return interp_ok(());
418        }
419        let this = self.eval_context_mut();
420
421        let mut data = vec![0; usize::try_from(len).unwrap()];
422
423        if this.machine.communicate() {
424            // Fill the buffer using the host's rng.
425            getrandom::fill(&mut data)
426                .map_err(|err| err_unsup_format!("host getrandom failed: {}", err))?;
427        } else {
428            let rng = this.machine.rng.get_mut();
429            rng.fill_bytes(&mut data);
430        }
431
432        this.write_bytes_ptr(ptr, data.iter().copied())
433    }
434
435    /// Call a function: Push the stack frame and pass the arguments.
436    /// For now, arguments must be scalars (so that the caller does not have to know the layout).
437    ///
438    /// If you do not provide a return place, a dangling zero-sized place will be created
439    /// for your convenience.
440    fn call_function(
441        &mut self,
442        f: ty::Instance<'tcx>,
443        caller_abi: ExternAbi,
444        args: &[ImmTy<'tcx>],
445        dest: Option<&MPlaceTy<'tcx>>,
446        stack_pop: StackPopCleanup,
447    ) -> InterpResult<'tcx> {
448        let this = self.eval_context_mut();
449
450        // Get MIR.
451        let mir = this.load_mir(f.def, None)?;
452        let dest = match dest {
453            Some(dest) => dest.clone(),
454            None => MPlaceTy::fake_alloc_zst(this.layout_of(mir.return_ty())?),
455        };
456
457        // Construct a function pointer type representing the caller perspective.
458        let sig = this.tcx.mk_fn_sig(
459            args.iter().map(|a| a.layout.ty),
460            dest.layout.ty,
461            /*c_variadic*/ false,
462            Safety::Safe,
463            caller_abi,
464        );
465        let caller_fn_abi = this.fn_abi_of_fn_ptr(ty::Binder::dummy(sig), ty::List::empty())?;
466
467        this.init_stack_frame(
468            f,
469            mir,
470            caller_fn_abi,
471            &args.iter().map(|a| FnArg::Copy(a.clone().into())).collect::<Vec<_>>(),
472            /*with_caller_location*/ false,
473            &dest,
474            stack_pop,
475        )
476    }
477
478    /// Visits the memory covered by `place`, sensitive to freezing: the 2nd parameter
479    /// of `action` will be true if this is frozen, false if this is in an `UnsafeCell`.
480    /// The range is relative to `place`.
481    fn visit_freeze_sensitive(
482        &self,
483        place: &MPlaceTy<'tcx>,
484        size: Size,
485        mut action: impl FnMut(AllocRange, bool) -> InterpResult<'tcx>,
486    ) -> InterpResult<'tcx> {
487        let this = self.eval_context_ref();
488        trace!("visit_frozen(place={:?}, size={:?})", *place, size);
489        debug_assert_eq!(
490            size,
491            this.size_and_align_of_mplace(place)?
492                .map(|(size, _)| size)
493                .unwrap_or_else(|| place.layout.size)
494        );
495        // Store how far we proceeded into the place so far. Everything to the left of
496        // this offset has already been handled, in the sense that the frozen parts
497        // have had `action` called on them.
498        let start_addr = place.ptr().addr();
499        let mut cur_addr = start_addr;
500        // Called when we detected an `UnsafeCell` at the given offset and size.
501        // Calls `action` and advances `cur_ptr`.
502        let mut unsafe_cell_action = |unsafe_cell_ptr: &Pointer, unsafe_cell_size: Size| {
503            // We assume that we are given the fields in increasing offset order,
504            // and nothing else changes.
505            let unsafe_cell_addr = unsafe_cell_ptr.addr();
506            assert!(unsafe_cell_addr >= cur_addr);
507            let frozen_size = unsafe_cell_addr - cur_addr;
508            // Everything between the cur_ptr and this `UnsafeCell` is frozen.
509            if frozen_size != Size::ZERO {
510                action(alloc_range(cur_addr - start_addr, frozen_size), /*frozen*/ true)?;
511            }
512            cur_addr += frozen_size;
513            // This `UnsafeCell` is NOT frozen.
514            if unsafe_cell_size != Size::ZERO {
515                action(
516                    alloc_range(cur_addr - start_addr, unsafe_cell_size),
517                    /*frozen*/ false,
518                )?;
519            }
520            cur_addr += unsafe_cell_size;
521            // Done
522            interp_ok(())
523        };
524        // Run a visitor
525        {
526            let mut visitor = UnsafeCellVisitor {
527                ecx: this,
528                unsafe_cell_action: |place| {
529                    trace!("unsafe_cell_action on {:?}", place.ptr());
530                    // We need a size to go on.
531                    let unsafe_cell_size = this
532                        .size_and_align_of_mplace(place)?
533                        .map(|(size, _)| size)
534                        // for extern types, just cover what we can
535                        .unwrap_or_else(|| place.layout.size);
536                    // Now handle this `UnsafeCell`, unless it is empty.
537                    if unsafe_cell_size != Size::ZERO {
538                        unsafe_cell_action(&place.ptr(), unsafe_cell_size)
539                    } else {
540                        interp_ok(())
541                    }
542                },
543            };
544            visitor.visit_value(place)?;
545        }
546        // The part between the end_ptr and the end of the place is also frozen.
547        // So pretend there is a 0-sized `UnsafeCell` at the end.
548        unsafe_cell_action(&place.ptr().wrapping_offset(size, this), Size::ZERO)?;
549        // Done!
550        return interp_ok(());
551
552        /// Visiting the memory covered by a `MemPlace`, being aware of
553        /// whether we are inside an `UnsafeCell` or not.
554        struct UnsafeCellVisitor<'ecx, 'tcx, F>
555        where
556            F: FnMut(&MPlaceTy<'tcx>) -> InterpResult<'tcx>,
557        {
558            ecx: &'ecx MiriInterpCx<'tcx>,
559            unsafe_cell_action: F,
560        }
561
562        impl<'ecx, 'tcx, F> ValueVisitor<'tcx, MiriMachine<'tcx>> for UnsafeCellVisitor<'ecx, 'tcx, F>
563        where
564            F: FnMut(&MPlaceTy<'tcx>) -> InterpResult<'tcx>,
565        {
566            type V = MPlaceTy<'tcx>;
567
568            #[inline(always)]
569            fn ecx(&self) -> &MiriInterpCx<'tcx> {
570                self.ecx
571            }
572
573            fn aggregate_field_iter(
574                memory_index: &IndexVec<FieldIdx, u32>,
575            ) -> impl Iterator<Item = FieldIdx> + 'static {
576                let inverse_memory_index = memory_index.invert_bijective_mapping();
577                inverse_memory_index.into_iter()
578            }
579
580            // Hook to detect `UnsafeCell`.
581            fn visit_value(&mut self, v: &MPlaceTy<'tcx>) -> InterpResult<'tcx> {
582                trace!("UnsafeCellVisitor: {:?} {:?}", *v, v.layout.ty);
583                let is_unsafe_cell = match v.layout.ty.kind() {
584                    ty::Adt(adt, _) =>
585                        Some(adt.did()) == self.ecx.tcx.lang_items().unsafe_cell_type(),
586                    _ => false,
587                };
588                if is_unsafe_cell {
589                    // We do not have to recurse further, this is an `UnsafeCell`.
590                    (self.unsafe_cell_action)(v)
591                } else if self.ecx.type_is_freeze(v.layout.ty) {
592                    // This is `Freeze`, there cannot be an `UnsafeCell`
593                    interp_ok(())
594                } else if matches!(v.layout.fields, FieldsShape::Union(..)) {
595                    // A (non-frozen) union. We fall back to whatever the type says.
596                    (self.unsafe_cell_action)(v)
597                } else if matches!(v.layout.ty.kind(), ty::Dynamic(_, _, ty::DynStar)) {
598                    // This needs to read the vtable pointer to proceed type-driven, but we don't
599                    // want to reentrantly read from memory here.
600                    (self.unsafe_cell_action)(v)
601                } else {
602                    // We want to not actually read from memory for this visit. So, before
603                    // walking this value, we have to make sure it is not a
604                    // `Variants::Multiple`.
605                    // FIXME: the current logic here is layout-dependent, so enums with
606                    // multiple variants where all but 1 are uninhabited will be recursed into.
607                    // Is that truly what we want?
608                    match v.layout.variants {
609                        Variants::Multiple { .. } => {
610                            // A multi-variant enum, or coroutine, or so.
611                            // Treat this like a union: without reading from memory,
612                            // we cannot determine the variant we are in. Reading from
613                            // memory would be subject to Stacked Borrows rules, leading
614                            // to all sorts of "funny" recursion.
615                            // We only end up here if the type is *not* freeze, so we just call the
616                            // `UnsafeCell` action.
617                            (self.unsafe_cell_action)(v)
618                        }
619                        Variants::Single { .. } | Variants::Empty => {
620                            // Proceed further, try to find where exactly that `UnsafeCell`
621                            // is hiding.
622                            self.walk_value(v)
623                        }
624                    }
625                }
626            }
627
628            fn visit_union(
629                &mut self,
630                _v: &MPlaceTy<'tcx>,
631                _fields: NonZero<usize>,
632            ) -> InterpResult<'tcx> {
633                bug!("we should have already handled unions in `visit_value`")
634            }
635        }
636    }
637
638    /// Helper function used inside the shims of foreign functions to check that isolation is
639    /// disabled. It returns an error using the `name` of the foreign function if this is not the
640    /// case.
641    fn check_no_isolation(&self, name: &str) -> InterpResult<'tcx> {
642        if !self.eval_context_ref().machine.communicate() {
643            self.reject_in_isolation(name, RejectOpWith::Abort)?;
644        }
645        interp_ok(())
646    }
647
648    /// Helper function used inside the shims of foreign functions which reject the op
649    /// when isolation is enabled. It is used to print a warning/backtrace about the rejection.
650    fn reject_in_isolation(&self, op_name: &str, reject_with: RejectOpWith) -> InterpResult<'tcx> {
651        let this = self.eval_context_ref();
652        match reject_with {
653            RejectOpWith::Abort => isolation_abort_error(op_name),
654            RejectOpWith::WarningWithoutBacktrace => {
655                let mut emitted_warnings = this.machine.reject_in_isolation_warned.borrow_mut();
656                if !emitted_warnings.contains(op_name) {
657                    // First time we are seeing this.
658                    emitted_warnings.insert(op_name.to_owned());
659                    this.tcx
660                        .dcx()
661                        .warn(format!("{op_name} was made to return an error due to isolation"));
662                }
663
664                interp_ok(())
665            }
666            RejectOpWith::Warning => {
667                this.emit_diagnostic(NonHaltingDiagnostic::RejectedIsolatedOp(op_name.to_string()));
668                interp_ok(())
669            }
670            RejectOpWith::NoWarning => interp_ok(()), // no warning
671        }
672    }
673
674    /// Helper function used inside the shims of foreign functions to assert that the target OS
675    /// is `target_os`. It panics showing a message with the `name` of the foreign function
676    /// if this is not the case.
677    fn assert_target_os(&self, target_os: &str, name: &str) {
678        assert_eq!(
679            self.eval_context_ref().tcx.sess.target.os,
680            target_os,
681            "`{name}` is only available on the `{target_os}` target OS",
682        )
683    }
684
685    /// Helper function used inside shims of foreign functions to check that the target OS
686    /// is one of `target_oses`. It returns an error containing the `name` of the foreign function
687    /// in a message if this is not the case.
688    fn check_target_os(&self, target_oses: &[&str], name: Symbol) -> InterpResult<'tcx> {
689        let target_os = self.eval_context_ref().tcx.sess.target.os.as_ref();
690        if !target_oses.contains(&target_os) {
691            throw_unsup_format!("`{name}` is not supported on {target_os}");
692        }
693        interp_ok(())
694    }
695
696    /// Helper function used inside the shims of foreign functions to assert that the target OS
697    /// is part of the UNIX family. It panics showing a message with the `name` of the foreign function
698    /// if this is not the case.
699    fn assert_target_os_is_unix(&self, name: &str) {
700        assert!(self.target_os_is_unix(), "`{name}` is only available for unix targets",);
701    }
702
703    fn target_os_is_unix(&self) -> bool {
704        self.eval_context_ref().tcx.sess.target.families.iter().any(|f| f == "unix")
705    }
706
707    /// Dereference a pointer operand to a place using `layout` instead of the pointer's declared type
708    fn deref_pointer_as(
709        &self,
710        op: &impl Projectable<'tcx, Provenance>,
711        layout: TyAndLayout<'tcx>,
712    ) -> InterpResult<'tcx, MPlaceTy<'tcx>> {
713        let this = self.eval_context_ref();
714        let ptr = this.read_pointer(op)?;
715        interp_ok(this.ptr_to_mplace(ptr, layout))
716    }
717
718    /// Calculates the MPlaceTy given the offset and layout of an access on an operand
719    fn deref_pointer_and_offset(
720        &self,
721        op: &impl Projectable<'tcx, Provenance>,
722        offset: u64,
723        base_layout: TyAndLayout<'tcx>,
724        value_layout: TyAndLayout<'tcx>,
725    ) -> InterpResult<'tcx, MPlaceTy<'tcx>> {
726        let this = self.eval_context_ref();
727        let op_place = this.deref_pointer_as(op, base_layout)?;
728        let offset = Size::from_bytes(offset);
729
730        // Ensure that the access is within bounds.
731        assert!(base_layout.size >= offset + value_layout.size);
732        let value_place = op_place.offset(offset, value_layout, this)?;
733        interp_ok(value_place)
734    }
735
736    fn deref_pointer_and_read(
737        &self,
738        op: &impl Projectable<'tcx, Provenance>,
739        offset: u64,
740        base_layout: TyAndLayout<'tcx>,
741        value_layout: TyAndLayout<'tcx>,
742    ) -> InterpResult<'tcx, Scalar> {
743        let this = self.eval_context_ref();
744        let value_place = this.deref_pointer_and_offset(op, offset, base_layout, value_layout)?;
745        this.read_scalar(&value_place)
746    }
747
748    fn deref_pointer_and_write(
749        &mut self,
750        op: &impl Projectable<'tcx, Provenance>,
751        offset: u64,
752        value: impl Into<Scalar>,
753        base_layout: TyAndLayout<'tcx>,
754        value_layout: TyAndLayout<'tcx>,
755    ) -> InterpResult<'tcx, ()> {
756        let this = self.eval_context_mut();
757        let value_place = this.deref_pointer_and_offset(op, offset, base_layout, value_layout)?;
758        this.write_scalar(value, &value_place)
759    }
760
761    /// Parse a `timespec` struct and return it as a `std::time::Duration`. It returns `None`
762    /// if the value in the `timespec` struct is invalid. Some libc functions will return
763    /// `EINVAL` in this case.
764    fn read_timespec(&mut self, tp: &MPlaceTy<'tcx>) -> InterpResult<'tcx, Option<Duration>> {
765        let this = self.eval_context_mut();
766        let seconds_place = this.project_field(tp, 0)?;
767        let seconds_scalar = this.read_scalar(&seconds_place)?;
768        let seconds = seconds_scalar.to_target_isize(this)?;
769        let nanoseconds_place = this.project_field(tp, 1)?;
770        let nanoseconds_scalar = this.read_scalar(&nanoseconds_place)?;
771        let nanoseconds = nanoseconds_scalar.to_target_isize(this)?;
772
773        interp_ok(
774            try {
775                // tv_sec must be non-negative.
776                let seconds: u64 = seconds.try_into().ok()?;
777                // tv_nsec must be non-negative.
778                let nanoseconds: u32 = nanoseconds.try_into().ok()?;
779                if nanoseconds >= 1_000_000_000 {
780                    // tv_nsec must not be greater than 999,999,999.
781                    None?
782                }
783                Duration::new(seconds, nanoseconds)
784            },
785        )
786    }
787
788    /// Read bytes from a byte slice.
789    fn read_byte_slice<'a>(&'a self, slice: &ImmTy<'tcx>) -> InterpResult<'tcx, &'a [u8]>
790    where
791        'tcx: 'a,
792    {
793        let this = self.eval_context_ref();
794        let (ptr, len) = slice.to_scalar_pair();
795        let ptr = ptr.to_pointer(this)?;
796        let len = len.to_target_usize(this)?;
797        let bytes = this.read_bytes_ptr_strip_provenance(ptr, Size::from_bytes(len))?;
798        interp_ok(bytes)
799    }
800
801    /// Read a sequence of bytes until the first null terminator.
802    fn read_c_str<'a>(&'a self, ptr: Pointer) -> InterpResult<'tcx, &'a [u8]>
803    where
804        'tcx: 'a,
805    {
806        let this = self.eval_context_ref();
807        let size1 = Size::from_bytes(1);
808
809        // Step 1: determine the length.
810        let mut len = Size::ZERO;
811        loop {
812            // FIXME: We are re-getting the allocation each time around the loop.
813            // Would be nice if we could somehow "extend" an existing AllocRange.
814            let alloc = this.get_ptr_alloc(ptr.wrapping_offset(len, this), size1)?.unwrap(); // not a ZST, so we will get a result
815            let byte = alloc.read_integer(alloc_range(Size::ZERO, size1))?.to_u8()?;
816            if byte == 0 {
817                break;
818            } else {
819                len += size1;
820            }
821        }
822
823        // Step 2: get the bytes.
824        this.read_bytes_ptr_strip_provenance(ptr, len)
825    }
826
827    /// Helper function to write a sequence of bytes with an added null-terminator, which is what
828    /// the Unix APIs usually handle. This function returns `Ok((false, length))` without trying
829    /// to write if `size` is not large enough to fit the contents of `c_str` plus a null
830    /// terminator. It returns `Ok((true, length))` if the writing process was successful. The
831    /// string length returned does include the null terminator.
832    fn write_c_str(
833        &mut self,
834        c_str: &[u8],
835        ptr: Pointer,
836        size: u64,
837    ) -> InterpResult<'tcx, (bool, u64)> {
838        // If `size` is smaller or equal than `bytes.len()`, writing `bytes` plus the required null
839        // terminator to memory using the `ptr` pointer would cause an out-of-bounds access.
840        let string_length = u64::try_from(c_str.len()).unwrap();
841        let string_length = string_length.strict_add(1);
842        if size < string_length {
843            return interp_ok((false, string_length));
844        }
845        self.eval_context_mut()
846            .write_bytes_ptr(ptr, c_str.iter().copied().chain(iter::once(0u8)))?;
847        interp_ok((true, string_length))
848    }
849
850    /// Helper function to read a sequence of unsigned integers of the given size and alignment
851    /// until the first null terminator.
852    fn read_c_str_with_char_size<T>(
853        &self,
854        mut ptr: Pointer,
855        size: Size,
856        align: Align,
857    ) -> InterpResult<'tcx, Vec<T>>
858    where
859        T: TryFrom<u128>,
860        <T as TryFrom<u128>>::Error: std::fmt::Debug,
861    {
862        assert_ne!(size, Size::ZERO);
863
864        let this = self.eval_context_ref();
865
866        this.check_ptr_align(ptr, align)?;
867
868        let mut wchars = Vec::new();
869        loop {
870            // FIXME: We are re-getting the allocation each time around the loop.
871            // Would be nice if we could somehow "extend" an existing AllocRange.
872            let alloc = this.get_ptr_alloc(ptr, size)?.unwrap(); // not a ZST, so we will get a result
873            let wchar_int = alloc.read_integer(alloc_range(Size::ZERO, size))?.to_bits(size)?;
874            if wchar_int == 0 {
875                break;
876            } else {
877                wchars.push(wchar_int.try_into().unwrap());
878                ptr = ptr.wrapping_offset(size, this);
879            }
880        }
881
882        interp_ok(wchars)
883    }
884
885    /// Read a sequence of u16 until the first null terminator.
886    fn read_wide_str(&self, ptr: Pointer) -> InterpResult<'tcx, Vec<u16>> {
887        self.read_c_str_with_char_size(ptr, Size::from_bytes(2), Align::from_bytes(2).unwrap())
888    }
889
890    /// Helper function to write a sequence of u16 with an added 0x0000-terminator, which is what
891    /// the Windows APIs usually handle. This function returns `Ok((false, length))` without trying
892    /// to write if `size` is not large enough to fit the contents of `os_string` plus a null
893    /// terminator. It returns `Ok((true, length))` if the writing process was successful. The
894    /// string length returned does include the null terminator. Length is measured in units of
895    /// `u16.`
896    fn write_wide_str(
897        &mut self,
898        wide_str: &[u16],
899        ptr: Pointer,
900        size: u64,
901    ) -> InterpResult<'tcx, (bool, u64)> {
902        // If `size` is smaller or equal than `bytes.len()`, writing `bytes` plus the required
903        // 0x0000 terminator to memory would cause an out-of-bounds access.
904        let string_length = u64::try_from(wide_str.len()).unwrap();
905        let string_length = string_length.strict_add(1);
906        if size < string_length {
907            return interp_ok((false, string_length));
908        }
909
910        // Store the UTF-16 string.
911        let size2 = Size::from_bytes(2);
912        let this = self.eval_context_mut();
913        this.check_ptr_align(ptr, Align::from_bytes(2).unwrap())?;
914        let mut alloc = this.get_ptr_alloc_mut(ptr, size2 * string_length)?.unwrap(); // not a ZST, so we will get a result
915        for (offset, wchar) in wide_str.iter().copied().chain(iter::once(0x0000)).enumerate() {
916            let offset = u64::try_from(offset).unwrap();
917            alloc.write_scalar(alloc_range(size2 * offset, size2), Scalar::from_u16(wchar))?;
918        }
919        interp_ok((true, string_length))
920    }
921
922    /// Read a sequence of wchar_t until the first null terminator.
923    /// Always returns a `Vec<u32>` no matter the size of `wchar_t`.
924    fn read_wchar_t_str(&self, ptr: Pointer) -> InterpResult<'tcx, Vec<u32>> {
925        let this = self.eval_context_ref();
926        let wchar_t = if this.tcx.sess.target.os == "windows" {
927            // We don't have libc on Windows so we have to hard-code the type ourselves.
928            this.machine.layouts.u16
929        } else {
930            this.libc_ty_layout("wchar_t")
931        };
932        self.read_c_str_with_char_size(ptr, wchar_t.size, wchar_t.align.abi)
933    }
934
935    /// Check that the ABI is what we expect.
936    fn check_abi<'a>(&self, fn_abi: &FnAbi<'tcx, Ty<'tcx>>, exp_abi: Conv) -> InterpResult<'a, ()> {
937        if fn_abi.conv != exp_abi {
938            throw_ub_format!(
939                "calling a function with ABI {:?} using caller ABI {:?}",
940                exp_abi,
941                fn_abi.conv
942            );
943        }
944        interp_ok(())
945    }
946
947    fn frame_in_std(&self) -> bool {
948        let this = self.eval_context_ref();
949        let frame = this.frame();
950        // Make an attempt to get at the instance of the function this is inlined from.
951        let instance: Option<_> = try {
952            let scope = frame.current_source_info()?.scope;
953            let inlined_parent = frame.body().source_scopes[scope].inlined_parent_scope?;
954            let source = &frame.body().source_scopes[inlined_parent];
955            source.inlined.expect("inlined_parent_scope points to scope without inline info").0
956        };
957        // Fall back to the instance of the function itself.
958        let instance = instance.unwrap_or(frame.instance());
959        // Now check the crate it is in. We could try to be clever here and e.g. check if this is
960        // the same crate as `start_fn`, but that would not work for running std tests in Miri, so
961        // we'd need some more hacks anyway. So we just check the name of the crate. If someone
962        // calls their crate `std` then we'll just let them keep the pieces.
963        let frame_crate = this.tcx.def_path(instance.def_id()).krate;
964        let crate_name = this.tcx.crate_name(frame_crate);
965        let crate_name = crate_name.as_str();
966        // On miri-test-libstd, the name of the crate is different.
967        crate_name == "std" || crate_name == "std_miri_test"
968    }
969
970    fn check_abi_and_shim_symbol_clash(
971        &mut self,
972        abi: &FnAbi<'tcx, Ty<'tcx>>,
973        exp_abi: Conv,
974        link_name: Symbol,
975    ) -> InterpResult<'tcx, ()> {
976        self.check_abi(abi, exp_abi)?;
977        if let Some((body, instance)) = self.eval_context_mut().lookup_exported_symbol(link_name)? {
978            // If compiler-builtins is providing the symbol, then don't treat it as a clash.
979            // We'll use our built-in implementation in `emulate_foreign_item_inner` for increased
980            // performance. Note that this means we won't catch any undefined behavior in
981            // compiler-builtins when running other crates, but Miri can still be run on
982            // compiler-builtins itself (or any crate that uses it as a normal dependency)
983            if self.eval_context_ref().tcx.is_compiler_builtins(instance.def_id().krate) {
984                return interp_ok(());
985            }
986
987            throw_machine_stop!(TerminationInfo::SymbolShimClashing {
988                link_name,
989                span: body.span.data(),
990            })
991        }
992        interp_ok(())
993    }
994
995    fn check_shim<'a, const N: usize>(
996        &mut self,
997        abi: &FnAbi<'tcx, Ty<'tcx>>,
998        exp_abi: Conv,
999        link_name: Symbol,
1000        args: &'a [OpTy<'tcx>],
1001    ) -> InterpResult<'tcx, &'a [OpTy<'tcx>; N]> {
1002        self.check_abi_and_shim_symbol_clash(abi, exp_abi, link_name)?;
1003
1004        if abi.c_variadic {
1005            throw_ub_format!(
1006                "calling a non-variadic function with a variadic caller-side signature"
1007            );
1008        }
1009        if let Ok(ops) = args.try_into() {
1010            return interp_ok(ops);
1011        }
1012        throw_ub_format!(
1013            "incorrect number of arguments for `{link_name}`: got {}, expected {}",
1014            args.len(),
1015            N
1016        )
1017    }
1018
1019    /// Check that the given `caller_fn_abi` matches the expected ABI described by
1020    /// `callee_abi`, `callee_input_tys`, `callee_output_ty`, and then returns the list of
1021    /// arguments.
1022    fn check_shim_abi<'a, const N: usize>(
1023        &mut self,
1024        link_name: Symbol,
1025        caller_fn_abi: &FnAbi<'tcx, Ty<'tcx>>,
1026        callee_abi: ExternAbi,
1027        callee_input_tys: [Ty<'tcx>; N],
1028        callee_output_ty: Ty<'tcx>,
1029        caller_args: &'a [OpTy<'tcx>],
1030    ) -> InterpResult<'tcx, &'a [OpTy<'tcx>; N]> {
1031        let this = self.eval_context_mut();
1032        let mut inputs_and_output = callee_input_tys.to_vec();
1033        inputs_and_output.push(callee_output_ty);
1034        let fn_sig_binder = Binder::dummy(FnSig {
1035            inputs_and_output: this.machine.tcx.mk_type_list(&inputs_and_output),
1036            c_variadic: false,
1037            // This does not matter for the ABI.
1038            safety: Safety::Safe,
1039            abi: callee_abi,
1040        });
1041        let callee_fn_abi = this.fn_abi_of_fn_ptr(fn_sig_binder, Default::default())?;
1042
1043        this.check_abi_and_shim_symbol_clash(caller_fn_abi, callee_fn_abi.conv, link_name)?;
1044
1045        if caller_fn_abi.c_variadic {
1046            throw_ub_format!(
1047                "ABI mismatch: calling a non-variadic function with a variadic caller-side signature"
1048            );
1049        }
1050
1051        if callee_fn_abi.fixed_count != caller_fn_abi.fixed_count {
1052            throw_ub_format!(
1053                "ABI mismatch: expected {} arguments, found {} arguments ",
1054                callee_fn_abi.fixed_count,
1055                caller_fn_abi.fixed_count
1056            );
1057        }
1058
1059        if callee_fn_abi.can_unwind && !caller_fn_abi.can_unwind {
1060            throw_ub_format!(
1061                "ABI mismatch: callee may unwind, but caller-side signature prohibits unwinding",
1062            );
1063        }
1064
1065        if !this.check_argument_compat(&caller_fn_abi.ret, &callee_fn_abi.ret)? {
1066            throw_ub!(AbiMismatchReturn {
1067                caller_ty: caller_fn_abi.ret.layout.ty,
1068                callee_ty: callee_fn_abi.ret.layout.ty
1069            });
1070        }
1071
1072        if let Some(index) = caller_fn_abi
1073            .args
1074            .iter()
1075            .zip(callee_fn_abi.args.iter())
1076            .map(|(caller_arg, callee_arg)| this.check_argument_compat(caller_arg, callee_arg))
1077            .collect::<InterpResult<'tcx, Vec<bool>>>()?
1078            .into_iter()
1079            .position(|b| !b)
1080        {
1081            throw_ub!(AbiMismatchArgument {
1082                caller_ty: caller_fn_abi.args[index].layout.ty,
1083                callee_ty: callee_fn_abi.args[index].layout.ty
1084            });
1085        }
1086
1087        if let Ok(ops) = caller_args.try_into() {
1088            return interp_ok(ops);
1089        }
1090        unreachable!()
1091    }
1092
1093    /// Check shim for variadic function.
1094    /// Returns a tuple that consisting of an array of fixed args, and a slice of varargs.
1095    fn check_shim_variadic<'a, const N: usize>(
1096        &mut self,
1097        abi: &FnAbi<'tcx, Ty<'tcx>>,
1098        exp_abi: Conv,
1099        link_name: Symbol,
1100        args: &'a [OpTy<'tcx>],
1101    ) -> InterpResult<'tcx, (&'a [OpTy<'tcx>; N], &'a [OpTy<'tcx>])>
1102    where
1103        &'a [OpTy<'tcx>; N]: TryFrom<&'a [OpTy<'tcx>]>,
1104    {
1105        self.check_abi_and_shim_symbol_clash(abi, exp_abi, link_name)?;
1106
1107        if !abi.c_variadic {
1108            throw_ub_format!(
1109                "calling a variadic function with a non-variadic caller-side signature"
1110            );
1111        }
1112        if abi.fixed_count != u32::try_from(N).unwrap() {
1113            throw_ub_format!(
1114                "incorrect number of fixed arguments for variadic function `{}`: got {}, expected {N}",
1115                link_name.as_str(),
1116                abi.fixed_count
1117            )
1118        }
1119        if let Some(args) = args.split_first_chunk() {
1120            return interp_ok(args);
1121        }
1122        panic!("mismatch between signature and `args` slice");
1123    }
1124
1125    /// Mark a machine allocation that was just created as immutable.
1126    fn mark_immutable(&mut self, mplace: &MPlaceTy<'tcx>) {
1127        let this = self.eval_context_mut();
1128        // This got just allocated, so there definitely is a pointer here.
1129        let provenance = mplace.ptr().into_pointer_or_addr().unwrap().provenance;
1130        this.alloc_mark_immutable(provenance.get_alloc_id().unwrap()).unwrap();
1131    }
1132
1133    /// Converts `src` from floating point to integer type `dest_ty`
1134    /// after rounding with mode `round`.
1135    /// Returns `None` if `f` is NaN or out of range.
1136    fn float_to_int_checked(
1137        &self,
1138        src: &ImmTy<'tcx>,
1139        cast_to: TyAndLayout<'tcx>,
1140        round: rustc_apfloat::Round,
1141    ) -> InterpResult<'tcx, Option<ImmTy<'tcx>>> {
1142        let this = self.eval_context_ref();
1143
1144        fn float_to_int_inner<'tcx, F: rustc_apfloat::Float>(
1145            ecx: &MiriInterpCx<'tcx>,
1146            src: F,
1147            cast_to: TyAndLayout<'tcx>,
1148            round: rustc_apfloat::Round,
1149        ) -> (Scalar, rustc_apfloat::Status) {
1150            let int_size = cast_to.layout.size;
1151            match cast_to.ty.kind() {
1152                // Unsigned
1153                ty::Uint(_) => {
1154                    let res = src.to_u128_r(int_size.bits_usize(), round, &mut false);
1155                    (Scalar::from_uint(res.value, int_size), res.status)
1156                }
1157                // Signed
1158                ty::Int(_) => {
1159                    let res = src.to_i128_r(int_size.bits_usize(), round, &mut false);
1160                    (Scalar::from_int(res.value, int_size), res.status)
1161                }
1162                // Nothing else
1163                _ =>
1164                    span_bug!(
1165                        ecx.cur_span(),
1166                        "attempted float-to-int conversion with non-int output type {}",
1167                        cast_to.ty,
1168                    ),
1169            }
1170        }
1171
1172        let ty::Float(fty) = src.layout.ty.kind() else {
1173            bug!("float_to_int_checked: non-float input type {}", src.layout.ty)
1174        };
1175
1176        let (val, status) = match fty {
1177            FloatTy::F16 =>
1178                float_to_int_inner::<Half>(this, src.to_scalar().to_f16()?, cast_to, round),
1179            FloatTy::F32 =>
1180                float_to_int_inner::<Single>(this, src.to_scalar().to_f32()?, cast_to, round),
1181            FloatTy::F64 =>
1182                float_to_int_inner::<Double>(this, src.to_scalar().to_f64()?, cast_to, round),
1183            FloatTy::F128 =>
1184                float_to_int_inner::<Quad>(this, src.to_scalar().to_f128()?, cast_to, round),
1185        };
1186
1187        if status.intersects(
1188            rustc_apfloat::Status::INVALID_OP
1189                | rustc_apfloat::Status::OVERFLOW
1190                | rustc_apfloat::Status::UNDERFLOW,
1191        ) {
1192            // Floating point value is NaN (flagged with INVALID_OP) or outside the range
1193            // of values of the integer type (flagged with OVERFLOW or UNDERFLOW).
1194            interp_ok(None)
1195        } else {
1196            // Floating point value can be represented by the integer type after rounding.
1197            // The INEXACT flag is ignored on purpose to allow rounding.
1198            interp_ok(Some(ImmTy::from_scalar(val, cast_to)))
1199        }
1200    }
1201
1202    /// Returns an integer type that is twice wide as `ty`
1203    fn get_twice_wide_int_ty(&self, ty: Ty<'tcx>) -> Ty<'tcx> {
1204        let this = self.eval_context_ref();
1205        match ty.kind() {
1206            // Unsigned
1207            ty::Uint(UintTy::U8) => this.tcx.types.u16,
1208            ty::Uint(UintTy::U16) => this.tcx.types.u32,
1209            ty::Uint(UintTy::U32) => this.tcx.types.u64,
1210            ty::Uint(UintTy::U64) => this.tcx.types.u128,
1211            // Signed
1212            ty::Int(IntTy::I8) => this.tcx.types.i16,
1213            ty::Int(IntTy::I16) => this.tcx.types.i32,
1214            ty::Int(IntTy::I32) => this.tcx.types.i64,
1215            ty::Int(IntTy::I64) => this.tcx.types.i128,
1216            _ => span_bug!(this.cur_span(), "unexpected type: {ty:?}"),
1217        }
1218    }
1219
1220    /// Checks that target feature `target_feature` is enabled.
1221    ///
1222    /// If not enabled, emits an UB error that states that the feature is
1223    /// required by `intrinsic`.
1224    fn expect_target_feature_for_intrinsic(
1225        &self,
1226        intrinsic: Symbol,
1227        target_feature: &str,
1228    ) -> InterpResult<'tcx, ()> {
1229        let this = self.eval_context_ref();
1230        if !this.tcx.sess.unstable_target_features.contains(&Symbol::intern(target_feature)) {
1231            throw_ub_format!(
1232                "attempted to call intrinsic `{intrinsic}` that requires missing target feature {target_feature}"
1233            );
1234        }
1235        interp_ok(())
1236    }
1237
1238    /// Lookup an array of immediates stored as a linker section of name `name`.
1239    fn lookup_link_section(&mut self, name: &str) -> InterpResult<'tcx, Vec<ImmTy<'tcx>>> {
1240        let this = self.eval_context_mut();
1241        let tcx = this.tcx.tcx;
1242
1243        let mut array = vec![];
1244
1245        iter_exported_symbols(tcx, |_cnum, def_id| {
1246            let attrs = tcx.codegen_fn_attrs(def_id);
1247            let Some(link_section) = attrs.link_section else {
1248                return interp_ok(());
1249            };
1250            if link_section.as_str() == name {
1251                let instance = ty::Instance::mono(tcx, def_id);
1252                let const_val = this.eval_global(instance).unwrap_or_else(|err| {
1253                    panic!(
1254                        "failed to evaluate static in required link_section: {def_id:?}\n{err:?}"
1255                    )
1256                });
1257                let val = this.read_immediate(&const_val)?;
1258                array.push(val);
1259            }
1260            interp_ok(())
1261        })?;
1262
1263        interp_ok(array)
1264    }
1265
1266    fn mangle_internal_symbol<'a>(&'a mut self, name: &'static str) -> &'a str
1267    where
1268        'tcx: 'a,
1269    {
1270        let this = self.eval_context_mut();
1271        let tcx = *this.tcx;
1272        this.machine
1273            .mangle_internal_symbol_cache
1274            .entry(name)
1275            .or_insert_with(|| mangle_internal_symbol(tcx, name))
1276    }
1277}
1278
1279impl<'tcx> MiriMachine<'tcx> {
1280    /// Get the current span in the topmost function which is workspace-local and not
1281    /// `#[track_caller]`.
1282    /// This function is backed by a cache, and can be assumed to be very fast.
1283    /// It will work even when the stack is empty.
1284    pub fn current_span(&self) -> Span {
1285        self.threads.active_thread_ref().current_span()
1286    }
1287
1288    /// Returns the span of the *caller* of the current operation, again
1289    /// walking down the stack to find the closest frame in a local crate, if the caller of the
1290    /// current operation is not in a local crate.
1291    /// This is useful when we are processing something which occurs on function-entry and we want
1292    /// to point at the call to the function, not the function definition generally.
1293    pub fn caller_span(&self) -> Span {
1294        // We need to go down at least to the caller (len - 2), or however
1295        // far we have to go to find a frame in a local crate which is also not #[track_caller].
1296        let frame_idx = self.top_user_relevant_frame().unwrap();
1297        let frame_idx = cmp::min(frame_idx, self.stack().len().saturating_sub(2));
1298        self.stack()[frame_idx].current_span()
1299    }
1300
1301    fn stack(&self) -> &[Frame<'tcx, Provenance, machine::FrameExtra<'tcx>>] {
1302        self.threads.active_thread_stack()
1303    }
1304
1305    fn top_user_relevant_frame(&self) -> Option<usize> {
1306        self.threads.active_thread_ref().top_user_relevant_frame()
1307    }
1308
1309    /// This is the source of truth for the `is_user_relevant` flag in our `FrameExtra`.
1310    pub fn is_user_relevant(&self, frame: &Frame<'tcx, Provenance>) -> bool {
1311        let def_id = frame.instance().def_id();
1312        (def_id.is_local() || self.local_crates.contains(&def_id.krate))
1313            && !frame.instance().def.requires_caller_location(self.tcx)
1314    }
1315}
1316
1317/// Check that the number of args is what we expect.
1318pub fn check_intrinsic_arg_count<'a, 'tcx, const N: usize>(
1319    args: &'a [OpTy<'tcx>],
1320) -> InterpResult<'tcx, &'a [OpTy<'tcx>; N]>
1321where
1322    &'a [OpTy<'tcx>; N]: TryFrom<&'a [OpTy<'tcx>]>,
1323{
1324    if let Ok(ops) = args.try_into() {
1325        return interp_ok(ops);
1326    }
1327    throw_ub_format!(
1328        "incorrect number of arguments for intrinsic: got {}, expected {}",
1329        args.len(),
1330        N
1331    )
1332}
1333
1334/// Check that the number of varargs is at least the minimum what we expect.
1335/// Fixed args should not be included.
1336/// Use `check_vararg_fixed_arg_count` to extract the varargs slice from full function arguments.
1337pub fn check_min_vararg_count<'a, 'tcx, const N: usize>(
1338    name: &'a str,
1339    args: &'a [OpTy<'tcx>],
1340) -> InterpResult<'tcx, &'a [OpTy<'tcx>; N]> {
1341    if let Some((ops, _)) = args.split_first_chunk() {
1342        return interp_ok(ops);
1343    }
1344    throw_ub_format!(
1345        "not enough variadic arguments for `{name}`: got {}, expected at least {}",
1346        args.len(),
1347        N
1348    )
1349}
1350
1351pub fn isolation_abort_error<'tcx>(name: &str) -> InterpResult<'tcx> {
1352    throw_machine_stop!(TerminationInfo::UnsupportedInIsolation(format!(
1353        "{name} not available when isolation is enabled",
1354    )))
1355}
1356
1357/// Retrieve the list of local crates that should have been passed by cargo-miri in
1358/// MIRI_LOCAL_CRATES and turn them into `CrateNum`s.
1359pub fn get_local_crates(tcx: TyCtxt<'_>) -> Vec<CrateNum> {
1360    // Convert the local crate names from the passed-in config into CrateNums so that they can
1361    // be looked up quickly during execution
1362    let local_crate_names = std::env::var("MIRI_LOCAL_CRATES")
1363        .map(|crates| crates.split(',').map(|krate| krate.to_string()).collect::<Vec<_>>())
1364        .unwrap_or_default();
1365    let mut local_crates = Vec::new();
1366    for &crate_num in tcx.crates(()) {
1367        let name = tcx.crate_name(crate_num);
1368        let name = name.as_str();
1369        if local_crate_names.iter().any(|local_name| local_name == name) {
1370            local_crates.push(crate_num);
1371        }
1372    }
1373    local_crates
1374}
1375
1376pub(crate) fn bool_to_simd_element(b: bool, size: Size) -> Scalar {
1377    // SIMD uses all-1 as pattern for "true". In two's complement,
1378    // -1 has all its bits set to one and `from_int` will truncate or
1379    // sign-extend it to `size` as required.
1380    let val = if b { -1 } else { 0 };
1381    Scalar::from_int(val, size)
1382}
1383
1384pub(crate) fn simd_element_to_bool(elem: ImmTy<'_>) -> InterpResult<'_, bool> {
1385    assert!(
1386        matches!(elem.layout.ty.kind(), ty::Int(_) | ty::Uint(_)),
1387        "SIMD mask element type must be an integer, but this is `{}`",
1388        elem.layout.ty
1389    );
1390    let val = elem.to_scalar().to_int(elem.layout.size)?;
1391    interp_ok(match val {
1392        0 => false,
1393        -1 => true,
1394        _ => throw_ub_format!("each element of a SIMD mask must be all-0-bits or all-1-bits"),
1395    })
1396}
1397
1398/// Check whether an operation that writes to a target buffer was successful.
1399/// Accordingly select return value.
1400/// Local helper function to be used in Windows shims.
1401pub(crate) fn windows_check_buffer_size((success, len): (bool, u64)) -> u32 {
1402    if success {
1403        // If the function succeeds, the return value is the number of characters stored in the target buffer,
1404        // not including the terminating null character.
1405        u32::try_from(len.strict_sub(1)).unwrap()
1406    } else {
1407        // If the target buffer was not large enough to hold the data, the return value is the buffer size, in characters,
1408        // required to hold the string and its terminating null character.
1409        u32::try_from(len).unwrap()
1410    }
1411}