summaryrefslogtreecommitdiffstats
path: root/compiler/rustc_symbol_mangling/src/legacy.rs
blob: 46c5fe78ffbf65697085e5bcd7874ed70e50595a (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
use rustc_hir::def_id::CrateNum;
use rustc_hir::definitions::{DefPathData, DisambiguatedDefPathData};
use rustc_middle::ty::print::{PrettyPrinter, Print, Printer};
use rustc_middle::ty::subst::{GenericArg, GenericArgKind};
use rustc_middle::ty::{self, Instance, Ty, TyCtxt, TypeVisitable};
use rustc_middle::util::common::record_time;

use std::fmt::{self, Write};
use std::mem::{self, discriminant};

pub(super) fn mangle<'tcx>(
    tcx: TyCtxt<'tcx>,
    instance: Instance<'tcx>,
    instantiating_crate: Option<CrateNum>,
) -> String {
    let def_id = instance.def_id();

    // We want to compute the "type" of this item. Unfortunately, some
    // kinds of items (e.g., closures) don't have an entry in the
    // item-type array. So walk back up the find the closest parent
    // that DOES have an entry.
    let mut ty_def_id = def_id;
    let instance_ty;
    loop {
        let key = tcx.def_key(ty_def_id);
        match key.disambiguated_data.data {
            DefPathData::TypeNs(_) | DefPathData::ValueNs(_) => {
                instance_ty = tcx.type_of(ty_def_id);
                debug!(?instance_ty);
                break;
            }
            _ => {
                // if we're making a symbol for something, there ought
                // to be a value or type-def or something in there
                // *somewhere*
                ty_def_id.index = key.parent.unwrap_or_else(|| {
                    bug!(
                        "finding type for {:?}, encountered def-id {:?} with no \
                         parent",
                        def_id,
                        ty_def_id
                    );
                });
            }
        }
    }

    // Erase regions because they may not be deterministic when hashed
    // and should not matter anyhow.
    let instance_ty = tcx.erase_regions(instance_ty);

    let hash = get_symbol_hash(tcx, instance, instance_ty, instantiating_crate);

    let mut printer = SymbolPrinter { tcx, path: SymbolPath::new(), keep_within_component: false };
    printer
        .print_def_path(
            def_id,
            if let ty::InstanceDef::DropGlue(_, _) = instance.def {
                // Add the name of the dropped type to the symbol name
                &*instance.substs
            } else {
                &[]
            },
        )
        .unwrap();

    if let ty::InstanceDef::VTableShim(..) = instance.def {
        let _ = printer.write_str("{{vtable-shim}}");
    }

    if let ty::InstanceDef::ReifyShim(..) = instance.def {
        let _ = printer.write_str("{{reify-shim}}");
    }

    printer.path.finish(hash)
}

fn get_symbol_hash<'tcx>(
    tcx: TyCtxt<'tcx>,

    // instance this name will be for
    instance: Instance<'tcx>,

    // type of the item, without any generic
    // parameters substituted; this is
    // included in the hash as a kind of
    // safeguard.
    item_type: Ty<'tcx>,

    instantiating_crate: Option<CrateNum>,
) -> u64 {
    let def_id = instance.def_id();
    let substs = instance.substs;
    debug!("get_symbol_hash(def_id={:?}, parameters={:?})", def_id, substs);

    tcx.with_stable_hashing_context(|mut hcx| {
        let mut hasher = StableHasher::new();

        record_time(&tcx.sess.perf_stats.symbol_hash_time, || {
            // the main symbol name is not necessarily unique; hash in the
            // compiler's internal def-path, guaranteeing each symbol has a
            // truly unique path
            tcx.def_path_hash(def_id).hash_stable(&mut hcx, &mut hasher);

            // Include the main item-type. Note that, in this case, the
            // assertions about `needs_subst` may not hold, but this item-type
            // ought to be the same for every reference anyway.
            assert!(!item_type.has_erasable_regions());
            hcx.while_hashing_spans(false, |hcx| {
                item_type.hash_stable(hcx, &mut hasher);

                // If this is a function, we hash the signature as well.
                // This is not *strictly* needed, but it may help in some
                // situations, see the `run-make/a-b-a-linker-guard` test.
                if let ty::FnDef(..) = item_type.kind() {
                    item_type.fn_sig(tcx).hash_stable(hcx, &mut hasher);
                }

                // also include any type parameters (for generic items)
                substs.hash_stable(hcx, &mut hasher);

                if let Some(instantiating_crate) = instantiating_crate {
                    tcx.def_path_hash(instantiating_crate.as_def_id())
                        .stable_crate_id()
                        .hash_stable(hcx, &mut hasher);
                }

                // We want to avoid accidental collision between different types of instances.
                // Especially, `VTableShim`s and `ReifyShim`s may overlap with their original
                // instances without this.
                discriminant(&instance.def).hash_stable(hcx, &mut hasher);
            });
        });

        // 64 bits should be enough to avoid collisions.
        hasher.finish::<u64>()
    })
}

// Follow C++ namespace-mangling style, see
// https://en.wikipedia.org/wiki/Name_mangling for more info.
//
// It turns out that on macOS you can actually have arbitrary symbols in
// function names (at least when given to LLVM), but this is not possible
// when using unix's linker. Perhaps one day when we just use a linker from LLVM
// we won't need to do this name mangling. The problem with name mangling is
// that it seriously limits the available characters. For example we can't
// have things like &T in symbol names when one would theoretically
// want them for things like impls of traits on that type.
//
// To be able to work on all platforms and get *some* reasonable output, we
// use C++ name-mangling.
#[derive(Debug)]
struct SymbolPath {
    result: String,
    temp_buf: String,
}

impl SymbolPath {
    fn new() -> Self {
        let mut result =
            SymbolPath { result: String::with_capacity(64), temp_buf: String::with_capacity(16) };
        result.result.push_str("_ZN"); // _Z == Begin name-sequence, N == nested
        result
    }

    fn finalize_pending_component(&mut self) {
        if !self.temp_buf.is_empty() {
            let _ = write!(self.result, "{}{}", self.temp_buf.len(), self.temp_buf);
            self.temp_buf.clear();
        }
    }

    fn finish(mut self, hash: u64) -> String {
        self.finalize_pending_component();
        // E = end name-sequence
        let _ = write!(self.result, "17h{:016x}E", hash);
        self.result
    }
}

struct SymbolPrinter<'tcx> {
    tcx: TyCtxt<'tcx>,
    path: SymbolPath,

    // When `true`, `finalize_pending_component` isn't used.
    // This is needed when recursing into `path_qualified`,
    // or `path_generic_args`, as any nested paths are
    // logically within one component.
    keep_within_component: bool,
}

// HACK(eddyb) this relies on using the `fmt` interface to get
// `PrettyPrinter` aka pretty printing of e.g. types in paths,
// symbol names should have their own printing machinery.

impl<'tcx> Printer<'tcx> for &mut SymbolPrinter<'tcx> {
    type Error = fmt::Error;

    type Path = Self;
    type Region = Self;
    type Type = Self;
    type DynExistential = Self;
    type Const = Self;

    fn tcx(&self) -> TyCtxt<'tcx> {
        self.tcx
    }

    fn print_region(self, _region: ty::Region<'_>) -> Result<Self::Region, Self::Error> {
        Ok(self)
    }

    fn print_type(mut self, ty: Ty<'tcx>) -> Result<Self::Type, Self::Error> {
        match *ty.kind() {
            // Print all nominal types as paths (unlike `pretty_print_type`).
            ty::FnDef(def_id, substs)
            | ty::Opaque(def_id, substs)
            | ty::Projection(ty::ProjectionTy { item_def_id: def_id, substs })
            | ty::Closure(def_id, substs)
            | ty::Generator(def_id, substs, _) => self.print_def_path(def_id, substs),

            // The `pretty_print_type` formatting of array size depends on
            // -Zverbose flag, so we cannot reuse it here.
            ty::Array(ty, size) => {
                self.write_str("[")?;
                self = self.print_type(ty)?;
                self.write_str("; ")?;
                if let Some(size) = size.kind().try_to_bits(self.tcx().data_layout.pointer_size) {
                    write!(self, "{}", size)?
                } else if let ty::ConstKind::Param(param) = size.kind() {
                    self = param.print(self)?
                } else {
                    self.write_str("_")?
                }
                self.write_str("]")?;
                Ok(self)
            }

            _ => self.pretty_print_type(ty),
        }
    }

    fn print_dyn_existential(
        mut self,
        predicates: &'tcx ty::List<ty::Binder<'tcx, ty::ExistentialPredicate<'tcx>>>,
    ) -> Result<Self::DynExistential, Self::Error> {
        let mut first = true;
        for p in predicates {
            if !first {
                write!(self, "+")?;
            }
            first = false;
            self = p.print(self)?;
        }
        Ok(self)
    }

    fn print_const(self, ct: ty::Const<'tcx>) -> Result<Self::Const, Self::Error> {
        // only print integers
        match (ct.kind(), ct.ty().kind()) {
            (ty::ConstKind::Value(ty::ValTree::Leaf(scalar)), ty::Int(_) | ty::Uint(_)) => {
                // The `pretty_print_const` formatting depends on -Zverbose
                // flag, so we cannot reuse it here.
                let signed = matches!(ct.ty().kind(), ty::Int(_));
                write!(
                    self,
                    "{:#?}",
                    ty::ConstInt::new(scalar, signed, ct.ty().is_ptr_sized_integral())
                )?;
            }
            _ => self.write_str("_")?,
        }
        Ok(self)
    }

    fn path_crate(self, cnum: CrateNum) -> Result<Self::Path, Self::Error> {
        self.write_str(self.tcx.crate_name(cnum).as_str())?;
        Ok(self)
    }
    fn path_qualified(
        self,
        self_ty: Ty<'tcx>,
        trait_ref: Option<ty::TraitRef<'tcx>>,
    ) -> Result<Self::Path, Self::Error> {
        // Similar to `pretty_path_qualified`, but for the other
        // types that are printed as paths (see `print_type` above).
        match self_ty.kind() {
            ty::FnDef(..)
            | ty::Opaque(..)
            | ty::Projection(_)
            | ty::Closure(..)
            | ty::Generator(..)
                if trait_ref.is_none() =>
            {
                self.print_type(self_ty)
            }

            _ => self.pretty_path_qualified(self_ty, trait_ref),
        }
    }

    fn path_append_impl(
        self,
        print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
        _disambiguated_data: &DisambiguatedDefPathData,
        self_ty: Ty<'tcx>,
        trait_ref: Option<ty::TraitRef<'tcx>>,
    ) -> Result<Self::Path, Self::Error> {
        self.pretty_path_append_impl(
            |mut cx| {
                cx = print_prefix(cx)?;

                if cx.keep_within_component {
                    // HACK(eddyb) print the path similarly to how `FmtPrinter` prints it.
                    cx.write_str("::")?;
                } else {
                    cx.path.finalize_pending_component();
                }

                Ok(cx)
            },
            self_ty,
            trait_ref,
        )
    }
    fn path_append(
        mut self,
        print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
        disambiguated_data: &DisambiguatedDefPathData,
    ) -> Result<Self::Path, Self::Error> {
        self = print_prefix(self)?;

        // Skip `::{{extern}}` blocks and `::{{constructor}}` on tuple/unit structs.
        if let DefPathData::ForeignMod | DefPathData::Ctor = disambiguated_data.data {
            return Ok(self);
        }

        if self.keep_within_component {
            // HACK(eddyb) print the path similarly to how `FmtPrinter` prints it.
            self.write_str("::")?;
        } else {
            self.path.finalize_pending_component();
        }

        write!(self, "{}", disambiguated_data.data)?;

        Ok(self)
    }
    fn path_generic_args(
        mut self,
        print_prefix: impl FnOnce(Self) -> Result<Self::Path, Self::Error>,
        args: &[GenericArg<'tcx>],
    ) -> Result<Self::Path, Self::Error> {
        self = print_prefix(self)?;

        let args =
            args.iter().cloned().filter(|arg| !matches!(arg.unpack(), GenericArgKind::Lifetime(_)));

        if args.clone().next().is_some() {
            self.generic_delimiters(|cx| cx.comma_sep(args))
        } else {
            Ok(self)
        }
    }
}

impl<'tcx> PrettyPrinter<'tcx> for &mut SymbolPrinter<'tcx> {
    fn should_print_region(&self, _region: ty::Region<'_>) -> bool {
        false
    }
    fn comma_sep<T>(mut self, mut elems: impl Iterator<Item = T>) -> Result<Self, Self::Error>
    where
        T: Print<'tcx, Self, Output = Self, Error = Self::Error>,
    {
        if let Some(first) = elems.next() {
            self = first.print(self)?;
            for elem in elems {
                self.write_str(",")?;
                self = elem.print(self)?;
            }
        }
        Ok(self)
    }

    fn generic_delimiters(
        mut self,
        f: impl FnOnce(Self) -> Result<Self, Self::Error>,
    ) -> Result<Self, Self::Error> {
        write!(self, "<")?;

        let kept_within_component = mem::replace(&mut self.keep_within_component, true);
        self = f(self)?;
        self.keep_within_component = kept_within_component;

        write!(self, ">")?;

        Ok(self)
    }
}

impl fmt::Write for SymbolPrinter<'_> {
    fn write_str(&mut self, s: &str) -> fmt::Result {
        // Name sanitation. LLVM will happily accept identifiers with weird names, but
        // gas doesn't!
        // gas accepts the following characters in symbols: a-z, A-Z, 0-9, ., _, $
        // NVPTX assembly has more strict naming rules than gas, so additionally, dots
        // are replaced with '$' there.

        for c in s.chars() {
            if self.path.temp_buf.is_empty() {
                match c {
                    'a'..='z' | 'A'..='Z' | '_' => {}
                    _ => {
                        // Underscore-qualify anything that didn't start as an ident.
                        self.path.temp_buf.push('_');
                    }
                }
            }
            match c {
                // Escape these with $ sequences
                '@' => self.path.temp_buf.push_str("$SP$"),
                '*' => self.path.temp_buf.push_str("$BP$"),
                '&' => self.path.temp_buf.push_str("$RF$"),
                '<' => self.path.temp_buf.push_str("$LT$"),
                '>' => self.path.temp_buf.push_str("$GT$"),
                '(' => self.path.temp_buf.push_str("$LP$"),
                ')' => self.path.temp_buf.push_str("$RP$"),
                ',' => self.path.temp_buf.push_str("$C$"),

                '-' | ':' | '.' if self.tcx.has_strict_asm_symbol_naming() => {
                    // NVPTX doesn't support these characters in symbol names.
                    self.path.temp_buf.push('$')
                }

                // '.' doesn't occur in types and functions, so reuse it
                // for ':' and '-'
                '-' | ':' => self.path.temp_buf.push('.'),

                // Avoid crashing LLVM in certain (LTO-related) situations, see #60925.
                'm' if self.path.temp_buf.ends_with(".llv") => self.path.temp_buf.push_str("$u6d$"),

                // These are legal symbols
                'a'..='z' | 'A'..='Z' | '0'..='9' | '_' | '.' | '$' => self.path.temp_buf.push(c),

                _ => {
                    self.path.temp_buf.push('$');
                    for c in c.escape_unicode().skip(1) {
                        match c {
                            '{' => {}
                            '}' => self.path.temp_buf.push('$'),
                            c => self.path.temp_buf.push(c),
                        }
                    }
                }
            }
        }

        Ok(())
    }
}