rustc_demangle/
lib.rs

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1//! Demangle Rust compiler symbol names.
2//!
3//! This crate provides a `demangle` function which will return a `Demangle`
4//! sentinel value that can be used to learn about the demangled version of a
5//! symbol name. The demangled representation will be the same as the original
6//! if it doesn't look like a mangled symbol name.
7//!
8//! `Demangle` can be formatted with the `Display` trait. The alternate
9//! modifier (`#`) can be used to format the symbol name without the
10//! trailing hash value.
11//!
12//! # Examples
13//!
14//! ```
15//! use rustc_demangle::demangle;
16//!
17//! assert_eq!(demangle("_ZN4testE").to_string(), "test");
18//! assert_eq!(demangle("_ZN3foo3barE").to_string(), "foo::bar");
19//! assert_eq!(demangle("foo").to_string(), "foo");
20//! // With hash
21//! assert_eq!(format!("{}", demangle("_ZN3foo17h05af221e174051e9E")), "foo::h05af221e174051e9");
22//! // Without hash
23//! assert_eq!(format!("{:#}", demangle("_ZN3foo17h05af221e174051e9E")), "foo");
24//! ```
25
26#![no_std]
27#![deny(missing_docs)]
28#![cfg_attr(docsrs, feature(doc_cfg))]
29
30#[cfg(any(test, feature = "std"))]
31#[macro_use]
32extern crate std;
33
34// HACK(eddyb) helper macros for tests.
35#[cfg(test)]
36macro_rules! assert_contains {
37    ($s:expr, $needle:expr) => {{
38        let (s, needle) = ($s, $needle);
39        assert!(
40            s.contains(needle),
41            "{:?} should've contained {:?}",
42            s,
43            needle
44        );
45    }};
46}
47#[cfg(test)]
48macro_rules! assert_ends_with {
49    ($s:expr, $suffix:expr) => {{
50        let (s, suffix) = ($s, $suffix);
51        assert!(
52            s.ends_with(suffix),
53            "{:?} should've ended in {:?}",
54            s,
55            suffix
56        );
57    }};
58}
59
60mod legacy;
61mod v0;
62
63use core::fmt::{self, Write as _};
64
65/// Representation of a demangled symbol name.
66pub struct Demangle<'a> {
67    style: Option<DemangleStyle<'a>>,
68    original: &'a str,
69    suffix: &'a str,
70}
71
72enum DemangleStyle<'a> {
73    Legacy(legacy::Demangle<'a>),
74    V0(v0::Demangle<'a>),
75}
76
77/// De-mangles a Rust symbol into a more readable version
78///
79/// This function will take a **mangled** symbol and return a value. When printed,
80/// the de-mangled version will be written. If the symbol does not look like
81/// a mangled symbol, the original value will be written instead.
82///
83/// # Examples
84///
85/// ```
86/// use rustc_demangle::demangle;
87///
88/// assert_eq!(demangle("_ZN4testE").to_string(), "test");
89/// assert_eq!(demangle("_ZN3foo3barE").to_string(), "foo::bar");
90/// assert_eq!(demangle("foo").to_string(), "foo");
91/// ```
92pub fn demangle(mut s: &str) -> Demangle {
93    // During ThinLTO LLVM may import and rename internal symbols, so strip out
94    // those endings first as they're one of the last manglings applied to symbol
95    // names.
96    let llvm = ".llvm.";
97    if let Some(i) = s.find(llvm) {
98        let candidate = &s[i + llvm.len()..];
99        let all_hex = candidate.chars().all(|c| match c {
100            'A'..='F' | '0'..='9' | '@' => true,
101            _ => false,
102        });
103
104        if all_hex {
105            s = &s[..i];
106        }
107    }
108
109    let mut suffix = "";
110    let mut style = match legacy::demangle(s) {
111        Ok((d, s)) => {
112            suffix = s;
113            Some(DemangleStyle::Legacy(d))
114        }
115        Err(()) => match v0::demangle(s) {
116            Ok((d, s)) => {
117                suffix = s;
118                Some(DemangleStyle::V0(d))
119            }
120            // FIXME(eddyb) would it make sense to treat an unknown-validity
121            // symbol (e.g. one that errored with `RecursedTooDeep`) as
122            // v0-mangled, and have the error show up in the demangling?
123            // (that error already gets past this initial check, and therefore
124            // will show up in the demangling, if hidden behind a backref)
125            Err(v0::ParseError::Invalid) | Err(v0::ParseError::RecursedTooDeep) => None,
126        },
127    };
128
129    // Output like LLVM IR adds extra period-delimited words. See if
130    // we are in that case and save the trailing words if so.
131    if !suffix.is_empty() {
132        if suffix.starts_with('.') && is_symbol_like(suffix) {
133            // Keep the suffix.
134        } else {
135            // Reset the suffix and invalidate the demangling.
136            suffix = "";
137            style = None;
138        }
139    }
140
141    Demangle {
142        style,
143        original: s,
144        suffix,
145    }
146}
147
148#[cfg(feature = "std")]
149fn demangle_line(
150    line: &str,
151    output: &mut impl std::io::Write,
152    include_hash: bool,
153) -> std::io::Result<()> {
154    let mut head = 0;
155    while head < line.len() {
156        // Move to the next potential match
157        let next_head = match (line[head..].find("_ZN"), line[head..].find("_R")) {
158            (Some(idx), None) | (None, Some(idx)) => head + idx,
159            (Some(idx1), Some(idx2)) => head + idx1.min(idx2),
160            (None, None) => {
161                // No more matches...
162                line.len()
163            }
164        };
165        output.write_all(line[head..next_head].as_bytes())?;
166        head = next_head;
167        // Find the non-matching character.
168        //
169        // If we do not find a character, then until the end of the line is the
170        // thing to demangle.
171        let match_end = line[head..]
172            .find(|ch: char| !(ch == '$' || ch == '.' || ch == '_' || ch.is_ascii_alphanumeric()))
173            .map(|idx| head + idx)
174            .unwrap_or(line.len());
175
176        let mangled = &line[head..match_end];
177        head = head + mangled.len();
178        if let Ok(demangled) = try_demangle(mangled) {
179            if include_hash {
180                write!(output, "{}", demangled)?;
181            } else {
182                write!(output, "{:#}", demangled)?;
183            }
184        } else {
185            output.write_all(mangled.as_bytes())?;
186        }
187    }
188    Ok(())
189}
190
191/// Process a stream of data from `input` into the provided `output`, demangling any symbols found
192/// within.
193///
194/// Note that the underlying implementation will perform many relatively small writes to the
195/// output. If the output is expensive to write to (e.g., requires syscalls), consider using
196/// `std::io::BufWriter`.
197#[cfg(feature = "std")]
198#[cfg_attr(docsrs, doc(cfg(feature = "std")))]
199pub fn demangle_stream<R: std::io::BufRead, W: std::io::Write>(
200    input: &mut R,
201    output: &mut W,
202    include_hash: bool,
203) -> std::io::Result<()> {
204    let mut buf = std::string::String::new();
205    // We read in lines to reduce the memory usage at any time.
206    //
207    // demangle_line is also more efficient with relatively small buffers as it will copy around
208    // trailing data during demangling. In the future we might directly stream to the output but at
209    // least right now that seems to be less efficient.
210    while input.read_line(&mut buf)? > 0 {
211        demangle_line(&buf, output, include_hash)?;
212        buf.clear();
213    }
214    Ok(())
215}
216
217/// Error returned from the `try_demangle` function below when demangling fails.
218#[derive(Debug, Clone)]
219pub struct TryDemangleError {
220    _priv: (),
221}
222
223/// The same as `demangle`, except return an `Err` if the string does not appear
224/// to be a Rust symbol, rather than "demangling" the given string as a no-op.
225///
226/// ```
227/// extern crate rustc_demangle;
228///
229/// let not_a_rust_symbol = "la la la";
230///
231/// // The `try_demangle` function will reject strings which are not Rust symbols.
232/// assert!(rustc_demangle::try_demangle(not_a_rust_symbol).is_err());
233///
234/// // While `demangle` will just pass the non-symbol through as a no-op.
235/// assert_eq!(rustc_demangle::demangle(not_a_rust_symbol).as_str(), not_a_rust_symbol);
236/// ```
237pub fn try_demangle(s: &str) -> Result<Demangle, TryDemangleError> {
238    let sym = demangle(s);
239    if sym.style.is_some() {
240        Ok(sym)
241    } else {
242        Err(TryDemangleError { _priv: () })
243    }
244}
245
246impl<'a> Demangle<'a> {
247    /// Returns the underlying string that's being demangled.
248    pub fn as_str(&self) -> &'a str {
249        self.original
250    }
251}
252
253fn is_symbol_like(s: &str) -> bool {
254    s.chars().all(|c| {
255        // Once `char::is_ascii_punctuation` and `char::is_ascii_alphanumeric`
256        // have been stable for long enough, use those instead for clarity
257        is_ascii_alphanumeric(c) || is_ascii_punctuation(c)
258    })
259}
260
261// Copied from the documentation of `char::is_ascii_alphanumeric`
262fn is_ascii_alphanumeric(c: char) -> bool {
263    match c {
264        '\u{0041}'..='\u{005A}' | '\u{0061}'..='\u{007A}' | '\u{0030}'..='\u{0039}' => true,
265        _ => false,
266    }
267}
268
269// Copied from the documentation of `char::is_ascii_punctuation`
270fn is_ascii_punctuation(c: char) -> bool {
271    match c {
272        '\u{0021}'..='\u{002F}'
273        | '\u{003A}'..='\u{0040}'
274        | '\u{005B}'..='\u{0060}'
275        | '\u{007B}'..='\u{007E}' => true,
276        _ => false,
277    }
278}
279
280impl<'a> fmt::Display for DemangleStyle<'a> {
281    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
282        match *self {
283            DemangleStyle::Legacy(ref d) => fmt::Display::fmt(d, f),
284            DemangleStyle::V0(ref d) => fmt::Display::fmt(d, f),
285        }
286    }
287}
288
289// Maximum size of the symbol that we'll print.
290const MAX_SIZE: usize = 1_000_000;
291
292#[derive(Copy, Clone, Debug)]
293struct SizeLimitExhausted;
294
295struct SizeLimitedFmtAdapter<F> {
296    remaining: Result<usize, SizeLimitExhausted>,
297    inner: F,
298}
299
300impl<F: fmt::Write> fmt::Write for SizeLimitedFmtAdapter<F> {
301    fn write_str(&mut self, s: &str) -> fmt::Result {
302        self.remaining = self
303            .remaining
304            .and_then(|r| r.checked_sub(s.len()).ok_or(SizeLimitExhausted));
305
306        match self.remaining {
307            Ok(_) => self.inner.write_str(s),
308            Err(SizeLimitExhausted) => Err(fmt::Error),
309        }
310    }
311}
312
313impl<'a> fmt::Display for Demangle<'a> {
314    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
315        match self.style {
316            None => f.write_str(self.original)?,
317            Some(ref d) => {
318                let alternate = f.alternate();
319                let mut size_limited_fmt = SizeLimitedFmtAdapter {
320                    remaining: Ok(MAX_SIZE),
321                    inner: &mut *f,
322                };
323                let fmt_result = if alternate {
324                    write!(size_limited_fmt, "{:#}", d)
325                } else {
326                    write!(size_limited_fmt, "{}", d)
327                };
328                let size_limit_result = size_limited_fmt.remaining.map(|_| ());
329
330                // Translate a `fmt::Error` generated by `SizeLimitedFmtAdapter`
331                // into an error message, instead of propagating it upwards
332                // (which could cause panicking from inside e.g. `std::io::print`).
333                match (fmt_result, size_limit_result) {
334                    (Err(_), Err(SizeLimitExhausted)) => f.write_str("{size limit reached}")?,
335
336                    _ => {
337                        fmt_result?;
338                        size_limit_result
339                            .expect("`fmt::Error` from `SizeLimitedFmtAdapter` was discarded");
340                    }
341                }
342            }
343        }
344        f.write_str(self.suffix)
345    }
346}
347
348impl<'a> fmt::Debug for Demangle<'a> {
349    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
350        fmt::Display::fmt(self, f)
351    }
352}
353
354#[cfg(test)]
355mod tests {
356    use std::prelude::v1::*;
357
358    macro_rules! t {
359        ($a:expr, $b:expr) => {
360            assert!(ok($a, $b))
361        };
362    }
363
364    macro_rules! t_err {
365        ($a:expr) => {
366            assert!(ok_err($a))
367        };
368    }
369
370    macro_rules! t_nohash {
371        ($a:expr, $b:expr) => {{
372            assert_eq!(format!("{:#}", super::demangle($a)), $b);
373        }};
374    }
375
376    fn ok(sym: &str, expected: &str) -> bool {
377        match super::try_demangle(sym) {
378            Ok(s) => {
379                if s.to_string() == expected {
380                    true
381                } else {
382                    println!("\n{}\n!=\n{}\n", s, expected);
383                    false
384                }
385            }
386            Err(_) => {
387                println!("error demangling");
388                false
389            }
390        }
391    }
392
393    fn ok_err(sym: &str) -> bool {
394        match super::try_demangle(sym) {
395            Ok(_) => {
396                println!("succeeded in demangling");
397                false
398            }
399            Err(_) => super::demangle(sym).to_string() == sym,
400        }
401    }
402
403    #[test]
404    fn demangle() {
405        t_err!("test");
406        t!("_ZN4testE", "test");
407        t_err!("_ZN4test");
408        t!("_ZN4test1a2bcE", "test::a::bc");
409    }
410
411    #[test]
412    fn demangle_dollars() {
413        t!("_ZN4$RP$E", ")");
414        t!("_ZN8$RF$testE", "&test");
415        t!("_ZN8$BP$test4foobE", "*test::foob");
416        t!("_ZN9$u20$test4foobE", " test::foob");
417        t!("_ZN35Bar$LT$$u5b$u32$u3b$$u20$4$u5d$$GT$E", "Bar<[u32; 4]>");
418    }
419
420    #[test]
421    fn demangle_many_dollars() {
422        t!("_ZN13test$u20$test4foobE", "test test::foob");
423        t!("_ZN12test$BP$test4foobE", "test*test::foob");
424    }
425
426    #[test]
427    fn demangle_osx() {
428        t!(
429            "__ZN5alloc9allocator6Layout9for_value17h02a996811f781011E",
430            "alloc::allocator::Layout::for_value::h02a996811f781011"
431        );
432        t!("__ZN38_$LT$core..option..Option$LT$T$GT$$GT$6unwrap18_MSG_FILE_LINE_COL17haf7cb8d5824ee659E", "<core::option::Option<T>>::unwrap::_MSG_FILE_LINE_COL::haf7cb8d5824ee659");
433        t!("__ZN4core5slice89_$LT$impl$u20$core..iter..traits..IntoIterator$u20$for$u20$$RF$$u27$a$u20$$u5b$T$u5d$$GT$9into_iter17h450e234d27262170E", "core::slice::<impl core::iter::traits::IntoIterator for &'a [T]>::into_iter::h450e234d27262170");
434    }
435
436    #[test]
437    fn demangle_windows() {
438        t!("ZN4testE", "test");
439        t!("ZN13test$u20$test4foobE", "test test::foob");
440        t!("ZN12test$RF$test4foobE", "test&test::foob");
441    }
442
443    #[test]
444    fn demangle_elements_beginning_with_underscore() {
445        t!("_ZN13_$LT$test$GT$E", "<test>");
446        t!("_ZN28_$u7b$$u7b$closure$u7d$$u7d$E", "{{closure}}");
447        t!("_ZN15__STATIC_FMTSTRE", "__STATIC_FMTSTR");
448    }
449
450    #[test]
451    fn demangle_trait_impls() {
452        t!(
453            "_ZN71_$LT$Test$u20$$u2b$$u20$$u27$static$u20$as$u20$foo..Bar$LT$Test$GT$$GT$3barE",
454            "<Test + 'static as foo::Bar<Test>>::bar"
455        );
456    }
457
458    #[test]
459    fn demangle_without_hash() {
460        let s = "_ZN3foo17h05af221e174051e9E";
461        t!(s, "foo::h05af221e174051e9");
462        t_nohash!(s, "foo");
463    }
464
465    #[test]
466    fn demangle_without_hash_edgecases() {
467        // One element, no hash.
468        t_nohash!("_ZN3fooE", "foo");
469        // Two elements, no hash.
470        t_nohash!("_ZN3foo3barE", "foo::bar");
471        // Longer-than-normal hash.
472        t_nohash!("_ZN3foo20h05af221e174051e9abcE", "foo");
473        // Shorter-than-normal hash.
474        t_nohash!("_ZN3foo5h05afE", "foo");
475        // Valid hash, but not at the end.
476        t_nohash!("_ZN17h05af221e174051e93fooE", "h05af221e174051e9::foo");
477        // Not a valid hash, missing the 'h'.
478        t_nohash!("_ZN3foo16ffaf221e174051e9E", "foo::ffaf221e174051e9");
479        // Not a valid hash, has a non-hex-digit.
480        t_nohash!("_ZN3foo17hg5af221e174051e9E", "foo::hg5af221e174051e9");
481    }
482
483    #[test]
484    fn demangle_thinlto() {
485        // One element, no hash.
486        t!("_ZN3fooE.llvm.9D1C9369", "foo");
487        t!("_ZN3fooE.llvm.9D1C9369@@16", "foo");
488        t_nohash!(
489            "_ZN9backtrace3foo17hbb467fcdaea5d79bE.llvm.A5310EB9",
490            "backtrace::foo"
491        );
492    }
493
494    #[test]
495    fn demangle_llvm_ir_branch_labels() {
496        t!("_ZN4core5slice77_$LT$impl$u20$core..ops..index..IndexMut$LT$I$GT$$u20$for$u20$$u5b$T$u5d$$GT$9index_mut17haf9727c2edfbc47bE.exit.i.i", "core::slice::<impl core::ops::index::IndexMut<I> for [T]>::index_mut::haf9727c2edfbc47b.exit.i.i");
497        t_nohash!("_ZN4core5slice77_$LT$impl$u20$core..ops..index..IndexMut$LT$I$GT$$u20$for$u20$$u5b$T$u5d$$GT$9index_mut17haf9727c2edfbc47bE.exit.i.i", "core::slice::<impl core::ops::index::IndexMut<I> for [T]>::index_mut.exit.i.i");
498    }
499
500    #[test]
501    fn demangle_ignores_suffix_that_doesnt_look_like_a_symbol() {
502        t_err!("_ZN3fooE.llvm moocow");
503    }
504
505    #[test]
506    fn dont_panic() {
507        super::demangle("_ZN2222222222222222222222EE").to_string();
508        super::demangle("_ZN5*70527e27.ll34csaғE").to_string();
509        super::demangle("_ZN5*70527a54.ll34_$b.1E").to_string();
510        super::demangle(
511            "\
512             _ZN5~saäb4e\n\
513             2734cOsbE\n\
514             5usage20h)3\0\0\0\0\0\0\07e2734cOsbE\
515             ",
516        )
517        .to_string();
518    }
519
520    #[test]
521    fn invalid_no_chop() {
522        t_err!("_ZNfooE");
523    }
524
525    #[test]
526    fn handle_assoc_types() {
527        t!("_ZN151_$LT$alloc..boxed..Box$LT$alloc..boxed..FnBox$LT$A$C$$u20$Output$u3d$R$GT$$u20$$u2b$$u20$$u27$a$GT$$u20$as$u20$core..ops..function..FnOnce$LT$A$GT$$GT$9call_once17h69e8f44b3723e1caE", "<alloc::boxed::Box<alloc::boxed::FnBox<A, Output=R> + 'a> as core::ops::function::FnOnce<A>>::call_once::h69e8f44b3723e1ca");
528    }
529
530    #[test]
531    fn handle_bang() {
532        t!(
533            "_ZN88_$LT$core..result..Result$LT$$u21$$C$$u20$E$GT$$u20$as$u20$std..process..Termination$GT$6report17hfc41d0da4a40b3e8E",
534            "<core::result::Result<!, E> as std::process::Termination>::report::hfc41d0da4a40b3e8"
535        );
536    }
537
538    #[test]
539    fn limit_recursion() {
540        assert_contains!(
541            super::demangle("_RNvB_1a").to_string(),
542            "{recursion limit reached}"
543        );
544        assert_contains!(
545            super::demangle("_RMC0RB2_").to_string(),
546            "{recursion limit reached}"
547        );
548    }
549
550    #[test]
551    fn limit_output() {
552        assert_ends_with!(
553            super::demangle("RYFG_FGyyEvRYFF_EvRYFFEvERLB_B_B_ERLRjB_B_B_").to_string(),
554            "{size limit reached}"
555        );
556        // NOTE(eddyb) somewhat reduced version of the above, effectively
557        // `<for<...> fn()>` with a larger number of lifetimes in `...`.
558        assert_ends_with!(
559            super::demangle("_RMC0FGZZZ_Eu").to_string(),
560            "{size limit reached}"
561        );
562    }
563
564    #[cfg(feature = "std")]
565    fn demangle_str(input: &str) -> String {
566        let mut output = Vec::new();
567        super::demangle_line(input, &mut output, false);
568        String::from_utf8(output).unwrap()
569    }
570
571    #[test]
572    #[cfg(feature = "std")]
573    fn find_multiple() {
574        assert_eq!(
575            demangle_str("_ZN3fooE.llvm moocow _ZN3fooE.llvm"),
576            "foo.llvm moocow foo.llvm"
577        );
578    }
579
580    #[test]
581    #[cfg(feature = "std")]
582    fn interleaved_new_legacy() {
583        assert_eq!(
584            demangle_str("_ZN3fooE.llvm moocow _RNvMNtNtNtNtCs8a2262Dv4r_3mio3sys4unix8selector5epollNtB2_8Selector6select _ZN3fooE.llvm"),
585            "foo.llvm moocow <mio::sys::unix::selector::epoll::Selector>::select foo.llvm"
586        );
587    }
588}
rustc_demangle/lib.rs

rustc_demangle/
lib.rs
