rustc_demangle/
legacy.rs

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1use core::char;
2use core::fmt;
3
4/// Representation of a demangled symbol name.
5pub struct Demangle<'a> {
6    inner: &'a str,
7    /// The number of ::-separated elements in the original name.
8    elements: usize,
9}
10
11/// De-mangles a Rust symbol into a more readable version
12///
13/// All Rust symbols by default are mangled as they contain characters that
14/// cannot be represented in all object files. The mangling mechanism is similar
15/// to C++'s, but Rust has a few specifics to handle items like lifetimes in
16/// symbols.
17///
18/// This function will take a **mangled** symbol and return a value. When printed,
19/// the de-mangled version will be written. If the symbol does not look like
20/// a mangled symbol, the original value will be written instead.
21///
22/// # Examples
23///
24/// ```
25/// use rustc_demangle::demangle;
26///
27/// assert_eq!(demangle("_ZN4testE").to_string(), "test");
28/// assert_eq!(demangle("_ZN3foo3barE").to_string(), "foo::bar");
29/// assert_eq!(demangle("foo").to_string(), "foo");
30/// ```
31
32// All Rust symbols are in theory lists of "::"-separated identifiers. Some
33// assemblers, however, can't handle these characters in symbol names. To get
34// around this, we use C++-style mangling. The mangling method is:
35//
36// 1. Prefix the symbol with "_ZN"
37// 2. For each element of the path, emit the length plus the element
38// 3. End the path with "E"
39//
40// For example, "_ZN4testE" => "test" and "_ZN3foo3barE" => "foo::bar".
41//
42// We're the ones printing our backtraces, so we can't rely on anything else to
43// demangle our symbols. It's *much* nicer to look at demangled symbols, so
44// this function is implemented to give us nice pretty output.
45//
46// Note that this demangler isn't quite as fancy as it could be. We have lots
47// of other information in our symbols like hashes, version, type information,
48// etc. Additionally, this doesn't handle glue symbols at all.
49pub fn demangle(s: &str) -> Result<(Demangle, &str), ()> {
50    // First validate the symbol. If it doesn't look like anything we're
51    // expecting, we just print it literally. Note that we must handle non-Rust
52    // symbols because we could have any function in the backtrace.
53    let inner = if s.starts_with("_ZN") {
54        &s[3..]
55    } else if s.starts_with("ZN") {
56        // On Windows, dbghelp strips leading underscores, so we accept "ZN...E"
57        // form too.
58        &s[2..]
59    } else if s.starts_with("__ZN") {
60        // On OSX, symbols are prefixed with an extra _
61        &s[4..]
62    } else {
63        return Err(());
64    };
65
66    // only work with ascii text
67    if inner.bytes().any(|c| c & 0x80 != 0) {
68        return Err(());
69    }
70
71    let mut elements = 0;
72    let mut chars = inner.chars();
73    let mut c = chars.next().ok_or(())?;
74    while c != 'E' {
75        // Decode an identifier element's length.
76        if !c.is_digit(10) {
77            return Err(());
78        }
79        let mut len = 0usize;
80        while let Some(d) = c.to_digit(10) {
81            len = len
82                .checked_mul(10)
83                .and_then(|len| len.checked_add(d as usize))
84                .ok_or(())?;
85            c = chars.next().ok_or(())?;
86        }
87
88        // `c` already contains the first character of this identifier, skip it and
89        // all the other characters of this identifier, to reach the next element.
90        for _ in 0..len {
91            c = chars.next().ok_or(())?;
92        }
93
94        elements += 1;
95    }
96
97    Ok((Demangle { inner, elements }, chars.as_str()))
98}
99
100// Rust hashes are hex digits with an `h` prepended.
101fn is_rust_hash(s: &str) -> bool {
102    s.starts_with('h') && s[1..].chars().all(|c| c.is_digit(16))
103}
104
105impl<'a> fmt::Display for Demangle<'a> {
106    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
107        // Alright, let's do this.
108        let mut inner = self.inner;
109        for element in 0..self.elements {
110            let mut rest = inner;
111            while rest.chars().next().unwrap().is_digit(10) {
112                rest = &rest[1..];
113            }
114            let i: usize = inner[..(inner.len() - rest.len())].parse().unwrap();
115            inner = &rest[i..];
116            rest = &rest[..i];
117            // Skip printing the hash if alternate formatting
118            // was requested.
119            if f.alternate() && element + 1 == self.elements && is_rust_hash(&rest) {
120                break;
121            }
122            if element != 0 {
123                f.write_str("::")?;
124            }
125            if rest.starts_with("_$") {
126                rest = &rest[1..];
127            }
128            loop {
129                if rest.starts_with('.') {
130                    if let Some('.') = rest[1..].chars().next() {
131                        f.write_str("::")?;
132                        rest = &rest[2..];
133                    } else {
134                        f.write_str(".")?;
135                        rest = &rest[1..];
136                    }
137                } else if rest.starts_with('$') {
138                    let (escape, after_escape) = if let Some(end) = rest[1..].find('$') {
139                        (&rest[1..=end], &rest[end + 2..])
140                    } else {
141                        break;
142                    };
143
144                    // see src/librustc_codegen_utils/symbol_names/legacy.rs for these mappings
145                    let unescaped = match escape {
146                        "SP" => "@",
147                        "BP" => "*",
148                        "RF" => "&",
149                        "LT" => "<",
150                        "GT" => ">",
151                        "LP" => "(",
152                        "RP" => ")",
153                        "C" => ",",
154
155                        _ => {
156                            if escape.starts_with('u') {
157                                let digits = &escape[1..];
158                                let all_lower_hex = digits.chars().all(|c| match c {
159                                    '0'..='9' | 'a'..='f' => true,
160                                    _ => false,
161                                });
162                                let c = u32::from_str_radix(digits, 16)
163                                    .ok()
164                                    .and_then(char::from_u32);
165                                if let (true, Some(c)) = (all_lower_hex, c) {
166                                    // FIXME(eddyb) do we need to filter out control codepoints?
167                                    if !c.is_control() {
168                                        c.fmt(f)?;
169                                        rest = after_escape;
170                                        continue;
171                                    }
172                                }
173                            }
174                            break;
175                        }
176                    };
177                    f.write_str(unescaped)?;
178                    rest = after_escape;
179                } else if let Some(i) = rest.find(|c| c == '$' || c == '.') {
180                    f.write_str(&rest[..i])?;
181                    rest = &rest[i..];
182                } else {
183                    break;
184                }
185            }
186            f.write_str(rest)?;
187        }
188
189        Ok(())
190    }
191}
192
193#[cfg(test)]
194mod tests {
195    use std::prelude::v1::*;
196
197    macro_rules! t {
198        ($a:expr, $b:expr) => {
199            assert!(ok($a, $b))
200        };
201    }
202
203    macro_rules! t_err {
204        ($a:expr) => {
205            assert!(ok_err($a))
206        };
207    }
208
209    macro_rules! t_nohash {
210        ($a:expr, $b:expr) => {{
211            assert_eq!(format!("{:#}", ::demangle($a)), $b);
212        }};
213    }
214
215    fn ok(sym: &str, expected: &str) -> bool {
216        match ::try_demangle(sym) {
217            Ok(s) => {
218                if s.to_string() == expected {
219                    true
220                } else {
221                    println!("\n{}\n!=\n{}\n", s, expected);
222                    false
223                }
224            }
225            Err(_) => {
226                println!("error demangling");
227                false
228            }
229        }
230    }
231
232    fn ok_err(sym: &str) -> bool {
233        match ::try_demangle(sym) {
234            Ok(_) => {
235                println!("succeeded in demangling");
236                false
237            }
238            Err(_) => ::demangle(sym).to_string() == sym,
239        }
240    }
241
242    #[test]
243    fn demangle() {
244        t_err!("test");
245        t!("_ZN4testE", "test");
246        t_err!("_ZN4test");
247        t!("_ZN4test1a2bcE", "test::a::bc");
248    }
249
250    #[test]
251    fn demangle_dollars() {
252        t!("_ZN4$RP$E", ")");
253        t!("_ZN8$RF$testE", "&test");
254        t!("_ZN8$BP$test4foobE", "*test::foob");
255        t!("_ZN9$u20$test4foobE", " test::foob");
256        t!("_ZN35Bar$LT$$u5b$u32$u3b$$u20$4$u5d$$GT$E", "Bar<[u32; 4]>");
257    }
258
259    #[test]
260    fn demangle_many_dollars() {
261        t!("_ZN13test$u20$test4foobE", "test test::foob");
262        t!("_ZN12test$BP$test4foobE", "test*test::foob");
263    }
264
265    #[test]
266    fn demangle_osx() {
267        t!(
268            "__ZN5alloc9allocator6Layout9for_value17h02a996811f781011E",
269            "alloc::allocator::Layout::for_value::h02a996811f781011"
270        );
271        t!("__ZN38_$LT$core..option..Option$LT$T$GT$$GT$6unwrap18_MSG_FILE_LINE_COL17haf7cb8d5824ee659E", "<core::option::Option<T>>::unwrap::_MSG_FILE_LINE_COL::haf7cb8d5824ee659");
272        t!("__ZN4core5slice89_$LT$impl$u20$core..iter..traits..IntoIterator$u20$for$u20$$RF$$u27$a$u20$$u5b$T$u5d$$GT$9into_iter17h450e234d27262170E", "core::slice::<impl core::iter::traits::IntoIterator for &'a [T]>::into_iter::h450e234d27262170");
273    }
274
275    #[test]
276    fn demangle_windows() {
277        t!("ZN4testE", "test");
278        t!("ZN13test$u20$test4foobE", "test test::foob");
279        t!("ZN12test$RF$test4foobE", "test&test::foob");
280    }
281
282    #[test]
283    fn demangle_elements_beginning_with_underscore() {
284        t!("_ZN13_$LT$test$GT$E", "<test>");
285        t!("_ZN28_$u7b$$u7b$closure$u7d$$u7d$E", "{{closure}}");
286        t!("_ZN15__STATIC_FMTSTRE", "__STATIC_FMTSTR");
287    }
288
289    #[test]
290    fn demangle_trait_impls() {
291        t!(
292            "_ZN71_$LT$Test$u20$$u2b$$u20$$u27$static$u20$as$u20$foo..Bar$LT$Test$GT$$GT$3barE",
293            "<Test + 'static as foo::Bar<Test>>::bar"
294        );
295    }
296
297    #[test]
298    fn demangle_without_hash() {
299        let s = "_ZN3foo17h05af221e174051e9E";
300        t!(s, "foo::h05af221e174051e9");
301        t_nohash!(s, "foo");
302    }
303
304    #[test]
305    fn demangle_without_hash_edgecases() {
306        // One element, no hash.
307        t_nohash!("_ZN3fooE", "foo");
308        // Two elements, no hash.
309        t_nohash!("_ZN3foo3barE", "foo::bar");
310        // Longer-than-normal hash.
311        t_nohash!("_ZN3foo20h05af221e174051e9abcE", "foo");
312        // Shorter-than-normal hash.
313        t_nohash!("_ZN3foo5h05afE", "foo");
314        // Valid hash, but not at the end.
315        t_nohash!("_ZN17h05af221e174051e93fooE", "h05af221e174051e9::foo");
316        // Not a valid hash, missing the 'h'.
317        t_nohash!("_ZN3foo16ffaf221e174051e9E", "foo::ffaf221e174051e9");
318        // Not a valid hash, has a non-hex-digit.
319        t_nohash!("_ZN3foo17hg5af221e174051e9E", "foo::hg5af221e174051e9");
320    }
321
322    #[test]
323    fn demangle_thinlto() {
324        // One element, no hash.
325        t!("_ZN3fooE.llvm.9D1C9369", "foo");
326        t!("_ZN3fooE.llvm.9D1C9369@@16", "foo");
327        t_nohash!(
328            "_ZN9backtrace3foo17hbb467fcdaea5d79bE.llvm.A5310EB9",
329            "backtrace::foo"
330        );
331    }
332
333    #[test]
334    fn demangle_llvm_ir_branch_labels() {
335        t!("_ZN4core5slice77_$LT$impl$u20$core..ops..index..IndexMut$LT$I$GT$$u20$for$u20$$u5b$T$u5d$$GT$9index_mut17haf9727c2edfbc47bE.exit.i.i", "core::slice::<impl core::ops::index::IndexMut<I> for [T]>::index_mut::haf9727c2edfbc47b.exit.i.i");
336        t_nohash!("_ZN4core5slice77_$LT$impl$u20$core..ops..index..IndexMut$LT$I$GT$$u20$for$u20$$u5b$T$u5d$$GT$9index_mut17haf9727c2edfbc47bE.exit.i.i", "core::slice::<impl core::ops::index::IndexMut<I> for [T]>::index_mut.exit.i.i");
337    }
338
339    #[test]
340    fn demangle_ignores_suffix_that_doesnt_look_like_a_symbol() {
341        t_err!("_ZN3fooE.llvm moocow");
342    }
343
344    #[test]
345    fn dont_panic() {
346        ::demangle("_ZN2222222222222222222222EE").to_string();
347        ::demangle("_ZN5*70527e27.ll34csaғE").to_string();
348        ::demangle("_ZN5*70527a54.ll34_$b.1E").to_string();
349        ::demangle(
350            "\
351             _ZN5~saäb4e\n\
352             2734cOsbE\n\
353             5usage20h)3\0\0\0\0\0\0\07e2734cOsbE\
354             ",
355        )
356        .to_string();
357    }
358
359    #[test]
360    fn invalid_no_chop() {
361        t_err!("_ZNfooE");
362    }
363
364    #[test]
365    fn handle_assoc_types() {
366        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$$GT$9call_once17h69e8f44b3723e1caE", "<alloc::boxed::Box<alloc::boxed::FnBox<A, Output=R> + 'a> as core::ops::function::FnOnce<A>>::call_once::h69e8f44b3723e1ca");
367    }
368
369    #[test]
370    fn handle_bang() {
371        t!(
372            "_ZN88_$LT$core..result..Result$LT$$u21$$C$$u20$E$GT$$u20$as$u20$std..process..Termination$GT$6report17hfc41d0da4a40b3e8E",
373            "<core::result::Result<!, E> as std::process::Termination>::report::hfc41d0da4a40b3e8"
374        );
375    }
376
377    #[test]
378    fn demangle_utf8_idents() {
379        t_nohash!(
380            "_ZN11utf8_idents157_$u10e1$$u10d0$$u10ed$$u10db$$u10d4$$u10da$$u10d0$$u10d3$_$u10d2$$u10d4$$u10db$$u10e0$$u10d8$$u10d4$$u10da$$u10d8$_$u10e1$$u10d0$$u10d3$$u10d8$$u10da$$u10d8$17h21634fd5714000aaE",
381            "utf8_idents::საჭმელად_გემრიელი_სადილი"
382        );
383    }
384
385    #[test]
386    fn demangle_issue_60925() {
387        t_nohash!(
388            "_ZN11issue_609253foo37Foo$LT$issue_60925..llv$u6d$..Foo$GT$3foo17h059a991a004536adE",
389            "issue_60925::foo::Foo<issue_60925::llvm::Foo>::foo"
390        );
391    }
392}
rustc_demangle/legacy.rs

rustc_demangle/
legacy.rs
