backtrace.rs.html -- source
Description: Source to the Rust file `src/libstd/sys_common/backtrace.rs`.
Keywords: rust, rustlang, rust-lang

      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

    // Copyright 2014 The Rust Project Developers. See the COPYRIGHT
    // file at the top-level directory of this distribution and at
    // http://rust-lang.org/COPYRIGHT.
    //
    // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
    // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
    // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
    // option. This file may not be copied, modified, or distributed
    // except according to those terms.

    #![cfg_attr(target_os = "nacl", allow(dead_code))]

    use env;
    use io::prelude::*;
    use io;
    use libc;
    use str;
    use sync::atomic::{self, Ordering};

    pub use sys::backtrace::write;

    #[cfg(target_pointer_width = "64")]
    pub const HEX_WIDTH: usize = 18;

    #[cfg(target_pointer_width = "32")]
    pub const HEX_WIDTH: usize = 10;

    // For now logging is turned off by default, and this function checks to see
    // whether the magical environment variable is present to see if it's turned on.
    pub fn log_enabled() -> bool {
        static ENABLED: atomic::AtomicIsize = atomic::AtomicIsize::new(0);
        match ENABLED.load(Ordering::SeqCst) {
            1 => return false,
            2 => return true,
            _ => {}
        }

        let val = match env::var_os("RUST_BACKTRACE") {
            Some(x) => if &x == "0" { 1 } else { 2 },
            None => 1,
        };
        ENABLED.store(val, Ordering::SeqCst);
        val == 2
    }

    // These output functions should now be used everywhere to ensure consistency.
    pub fn output(w: &mut Write, idx: isize, addr: *mut libc::c_void,
                  s: Option<&[u8]>) -> io::Result<()> {
        write!(w, "  {:2}: {:2$?} - ", idx, addr, HEX_WIDTH)?;
        match s.and_then(|s| str::from_utf8(s).ok()) {
            Some(string) => demangle(w, string)?,
            None => write!(w, "<unknown>")?,
        }
        w.write_all(&['\n' as u8])
    }

    #[allow(dead_code)]
    pub fn output_fileline(w: &mut Write, file: &[u8], line: libc::c_int,
                           more: bool) -> io::Result<()> {
        let file = str::from_utf8(file).unwrap_or("<unknown>");
        // prior line: "  ##: {:2$} - func"
        write!(w, "      {:3$}at {}:{}", "", file, line, HEX_WIDTH)?;
        if more {
            write!(w, " <... and possibly more>")?;
        }
        w.write_all(&['\n' as u8])
    }

    // All rust symbols are in theory lists of "::"-separated identifiers. Some
    // assemblers, however, can't handle these characters in symbol names. To get
    // around this, we use C++-style mangling. The mangling method is:
    //
    // 1. Prefix the symbol with "_ZN"
    // 2. For each element of the path, emit the length plus the element
    // 3. End the path with "E"
    //
    // For example, "_ZN4testE" => "test" and "_ZN3foo3barE" => "foo::bar".
    //
    // We're the ones printing our backtraces, so we can't rely on anything else to
    // demangle our symbols. It's *much* nicer to look at demangled symbols, so
    // this function is implemented to give us nice pretty output.
    //
    // Note that this demangler isn't quite as fancy as it could be. We have lots
    // of other information in our symbols like hashes, version, type information,
    // etc. Additionally, this doesn't handle glue symbols at all.
    pub fn demangle(writer: &mut Write, s: &str) -> io::Result<()> {
        // First validate the symbol. If it doesn't look like anything we're
        // expecting, we just print it literally. Note that we must handle non-rust
        // symbols because we could have any function in the backtrace.
        let mut valid = true;
        let mut inner = s;
        if s.len() > 4 && s.starts_with("_ZN") && s.ends_with("E") {
            inner = &s[3 .. s.len() - 1];
        // On Windows, dbghelp strips leading underscores, so we accept "ZN...E" form too.
        } else if s.len() > 3 && s.starts_with("ZN") && s.ends_with("E") {
            inner = &s[2 .. s.len() - 1];
        } else {
            valid = false;
        }

        if valid {
            let mut chars = inner.chars();
            while valid {
                let mut i = 0;
                for c in chars.by_ref() {
                    if c.is_numeric() {
                        i = i * 10 + c as usize - '0' as usize;
                    } else {
                        break
                    }
                }
                if i == 0 {
                    valid = chars.next().is_none();
                    break
                } else if chars.by_ref().take(i - 1).count() != i - 1 {
                    valid = false;
                }
            }
        }

        // Alright, let's do this.
        if !valid {
            writer.write_all(s.as_bytes())?;
        } else {
            let mut first = true;
            while !inner.is_empty() {
                if !first {
                    writer.write_all(b"::")?;
                } else {
                    first = false;
                }
                let mut rest = inner;
                while rest.chars().next().unwrap().is_numeric() {
                    rest = &rest[1..];
                }
                let i: usize = inner[.. (inner.len() - rest.len())].parse().unwrap();
                inner = &rest[i..];
                rest = &rest[..i];
                if rest.starts_with("_$") {
                    rest = &rest[1..];
                }
                while !rest.is_empty() {
                    if rest.starts_with(".") {
                        if let Some('.') = rest[1..].chars().next() {
                            writer.write_all(b"::")?;
                            rest = &rest[2..];
                        } else {
                            writer.write_all(b".")?;
                            rest = &rest[1..];
                        }
                    } else if rest.starts_with("$") {
                        macro_rules! demangle {
                            ($($pat:expr => $demangled:expr),*) => ({
                                $(if rest.starts_with($pat) {
                                    writer.write_all($demangled)?;
                                    rest = &rest[$pat.len()..];
                                  } else)*
                                {
                                    writer.write_all(rest.as_bytes())?;
                                    break;
                                }

                            })
                        }

                        // see src/librustc/back/link.rs for these mappings
                        demangle! (
                            "$SP$" => b"@",
                            "$BP$" => b"*",
                            "$RF$" => b"&",
                            "$LT$" => b"<",
                            "$GT$" => b">",
                            "$LP$" => b"(",
                            "$RP$" => b")",
                            "$C$" => b",",

                            // in theory we can demangle any Unicode code point, but
                            // for simplicity we just catch the common ones.
                            "$u7e$" => b"~",
                            "$u20$" => b" ",
                            "$u27$" => b"'",
                            "$u5b$" => b"[",
                            "$u5d$" => b"]",
                            "$u7b$" => b"{",
                            "$u7d$" => b"}",
                            "$u3b$" => b";",
                            "$u2b$" => b"+",
                            "$u22$" => b"\""
                        )
                    } else {
                        let idx = match rest.char_indices().find(|&(_, c)| c == '$' || c == '.') {
                            None => rest.len(),
                            Some((i, _)) => i,
                        };
                        writer.write_all(rest[..idx].as_bytes())?;
                        rest = &rest[idx..];
                    }
                }
            }
        }

        Ok(())
    }

    #[cfg(test)]
    mod tests {
        use sys_common;
        macro_rules! t { ($a:expr, $b:expr) => ({
            let mut m = Vec::new();
            sys_common::backtrace::demangle(&mut m, $a).unwrap();
            assert_eq!(String::from_utf8(m).unwrap(), $b);
        }) }

        #[test]
        fn demangle() {
            t!("test", "test");
            t!("_ZN4testE", "test");
            t!("_ZN4test", "_ZN4test");
            t!("_ZN4test1a2bcE", "test::a::bc");
        }

        #[test]
        fn demangle_dollars() {
            t!("_ZN4$RP$E", ")");
            t!("_ZN8$RF$testE", "&test");
            t!("_ZN8$BP$test4foobE", "*test::foob");
            t!("_ZN9$u20$test4foobE", " test::foob");
            t!("_ZN35Bar$LT$$u5b$u32$u3b$$u20$4$u5d$$GT$E", "Bar<[u32; 4]>");
        }

        #[test]
        fn demangle_many_dollars() {
            t!("_ZN13test$u20$test4foobE", "test test::foob");
            t!("_ZN12test$BP$test4foobE", "test*test::foob");
        }

        #[test]
        fn demangle_windows() {
            t!("ZN4testE", "test");
            t!("ZN13test$u20$test4foobE", "test test::foob");
            t!("ZN12test$RF$test4foobE", "test&test::foob");
        }

        #[test]
        fn demangle_elements_beginning_with_underscore() {
            t!("_ZN13_$LT$test$GT$E", "<test>");
            t!("_ZN28_$u7b$$u7b$closure$u7d$$u7d$E", "{{closure}}");
            t!("_ZN15__STATIC_FMTSTRE", "__STATIC_FMTSTR");
        }

        #[test]
        fn demangle_trait_impls() {
            t!("_ZN71_$LT$Test$u20$$u2b$$u20$$u27$static$u20$as$u20$foo..Bar$LT$Test$GT$$GT$3barE",
               "<Test + 'static as foo::Bar<Test>>::bar");
        }
    }

# Help

## Keyboard Shortcuts

?
  Show this help dialog
S
  Focus the search field
⇤
  Move up in search results
⇥
  Move down in search results
⏎
  Go to active search result
+
  Collapse/expand all sections

## Search Tricks

Prefix searches with a type followed by a colon (e.g. `fn:`) to restrict the search to a given type.

Accepted types are: `fn`, `mod`, `struct`, `enum`, `trait`, `type`, `macro`, and `const`.

Search functions by type signature (e.g. `vec -> usize` or `* -> vec`)