backtrace 0.3.77

A library to acquire a stack trace (backtrace) at runtime in a Rust program.
Documentation 
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

mod auxiliary;

macro_rules! pos {
    () => {
        (file!(), line!())
    };
}

#[collapse_debuginfo(yes)]
macro_rules! check {
    ($($pos:expr),*) => ({
        verify(&[$($pos,)* pos!()]);
    })
}

type Pos = (&'static str, u32);

#[test]
fn doit() {
    if
    // Skip musl which is by default statically linked and doesn't support
    // dynamic libraries.
    !cfg!(target_env = "musl")
    // Skip Miri, since it doesn't support dynamic libraries.
    && !cfg!(miri)
    {
        // TODO(#238) this shouldn't have to happen first in this function, but
        // currently it does.
        let path = dylib_dep_path();
        unsafe {
            let lib = libloading::Library::new(&path).unwrap();
            let api = lib.get::<extern "C" fn(Pos, fn(Pos, Pos))>(b"foo").unwrap();
            api(pos!(), |a, b| {
                check!(a, b);
            });
        }
    }

    outer(pos!());
}

fn dylib_dep_path() -> std::path::PathBuf {
    let name = format!(
        "{}dylib_dep{}",
        std::env::consts::DLL_PREFIX,
        std::env::consts::DLL_SUFFIX
    );
    let exe = std::env::current_exe().unwrap();

    // Old layout: test and dylib are both in `<profile>/deps/`
    let path = exe.ancestors().nth(1).unwrap().join(&name);
    if path.exists() {
        return path;
    }

    // New layout:
    // test is in `<profile>/build/backtrace/<hash1>/out/`
    // dylib is in `<profile>/build/dylib-dep/<hash2>/out/`
    let dir = exe
        .ancestors()
        .nth(4)
        .unwrap_or_else(|| panic!("unexpected exe path {}", exe.display()))
        .join("dylib-dep");
    std::fs::read_dir(&dir)
        .unwrap_or_else(|err| panic!("read_dir({}) failed: {err}", dir.display()))
        .flatten()
        .map(|entry| entry.path().join("out").join(&name))
        .find(|p| p.exists())
        .unwrap_or_else(|| panic!("missing {} in {}/*/out/", name, dir.display()))
}

#[inline(never)]
fn outer(main_pos: Pos) {
    inner(main_pos, pos!());
    inner_inlined(main_pos, pos!());
}

#[inline(never)]
#[rustfmt::skip]
fn inner(main_pos: Pos, outer_pos: Pos) {
    check!(main_pos, outer_pos);
    check!(main_pos, outer_pos);
    let inner_pos = pos!(); auxiliary::callback(|aux_pos| {
        check!(main_pos, outer_pos, inner_pos, aux_pos);
    });
    let inner_pos = pos!(); auxiliary::callback_inlined(|aux_pos| {
        check!(main_pos, outer_pos, inner_pos, aux_pos);
    });
}

#[inline(always)]
#[rustfmt::skip]
fn inner_inlined(main_pos: Pos, outer_pos: Pos) {
    check!(main_pos, outer_pos);
    check!(main_pos, outer_pos);

    #[inline(always)]
    fn inner_further_inlined(main_pos: Pos, outer_pos: Pos, inner_pos: Pos) {
        check!(main_pos, outer_pos, inner_pos);
    }
    inner_further_inlined(main_pos, outer_pos, pos!());

    let inner_pos = pos!(); auxiliary::callback(|aux_pos| {
        check!(main_pos, outer_pos, inner_pos, aux_pos);
    });
    let inner_pos = pos!(); auxiliary::callback_inlined(|aux_pos| {
        check!(main_pos, outer_pos, inner_pos, aux_pos);
    });

    // this tests a distinction between two independent calls to the inlined function.
    // (un)fortunately, LLVM somehow merges two consecutive such calls into one node.
    inner_further_inlined(main_pos, outer_pos, pos!());
}

fn verify(filelines: &[Pos]) {
    let trace = backtrace::Backtrace::new();
    println!("-----------------------------------");
    println!("looking for:");
    for (file, line) in filelines.iter().rev() {
        println!("\t{file}:{line}");
    }
    println!("found:\n{trace:?}");
    let mut symbols = trace.frames().iter().flat_map(|frame| frame.symbols());
    let mut iter = filelines.iter().rev();
    while let Some((file, line)) = iter.next() {
        loop {
            let sym = match symbols.next() {
                Some(sym) => sym,
                None => panic!("failed to find {file}:{line}"),
            };
            if let Some(filename) = sym.filename() {
                if let Some(lineno) = sym.lineno() {
                    if filename.ends_with(file) && lineno == *line {
                        break;
                    }
                }
            }
        }
    }
}