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
//! A library for acquiring a backtrace at runtime
//!
//! This library is meant to supplement the `RUST_BACKTRACE=1` support of the
//! standard library by allowing an acquisition of a backtrace at runtime
//! programmatically. The backtraces generated by this library do not need to be
//! parsed, for example, and expose the functionality of multiple backend
//! implementations.
//!
//! # Usage
//!
//! First, add this to your Cargo.toml
//!
//! ```toml
//! [dependencies]
//! backtrace = "0.3"
//! ```
//!
//! Next:
//!
//! ```
//! fn main() {
//! # // Unsafe here so test passes on no_std.
//! # #[cfg(feature = "std")] {
//!     backtrace::trace(|frame| {
//!         let ip = frame.ip();
//!         let symbol_address = frame.symbol_address();
//!
//!         // Resolve this instruction pointer to a symbol name
//!         backtrace::resolve_frame(frame, |symbol| {
//!             if let Some(name) = symbol.name() {
//!                 // ...
//!             }
//!             if let Some(filename) = symbol.filename() {
//!                 // ...
//!             }
//!         });
//!
//!         true // keep going to the next frame
//!     });
//! }
//! # }
//! ```
//!
//! # Backtrace accuracy
//!
//! This crate implements best-effort attempts to get the native backtrace. This
//! is not always guaranteed to work, and some platforms don't return any
//! backtrace at all. If your application requires accurate backtraces then it's
//! recommended to closely evaluate this crate to see whether it's suitable
//! for your use case on your target platforms.
//!
//! Even on supported platforms, there's a number of reasons that backtraces may
//! be less-than-accurate, including but not limited to:
//!
//! * Unwind information may not be available. This crate primarily implements
//!   backtraces by unwinding the stack, but not all functions may have
//!   unwinding information (e.g. DWARF unwinding information).
//!
//! * Rust code may be compiled without unwinding information for some
//!   functions. This can also happen for Rust code compiled with
//!   `-Cpanic=abort`. You can remedy this, however, with
//!   `-Cforce-unwind-tables` as a compiler option.
//!
//! * Unwind information may be inaccurate or corrupt. In the worst case
//!   inaccurate unwind information can lead this library to segfault. In the
//!   best case inaccurate information will result in a truncated stack trace.
//!
//! * Backtraces may not report filenames/line numbers correctly due to missing
//!   or corrupt debug information. This won't lead to segfaults unlike corrupt
//!   unwinding information, but missing or malformed debug information will
//!   mean that filenames and line numbers will not be available. This may be
//!   because debug information wasn't generated by the compiler, or it's just
//!   missing on the filesystem.
//!
//! * Not all platforms are supported. For example there's no way to get a
//!   backtrace on WebAssembly at the moment.
//!
//! * Crate features may be disabled. Currently this crate supports using Gimli
//!   libbacktrace on non-Windows platforms for reading debuginfo for
//!   backtraces. If both crate features are disabled, however, then these
//!   platforms will generate a backtrace but be unable to generate symbols for
//!   it.
//!
//! In most standard workflows for most standard platforms you generally don't
//! need to worry about these caveats. We'll try to fix ones where we can over
//! time, but otherwise it's important to be aware of the limitations of
//! unwinding-based backtraces!

#![doc(html_root_url = "https://docs.rs/backtrace")]
#![deny(missing_docs)]
#![no_std]
#![cfg_attr(
    all(feature = "std", target_env = "sgx", target_vendor = "fortanix"),
    feature(sgx_platform)
)]
#![warn(rust_2018_idioms)]
// When we're building as part of libstd, silence all warnings since they're
// irrelevant as this crate is developed out-of-tree.
#![cfg_attr(backtrace_in_libstd, allow(warnings))]
#![cfg_attr(not(feature = "std"), allow(dead_code))]
// We know this is deprecated, it's only here for back-compat reasons.
#![cfg_attr(feature = "rustc-serialize", allow(deprecated))]

#[cfg(feature = "std")]
#[macro_use]
extern crate std;

// This is only used for gimli right now, which is only used on some platforms,
// so don't worry if it's unused in other configurations.
#[allow(unused_extern_crates)]
extern crate alloc;

pub use self::backtrace::{trace_unsynchronized, Frame};
mod backtrace;

pub use self::symbolize::resolve_frame_unsynchronized;
pub use self::symbolize::{resolve_unsynchronized, Symbol, SymbolName};
mod symbolize;

pub use self::types::BytesOrWideString;
mod types;

#[cfg(feature = "std")]
pub use self::symbolize::clear_symbol_cache;

mod print;
pub use print::{BacktraceFmt, BacktraceFrameFmt, PrintFmt};

cfg_if::cfg_if! {
    if #[cfg(feature = "std")] {
        pub use self::backtrace::trace;
        pub use self::symbolize::{resolve, resolve_frame};
        pub use self::capture::{Backtrace, BacktraceFrame, BacktraceSymbol};
        mod capture;
    }
}

#[allow(dead_code)]
struct Bomb {
    enabled: bool,
}

#[allow(dead_code)]
impl Drop for Bomb {
    fn drop(&mut self) {
        if self.enabled {
            panic!("cannot panic during the backtrace function");
        }
    }
}

#[allow(dead_code)]
#[cfg(feature = "std")]
mod lock {
    use std::boxed::Box;
    use std::cell::Cell;
    use std::sync::{Mutex, MutexGuard, Once};

    pub struct LockGuard(Option<MutexGuard<'static, ()>>);

    static mut LOCK: *mut Mutex<()> = 0 as *mut _;
    static INIT: Once = Once::new();
    thread_local!(static LOCK_HELD: Cell<bool> = Cell::new(false));

    impl Drop for LockGuard {
        fn drop(&mut self) {
            if self.0.is_some() {
                LOCK_HELD.with(|slot| {
                    assert!(slot.get());
                    slot.set(false);
                });
            }
        }
    }

    pub fn lock() -> LockGuard {
        if LOCK_HELD.with(|l| l.get()) {
            return LockGuard(None);
        }
        LOCK_HELD.with(|s| s.set(true));
        unsafe {
            INIT.call_once(|| {
                LOCK = Box::into_raw(Box::new(Mutex::new(())));
            });
            LockGuard(Some((*LOCK).lock().unwrap()))
        }
    }
}

#[cfg(all(windows, not(target_vendor = "uwp")))]
mod dbghelp;
#[cfg(windows)]
mod windows;