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

use core::ffi::c_void;
use core::fmt;

/// Inspects the current call-stack, passing all active frames into the closure
/// provided to calculate a stack trace.
///
/// This function is the workhorse of this library in calculating the stack
/// traces for a program. The given closure `cb` is yielded instances of a
/// `Frame` which represent information about that call frame on the stack. The
/// closure is yielded frames in a top-down fashion (most recently called
/// functions first).
///
/// The closure's return value is an indication of whether the backtrace should
/// continue. A return value of `false` will terminate the backtrace and return
/// immediately.
///
/// Once a `Frame` is acquired you will likely want to call `backtrace::resolve`
/// to convert the `ip` (instruction pointer) or symbol address to a `Symbol`
/// through which the name and/or filename/line number can be learned.
///
/// Note that this is a relatively low-level function and if you'd like to, for
/// example, capture a backtrace to be inspected later, then the `Backtrace`
/// type may be more appropriate.
///
/// # Required features
///
/// This function requires the `std` feature of the `backtrace` crate to be
/// enabled, and the `std` feature is enabled by default.
///
/// # Panics
///
/// This function strives to never panic, but if the `cb` provided panics then
/// some platforms will force a double panic to abort the process. Some
/// platforms use a C library which internally uses callbacks which cannot be
/// unwound through, so panicking from `cb` may trigger a process abort.
///
/// # Example
///
/// ```
/// extern crate backtrace;
///
/// fn main() {
///     backtrace::trace(|frame| {
///         // ...
///
///         true // continue the backtrace
///     });
/// }
/// ```
#[cfg(feature = "std")]
pub fn trace<F: FnMut(&Frame) -> bool>(cb: F) {
    let _guard = crate::lock::lock();
    unsafe { trace_unsynchronized(cb) }
}

/// Same as `trace`, only unsafe as it's unsynchronized.
///
/// This function does not have synchronization guarentees but is available
/// when the `std` feature of this crate isn't compiled in. See the `trace`
/// function for more documentation and examples.
///
/// # Panics
///
/// See information on `trace` for caveats on `cb` panicking.
pub unsafe fn trace_unsynchronized<F: FnMut(&Frame) -> bool>(mut cb: F) {
    trace_imp(&mut cb)
}

/// A trait representing one frame of a backtrace, yielded to the `trace`
/// function of this crate.
///
/// The tracing function's closure will be yielded frames, and the frame is
/// virtually dispatched as the underlying implementation is not always known
/// until runtime.
#[derive(Clone)]
pub struct Frame {
    pub(crate) inner: FrameImp,
}

impl Frame {
    /// Returns the current instruction pointer of this frame.
    ///
    /// This is normally the next instruction to execute in the frame, but not
    /// all implementations list this with 100% accuracy (but it's generally
    /// pretty close).
    ///
    /// It is recommended to pass this value to `backtrace::resolve` to turn it
    /// into a symbol name.
    pub fn ip(&self) -> *mut c_void {
        self.inner.ip()
    }

    /// Returns the current stack pointer of this frame.
    ///
    /// In the case that a backend cannot recover the stack pointer for this
    /// frame, a null pointer is returned.
    pub fn sp(&self) -> *mut c_void {
        self.inner.sp()
    }

    /// Returns the starting symbol address of the frame of this function.
    ///
    /// This will attempt to rewind the instruction pointer returned by `ip` to
    /// the start of the function, returning that value. In some cases, however,
    /// backends will just return `ip` from this function.
    ///
    /// The returned value can sometimes be used if `backtrace::resolve` failed
    /// on the `ip` given above.
    pub fn symbol_address(&self) -> *mut c_void {
        self.inner.symbol_address()
    }

    /// Returns the base address of the module to which the frame belongs.
    pub fn module_base_address(&self) -> Option<*mut c_void> {
        self.inner.module_base_address()
    }
}

impl fmt::Debug for Frame {
    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
        f.debug_struct("Frame")
            .field("ip", &self.ip())
            .field("symbol_address", &self.symbol_address())
            .finish()
    }
}

cfg_if::cfg_if! {
    // This needs to come first, to ensure that
    // Miri takes priority over the host platform
    if #[cfg(miri)] {
        pub(crate) mod miri;
        use self::miri::trace as trace_imp;
        pub(crate) use self::miri::Frame as FrameImp;
    } else if #[cfg(
        any(
            all(
                unix,
                not(target_os = "emscripten"),
                not(all(target_os = "ios", target_arch = "arm")),
            ),
            all(
                target_env = "sgx",
                target_vendor = "fortanix",
            ),
        )
    )] {
        mod libunwind;
        use self::libunwind::trace as trace_imp;
        pub(crate) use self::libunwind::Frame as FrameImp;
    } else if #[cfg(all(windows, not(target_vendor = "uwp")))] {
        mod dbghelp;
        use self::dbghelp::trace as trace_imp;
        pub(crate) use self::dbghelp::Frame as FrameImp;
        #[cfg(target_env = "msvc")] // only used in dbghelp symbolize
        pub(crate) use self::dbghelp::StackFrame;
    } else {
        mod noop;
        use self::noop::trace as trace_imp;
        pub(crate) use self::noop::Frame as FrameImp;
    }
}