gcc_s.rs.html -- source
Description: Source to the Rust file `src/libstd/sys/unix/backtrace/tracing/gcc_s.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

    // Copyright 2014-2015 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.

    use io;
    use io::prelude::*;
    use libc;
    use mem;
    use sys_common::mutex::Mutex;

    use super::super::printing::print;
    use unwind as uw;

    #[inline(never)] // if we know this is a function call, we can skip it when
                     // tracing
    pub fn write(w: &mut Write) -> io::Result<()> {
        struct Context<'a> {
            idx: isize,
            writer: &'a mut (Write+'a),
            last_error: Option<io::Error>,
        }

        // When using libbacktrace, we use some necessary global state, so we
        // need to prevent more than one thread from entering this block. This
        // is semi-reasonable in terms of printing anyway, and we know that all
        // I/O done here is blocking I/O, not green I/O, so we don't have to
        // worry about this being a native vs green mutex.
        static LOCK: Mutex = Mutex::new();
        unsafe {
            LOCK.lock();

            writeln!(w, "stack backtrace:")?;

            let mut cx = Context { writer: w, last_error: None, idx: 0 };
            let ret = match {
                uw::_Unwind_Backtrace(trace_fn,
                                      &mut cx as *mut Context as *mut libc::c_void)
            } {
                uw::_URC_NO_REASON => {
                    match cx.last_error {
                        Some(err) => Err(err),
                        None => Ok(())
                    }
                }
                _ => Ok(()),
            };
            LOCK.unlock();
            return ret
        }

        extern fn trace_fn(ctx: *mut uw::_Unwind_Context,
                           arg: *mut libc::c_void) -> uw::_Unwind_Reason_Code {
            let cx: &mut Context = unsafe { mem::transmute(arg) };
            let mut ip_before_insn = 0;
            let mut ip = unsafe {
                uw::_Unwind_GetIPInfo(ctx, &mut ip_before_insn) as *mut libc::c_void
            };
            if !ip.is_null() && ip_before_insn == 0 {
                // this is a non-signaling frame, so `ip` refers to the address
                // after the calling instruction. account for that.
                ip = (ip as usize - 1) as *mut _;
            }

            // dladdr() on osx gets whiny when we use FindEnclosingFunction, and
            // it appears to work fine without it, so we only use
            // FindEnclosingFunction on non-osx platforms. In doing so, we get a
            // slightly more accurate stack trace in the process.
            //
            // This is often because panic involves the last instruction of a
            // function being "call std::rt::begin_unwind", with no ret
            // instructions after it. This means that the return instruction
            // pointer points *outside* of the calling function, and by
            // unwinding it we go back to the original function.
            let symaddr = if cfg!(target_os = "macos") || cfg!(target_os = "ios") {
                ip
            } else {
                unsafe { uw::_Unwind_FindEnclosingFunction(ip) }
            };

            // Don't print out the first few frames (they're not user frames)
            cx.idx += 1;
            if cx.idx <= 0 { return uw::_URC_NO_REASON }
            // Don't print ginormous backtraces
            if cx.idx > 100 {
                match write!(cx.writer, " ... <frames omitted>\n") {
                    Ok(()) => {}
                    Err(e) => { cx.last_error = Some(e); }
                }
                return uw::_URC_FAILURE
            }

            // Once we hit an error, stop trying to print more frames
            if cx.last_error.is_some() { return uw::_URC_FAILURE }

            match print(cx.writer, cx.idx, ip, symaddr) {
                Ok(()) => {}
                Err(e) => { cx.last_error = Some(e); }
            }

            // keep going
            uw::_URC_NO_REASON
        }
    }

# 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`)