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use crate::error::Error;
use crate::ffi::CStr;
use crate::fmt;
use crate::intrinsics;
use crate::io;
use crate::sys_common::backtrace::Frame;
use unwind as uw;
pub struct BacktraceContext;
struct Context<'a> {
idx: usize,
frames: &'a mut [Frame],
}
#[derive(Debug)]
struct UnwindError(uw::_Unwind_Reason_Code);
impl Error for UnwindError {
fn description(&self) -> &'static str {
"unexpected return value while unwinding"
}
}
impl fmt::Display for UnwindError {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "{}: {:?}", self.description(), self.0)
}
}
#[inline(never)] // if we know this is a function call, we can skip it when
// tracing
pub fn unwind_backtrace(frames: &mut [Frame]) -> io::Result<(usize, BacktraceContext)> {
let mut cx = Context { idx: 0, frames };
let result_unwind = unsafe {
uw::_Unwind_Backtrace(trace_fn, &mut cx as *mut Context<'_> as *mut libc::c_void)
};
// See libunwind:src/unwind/Backtrace.c for the return values.
// No, there is no doc.
match result_unwind {
// These return codes seem to be benign and need to be ignored for backtraces
// to show up properly on all tested platforms.
uw::_URC_END_OF_STACK | uw::_URC_FATAL_PHASE1_ERROR | uw::_URC_FAILURE => {
Ok((cx.idx, BacktraceContext))
}
_ => Err(io::Error::new(
io::ErrorKind::Other,
UnwindError(result_unwind),
)),
}
}
extern "C" fn trace_fn(
ctx: *mut uw::_Unwind_Context,
arg: *mut libc::c_void,
) -> uw::_Unwind_Reason_Code {
let cx = unsafe { &mut *(arg as *mut Context<'_>) };
if cx.idx >= cx.frames.len() {
return uw::_URC_NORMAL_STOP;
}
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 _;
}
let symaddr = unsafe { uw::_Unwind_FindEnclosingFunction(ip) };
cx.frames[cx.idx] = Frame {
symbol_addr: symaddr as *mut u8,
exact_position: ip as *mut u8,
inline_context: 0,
};
cx.idx += 1;
uw::_URC_NO_REASON
}
pub fn foreach_symbol_fileline<F>(_: Frame, _: F, _: &BacktraceContext) -> io::Result<bool>
where
F: FnMut(&[u8], u32) -> io::Result<()>,
{
// No way to obtain this information on CloudABI.
Ok(false)
}
pub fn resolve_symname<F>(frame: Frame, callback: F, _: &BacktraceContext) -> io::Result<()>
where
F: FnOnce(Option<&str>) -> io::Result<()>,
{
unsafe {
let mut info: Dl_info = intrinsics::init();
let symname =
if dladdr(frame.exact_position as *mut _, &mut info) == 0 || info.dli_sname.is_null() {
None
} else {
CStr::from_ptr(info.dli_sname).to_str().ok()
};
callback(symname)
}
}
#[repr(C)]
struct Dl_info {
dli_fname: *const libc::c_char,
dli_fbase: *mut libc::c_void,
dli_sname: *const libc::c_char,
dli_saddr: *mut libc::c_void,
}
extern "C" {
fn dladdr(addr: *const libc::c_void, info: *mut Dl_info) -> libc::c_int;
}
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