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pub use self::imp::{Backtrace, InternalBacktrace};
#[cfg(feature = "backtrace")]
mod imp {
extern crate backtrace;
use std::cell::UnsafeCell;
use std::env;
use std::fmt;
use std::sync::atomic::{AtomicUsize, Ordering};
use std::sync::{Arc, Mutex};
/// Internal representation of a backtrace
#[doc(hidden)]
#[derive(Clone)]
pub struct InternalBacktrace {
backtrace: Option<Arc<MaybeResolved>>,
}
struct MaybeResolved {
resolved: Mutex<bool>,
backtrace: UnsafeCell<Backtrace>,
}
unsafe impl Send for MaybeResolved {}
unsafe impl Sync for MaybeResolved {}
pub use self::backtrace::Backtrace;
impl InternalBacktrace {
/// Returns a backtrace of the current call stack if `RUST_BACKTRACE`
/// is set to anything but ``0``, and `None` otherwise. This is used
/// in the generated error implementations.
#[doc(hidden)]
pub fn new() -> InternalBacktrace {
static ENABLED: AtomicUsize = AtomicUsize::new(0);
match ENABLED.load(Ordering::SeqCst) {
0 => {
let enabled = match env::var_os("RUST_BACKTRACE") {
Some(ref val) if val != "0" => true,
_ => false,
};
ENABLED.store(enabled as usize + 1, Ordering::SeqCst);
if !enabled {
return InternalBacktrace { backtrace: None };
}
}
1 => return InternalBacktrace { backtrace: None },
_ => {}
}
InternalBacktrace {
backtrace: Some(Arc::new(MaybeResolved {
resolved: Mutex::new(false),
backtrace: UnsafeCell::new(Backtrace::new_unresolved()),
})),
}
}
/// Acquire the internal backtrace
#[doc(hidden)]
pub fn as_backtrace(&self) -> Option<&Backtrace> {
let bt = match self.backtrace {
Some(ref bt) => bt,
None => return None,
};
let mut resolved = bt.resolved.lock().unwrap();
unsafe {
if !*resolved {
(*bt.backtrace.get()).resolve();
*resolved = true;
}
Some(&*bt.backtrace.get())
}
}
}
impl fmt::Debug for InternalBacktrace {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
f.debug_struct("InternalBacktrace")
.field("backtrace", &self.as_backtrace())
.finish()
}
}
}
#[cfg(not(feature = "backtrace"))]
mod imp {
/// Dummy type used when the `backtrace` feature is disabled.
pub type Backtrace = ();
/// Internal representation of a backtrace
#[doc(hidden)]
#[derive(Clone, Debug)]
pub struct InternalBacktrace {}
impl InternalBacktrace {
/// Returns a new backtrace
#[doc(hidden)]
pub fn new() -> InternalBacktrace {
InternalBacktrace {}
}
/// Returns the internal backtrace
#[doc(hidden)]
pub fn as_backtrace(&self) -> Option<&Backtrace> {
None
}
}
}
|
