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//! Functionality for capturing and rendering backtraces.
use std::{env, fmt, sync::atomic};
use console::style;
use crate::renderer::Renderer;
/// Backtrace implementation.
pub(crate) trait BacktraceImpl {
/// Capture a backtrace, if backtraces are enabled.
fn capture() -> Self;
/// Forcibly capture a backtrace even if backtraces are not enabled.
fn force_capture() -> Self;
/// Indicates whether a backtrace has been captured.
fn captured(&self) -> bool;
/// Render the backtrace.
fn render(&self, renderer: &mut Renderer) -> fmt::Result;
}
impl BacktraceImpl for std::backtrace::Backtrace {
fn capture() -> Self {
std::backtrace::Backtrace::capture()
}
fn force_capture() -> Self {
std::backtrace::Backtrace::force_capture()
}
fn captured(&self) -> bool {
matches!(self.status(), std::backtrace::BacktraceStatus::Captured)
}
fn render(&self, renderer: &mut Renderer) -> fmt::Result {
use std::fmt::Write;
write!(renderer, "{self}")
}
}
#[cfg(feature = "backtrace")]
impl BacktraceImpl for Option<backtrace::Backtrace> {
fn capture() -> Self {
if backtrace_enabled() {
Self::force_capture()
} else {
None
}
}
fn force_capture() -> Self {
Some(backtrace::Backtrace::new())
}
fn captured(&self) -> bool {
self.is_some()
}
fn render(&self, renderer: &mut Renderer) -> fmt::Result {
use std::fmt::Write;
#[derive(Clone, Copy, Debug)]
enum FramesSegment {
Backtrace,
Reportify,
User,
}
match self {
Some(backtrace) => {
let mut segment = FramesSegment::Backtrace;
'frame: for (frame_idx, frame) in backtrace.frames().iter().enumerate() {
let symbols = frame.symbols();
// XXX: Some crude logic to skip frames based on symbol names. This should be
// improved in the future. Have a look at how `color-eyre` does it.
for symbol in symbols {
if let Some(name) = symbol.name() {
// spell-checker:ignore demangle
// We need to demangle the symbol.
let name = name.to_string();
match segment {
FramesSegment::Backtrace => {
if name.starts_with("reportify") {
segment = FramesSegment::Reportify;
}
continue 'frame;
}
FramesSegment::Reportify => {
if !name.contains("reportify") {
segment = FramesSegment::User;
writeln!(
renderer,
" ⋮ skipped {} frames\n",
frame_idx - 1
)?;
} else {
continue 'frame;
}
}
FramesSegment::User => {
if name.starts_with(
"std::sys::backtrace::__rust_begin_short_backtrace",
) {
writeln!(
renderer,
"\n ⋮ skipped {} frames",
backtrace.frames().len() - frame_idx
)?;
break 'frame;
}
}
}
}
}
if symbols.is_empty() {
writeln!(renderer, "{frame_idx:>4}: {:?}", frame.ip())?;
} else {
for (symbol_idx, symbol) in frame.symbols().iter().enumerate() {
if symbol_idx == 0 {
write!(renderer, "{frame_idx:>4}:")?;
} else {
write!(renderer, " ")?;
}
if let Some(name) = symbol.name() {
write!(renderer, " {}", style(format_args!("{name:#}")).cyan())?;
}
if let Some(addr) = symbol.addr() {
write!(renderer, " {}", style(format_args!("({addr:?})")).black())?;
}
if let Some(file) = symbol.filename() {
write!(renderer, "\n at {}", file.to_string_lossy())?;
if let Some(line) = symbol.lineno() {
write!(renderer, ":{line}")?;
if let Some(column) = symbol.colno() {
write!(renderer, ":{column}")?;
}
}
}
writeln!(renderer)?;
}
}
}
Ok(())
}
None => write!(renderer, "<no backtrace>"),
}
}
}
/// Wrapper to hide the concrete type of the backtrace implementation.
pub(crate) struct BacktraceWrapped<B> {
backtrace: B,
}
impl<B: BacktraceImpl> BacktraceImpl for BacktraceWrapped<B> {
fn capture() -> Self {
Self {
backtrace: B::capture(),
}
}
fn force_capture() -> Self {
Self {
backtrace: B::force_capture(),
}
}
fn captured(&self) -> bool {
self.backtrace.captured()
}
fn render(&self, renderer: &mut Renderer) -> fmt::Result {
self.backtrace.render(renderer)
}
}
/// Backtrace.
#[cfg(not(feature = "backtrace"))]
pub(crate) type Backtrace = BacktraceWrapped<std::backtrace::Backtrace>;
/// Backtrace.
#[cfg(feature = "backtrace")]
pub(crate) type Backtrace = BacktraceWrapped<Option<backtrace::Backtrace>>;
/// Indicates whether backtraces should be captured.
fn backtrace_enabled() -> bool {
// This code has been taken from the standard library's `backtrace.rs`. The result is
// cached to avoid querying the environment every time which can be slow.
static ENABLED: atomic::AtomicU8 = atomic::AtomicU8::new(0);
match ENABLED.load(atomic::Ordering::Relaxed) {
0 => {}
1 => return false,
_ => return true,
}
let enabled = match env::var("RUST_LIB_BACKTRACE") {
Ok(s) => s != "0",
Err(_) => match env::var("RUST_BACKTRACE") {
Ok(s) => s != "0",
Err(_) => false,
},
};
ENABLED.store(enabled as u8 + 1, atomic::Ordering::Relaxed);
enabled
}