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Merged
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Dec 5, 2024
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Improve comments for the default backtrace printer #133882

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26 changes: 12 additions & 14 deletions library/std/src/sys/backtrace.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -58,8 +58,8 @@ unsafe fn _print_fmt(fmt: &mut fmt::Formatter<'_>, print_fmt: PrintFmt) -> fmt::
let mut res = Ok(());
let mut omitted_count: usize = 0;
let mut first_omit = true;
// Start immediately if we're not using a short backtrace.
let mut start = print_fmt != PrintFmt::Short;
// If we're using a short backtrace, ignore all frames until we're told to start printing.
let mut print = print_fmt != PrintFmt::Short;
set_image_base();
// SAFETY: we roll our own locking in this town
unsafe {
Expand All @@ -72,27 +72,25 @@ unsafe fn _print_fmt(fmt: &mut fmt::Formatter<'_>, print_fmt: PrintFmt) -> fmt::
backtrace_rs::resolve_frame_unsynchronized(frame, |symbol| {
hit = true;

// Any frames between `__rust_begin_short_backtrace` and `__rust_end_short_backtrace`
// are omitted from the backtrace in short mode, `__rust_end_short_backtrace` will be
// called before the panic hook, so we won't ignore any frames if there is no
// invoke of `__rust_begin_short_backtrace`.
// `__rust_end_short_backtrace` means we are done hiding symbols
// for now. Print until we see `__rust_begin_short_backtrace`.
if print_fmt == PrintFmt::Short {
if let Some(sym) = symbol.name().and_then(|s| s.as_str()) {
if start && sym.contains("__rust_begin_short_backtrace") {
start = false;
if sym.contains("__rust_end_short_backtrace") {
print = true;
return;
}
if sym.contains("__rust_end_short_backtrace") {
start = true;
if print && sym.contains("__rust_begin_short_backtrace") {
print = false;
return;
}
if !start {
if !print {
omitted_count += 1;
}
}
}

if start {
if print {
if omitted_count > 0 {
debug_assert!(print_fmt == PrintFmt::Short);
// only print the message between the middle of frames
Expand All @@ -112,7 +110,7 @@ unsafe fn _print_fmt(fmt: &mut fmt::Formatter<'_>, print_fmt: PrintFmt) -> fmt::
});
#[cfg(target_os = "nto")]
if libc::__my_thread_exit as *mut libc::c_void == frame.ip() {
if !hit && start {
if !hit && print {
use crate::backtrace_rs::SymbolName;
res = bt_fmt.frame().print_raw(
frame.ip(),
Expand All @@ -123,7 +121,7 @@ unsafe fn _print_fmt(fmt: &mut fmt::Formatter<'_>, print_fmt: PrintFmt) -> fmt::
}
return false;
}
if !hit && start {
if !hit && print {
res = bt_fmt.frame().print_raw(frame.ip(), None, None, None);
}

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