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Commit 92bc467

Browse files
Rollup merge of #146068 - Zalathar:panic-hook, r=jieyouxu
compiletest: Capture panic messages via a custom panic hook Currently, output-capture of panic messages relies on special cooperation between `#![feature(internal_output_capture)]` and the default panic hook. That's a problem if we want to perform our own output capture, because the default panic hook won't know about our custom output-capture mechanism. We can work around that by installing a custom panic hook that prints equivalent panic messages to a buffer instead. The custom hook is always installed, but delegates to the default panic hook unless a panic-capture buffer has been installed on the current thread. A panic-capture buffer is only installed on compiletest test threads (by the executor), and only if output-capture is enabled. --- Right now this PR doesn't provide any particular concrete benefits. But it will be essential as part of further efforts to replace compiletest's use of `#![feature(internal_output_capture)]` with our own output-capture mechanism. r? jieyouxu
2 parents 325bb43 + e7519c6 commit 92bc467

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‎src/tools/compiletest/src/executor.rs

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Original file line numberDiff line numberDiff line change
@@ -13,6 +13,7 @@ use std::sync::{Arc, Mutex, mpsc};
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use std::{env, hint, io, mem, panic, thread};
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use crate::common::{Config, TestPaths};
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use crate::panic_hook;
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mod deadline;
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mod json;
@@ -120,6 +121,11 @@ fn run_test_inner(
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completion_sender: mpsc::Sender<TestCompletion>,
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) {
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let is_capture = !runnable_test.config.nocapture;
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// Install a panic-capture buffer for use by the custom panic hook.
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if is_capture {
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panic_hook::set_capture_buf(Default::default());
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}
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let capture_buf = is_capture.then(|| Arc::new(Mutex::new(vec![])));
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if let Some(capture_buf) = &capture_buf {
@@ -128,6 +134,13 @@ fn run_test_inner(
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129135
let panic_payload = panic::catch_unwind(move || runnable_test.run()).err();
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137+
if let Some(panic_buf) = panic_hook::take_capture_buf() {
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let panic_buf = panic_buf.lock().unwrap_or_else(|e| e.into_inner());
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// For now, forward any captured panic message to (captured) stderr.
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// FIXME(Zalathar): Once we have our own output-capture buffer for
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// non-panic output, append the panic message to that buffer instead.
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eprint!("{panic_buf}");
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}
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if is_capture {
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io::set_output_capture(None);
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}

‎src/tools/compiletest/src/lib.rs

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Original file line numberDiff line numberDiff line change
@@ -15,6 +15,7 @@ pub mod directives;
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pub mod errors;
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mod executor;
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mod json;
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mod panic_hook;
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mod raise_fd_limit;
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mod read2;
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pub mod runtest;
@@ -493,6 +494,8 @@ pub fn opt_str2(maybestr: Option<String>) -> String {
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pub fn run_tests(config: Arc<Config>) {
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debug!(?config, "run_tests");
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497+
panic_hook::install_panic_hook();
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496499
// If we want to collect rustfix coverage information,
497500
// we first make sure that the coverage file does not exist.
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// It will be created later on.

‎src/tools/compiletest/src/panic_hook.rs

Lines changed: 136 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,136 @@
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use std::backtrace::{Backtrace, BacktraceStatus};
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use std::cell::Cell;
3+
use std::fmt::{Display, Write};
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use std::panic::PanicHookInfo;
5+
use std::sync::{Arc, LazyLock, Mutex};
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use std::{env, mem, panic, thread};
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type PanicHook = Box<dyn Fn(&PanicHookInfo<'_>) + Sync + Send + 'static>;
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type CaptureBuf = Arc<Mutex<String>>;
10+
11+
thread_local!(
12+
static CAPTURE_BUF: Cell<Option<CaptureBuf>> = const { Cell::new(None) };
13+
);
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/// Installs a custom panic hook that will divert panic output to a thread-local
16+
/// capture buffer, but only for threads that have a capture buffer set.
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///
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/// Otherwise, the custom hook delegates to a copy of the default panic hook.
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pub(crate) fn install_panic_hook() {
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let default_hook = panic::take_hook();
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panic::set_hook(Box::new(move |info| custom_panic_hook(&default_hook, info)));
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}
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pub(crate) fn set_capture_buf(buf: CaptureBuf) {
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CAPTURE_BUF.set(Some(buf));
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}
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pub(crate) fn take_capture_buf() -> Option<CaptureBuf> {
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CAPTURE_BUF.take()
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}
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fn custom_panic_hook(default_hook: &PanicHook, info: &panic::PanicHookInfo<'_>) {
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// Temporarily taking the capture buffer means that if a panic occurs in
34+
// the subsequent code, that panic will fall back to the default hook.
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let Some(buf) = take_capture_buf() else {
36+
// There was no capture buffer, so delegate to the default hook.
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default_hook(info);
38+
return;
39+
};
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let mut out = buf.lock().unwrap_or_else(|e| e.into_inner());
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let thread = thread::current().name().unwrap_or("(test runner)").to_owned();
44+
let location = get_location(info);
45+
let payload = payload_as_str(info).unwrap_or("Box<dyn Any>");
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let backtrace = Backtrace::capture();
47+
48+
writeln!(out, "\nthread '{thread}' panicked at {location}:\n{payload}").unwrap();
49+
match backtrace.status() {
50+
BacktraceStatus::Captured => {
51+
let bt = trim_backtrace(backtrace.to_string());
52+
write!(out, "stack backtrace:\n{bt}",).unwrap();
53+
}
54+
BacktraceStatus::Disabled => {
55+
writeln!(
56+
out,
57+
"note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace",
58+
)
59+
.unwrap();
60+
}
61+
_ => {}
62+
}
63+
64+
drop(out);
65+
set_capture_buf(buf);
66+
}
67+
68+
fn get_location<'a>(info: &'a PanicHookInfo<'_>) -> &'a dyn Display {
69+
match info.location() {
70+
Some(location) => location,
71+
None => &"(unknown)",
72+
}
73+
}
74+
75+
/// FIXME(Zalathar): Replace with `PanicHookInfo::payload_as_str` when that's
76+
/// stable in beta.
77+
fn payload_as_str<'a>(info: &'a PanicHookInfo<'_>) -> Option<&'a str> {
78+
let payload = info.payload();
79+
if let Some(s) = payload.downcast_ref::<&str>() {
80+
Some(s)
81+
} else if let Some(s) = payload.downcast_ref::<String>() {
82+
Some(s)
83+
} else {
84+
None
85+
}
86+
}
87+
88+
fn rust_backtrace_full() -> bool {
89+
static RUST_BACKTRACE_FULL: LazyLock<bool> =
90+
LazyLock::new(|| matches!(env::var("RUST_BACKTRACE").as_deref(), Ok("full")));
91+
*RUST_BACKTRACE_FULL
92+
}
93+
94+
/// On stable, short backtraces are only available to the default panic hook,
95+
/// so if we want something similar we have to resort to string processing.
96+
fn trim_backtrace(full_backtrace: String) -> String {
97+
if rust_backtrace_full() {
98+
return full_backtrace;
99+
}
100+
101+
let mut buf = String::with_capacity(full_backtrace.len());
102+
// Don't print any frames until after the first `__rust_end_short_backtrace`.
103+
let mut on = false;
104+
// After the short-backtrace state is toggled, skip its associated "at" if present.
105+
let mut skip_next_at = false;
106+
107+
let mut lines = full_backtrace.lines();
108+
while let Some(line) = lines.next() {
109+
if mem::replace(&mut skip_next_at, false) && line.trim_start().starts_with("at ") {
110+
continue;
111+
}
112+
113+
if line.contains("__rust_end_short_backtrace") {
114+
on = true;
115+
skip_next_at = true;
116+
continue;
117+
}
118+
if line.contains("__rust_begin_short_backtrace") {
119+
on = false;
120+
skip_next_at = true;
121+
continue;
122+
}
123+
124+
if on {
125+
writeln!(buf, "{line}").unwrap();
126+
}
127+
}
128+
129+
writeln!(
130+
buf,
131+
"note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace."
132+
)
133+
.unwrap();
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buf
136+
}

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