On nightly, dump ICE backtraces to disk

Implement rust-lang/compiler-team#578.

When an ICE is encountered on nightly releases, the new rustc panic
handler will also write the contents of the backtrace to disk. If any
`delay_span_bug`s are encountered, their backtrace is also added to the
file. The platform and rustc version will also be collected.

Cargo.lock

@@ -3212,6 +3212,7 @@ dependencies = [
  "rustc_trait_selection",
  "rustc_ty_utils",
  "serde_json",
+ "time",
  "tracing",
  "windows",
 ]
@@ -4815,6 +4816,33 @@ dependencies = [
 name = "tier-check"
 version = "0.1.0"
 
+[[package]]
+name = "time"
+version = "0.3.22"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ea9e1b3cf1243ae005d9e74085d4d542f3125458f3a81af210d901dcd7411efd"
+dependencies = [
+ "itoa",
+ "serde",
+ "time-core",
+ "time-macros",
+]
+
+[[package]]
+name = "time-core"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7300fbefb4dadc1af235a9cef3737cea692a9d97e1b9cbcd4ebdae6f8868e6fb"
+
+[[package]]
+name = "time-macros"
+version = "0.2.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "372950940a5f07bf38dbe211d7283c9e6d7327df53794992d293e534c733d09b"
+dependencies = [
+ "time-core",
+]
+
 [[package]]
 name = "tinystr"
 version = "0.7.1"

compiler/rustc_codegen_ssa/src/back/write.rs

@@ -362,7 +362,7 @@ pub struct CodegenContext<B: WriteBackendMethods> {
 
 impl<B: WriteBackendMethods> CodegenContext<B> {
     pub fn create_diag_handler(&self) -> Handler {
-        Handler::with_emitter(true, None, Box::new(self.diag_emitter.clone()))
+        Handler::with_emitter(true, None, Box::new(self.diag_emitter.clone()), None)
     }
 
     pub fn config(&self, kind: ModuleKind) -> &ModuleConfig {

compiler/rustc_driver_impl/Cargo.toml

@@ -6,6 +6,7 @@ edition = "2021"
 [lib]
 
 [dependencies]
+time = { version = "0.3", default-features = false, features = ["formatting", ] }
 tracing = { version = "0.1.35" }
 serde_json = "1.0.59"
 rustc_log = { path = "../rustc_log" }

compiler/rustc_driver_impl/messages.ftl

@@ -3,7 +3,11 @@ driver_impl_ice_bug_report = we would appreciate a bug report: {$bug_report_url}
 driver_impl_ice_exclude_cargo_defaults = some of the compiler flags provided by cargo are hidden
 
 driver_impl_ice_flags = compiler flags: {$flags}
+driver_impl_ice_path = please attach the file at `{$path}` to your bug report
+driver_impl_ice_path_error = the ICE couldn't be written to `{$path}`: {$error}
+driver_impl_ice_path_error_env = the environment variable `RUSTC_ICE` is set to `{$env_var}`
 driver_impl_ice_version = rustc {$version} running on {$triple}
+
 driver_impl_rlink_empty_version_number = The input does not contain version number
 
 driver_impl_rlink_encoding_version_mismatch = .rlink file was produced with encoding version `{$version_array}`, but the current version is `{$rlink_version}`

compiler/rustc_driver_impl/src/lib.rs

@@ -7,6 +7,8 @@
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
 #![feature(lazy_cell)]
 #![feature(decl_macro)]
+#![feature(ice_to_disk)]
+#![feature(let_chains)]
 #![recursion_limit = "256"]
 #![allow(rustc::potential_query_instability)]
 #![deny(rustc::untranslatable_diagnostic)]
@@ -57,8 +59,11 @@ use std::panic::{self, catch_unwind};
 use std::path::PathBuf;
 use std::process::{self, Command, Stdio};
 use std::str;
+use std::sync::atomic::{AtomicBool, Ordering};
 use std::sync::OnceLock;
-use std::time::Instant;
+use std::time::{Instant, SystemTime};
+use time::format_description::well_known::Rfc3339;
+use time::OffsetDateTime;
 
 #[allow(unused_macros)]
 macro do_not_use_print($($t:tt)*) {
@@ -297,6 +302,7 @@ fn run_compiler(
         input: Input::File(PathBuf::new()),
         output_file: ofile,
         output_dir: odir,
+        ice_file: ice_path().clone(),
         file_loader,
         locale_resources: DEFAULT_LOCALE_RESOURCES,
         lint_caps: Default::default(),
@@ -1295,9 +1301,35 @@ pub fn catch_with_exit_code(f: impl FnOnce() -> interface::Result<()>) -> i32 {
     }
 }
 
-/// Stores the default panic hook, from before [`install_ice_hook`] was called.
-static DEFAULT_HOOK: OnceLock<Box<dyn Fn(&panic::PanicInfo<'_>) + Sync + Send + 'static>> =
-    OnceLock::new();
+pub static ICE_PATH: OnceLock<Option<PathBuf>> = OnceLock::new();
+
+pub fn ice_path() -> &'static Option<PathBuf> {
+    ICE_PATH.get_or_init(|| {
+        if !rustc_feature::UnstableFeatures::from_environment(None).is_nightly_build() {
+            return None;
+        }
+        if let Ok("0") = std::env::var("RUST_BACKTRACE").as_deref() {
+            return None;
+        }
+        let mut path = match std::env::var("RUSTC_ICE").as_deref() {
+            // Explicitly opting out of writing ICEs to disk.
+            Ok("0") => return None,
+            Ok(s) => match PathBuf::try_from(s) {
+                Ok(p) => p,
+                // On parse error, fallback to the default directory, otherwise the backtraces might be
+                // accidentally lost due to a simple typo. The directory might still not be accessible
+                // for some other reason.
+                Err(_) => std::env::current_dir().unwrap_or_default(),
+            },
+            Err(_) => std::env::current_dir().unwrap_or_default(),
+        };
+        let now: OffsetDateTime = SystemTime::now().into();
+        let file_now = now.format(&Rfc3339).unwrap_or(String::new());
+        let pid = std::process::id();
+        path.push(format!("rustc-ice-{file_now}-{pid}.txt"));
+        Some(path)
+    })
+}
 
 /// Installs a panic hook that will print the ICE message on unexpected panics.
 ///
@@ -1321,8 +1353,6 @@ pub fn install_ice_hook(bug_report_url: &'static str, extra_info: fn(&Handler))
         std::env::set_var("RUST_BACKTRACE", "full");
     }
 
-    let default_hook = DEFAULT_HOOK.get_or_init(panic::take_hook);
-
     panic::set_hook(Box::new(move |info| {
         // If the error was caused by a broken pipe then this is not a bug.
         // Write the error and return immediately. See #98700.
@@ -1339,7 +1369,7 @@ pub fn install_ice_hook(bug_report_url: &'static str, extra_info: fn(&Handler))
         // Invoke the default handler, which prints the actual panic message and optionally a backtrace
         // Don't do this for delayed bugs, which already emit their own more useful backtrace.
         if !info.payload().is::<rustc_errors::DelayedBugPanic>() {
-            (*default_hook)(info);
+            std::panic_hook_with_disk_dump(info, ice_path().as_deref());
 
             // Separate the output with an empty line
             eprintln!();
@@ -1371,7 +1401,7 @@ pub fn report_ice(info: &panic::PanicInfo<'_>, bug_report_url: &str, extra_info:
         false,
         TerminalUrl::No,
     ));
-    let handler = rustc_errors::Handler::with_emitter(true, None, emitter);
+    let handler = rustc_errors::Handler::with_emitter(true, None, emitter, None);
 
     // a .span_bug or .bug call has already printed what
     // it wants to print.
@@ -1382,10 +1412,40 @@ pub fn report_ice(info: &panic::PanicInfo<'_>, bug_report_url: &str, extra_info:
     }
 
     handler.emit_note(session_diagnostics::IceBugReport { bug_report_url });
-    handler.emit_note(session_diagnostics::IceVersion {
-        version: util::version_str!().unwrap_or("unknown_version"),
-        triple: config::host_triple(),
-    });
+
+    let version = util::version_str!().unwrap_or("unknown_version");
+    let triple = config::host_triple();
+
+    static FIRST_PANIC: AtomicBool = AtomicBool::new(true);
+
+    let file = if let Some(path) = ice_path().as_ref() {
+        // Create the ICE dump target file.
+        match crate::fs::File::options().create(true).append(true).open(&path) {
+            Ok(mut file) => {
+                handler
+                    .emit_note(session_diagnostics::IcePath { path: path.display().to_string() });
+                if FIRST_PANIC.swap(false, Ordering::SeqCst) {
+                    let _ = write!(file, "\n\nrustc version: {version}\nplatform: {triple}");
+                }
+                Some(file)
+            }
+            Err(err) => {
+                // The path ICE couldn't be written to disk, provide feedback to the user as to why.
+                handler.emit_warning(session_diagnostics::IcePathError {
+                    path: path.display().to_string(),
+                    error: err.to_string(),
+                    env_var: std::env::var("RUSTC_ICE")
+                        .ok()
+                        .map(|env_var| session_diagnostics::IcePathErrorEnv { env_var }),
+                });
+                handler.emit_note(session_diagnostics::IceVersion { version, triple });
+                None
+            }
+        }
+    } else {
+        handler.emit_note(session_diagnostics::IceVersion { version, triple });
+        None
+    };
 
     if let Some((flags, excluded_cargo_defaults)) = extra_compiler_flags() {
         handler.emit_note(session_diagnostics::IceFlags { flags: flags.join(" ") });
@@ -1399,7 +1459,7 @@ pub fn report_ice(info: &panic::PanicInfo<'_>, bug_report_url: &str, extra_info:
 
     let num_frames = if backtrace { None } else { Some(2) };
 
-    interface::try_print_query_stack(&handler, num_frames);
+    interface::try_print_query_stack(&handler, num_frames, file);
 
     // We don't trust this callback not to panic itself, so run it at the end after we're sure we've
     // printed all the relevant info.

compiler/rustc_driver_impl/src/session_diagnostics.rs

@@ -1,4 +1,4 @@
-use rustc_macros::Diagnostic;
+use rustc_macros::{Diagnostic, Subdiagnostic};
 
 #[derive(Diagnostic)]
 #[diag(driver_impl_rlink_unable_to_read)]
@@ -56,6 +56,27 @@ pub(crate) struct IceVersion<'a> {
     pub triple: &'a str,
 }
 
+#[derive(Diagnostic)]
+#[diag(driver_impl_ice_path)]
+pub(crate) struct IcePath {
+    pub path: String,
+}
+
+#[derive(Diagnostic)]
+#[diag(driver_impl_ice_path_error)]
+pub(crate) struct IcePathError {
+    pub path: String,
+    pub error: String,
+    #[subdiagnostic]
+    pub env_var: Option<IcePathErrorEnv>,
+}
+
+#[derive(Subdiagnostic)]
+#[note(driver_impl_ice_path_error_env)]
+pub(crate) struct IcePathErrorEnv {
+    pub env_var: String,
+}
+
 #[derive(Diagnostic)]
 #[diag(driver_impl_ice_flags)]
 pub(crate) struct IceFlags {

compiler/rustc_error_messages/src/lib.rs

@@ -355,6 +355,13 @@ impl DiagnosticMessage {
             }
         }
     }
+
+    pub fn as_str(&self) -> Option<&str> {
+        match self {
+            DiagnosticMessage::Eager(s) | DiagnosticMessage::Str(s) => Some(s),
+            DiagnosticMessage::FluentIdentifier(_, _) => None,
+        }
+    }
 }
 
 impl From<String> for DiagnosticMessage {

compiler/rustc_errors/src/json/tests.rs

@@ -64,7 +64,7 @@ fn test_positions(code: &str, span: (u32, u32), expected_output: SpanTestData) {
         );
 
         let span = Span::with_root_ctxt(BytePos(span.0), BytePos(span.1));
-        let handler = Handler::with_emitter(true, None, Box::new(je));
+        let handler = Handler::with_emitter(true, None, Box::new(je), None);
         handler.span_err(span, "foo");
 
         let bytes = output.lock().unwrap();

compiler/rustc_errors/src/lib.rs

@@ -47,9 +47,10 @@ use std::borrow::Cow;
 use std::error::Report;
 use std::fmt;
 use std::hash::Hash;
+use std::io::Write;
 use std::num::NonZeroUsize;
 use std::panic;
-use std::path::Path;
+use std::path::{Path, PathBuf};
 
 use termcolor::{Color, ColorSpec};
 
@@ -461,6 +462,10 @@ struct HandlerInner {
     ///
     /// [RFC-2383]: https://rust-lang.github.io/rfcs/2383-lint-reasons.html
     fulfilled_expectations: FxHashSet<LintExpectationId>,
+
+    /// The file where the ICE information is stored. This allows delayed_span_bug backtraces to be
+    /// stored along side the main panic backtrace.
+    ice_file: Option<PathBuf>,
 }
 
 /// A key denoting where from a diagnostic was stashed.
@@ -550,13 +555,15 @@ impl Handler {
         sm: Option<Lrc<SourceMap>>,
         fluent_bundle: Option<Lrc<FluentBundle>>,
         fallback_bundle: LazyFallbackBundle,
+        ice_file: Option<PathBuf>,
     ) -> Self {
         Self::with_tty_emitter_and_flags(
             color_config,
             sm,
             fluent_bundle,
             fallback_bundle,
             HandlerFlags { can_emit_warnings, treat_err_as_bug, ..Default::default() },
+            ice_file,
         )
     }
 
@@ -566,6 +573,7 @@ impl Handler {
         fluent_bundle: Option<Lrc<FluentBundle>>,
         fallback_bundle: LazyFallbackBundle,
         flags: HandlerFlags,
+        ice_file: Option<PathBuf>,
     ) -> Self {
         let emitter = Box::new(EmitterWriter::stderr(
             color_config,
@@ -579,23 +587,26 @@ impl Handler {
             flags.track_diagnostics,
             TerminalUrl::No,
         ));
-        Self::with_emitter_and_flags(emitter, flags)
+        Self::with_emitter_and_flags(emitter, flags, ice_file)
     }
 
     pub fn with_emitter(
         can_emit_warnings: bool,
         treat_err_as_bug: Option<NonZeroUsize>,
         emitter: Box<dyn Emitter + sync::Send>,
+        ice_file: Option<PathBuf>,
     ) -> Self {
         Handler::with_emitter_and_flags(
             emitter,
             HandlerFlags { can_emit_warnings, treat_err_as_bug, ..Default::default() },
+            ice_file,
         )
     }
 
     pub fn with_emitter_and_flags(
         emitter: Box<dyn Emitter + sync::Send>,
         flags: HandlerFlags,
+        ice_file: Option<PathBuf>,
     ) -> Self {
         Self {
             flags,
@@ -618,6 +629,7 @@ impl Handler {
                 check_unstable_expect_diagnostics: false,
                 unstable_expect_diagnostics: Vec::new(),
                 fulfilled_expectations: Default::default(),
+                ice_file,
             }),
         }
     }
@@ -1657,8 +1669,21 @@ impl HandlerInner {
         explanation: impl Into<DiagnosticMessage> + Copy,
     ) {
         let mut no_bugs = true;
+        // If backtraces are enabled, also print the query stack
+        let backtrace = std::env::var_os("RUST_BACKTRACE").map_or(true, |x| &x != "0");
         for bug in bugs {
-            let mut bug = bug.decorate();
+            if let Some(file) = self.ice_file.as_ref()
+                && let Ok(mut out) = std::fs::File::options().append(true).open(file)
+            {
+                let _ = write!(
+                    &mut out,
+                    "\n\ndelayed span bug: {}\n{}",
+                    bug.inner.styled_message().iter().filter_map(|(msg, _)| msg.as_str()).collect::<String>(),
+                    &bug.note
+                );
+            }
+            let mut bug =
+                if backtrace || self.ice_file.is_none() { bug.decorate() } else { bug.inner };
 
             if no_bugs {
                 // Put the overall explanation before the `DelayedBug`s, to

compiler/rustc_expand/src/tests.rs

@@ -161,7 +161,7 @@ fn test_harness(file_text: &str, span_labels: Vec<SpanLabel>, expected_output: &
             false,
             TerminalUrl::No,
         );
-        let handler = Handler::with_emitter(true, None, Box::new(emitter));
+        let handler = Handler::with_emitter(true, None, Box::new(emitter), None);
         #[allow(rustc::untranslatable_diagnostic)]
         handler.span_err(msp, "foo");