From 83f51421830a3939bbd06d780221a794aa69829b Mon Sep 17 00:00:00 2001
From: bjorn3 <17426603+bjorn3@users.noreply.github.com>
Date: Thu, 28 Nov 2024 14:47:21 +0000
Subject: [PATCH] Handle unwinding out of the closure argument of run_compiler
 with pending delayed bugs

---
 compiler/rustc_errors/src/lib.rs          | 14 +++++++---
 compiler/rustc_interface/src/interface.rs | 31 +++++++++++++----------
 2 files changed, 28 insertions(+), 17 deletions(-)

diff --git a/compiler/rustc_errors/src/lib.rs b/compiler/rustc_errors/src/lib.rs
index 8eb55e3084770..c8e45e294b667 100644
--- a/compiler/rustc_errors/src/lib.rs
+++ b/compiler/rustc_errors/src/lib.rs
@@ -493,6 +493,7 @@ struct DiagCtxtInner {
     lint_err_guars: Vec<ErrorGuaranteed>,
     /// The delayed bugs and their error guarantees.
     delayed_bugs: Vec<(DelayedDiagInner, ErrorGuaranteed)>,
+    emitted_delayed_bug: Option<ErrorGuaranteed>,
 
     /// The error count shown to the user at the end.
     deduplicated_err_count: usize,
@@ -622,9 +623,7 @@ impl Drop for DiagCtxtInner {
         // Important: it is sound to produce an `ErrorGuaranteed` when emitting
         // delayed bugs because they are guaranteed to be emitted here if
         // necessary.
-        if self.err_guars.is_empty() {
-            self.flush_delayed()
-        }
+        self.flush_delayed();
 
         // Sanity check: did we use some of the expensive `trimmed_def_paths` functions
         // unexpectedly, that is, without producing diagnostics? If so, for debugging purposes, we
@@ -770,6 +769,7 @@ impl DiagCtxt {
             registry: _,
             err_guars,
             lint_err_guars,
+            emitted_delayed_bug,
             delayed_bugs,
             deduplicated_err_count,
             deduplicated_warn_count,
@@ -790,6 +790,7 @@ impl DiagCtxt {
         // underlying memory (which `clear` would not do).
         *err_guars = Default::default();
         *lint_err_guars = Default::default();
+        *emitted_delayed_bug = None;
         *delayed_bugs = Default::default();
         *deduplicated_err_count = 0;
         *deduplicated_warn_count = 0;
@@ -1421,6 +1422,7 @@ impl DiagCtxtInner {
             registry: Registry::new(&[]),
             err_guars: Vec::new(),
             lint_err_guars: Vec::new(),
+            emitted_delayed_bug: None,
             delayed_bugs: Vec::new(),
             deduplicated_err_count: 0,
             deduplicated_warn_count: 0,
@@ -1705,7 +1707,13 @@ impl DiagCtxtInner {
         // eventually happened.
         assert!(self.stashed_diagnostics.is_empty());
 
+        if !self.err_guars.is_empty() {
+            // If an error happened already. We shouldn't expose delayed bugs.
+            return;
+        }
+
         if self.delayed_bugs.is_empty() {
+            // Nothing to do.
             return;
         }
 
diff --git a/compiler/rustc_interface/src/interface.rs b/compiler/rustc_interface/src/interface.rs
index 71095ca8899e3..a631e9cd93ccc 100644
--- a/compiler/rustc_interface/src/interface.rs
+++ b/compiler/rustc_interface/src/interface.rs
@@ -5,9 +5,9 @@ use std::sync::Arc;
 use rustc_ast::{LitKind, MetaItemKind, token};
 use rustc_codegen_ssa::traits::CodegenBackend;
 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
+use rustc_data_structures::jobserver;
 use rustc_data_structures::stable_hasher::StableHasher;
 use rustc_data_structures::sync::Lrc;
-use rustc_data_structures::{defer, jobserver};
 use rustc_errors::registry::Registry;
 use rustc_errors::{DiagCtxtHandle, ErrorGuaranteed};
 use rustc_lint::LintStore;
@@ -492,21 +492,13 @@ pub fn run_compiler<R: Send>(config: Config, f: impl FnOnce(&Compiler) -> R + Se
 
             // There are two paths out of `f`.
             // - Normal exit.
-            // - Panic, e.g. triggered by `abort_if_errors`.
+            // - Panic, e.g. triggered by `abort_if_errors` or a fatal error.
             //
             // We must run `finish_diagnostics` in both cases.
             let res = {
-                // If `f` panics, `finish_diagnostics` will run during
-                // unwinding because of the `defer`.
-                let sess_abort_guard = defer(|| {
-                    compiler.sess.finish_diagnostics();
-                });
+                let res = std::panic::catch_unwind(std::panic::AssertUnwindSafe(|| f(&compiler)));
 
-                let res = f(&compiler);
-
-                // If `f` doesn't panic, `finish_diagnostics` will run
-                // normally when `sess_abort_guard` is dropped.
-                drop(sess_abort_guard);
+                compiler.sess.finish_diagnostics();
 
                 // If error diagnostics have been emitted, we can't return an
                 // error directly, because the return type of this function
@@ -515,9 +507,20 @@ pub fn run_compiler<R: Send>(config: Config, f: impl FnOnce(&Compiler) -> R + Se
                 // mistakenly think that no errors occurred and return a zero
                 // exit code. So we abort (panic) instead, similar to if `f`
                 // had panicked.
-                compiler.sess.dcx().abort_if_errors();
+                if res.is_ok() {
+                    compiler.sess.dcx().abort_if_errors();
+                }
 
-                res
+                // Also make sure to flush delayed bugs as if we panicked, the
+                // bugs would be flushed by the Drop impl of DiagCtxt while
+                // unwinding, which would result in an abort with
+                // "panic in a destructor during cleanup".
+                compiler.sess.dcx().flush_delayed();
+
+                match res {
+                    Ok(res) => res,
+                    Err(err) => std::panic::resume_unwind(err),
+                }
             };
 
             let prof = compiler.sess.prof.clone();