make better use of label for data-race and some other errors

Author: RalfJung

src/tools/miri/src/diagnostics.rs

@@ -85,7 +85,7 @@ impl fmt::Display for TerminationInfo {
             DataRace { involves_non_atomic, ptr, op1, op2, .. } =>
                 write!(
                     f,
-                    "{} detected between (1) {} on {} and (2) {} on {} at {ptr:?}. (2) just happened here",
+                    "{} detected between (1) {} on {} and (2) {} on {} at {ptr:?}",
                     if *involves_non_atomic { "Data race" } else { "Race condition" },
                     op1.action,
                     op1.thread_info,
@@ -224,7 +224,7 @@ pub fn report_error<'tcx>(
     use InterpErrorKind::*;
     use UndefinedBehaviorInfo::*;
 
-    let mut msg = vec![];
+    let mut labels = vec![];
 
     let (title, helps) = if let MachineStop(info) = e.kind() {
         let info = info.downcast_ref::<TerminationInfo>().expect("invalid MachineStop payload");
@@ -237,7 +237,10 @@ pub fn report_error<'tcx>(
                 Some("unsupported operation"),
             StackedBorrowsUb { .. } | TreeBorrowsUb { .. } | DataRace { .. } =>
                 Some("Undefined Behavior"),
-            Deadlock => Some("deadlock"),
+            Deadlock => {
+                labels.push(format!("this thread got stuck here"));
+                None
+            }
             GenmcStuckExecution => {
                 // This case should only happen in GenMC mode. We treat it like a normal program exit.
                 assert!(ecx.machine.data_race.as_genmc_ref().is_some());
@@ -259,7 +262,7 @@ pub fn report_error<'tcx>(
                 ]
             }
             StackedBorrowsUb { help, history, .. } => {
-                msg.extend(help.clone());
+                labels.extend(help.clone());
                 let mut helps = vec![
                     note!("this indicates a potential bug in the program: it performed an invalid operation, but the Stacked Borrows rules it violated are still experimental"),
                     note!("see https://github.com/rust-lang/unsafe-code-guidelines/blob/master/wip/stacked-borrows.md for further information"),
@@ -297,6 +300,7 @@ pub fn report_error<'tcx>(
             Int2PtrWithStrictProvenance =>
                 vec![note!("use Strict Provenance APIs (https://doc.rust-lang.org/nightly/std/ptr/index.html#strict-provenance, https://crates.io/crates/sptr) instead")],
             DataRace { op1, extra, retag_explain, .. } => {
+                labels.push(format!("(2) just happened here"));
                 let mut helps = vec![note_span!(op1.span, "and (1) occurred earlier here")];
                 if let Some(extra) = extra {
                     helps.push(note!("{extra}"));
@@ -432,12 +436,14 @@ pub fn report_error<'tcx>(
     }
     write!(primary_msg, "{}", format_interp_error(ecx.tcx.dcx(), e)).unwrap();
 
-    msg.insert(0, format!("{} occurred here", title.unwrap_or("error")));
+    if labels.is_empty() {
+        labels.push(format!("{} occurred here", title.unwrap_or("error")));
+    }
 
     report_msg(
         DiagLevel::Error,
         primary_msg,
-        msg,
+        labels,
         vec![],
         helps,
         &stacktrace,
@@ -455,8 +461,8 @@ pub fn report_error<'tcx>(
                 any_pruned |= was_pruned;
                 report_msg(
                     DiagLevel::Error,
-                    format!("deadlock: the evaluated program deadlocked"),
-                    vec![format!("the evaluated program deadlocked")],
+                    format!("the evaluated program deadlocked"),
+                    vec![format!("this thread got stuck here")],
                     vec![],
                     vec![],
                     &stacktrace,
@@ -617,7 +623,7 @@ impl<'tcx> MiriMachine<'tcx> {
         let stacktrace = Frame::generate_stacktrace_from_stack(self.threads.active_thread_stack());
         let (stacktrace, _was_pruned) = prune_stacktrace(stacktrace, self);
 
-        let (title, diag_level) = match &e {
+        let (label, diag_level) = match &e {
             RejectedIsolatedOp(_) =>
                 ("operation rejected by isolation".to_string(), DiagLevel::Warning),
             Int2Ptr { .. } => ("integer-to-pointer cast".to_string(), DiagLevel::Warning),
@@ -632,10 +638,10 @@ impl<'tcx> MiriMachine<'tcx> {
             | FreedAlloc(..)
             | ProgressReport { .. }
             | WeakMemoryOutdatedLoad { .. } =>
-                ("tracking was triggered".to_string(), DiagLevel::Note),
+                ("tracking was triggered here".to_string(), DiagLevel::Note),
         };
 
-        let msg = match &e {
+        let title = match &e {
             CreatedPointerTag(tag, None, _) => format!("created base tag {tag:?}"),
             CreatedPointerTag(tag, Some(perm), None) =>
                 format!("created {tag:?} with {perm} derived from unknown tag"),
@@ -738,7 +744,7 @@ impl<'tcx> MiriMachine<'tcx> {
         report_msg(
             diag_level,
             title,
-            vec![msg],
+            vec![label],
             notes,
             helps,
             &stacktrace,

src/tools/miri/tests/fail-dep/concurrency/libc_pthread_mutex_deadlock.stderr

@@ -1,17 +1,17 @@
-error: deadlock: the evaluated program deadlocked
+error: the evaluated program deadlocked
   --> tests/fail-dep/concurrency/libc_pthread_mutex_deadlock.rs:LL:CC
    |
 LL |             assert_eq!(libc::pthread_mutex_lock(lock_copy.0.get() as *mut _), 0);
-   |                                                                            ^ deadlock occurred here
+   |                                                                            ^ this thread got stuck here
    |
    = note: BACKTRACE on thread `unnamed-ID`:
    = note: inside closure at tests/fail-dep/concurrency/libc_pthread_mutex_deadlock.rs:LL:CC
 
-error: deadlock: the evaluated program deadlocked
+error: the evaluated program deadlocked
   --> RUSTLIB/std/src/sys/pal/PLATFORM/thread.rs:LL:CC
    |
 LL |         let ret = unsafe { libc::pthread_join(id, ptr::null_mut()) };
-   |                                                                  ^ the evaluated program deadlocked
+   |                                                                  ^ this thread got stuck here
    |
    = note: BACKTRACE:
    = note: inside `std::sys::pal::PLATFORM::thread::Thread::join` at RUSTLIB/std/src/sys/pal/PLATFORM/thread.rs:LL:CC

src/tools/miri/tests/fail-dep/concurrency/libc_pthread_mutex_normal_reentrant.rs

@@ -12,6 +12,6 @@ fn main() {
         assert_eq!(libc::pthread_mutex_lock(&mut mutex as *mut _), 0);
         // A "normal" mutex properly tries to acquire the lock even if its is already held
         // by the current thread -- and then we deadlock.
-        libc::pthread_mutex_lock(&mut mutex as *mut _); //~ ERROR: deadlock: the evaluated program deadlocked
+        libc::pthread_mutex_lock(&mut mutex as *mut _); //~ ERROR: the evaluated program deadlocked
     }
 }

src/tools/miri/tests/fail-dep/concurrency/libc_pthread_mutex_normal_reentrant.stderr

@@ -1,8 +1,8 @@
-error: deadlock: the evaluated program deadlocked
+error: the evaluated program deadlocked
   --> tests/fail-dep/concurrency/libc_pthread_mutex_normal_reentrant.rs:LL:CC
    |
 LL |         libc::pthread_mutex_lock(&mut mutex as *mut _);
-   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ deadlock occurred here
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ this thread got stuck here
    |
    = note: BACKTRACE:
    = note: inside `main` at tests/fail-dep/concurrency/libc_pthread_mutex_normal_reentrant.rs:LL:CC

src/tools/miri/tests/fail-dep/concurrency/libc_pthread_rwlock_read_write_deadlock_single_thread.stderr

@@ -1,8 +1,8 @@
-error: deadlock: the evaluated program deadlocked
+error: the evaluated program deadlocked
   --> tests/fail-dep/concurrency/libc_pthread_rwlock_read_write_deadlock_single_thread.rs:LL:CC
    |
 LL |         libc::pthread_rwlock_wrlock(rw.get());
-   |                                             ^ deadlock occurred here
+   |                                             ^ this thread got stuck here
    |
    = note: BACKTRACE:
    = note: inside `main` at tests/fail-dep/concurrency/libc_pthread_rwlock_read_write_deadlock_single_thread.rs:LL:CC

src/tools/miri/tests/fail-dep/concurrency/libc_pthread_rwlock_write_read_deadlock.stderr

@@ -1,17 +1,17 @@
-error: deadlock: the evaluated program deadlocked
+error: the evaluated program deadlocked
   --> tests/fail-dep/concurrency/libc_pthread_rwlock_write_read_deadlock.rs:LL:CC
    |
 LL |             assert_eq!(libc::pthread_rwlock_wrlock(lock_copy.0.get() as *mut _), 0);
-   |                                                                               ^ deadlock occurred here
+   |                                                                               ^ this thread got stuck here
    |
    = note: BACKTRACE on thread `unnamed-ID`:
    = note: inside closure at tests/fail-dep/concurrency/libc_pthread_rwlock_write_read_deadlock.rs:LL:CC
 
-error: deadlock: the evaluated program deadlocked
+error: the evaluated program deadlocked
   --> RUSTLIB/std/src/sys/pal/PLATFORM/thread.rs:LL:CC
    |
 LL |         let ret = unsafe { libc::pthread_join(id, ptr::null_mut()) };
-   |                                                                  ^ the evaluated program deadlocked
+   |                                                                  ^ this thread got stuck here
    |
    = note: BACKTRACE:
    = note: inside `std::sys::pal::PLATFORM::thread::Thread::join` at RUSTLIB/std/src/sys/pal/PLATFORM/thread.rs:LL:CC

src/tools/miri/tests/fail-dep/concurrency/libc_pthread_rwlock_write_read_deadlock_single_thread.stderr

@@ -1,8 +1,8 @@
-error: deadlock: the evaluated program deadlocked
+error: the evaluated program deadlocked
   --> tests/fail-dep/concurrency/libc_pthread_rwlock_write_read_deadlock_single_thread.rs:LL:CC
    |
 LL |         libc::pthread_rwlock_rdlock(rw.get());
-   |                                             ^ deadlock occurred here
+   |                                             ^ this thread got stuck here
    |
    = note: BACKTRACE:
    = note: inside `main` at tests/fail-dep/concurrency/libc_pthread_rwlock_write_read_deadlock_single_thread.rs:LL:CC

src/tools/miri/tests/fail-dep/concurrency/libc_pthread_rwlock_write_write_deadlock.stderr

@@ -1,17 +1,17 @@
-error: deadlock: the evaluated program deadlocked
+error: the evaluated program deadlocked
   --> tests/fail-dep/concurrency/libc_pthread_rwlock_write_write_deadlock.rs:LL:CC
    |
 LL |             assert_eq!(libc::pthread_rwlock_wrlock(lock_copy.0.get() as *mut _), 0);
-   |                                                                               ^ deadlock occurred here
+   |                                                                               ^ this thread got stuck here
    |
    = note: BACKTRACE on thread `unnamed-ID`:
    = note: inside closure at tests/fail-dep/concurrency/libc_pthread_rwlock_write_write_deadlock.rs:LL:CC
 
-error: deadlock: the evaluated program deadlocked
+error: the evaluated program deadlocked
   --> RUSTLIB/std/src/sys/pal/PLATFORM/thread.rs:LL:CC
    |
 LL |         let ret = unsafe { libc::pthread_join(id, ptr::null_mut()) };
-   |                                                                  ^ the evaluated program deadlocked
+   |                                                                  ^ this thread got stuck here
    |
    = note: BACKTRACE:
    = note: inside `std::sys::pal::PLATFORM::thread::Thread::join` at RUSTLIB/std/src/sys/pal/PLATFORM/thread.rs:LL:CC

src/tools/miri/tests/fail-dep/concurrency/libc_pthread_rwlock_write_write_deadlock_single_thread.stderr

@@ -1,8 +1,8 @@
-error: deadlock: the evaluated program deadlocked
+error: the evaluated program deadlocked
   --> tests/fail-dep/concurrency/libc_pthread_rwlock_write_write_deadlock_single_thread.rs:LL:CC
    |
 LL |         libc::pthread_rwlock_wrlock(rw.get());
-   |                                             ^ deadlock occurred here
+   |                                             ^ this thread got stuck here
    |
    = note: BACKTRACE:
    = note: inside `main` at tests/fail-dep/concurrency/libc_pthread_rwlock_write_write_deadlock_single_thread.rs:LL:CC

src/tools/miri/tests/fail-dep/libc/env-set_var-data-race.stderr

@@ -1,8 +1,8 @@
-error: Undefined Behavior: Data race detected between (1) non-atomic write on thread `main` and (2) non-atomic read on thread `unnamed-ID` at ALLOC. (2) just happened here
+error: Undefined Behavior: Data race detected between (1) non-atomic write on thread `main` and (2) non-atomic read on thread `unnamed-ID` at ALLOC
   --> tests/fail-dep/libc/env-set_var-data-race.rs:LL:CC
    |
 LL |         libc::getenv(b"TZ/0".as_ptr().cast());
-   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Undefined Behavior occurred here
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ (2) just happened here
    |
 help: and (1) occurred earlier here
   --> tests/fail-dep/libc/env-set_var-data-race.rs:LL:CC