when terminating during unwinding, show the reason why

Author: RalfJung

src/machine.rs

@@ -975,9 +975,9 @@ impl<'mir, 'tcx> Machine<'mir, 'tcx> for MiriMachine<'mir, 'tcx> {
         ecx.start_panic_nounwind(msg)
     }
 
-    fn unwind_terminate(ecx: &mut InterpCx<'mir, 'tcx, Self>) -> InterpResult<'tcx> {
+    fn unwind_terminate(ecx: &mut InterpCx<'mir, 'tcx, Self>, reason: mir::UnwindTerminateReason) -> InterpResult<'tcx> {
         // Call the lang item.
-        let panic = ecx.tcx.lang_items().panic_cannot_unwind().unwrap();
+        let panic = ecx.tcx.lang_items().get(reason.lang_item()).unwrap();
         let panic = ty::Instance::mono(ecx.tcx.tcx, panic);
         ecx.call_function(
             panic,

tests/fail/panic/double_panic.stderr

@@ -5,7 +5,7 @@ thread 'main' panicked at $DIR/double_panic.rs:LL:CC:
 second
 stack backtrace:
 thread 'main' panicked at RUSTLIB/core/src/panicking.rs:LL:CC:
-panic in a function that cannot unwind
+panic in a destructor during cleanup
 stack backtrace:
 thread caused non-unwinding panic. aborting.
 error: abnormal termination: the program aborted execution
@@ -20,7 +20,7 @@ LL |     ABORT();
    = note: inside `std::sys_common::backtrace::__rust_end_short_backtrace::<[closure@std::panicking::begin_panic_handler::{closure#0}], !>` at RUSTLIB/std/src/sys_common/backtrace.rs:LL:CC
    = note: inside `std::panicking::begin_panic_handler` at RUSTLIB/std/src/panicking.rs:LL:CC
    = note: inside `core::panicking::panic_nounwind` at RUSTLIB/core/src/panicking.rs:LL:CC
-   = note: inside `core::panicking::panic_cannot_unwind` at RUSTLIB/core/src/panicking.rs:LL:CC
+   = note: inside `core::panicking::panic_in_cleanup` at RUSTLIB/core/src/panicking.rs:LL:CC
 note: inside `main`
   --> $DIR/double_panic.rs:LL:CC
    |