show where the interpreter was interpreting when an ICE occurs

Author: RalfJung

src/diagnostics.rs

@@ -505,4 +505,22 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
             }
         });
     }
+
+    /// We had a panic in Miri itself, try to print something useful.
+    fn handle_ice(&self) {
+        eprintln!();
+        eprintln!(
+            "Miri caused an ICE during evaluation. Here's the interpreter backtrace at the time of the panic:"
+        );
+        let this = self.eval_context_ref();
+        let stacktrace = this.generate_stacktrace();
+        report_msg(
+            this,
+            DiagLevel::Note,
+            "the place in the program where the ICE was triggered",
+            vec![],
+            vec![],
+            &stacktrace,
+        );
+    }
 }

src/eval.rs

@@ -1,7 +1,10 @@
 //! Main evaluator loop and setting up the initial stack frame.
 
+use std::collections::HashSet;
 use std::ffi::OsStr;
 use std::iter;
+use std::panic::{self, AssertUnwindSafe};
+use std::thread;
 
 use log::info;
 
@@ -15,8 +18,6 @@ use rustc_target::spec::abi::Abi;
 
 use rustc_session::config::EntryFnType;
 
-use std::collections::HashSet;
-
 use crate::*;
 
 #[derive(Copy, Clone, Debug, PartialEq)]
@@ -332,7 +333,7 @@ pub fn eval_entry<'tcx>(
     };
 
     // Perform the main execution.
-    let res: InterpResult<'_, i64> = (|| {
+    let res: thread::Result<InterpResult<'_, i64>> = panic::catch_unwind(AssertUnwindSafe(|| {
         // Main loop.
         loop {
             let info = ecx.preprocess_diagnostics();
@@ -362,7 +363,11 @@ pub fn eval_entry<'tcx>(
         }
         let return_code = ecx.read_scalar(&ret_place.into())?.to_machine_isize(&ecx)?;
         Ok(return_code)
-    })();
+    }));
+    let res = res.unwrap_or_else(|panic_payload| {
+        ecx.handle_ice();
+        panic::resume_unwind(panic_payload)
+    });
 
     // Machine cleanup.
     // Execution of the program has halted so any memory access we do here