[fix, WIP] Fix recording of initial event when recorder is empty.

Author: S1eGa

lib/Core/EventRecorder.cpp

@@ -78,6 +78,8 @@ bool EventRecorder::empty() const { return events.empty(); }
 ref<CodeEvent> EventRecorder::last() const { return events.back(); }
 
 EventRecorder EventRecorder::tail(const Path::PathIndex &begin) const {
-  assert(!events.empty());
+  if (events.empty()) {
+    return EventRecorder();
+  }
   return inRange(begin, events.back()->location->pathIndex);
 }

lib/Core/ExecutionState.h

@@ -330,7 +330,8 @@ class ExecutionState {
   /// @brief Constraints collected so far
   PathConstraints constraints;
 
-  // TODO: union into history object
+  /// @brief Storage for the source code events (e.g. changing control flow or
+  /// errors)
   EventRecorder eventsRecorder;
 
   /// @brief Key points which should be visited through execution

lib/Core/Executor.cpp

@@ -5032,11 +5032,10 @@ void Executor::terminateStateOnProgramError(ExecutionState &state,
 
   if (reason->source.has_value()) {
     const ref<CodeEvent> &sourceEvent = reason->source.value();
-
-    if (!state.eventsRecorder.empty() && sourceEvent->location) {
+    if (sourceEvent->location) {
       EventRecorder traceRecorder;
-      traceRecorder.record(sourceEvent);
 
+      traceRecorder.record(sourceEvent);
       traceRecorder.append(
           state.eventsRecorder.tail(sourceEvent->location->pathIndex));
 
@@ -6593,6 +6592,7 @@ void Executor::executeMemoryOperation(
                                                   uniqueBase, baseTargetType,
                                                   baseID, uniqueBaseResolved)) {
       terminateStateOnSolverError(*unbound, "Query timed out (resolve)");
+      return;
     }
 
     if (uniqueBaseResolved) {

lib/Module/LocationInfo.cpp

@@ -104,6 +104,11 @@ LocationInfo getLocationInfo(const llvm::GlobalVariable *globalVar) {
     }
   }
 
+  // For `extern` variables return `external` file.
+  if (globalVar->hasExternalLinkage()) {
+    return {"external", 0, {}};
+  }
+
   // Fallback to empty location if there is no appropriate debug
   // info.
   return {"", 0, {}};