Improve handling of uncaught exceptions by catching them early and displaying in a message box

main.cpp

@@ -52,6 +52,38 @@ namespace
       qsrand (seed);            // this is good for rand() as well
     }
   } seeding;
+
+  // We  can't use  the GUI  after QApplication::exit()  is called  so
+  // uncaught exceptions can  get lost on Windows  systems where there
+  // is    no    console    terminal,     so    here    we    override
+  // QApplication::notify() and  wrap the base  class call with  a try
+  // block to catch and display exceptions in a message box.
+  class ExceptionCatchingApplication final
+    : public QApplication
+  {
+  public:
+    explicit ExceptionCatchingApplication (int& argc, char * * argv)
+      : QApplication {argc, argv}
+    {
+    }
+    bool notify (QObject * receiver, QEvent * e) override
+    {
+      try
+        {
+          return QApplication::notify (receiver, e);
+        }
+      catch (std::exception const& e)
+        {
+          MessageBox::critical_message (nullptr, translate ("main", "Fatal error"), e.what ());
+          throw;
+        }
+      catch (...)
+        {
+          MessageBox::critical_message (nullptr, translate ("main", "Unexpected fatal error"));
+          throw;
+        }
+    }
+  };
 }
 
 int main(int argc, char *argv[])
@@ -68,7 +100,7 @@ int main(int argc, char *argv[])
   // Multiple instances communicate with jt9 via this
   QSharedMemory mem_jt9;
 
-  QApplication a(argc, argv);
+  ExceptionCatchingApplication a(argc, argv);
   try
     {
       setlocale (LC_NUMERIC, "C"); // ensure number forms are in
@@ -339,12 +371,10 @@ int main(int argc, char *argv[])
     }
   catch (std::exception const& e)
     {
-      MessageBox::critical_message (nullptr, a.translate ("main", "Fatal error"), e.what ());
       std::cerr << "Error: " << e.what () << '\n';
     }
   catch (...)
     {
-      MessageBox::critical_message (nullptr, a.translate ("main", "Unexpected fatal error"));
       std::cerr << "Unexpected fatal error\n";
       throw;			// hoping the runtime might tell us more about the exception
     }