Failed assertion throws runtime_error; message box moved to GUI main loop try..catch wrapper (#496)

Failed assertions were not properly handled in extant code. We launched a QMessageBox from a thread, which is unsafe according to the Qt docs, and actually failed (it could be repaired by shortening the error message, e.g. by ommitting the file name, but that would be quite fragile a solution).

Now, a failed assertion just throws a std::runtime_error. We don't use qFatal any longer. This allows us to remove the failedAssert function pointer and the QMessageHandler.

If catched inside the GUI, the failed assertion is displayed in the message frame. Otherwise, the exception is catched in the main program, which launches a QMessageBox within a fresh QApplication.

This leaves one specific case uncovered, namely: Failed assertions (and other exceptions) thrown in event handlers but outside specific try blocks.

App/main.cpp

@@ -13,7 +13,6 @@
 //  ************************************************************************************************
 
 #include "App/AppOptions.h"
-#include "App/MessageHandler.h"
 #include "Base/Util/Assert.h"
 #include "GUI/Application/ApplicationSettings.h"
 #include "GUI/Support/Util/Path.h"
@@ -21,6 +20,7 @@
 #include "GUI/View/Main/MainWindow.h"
 #include "GUI/View/Tool/Globals.h"
 #include "config_build.h"
+#include <QApplication>
 #include <QDir>
 #include <QIcon>
 #include <QLocale>
@@ -28,15 +28,6 @@
 #include <QMetaType>
 #include <QtGlobal>
 
-auto guiFailedAssertion = [](std::string msg) {
-#ifdef BA_DEBUG
-    std::cerr << "FATAL (catched in debug mode): " << msg << std::endl;
-    std::raise(11); // abort so that we can inspect the backtrace
-#else
-    qFatal("%s", msg.c_str());
-#endif
-};
-
 int main(int argc, char* argv[])
 {
     ApplicationOptions options(argc, argv);
@@ -44,35 +35,46 @@ int main(int argc, char* argv[])
     QLocale::setDefault(QLocale(QLocale::English, QLocale::UnitedStates));
     qRegisterMetaType<QVector<double>>("QVector<double>");
 
-    QApplication app(argc, argv);
-    QApplication::setApplicationName("BornAgain");
-    QApplication::setApplicationVersion(GUI::Util::Path::getBornAgainVersionString());
-    QApplication::setOrganizationName("BornAgain");
+    int ret = -1;
+    try {
+        QApplication app(argc, argv);
+        app.setApplicationName("BornAgain");
+        app.setApplicationVersion(GUI::Util::Path::getBornAgainVersionString());
+        app.setOrganizationName("BornAgain");
 #ifndef Q_OS_MAC
-    QApplication::setWindowIcon(QIcon(":/images/BornAgain.ico"));
+        app.setWindowIcon(QIcon(":/images/BornAgain.ico"));
 #endif
 
-    ApplicationSettings applicationSettings;
-
-    qInstallMessageHandler(messageHandler);
-    failedAssertion = guiFailedAssertion;
+        ApplicationSettings applicationSettings;
 
-    register1DDataLoaders();
+        register1DDataLoaders();
 
-    auto style = applicationSettings.styleToUse();
-    applicationSettings.loadStyle(style);
+        auto style = applicationSettings.styleToUse();
+        applicationSettings.loadStyle(style);
 
-    QString dir = GUI::Util::Path::appDataFolder();
-    if (!QDir().exists(dir))
-        QDir().mkpath(dir);
+        QString dir = GUI::Util::Path::appDataFolder();
+        if (!QDir().exists(dir))
+            QDir().mkpath(dir);
 
-    MainWindow win;
-    GUI::Global::mainWindow = &win;
-    if (options.find("geometry"))
-        win.resize(options.mainWindowSize());
-    if (options.find("project-file"))
-        win.loadProject(options.projectFile());
-    win.show();
+        MainWindow win;
+        GUI::Global::mainWindow = &win;
+        if (options.find("geometry"))
+            win.resize(options.mainWindowSize());
+        if (options.find("project-file"))
+            win.loadProject(options.projectFile());
+        win.show();
 
-    return QApplication::exec();
+        ret = app.exec();
+    } catch (const std::exception& ex) {
+        QApplication app(argc, argv);
+        QMessageBox msgbox(QMessageBox::Critical, "BornAgain: fatal bug",
+                           QString("Sorry, you encountered a fatal bug.\n"
+                                   "The application will terminate.\n"
+                                   "Please note the following and inform the maintainers.\n\n")
+                           + ex.what() + "\n",
+                           QMessageBox::Ok, nullptr);
+        msgbox.exec();
+        return 1;
+    }
+    return ret;
 }