Addressed Bunnei's review comments, and made some other tweaks:

 - Deleted GetStatus() because it wasn't used anywhere outside of Core::System.
 - Fixed design flaw where the message bar status could be set despite the game being stopped.

src/citra_qt/main.cpp

@@ -663,10 +663,11 @@ void GMainWindow::OnCoreError(Core::System::ResultStatus result, std::string det
     switch (result) {
     case Core::System::ResultStatus::ErrorSystemFiles: {
         QString message = "Citra was unable to locate a 3DS system archive";
-        if (details != std::string())
+        if (!details.empty()) {
             message.append(tr(": %1. ").arg(details.c_str()));
-        else
+        } else {
             message.append(". ");
+        }
         message.append(common_message);
 
         answer = QMessageBox::question(this, tr("System Archive Not Found"), message,
@@ -698,11 +699,15 @@ void GMainWindow::OnCoreError(Core::System::ResultStatus result, std::string det
     }
 
     if (answer == QMessageBox::Yes) {
-        if (emu_thread != nullptr)
+        if (emu_thread) {
             ShutdownGame();
+        }
     } else {
-        message_label->setText(status_message);
-        message_label->setVisible(true);
+        // Only show the message if the game is still running.
+        if (emu_thread) {
+            message_label->setText(status_message);
+            message_label->setVisible(true);
+        }
     }
 }
 

src/core/core.cpp

@@ -26,7 +26,7 @@ namespace Core {
 /*static*/ System System::s_instance;
 
 System::ResultStatus System::RunLoop(int tight_loop) {
-    this->status = ResultStatus::Success;
+    status = ResultStatus::Success;
     if (!cpu_core) {
         return ResultStatus::ErrorNotInitialized;
     }
@@ -60,7 +60,7 @@ System::ResultStatus System::RunLoop(int tight_loop) {
     HW::Update();
     Reschedule();
 
-    return GetStatus();
+    return status;
 }
 
 System::ResultStatus System::SingleStep() {
@@ -99,8 +99,8 @@ System::ResultStatus System::Load(EmuWindow* emu_window, const std::string& file
         return init_result;
     }
 
-    Loader::ResultStatus load_result = app_loader->Load();
-    if (load_result != Loader::ResultStatus::Success) {
+    const Loader::ResultStatus load_result{app_loader->Load()};
+    if (Loader::ResultStatus::Success != load_result) {
         LOG_CRITICAL(Core, "Failed to load ROM (Error %i)!", load_result);
         System::Shutdown();
 
@@ -113,9 +113,8 @@ System::ResultStatus System::Load(EmuWindow* emu_window, const std::string& file
             return ResultStatus::ErrorLoader;
         }
     }
-    // this->status will be used for errors while actually running the game
     status = ResultStatus::Success;
-    return ResultStatus::Success;
+    return status;
 }
 
 void System::PrepareReschedule() {

src/core/core.h

@@ -108,16 +108,14 @@ public:
     PerfStats perf_stats;
     FrameLimiter frame_limiter;
 
-    ResultStatus GetStatus() {
-        return status;
-    }
-
-    void SetStatus(ResultStatus new_status, std::string details = std::string()) {
+    void SetStatus(ResultStatus new_status, const char* details = nullptr) {
         status = new_status;
-        status_details = details;
+        if (details) {
+            status_details = details;
+        }
     }
 
-    std::string GetStatusDetails() {
+    const std::string& GetStatusDetails() const {
         return status_details;
     }
 
@@ -147,8 +145,8 @@ private:
 
     static System s_instance;
 
-    ResultStatus status;
-    std::string status_details;
+    ResultStatus status = ResultStatus::Success;
+    std::string status_details = "";
 };
 
 inline ARM_Interface& CPU() {

src/core/file_sys/archive_ncch.cpp

@@ -42,13 +42,13 @@ ResultVal<std::unique_ptr<ArchiveBackend>> ArchiveFactory_NCCH::Open(const Path&
 
     if (!file->IsOpen()) {
         // High Title ID of the archive: The category (https://3dbrew.org/wiki/Title_list).
-        const u32 shared_data_archive = 0x0004009B;
-        const u32 system_data_archive = 0x000400DB;
+        constexpr u32 shared_data_archive = 0x0004009B;
+        constexpr u32 system_data_archive = 0x000400DB;
 
         // Low Title IDs.
-        const u32 mii_data = 0x00010202;
-        const u32 region_manifest = 0x00010402;
-        const u32 ng_word_list = 0x00010302;
+        constexpr u32 mii_data = 0x00010202;
+        constexpr u32 region_manifest = 0x00010402;
+        constexpr u32 ng_word_list = 0x00010302;
 
         LOG_DEBUG(Service_FS, "Full Path: %s. Category: 0x%X. Path: 0x%X.", path.DebugStr().c_str(),
                   high, low);
@@ -60,7 +60,7 @@ ResultVal<std::unique_ptr<ArchiveBackend>> ArchiveFactory_NCCH::Open(const Path&
                                                       "Mii data");
             } else if (low == region_manifest) {
                 LOG_ERROR(Service_FS,
-                          "Failed to get a handle for shared data archive: region manifes");
+                          "Failed to get a handle for shared data archive: region manifest.");
                 Core::System::GetInstance().SetStatus(Core::System::ResultStatus::ErrorSystemFiles,
                                                       "Region manifest");
             }

src/core/hle/service/fs/archive.cpp

@@ -257,8 +257,9 @@ ResultVal<ArchiveHandle> OpenArchive(ArchiveIdCode id_code, FileSys::Path& archi
     LOG_TRACE(Service_FS, "Opening archive with id code 0x%08X", id_code);
 
     auto itr = id_code_map.find(id_code);
-    if (itr == id_code_map.end())
+    if (itr == id_code_map.end()) {
         return FileSys::ERROR_NOT_FOUND;
+    }
 
     CASCADE_RESULT(std::unique_ptr<ArchiveBackend> res, itr->second->Open(archive_path));
 

src/core/loader/loader.h

@@ -101,7 +101,7 @@ public:
      * Loads the system mode that this application needs.
      * This function defaults to 2 (96MB allocated to the application) if it can't read the
      * information.
-     * @returns a pair of Optional with the kernel system mode and ResultStatus.
+     * @returns A pair with the optional system mode, and and the status.
      */
     virtual std::pair<boost::optional<u32>, ResultStatus> LoadKernelSystemMode() {
         // 96MB allocated to the application.

src/core/loader/ncch.h

@@ -179,7 +179,7 @@ public:
 
     /**
      * Loads the Exheader and returns the system mode for this application.
-     * @returns a pair of Optional with the kernel system mode and ResultStatus
+     * @returns A pair with the optional system mode, and and the status.
      */
     std::pair<boost::optional<u32>, ResultStatus> LoadKernelSystemMode() override;