Do not ask a UI question from bitcoind

src/init.cpp

@@ -1317,8 +1317,9 @@ bool AppInit2(boost::thread_group& threadGroup, CScheduler& scheduler)
         if (!fLoaded) {
             // first suggest a reindex
             if (!fReset) {
-                bool fRet = uiInterface.ThreadSafeMessageBox(
+                bool fRet = uiInterface.ThreadSafeQuestion(
                     strLoadError + ".\n\n" + _("Do you want to rebuild the block database now?"),
+                    strLoadError + ".\nPlease restart with -reindex or -reindex-chainstate to recover.",
                     "", CClientUIInterface::MSG_ERROR | CClientUIInterface::BTN_ABORT);
                 if (fRet) {
                     fReindex = true;

src/noui.cpp

@@ -39,6 +39,11 @@ static bool noui_ThreadSafeMessageBox(const std::string& message, const std::str
     return false;
 }
 
+static bool noui_ThreadSafeQuestion(const std::string& /* ignored interactive message */, const std::string& message, const std::string& caption, unsigned int style)
+{
+    return noui_ThreadSafeMessageBox(message, caption, style);
+}
+
 static void noui_InitMessage(const std::string& message)
 {
     LogPrintf("init message: %s\n", message);
@@ -48,5 +53,6 @@ void noui_connect()
 {
     // Connect bitcoind signal handlers
     uiInterface.ThreadSafeMessageBox.connect(noui_ThreadSafeMessageBox);
+    uiInterface.ThreadSafeQuestion.connect(noui_ThreadSafeQuestion);
     uiInterface.InitMessage.connect(noui_InitMessage);
 }

src/qt/bitcoingui.cpp

@@ -1105,12 +1105,14 @@ void BitcoinGUI::subscribeToCoreSignals()
 {
     // Connect signals to client
     uiInterface.ThreadSafeMessageBox.connect(boost::bind(ThreadSafeMessageBox, this, _1, _2, _3));
+    uiInterface.ThreadSafeQuestion.connect(boost::bind(ThreadSafeMessageBox, this, _1, _3, _4));
 }
 
 void BitcoinGUI::unsubscribeFromCoreSignals()
 {
     // Disconnect signals from client
     uiInterface.ThreadSafeMessageBox.disconnect(boost::bind(ThreadSafeMessageBox, this, _1, _2, _3));
+    uiInterface.ThreadSafeQuestion.disconnect(boost::bind(ThreadSafeMessageBox, this, _1, _3, _4));
 }
 
 UnitDisplayStatusBarControl::UnitDisplayStatusBarControl(const PlatformStyle *platformStyle) :

src/ui_interface.h

@@ -76,6 +76,9 @@ public:
     /** Show message box. */
     boost::signals2::signal<bool (const std::string& message, const std::string& caption, unsigned int style), boost::signals2::last_value<bool> > ThreadSafeMessageBox;
 
+    /** If possible, ask the user a question. If not, falls back to ThreadSafeMessageBox(noninteractive_message, caption, style) and returns false. */
+    boost::signals2::signal<bool (const std::string& message, const std::string& noninteractive_message, const std::string& caption, unsigned int style), boost::signals2::last_value<bool> > ThreadSafeQuestion;
+
     /** Progress message during initialization. */
     boost::signals2::signal<void (const std::string &message)> InitMessage;