index: Avoid async shutdown on init error

src/index/base.cpp

@@ -98,9 +98,7 @@ bool BaseIndex::Init()
             }
         }
         if (prune_violation) {
-            // throw error and graceful shutdown if we can't build the index
-            FatalError("%s: %s best block of the index goes beyond pruned data. Please disable the index or reindex (which will download the whole blockchain again)", __func__, GetName());
-            return false;
+            return InitError(strprintf(Untranslated("%s best block of the index goes beyond pruned data. Please disable the index or reindex (which will download the whole blockchain again)"), GetName()));
         }
     }
     return true;
@@ -339,17 +337,17 @@ void BaseIndex::Interrupt()
     m_interrupt();
 }
 
-void BaseIndex::Start()
+bool BaseIndex::Start()
 {
     // Need to register this ValidationInterface before running Init(), so that
     // callbacks are not missed if Init sets m_synced to true.
     RegisterValidationInterface(this);
     if (!Init()) {
-        FatalError("%s: %s failed to initialize", __func__, GetName());
-        return;
+        return false;
     }
 
     m_thread_sync = std::thread(&util::TraceThread, GetName(), [this] { ThreadSync(); });
+    return true;
 }
 
 void BaseIndex::Stop()

src/index/base.h

@@ -84,7 +84,7 @@ protected:
     const CBlockIndex* CurrentIndex() { return m_best_block_index.load(); };
 
     /// Initialize internal state from the database and block index.
-    virtual bool Init();
+    [[nodiscard]] virtual bool Init();
 
     /// Write update index entries for a newly connected block.
     virtual bool WriteBlock(const CBlock& block, const CBlockIndex* pindex) { return true; }
@@ -117,7 +117,7 @@ public:
 
     /// Start initializes the sync state and registers the instance as a
     /// ValidationInterface so that it stays in sync with blockchain updates.
-    void Start();
+    [[nodiscard]] bool Start();
 
     /// Stops the instance from staying in sync with blockchain updates.
     void Stop();