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src/init.cpp

@@ -1747,6 +1747,20 @@ bool AppInit2(boost::thread_group& threadGroup, CScheduler& scheduler)
         }
  #endif // ENABLE_WALLET
 
+        // This is leveraging the fact that boost::signals2 executes connected
+        // handlers in-order. Further up, the wallet is connected to this signal
+        // if the wallet is enabled. The wallet's ScriptForMining handler does
+        // nothing if -mineraddress is set, and GetScriptForMinerAddress() does
+        // nothing if -mineraddress is not set (or set to an invalid address).
+        //
+        // The upshot is that when ScriptForMining(script) is called:
+        // - If -mineraddress is set (whether or not the wallet is enabled), the
+        //   CScript argument is set to -mineraddress.
+        // - If the wallet is enabled and -mineraddress is not set, the CScript
+        //   argument is set to a wallet address.
+        // - If the wallet is disabled and -mineraddress is not set, the CScript
+        //   argument is not modified; in practice this means it is empty, and
+        //   GenerateBitcoins() returns an error.
         GetMainSignals().ScriptForMining.connect(GetScriptForMinerAddress);
     }
 #endif // ENABLE_MINING

src/miner.cpp

@@ -407,6 +407,11 @@ CBlockTemplate* CreateNewBlock(const CScript& scriptPubKeyIn)
 
 class MinerAddressScript : public CReserveScript
 {
+    // CReserveScript requires implementing this function, so that if an
+    // internal (not-visible) wallet address is used, the wallet can mark it as
+    // important when a block is mined (so it then appears to the user).
+    // If -mineraddress is set, the user already knows about and is managing the
+    // address, so we don't need to do anything here.
     void KeepScript() {}
 };