gui: crash fix, disconnect numBlocksChanged() signal during shutdown

furszy · fanquake · commit 5aa4956cd3ad · 2025-05-06T18:04:28.000+01:00
The crash stems from the order of the shutdown procedure: We first unset the client model, then destroy the wallet controller—but we leave the internal wallet models ('m_wallets') untouched for a brief period. As a result, there’s a point in time where views still have connected signals and access to wallet models that are not connected to any wallet controller. Now.. since the clientModel is only replaced with nullptr locally and not destroyed yet, signals like numBlocksChanged can still emit. Thus, when wallet views receive them, they see a non-null wallet model ptr, and proceed to call backend functions from a model that is being torn down. As the shutdown procedure begins by unsetting clientModel from all views. It’s safe to ignore events when clientModel is nullptr. Github-Pull: gui#864 Rebased-From: 71656bd
diff --git a/src/qt/sendcoinsdialog.cpp b/src/qt/sendcoinsdialog.cpp
@@ -851,6 +851,10 @@ void SendCoinsDialog::updateCoinControlState()
 }
 
 void SendCoinsDialog::updateNumberOfBlocks(int count, const QDateTime& blockDate, double nVerificationProgress, SyncType synctype, SynchronizationState sync_state) {
+    // During shutdown, clientModel will be nullptr. Attempting to update views at this point may cause a crash
+    // due to accessing backend models that might no longer exist.
+    if (!clientModel) return;
+    // Process event
     if (sync_state == SynchronizationState::POST_INIT) {
         updateSmartFeeLabel();
     }

Original file line number	Diff line number	Diff line change
`@@ -851,6 +851,10 @@ void SendCoinsDialog::updateCoinControlState()`
`851`	`851`	`}`
`852`	`852`
`853`	`853`	`void SendCoinsDialog::updateNumberOfBlocks(int count, const QDateTime& blockDate, double nVerificationProgress, SyncType synctype, SynchronizationState sync_state) {`
	`854`	`+ // During shutdown, clientModel will be nullptr. Attempting to update views at this point may cause a crash`
	`855`	`+ // due to accessing backend models that might no longer exist.`
	`856`	`+ if (!clientModel) return;`
	`857`	`+ // Process event`
`854`	`858`	`if (sync_state == SynchronizationState::POST_INIT) {`
`855`	`859`	`updateSmartFeeLabel();`
`856`	`860`	`}`