[network/ktorrent/release/26.08] plugins/scanfolder: Fix crash in ScanFolder plugin due to non-threadsafe KDirWatch destructor

Git commit 1840cb79a053cd6f7c1308e2d1ca568fe4929c50 by Jack Hill.
Committed on 21/07/2026 at 21:15.
Pushed by jackh into branch 'release/26.08'.

Fix crash in ScanFolder plugin due to non-threadsafe KDirWatch destructor

KDirWatch has an internal QThreadLocalStorage object which is cleaned
up automatically when the last KDirWatch is deleted. Therefore
KDirWatch is not thread-safe, and each ScanFolder must be deleted in
its own thread. stop() can be called from any thread, so use
deleteLater() instead of normal delete.

To reproduce:
1. Enable Scan Folder plugin
2. Open the settings page and add a folder, doesn't need to contain
   any files
3. Disable the Scan Folder plugin

Before:
- Crash

Now:
- No crash

Fixes sentry issue KTORRENT-W8


(cherry picked from commit 16b1ff640d147552d5300871c71499d0f15f1698)

Co-authored-by: Jack Hill <[email protected]>

M  +12   -11   plugins/scanfolder/scanthread.cpp
M  +1    -1    plugins/scanfolder/scanthread.h

https://invent.kde.org/network/ktorrent/-/commit/1840cb79a053cd6f7c1308e2d1ca568fe4929c50

diff --git a/plugins/scanfolder/scanthread.cpp b/plugins/scanfolder/scanthread.cpp
index 676fb146d..4ce195691 100644
--- a/plugins/scanfolder/scanthread.cpp
+++ b/plugins/scanfolder/scanthread.cpp
@@ -52,7 +52,6 @@ ScanThread::ScanThread()
     : stop_requested(false)
     , recursive(false)
 {
-    scan_folders.setAutoDelete(true);
     moveToThread(this);
 }
 
@@ -100,20 +99,19 @@ void ScanThread::updateFolders()
     mutex.unlock();
 
     // first erase folders we don't need anymore
-    bt::PtrMap<QString, ScanFolder>::iterator i = scan_folders.begin();
+    auto i = scan_folders.begin();
     while (i != scan_folders.end()) {
-        if (!tmp.contains(i->first)) {
-            QString f = i->first;
-            i++;
-            scan_folders.erase(f);
+        if (!tmp.contains(i.key())) {
+            i.value()->deleteLater();
+            i = scan_folders.erase(i);
         } else {
-            i->second->setRecursive(recursive);
+            i.value()->setRecursive(recursive);
             i++;
         }
     }
 
     for (const QString &folder : std::as_const(tmp)) {
-        if (scan_folders.find(folder)) {
+        if (scan_folders.value(folder)) {
             continue;
         }
 
@@ -135,9 +133,12 @@ void ScanThread::stop()
 {
     stop_requested = true;
 
-    // XXX seems like deleting KDirWatch object(s) created in scan_folders
-    // in destructor of this QThread after it has been stopped
-    // causes memory corruption, so we delete them early
+    // Make sure QObjects are deleted in their own thread.
+    // Also KDirWatch uses thread-local storage which must
+    // be cleaned up by deleting in the proper thread.
+    for (auto *scan_folder : scan_folders) {
+        scan_folder->deleteLater();
+    }
     scan_folders.clear();
     exit();
     wait();
diff --git a/plugins/scanfolder/scanthread.h b/plugins/scanfolder/scanthread.h
index db1b282e5..12da8a660 100644
--- a/plugins/scanfolder/scanthread.h
+++ b/plugins/scanfolder/scanthread.h
@@ -75,7 +75,7 @@ private:
     QStringList folders;
     std::atomic<bool> stop_requested;
     std::atomic<bool> recursive;
-    bt::PtrMap<QString, ScanFolder> scan_folders;
+    QMap<QString, ScanFolder *> scan_folders;
 };
 
 }