fix(folderwatcher): align overflow handling across platforms

src/gui/folderwatcher_linux.cpp

@@ -1,10 +1,10 @@
 /*
  * SPDX-FileCopyrightText: 2018 Nextcloud GmbH and Nextcloud contributors
  * SPDX-FileCopyrightText: 2014 ownCloud GmbH
  * SPDX-License-Identifier: GPL-2.0-or-later
  */
 
 #include "config.h"
 
 #include <sys/inotify.h>
 
@@ -149,14 +149,21 @@
 
     // iterate events in buffer
     unsigned int ulen = len;
-    for (i = 0; i + sizeof(inotify_event) < ulen; i += sizeof(inotify_event) + (event ? event->len : 0)) {
+    for (i = 0; i + sizeof(inotify_event) <= ulen; i += sizeof(inotify_event) + (event ? event->len : 0)) {
         // cast an inotify_event
         event = (struct inotify_event *)&buffer[i];
         if (!event) {
             qCDebug(lcFolderWatcher) << "NULL event";
             continue;
         }
 
+        if (event->mask & IN_Q_OVERFLOW) {
+            qCWarning(lcFolderWatcher)
+                << "The inotify event queue overflowed; triggering a full local discovery";
+            emit _parent->lostChanges();
+            continue;
+        }
+
         // Fire event for the path that was changed.
         if (event->len == 0 || event->wd <= -1)
             continue;

src/gui/folderwatcher_win.cpp

@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: GPL-2.0-or-later
  */
 
 #include <QThread>
 #include <QDir>
 
 #include "common/asserts.h"
@@ -72,6 +72,7 @@
             const DWORD errorCode = GetLastError();
             if (errorCode == ERROR_NOTIFY_ENUM_DIR) {
                 qCDebug(lcFolderWatcher) << "The buffer for changes overflowed! Triggering a generic change and resizing";
+                emit lostChanges();
                 emit changed(_path);
                 *increaseBufferSize = true;
             } else {