DirectChatEvent: be careful with range-for over temporaries

...because temporaries returned by temporaries tend to disappear before you enter the loop body (see the bottom of http://en.cppreference.com/w/cpp/language/range-for#Explanation).

2 files changed, 11 insertions, 10 deletions

diff --git a/lib/connection.cpp b/lib/connection.cpp
index 9d0a34f3..71ada8f7 100644
--- a/lib/connection.cpp
+++ b/lib/connection.cpp
@@ -281,8 +281,7 @@ void Connection::sync(int timeout)
 
 void Connection::onSyncSuccess(SyncData &&data) {
     d->data->setLastEvent(data.nextBatch());
-    auto allRoomData = data.takeRoomData();
-    for (auto&& roomData: allRoomData)
+    for (auto&& roomData: data.takeRoomData())
     {
         const auto forgetIdx = d->roomIdsToForget.indexOf(roomData.roomId);
         if (forgetIdx != -1)
@@ -303,12 +302,7 @@ void Connection::onSyncSuccess(SyncData &&data) {
             r->updateData(std::move(roomData));
         QCoreApplication::processEvents();
     }
-    // `for (auto&& accountEvent: data.takeAccountData())` doesn't work well
-    // with Clang on FreeBSD in Release configuration; it seems that
-    // the lifetime of the returned rvalue does not extend (violating the
-    // standard) and accountEvent refers to garbage in the loop body as a result.
-    auto allAccountData = data.takeAccountData();
-    for (auto&& accountEvent: allAccountData)
+    for (auto&& accountEvent: data.takeAccountData())
     {
         if (accountEvent->type() == EventType::DirectChat)
         {
diff --git a/lib/events/directchatevent.cpp b/lib/events/directchatevent.cpp
index 7049d967..63d638a3 100644
--- a/lib/events/directchatevent.cpp
+++ b/lib/events/directchatevent.cpp
@@ -29,8 +29,15 @@ DirectChatEvent::DirectChatEvent(const QJsonObject& obj)
 QMultiHash<QString, QString> DirectChatEvent::usersToDirectChats() const
 {
     QMultiHash<QString, QString> result;
-    for (auto it = contentJson().begin(); it != contentJson().end(); ++it)
-        for (auto roomIdValue: it.value().toArray())
+    const auto json = contentJson();
+    for (auto it = json.begin(); it != json.end(); ++it)
+    {
+        // Beware of range-for's over temporary returned from temporary
+        // (see the bottom of
+        // http://en.cppreference.com/w/cpp/language/range-for#Explanation)
+        const auto roomIds = it.value().toArray();
+        for (const auto& roomIdValue: roomIds)
             result.insert(it.key(), roomIdValue.toString());
+    }
     return result;
 }