QJsonObject m_obj;
void updateJson(const QJsonValue &val) {m_obj["key"] = val;}

void set1(const QStringList &val) {
    updateJson(QJsonArray::fromStringList(val));
}

void set2(const QStringList &val) {
    QJsonArray tObj = QJsonArray::fromStringList(val);
    updateJson(tObj);
}

QStringList get() const {
    return m_obj["key"].toVariant().toStringList();
}

main (){
  set1({"testing"});
  qDebug() << get();
  // CLANG: QVariant(QVariantList, QList(QVariant(QString, "testing")))
  // GCC: QVariant(QVariantList, QList(QVariant(QString, "testing")))

  set2({"testing"});
  qDebug() << get();
  // CLANG: QVariant(QVariantList, QList(QVariant(QString, "testing")))
  // GCC: QVariant(QVariantList, QList(QVariant(QVariantList, QList(QVariant(QString, "testing")))))
}