Deleting allocated memory by pointer doesn't work

Question

I'm creating a application in C++ with the QT framework which includes a HTTP POST request. The value the reply pointer points to doesn't get deleted and causes a memory leak. I have tried to delete this memory allocation like this:

if (reply)
{
    qDebug() << "reply deleted";
    delete reply;
}
reply = m_qnam->post(request, jsonString);
qDebug() << reply;
connect(reply, SIGNAL(finished()), this, SLOT(handleNetworkData()));
connect(reply, SIGNAL(sslErrors(QList<QSslError>)), this, SLOT(handleSSLErrors()));

Whenever I try to do so, the program crashes instantly. In the header of this class the reply is initiated as a pointer:

QNetworkReply * reply;

Does anyone know why my program crashes by deleting the memory allocation the pointer points to? What would be a possible solution for my problem?

Answer 1

也许你应该使用reply.deleteLater()

Answer 2

Instead of using raw pointers, you might want to consider switching to Smartpointers (such as std::unique_ptr ) instead.

Smartpointers make usage of RAII, in which the Instance of the class std::unique_ptr<T> holds the pointer and deletes it upon destruction.

To answer your question: it crashes because reply = m_qnam->post(request, jsonString); may return a nullptr and you (presumably) try to dereference this nullptr .