c++ - Why does my application crash on exit after invoked QNetowrkAccessManager::get? -

i using qt 5.7 32bit in visual studio 2015. want http qnetworkaccessmanager. but, application crashed when closing application. because, when calling qnetworkmanager::get function , closing window, access violation exception occurs in qnetwork.dll , application abort . (if comment out line calling qnetworkmanager::get function, abnormal termination doesn't occur.) specifically, call stack follows. happened in qnetwork.dll , others.

ntdll.dll!7770904e()  unknown [frames below may incorrect and/or missing, no symbols loaded ntdll.dll]  [external code]  libeay32.dll!020b122e() unknown libeay32.dll!02120e0c() unknown libeay32.dll!02117592() unknown libeay32.dll!021176cb() unknown libeay32.dll!0211764c() unknown libeay32.dll!021177e0() unknown libeay32.dll!021174e0() unknown libeay32.dll!02113d7e() unknown qt5networkd.dll!q_x509_free(x509_st * a) line 354 c++ qt5networkd.dll!qsslcertificateprivate::~qsslcertificateprivate() line 92 c++ [external code]  qt5networkd.dll!qexplicitlyshareddatapointer<qsslcertificateprivate>::~qexplicitlyshareddatapointer<qsslcertificateprivate>() line 165  c++ qt5networkd.dll!qsslcertificate::~qsslcertificate() line 175  c++ [external code]  qt5networkd.dll!qlist<qsslcertificate>::node_destruct(qlist<qsslcertificate>::node * from, qlist<qsslcertificate>::node * to) line 492 c++ qt5networkd.dll!qlist<qsslcertificate>::dealloc(qlistdata::data * data) line 863  c++ qt5networkd.dll!qlist<qsslcertificate>::~qlist<qsslcertificate>() line 824  c++ [external code]  qt5networkd.dll!qexplicitlyshareddatapointer<qsslconfigurationprivate>::~qexplicitlyshareddatapointer<qsslconfigurationprivate>() line 165 c++ [external code]  

the main parts of source code shown below. htmldocument class contains html document , uri omit source codes.

mainwindow.hpp

#ifndef mainwindow_hpp #define mainwindow_hpp  #include <qmainwindow> #include <qwidget> #include <qnetworkaccessmanager> #include <qgraphicsscene> #include <qgraphicsitem> #include "testquery.hpp" #include "htmldocument.hpp"  class mainwindow : public qmainwindow {   q_object  public:   mainwindow(qwidget *parent = 0);  public slots:   void onreceived(htmldocument const& doc);  private:   testquery* query; };  #endif // mainwindow_hpp 

mainwindow.cpp

#include "mainwindow.hpp"  #include <qfile>  mainwindow::mainwindow(qwidget *parent)   : qmainwindow(parent) {   this->query = new testquery(this);   this->query->seturi("any url http request.").query();    this->connect(this->query, signal(queryfinished(htmldocument)), this, slot(onreceived(htmldocument))); }  void mainwindow::onreceived(const htmldocument& doc) {   qdebug() << "[received]:html document";   qfile file("output.html");   file.open(qfile::openmodeflag::truncate | qfile::openmodeflag::writeonly);   auto binary = doc.document().tolocal8bit();   file.write(binary);   file.flush();   file.close(); } 

testquery.hpp

#ifndef testquery_hpp #define testquery_hpp  #include <qnetworkaccessmanager> #include <qnetworkreply> #include <qnetworkaccessmanager> #include <qurl> #include "htmldocument.hpp"  class testquery :     public qobject {   q_object public:   explicit testquery(qobject* parent = nullptr);    void query();    testquery& seturi(qstring const& uri);  public slots:   void onreply(qnetworkreply* reply);  signals:   void queryfinished(htmldocument);  private:   void generateuriquery(qurl& uri, qurlquery& query);   htmldocument generatehtmldocument(qbytearray const& data);  private:   qnetworkaccessmanager* manager_;   qurl uri_; };  #endif // !testquery_hpp 

testquery.cpp

#include "testquery.hpp"  #include <qnetworkreply> #include <qfile> #include <qurl> #include <qurlquery>  testquery::testquery(qobject* parent) :   qobject(parent) {   this->manager_ = new qnetworkaccessmanager(this); }  void testquery::query() {   qurl uri;   qurlquery query;   this->generateuriquery(uri, query);    qdebug() << "[url]:" << uri.tostring();   qdebug() << "[query]:" << query.tostring();   qnetworkrequest request(qurl(uri.tostring() + query.tostring(qurl::fullyencoded)));   auto result = this->manager_->get(request);   this->connect(this->manager_, &qnetworkaccessmanager::finished, this, &testquery::onreply); }  testquery & testquery::seturi(qstring const & uri) {   this->uri_ = uri;   return *this; }  void testquery::onreply(qnetworkreply* reply) {   qdebug() << "[reply]:come respond.";   if (reply->error())   {     qdebug() << tr("[error]:")       << reply->errorstring();   }   else   {     emit this->queryfinished(this->generatehtmldocument(reply->readall()));   }    reply->deletelater(); }  void testquery::generateuriquery(qurl& uri, qurlquery& query) {   uri = this->uri_; }  htmldocument testquery::generatehtmldocument(const qbytearray& data) {   return htmldocument(qstring::fromlocal8bit(data), this->uri_); }