SIGSEGV error when declaring QNetworkReply

[TokiiWalkie]

Hello everyone. I am working on my first Qt project. For this project I need to use the spotify API. I have seen on internet how to make an http request.

When I debug my program, I have a SIGSEGV error on my QNetworkReply declaration. Here's the error :

Here's my .cpp file :

#include "spotifyplayer.h"
#include "QtNetwork/QNetworkAccessManager"
#include "QtNetwork/QNetworkRequest"
#include "QtNetwork/QNetworkReply"
#include "QObject"

#include <iostream>
#include <sstream>

std::string authorization;
std::string authBearer;

SpotifyPlayer::SpotifyPlayer(std::string auth) {
    authorization = auth;
    authBearer = "Bearer " + authorization;
}

void SpotifyPlayer::pauseMusic() {
    QByteArray authByteArray(authBearer.c_str(), authBearer.length());
    std::cout << authBearer << std::endl;

    QNetworkAccessManager *manager;
    QNetworkRequest request(QUrl("https://api.spotify.com/v1/me/player/pause"));
    request.setRawHeader("Accept", "application/json");
    request.setRawHeader("Content-Type", "application/json");
    request.setRawHeader("Authorization", authByteArray);

    QString postVar = "device_id=709017e7c2fbc5e92ce9e80b9f983f25428e6916";
    QNetworkReply *res = SpotifyPlayer::manager->put(request, postVar.toUtf8());
}

.h :

#ifndef SPOTIFYPLAYER_H
#define SPOTIFYPLAYER_H

#include <iostream>

#include <QtNetwork/QNetworkAccessManager>

class SpotifyPlayer : QObject
{
Q_OBJECT
public:
    SpotifyPlayer(std::string authorization);
    void pauseMusic();
private:
    QNetworkAccessManager *manager;
    QNetworkRequest request;
    QNetworkReply *res;

    std::string authorization;
    std::string authBearer;
    QByteArray authByteArray;
};

#endif // SPOTIFYPLAYER_H

Thank you all ! :D

[SGaist]

Hi and welcome to devnet,

@TokiiWalkie said in SIGSEGV error when declaring QNetworkReply:

QNetworkAccessManager *manager;

You do not initialise your manager class member variable nor the function local variable of the same name.

[TokiiWalkie]

ok, so what should i write now?
(sorry, im really new ^^')

[SGaist]

Well, it's basic C++ pointer handling. You need to allocate a QNetworkAccessManager object.

If this is cryptic, then I encourage you to take some time to learn the ropes of the language before going further.

[Cobra91151]

@TokiiWalkie

In your case, you have 2 issues. The first one, you created 2 QNetworkAccessManager objects:

private:
    QNetworkAccessManager *manager;

And

void SpotifyPlayer::pauseMusic() {
    QByteArray authByteArray(authBearer.c_str(), authBearer.length());
    std::cout << authBearer << std::endl;

    QNetworkAccessManager *manager;

Keep in mind, you can only have 1 QNetworkAccessManager *manager; object for the whole program. The second issue, you do not allocate the created QNetworkAccessManager object.

So, to fix it you have to replace this line: QNetworkAccessManager *manager; from pauseMusic() method with manager = new QNetworkAccessManager(this);

Code:

void SpotifyPlayer::pauseMusic() {
    QByteArray authByteArray(authBearer.c_str(), authBearer.length());
    std::cout << authBearer << std::endl;

    manager = new QNetworkAccessManager(this);
    QNetworkReply *res = SpotifyPlayer::manager->put(request, postVar.toUtf8());
    
    // You need to deallocate the object and free the memory to prevent the memory leaks
    // Check out the code below
    connect(res, &QNetworkReply::finished, [this, res]() {
       res->close();
       res->deleteLater();
       manager->deleteLater();   
    }

Or initialize it only in the constructor:

SpotifyPlayer::SpotifyPlayer(std::string auth) {
    authorization = auth;
    authBearer = "Bearer " + authorization;
    manager = new QNetworkAccessManager(this);
}

Happy coding!

[SGaist]

@Cobra91151 said in SIGSEGV error when declaring QNetworkReply:

void SpotifyPlayer::pauseMusic() {
QByteArray authByteArray(authBearer.c_str(), authBearer.length());
std::cout << authBearer << std::endl;

manager = new QNetworkAccessManager(this);

This one is problematic as it will create a new instance of QNetworkAccessManager each time pauseMusic is called.

[Cobra91151]

@SGaist

Yes, I updated my post. Thanks.