Android dns resolve crash

[SGaist]

Hi,

Why are you creating 10 threads making get requests almost as fast as possible all the time your application is running ?

On a side note, you are leaking QNetworkAccessManager and QTimer objects.

[wantfat]

@sgaist If I had two threads, It would still crash, just for a long time. the request is serial execution .
thank you.

[wantfat]

I run on another phone (Android 9, armv7) , The code work well. The mobile phone that had abnormalities is Android 5.1 armv7. I am not sure whether it depend on mobile phone .

[J.Hilk]

@wantfat you do realize that

QThread *thr = new QThread();
    thr->start();

    while (!QAbstractEventDispatcher::instance(thr)) {
        thr->wait(1);
    }

is doing nothing but delay forcefully delay the loop by 1 millisecond?
Also you don't need a QNetworkAccessManager instance for each get request. QNetworkAccessManager can handle 5 get requests in parallel, IIRC, and the rest is automatically queued

[wantfat]

@j-hilk After call QThread::start the eventDispatcher of thread is null, so must take a sleep wait for eventDispatcher be create, QNetworkAccessManager only one instance for per thread .

[J.Hilk]

@wantfat said in Android dns resolve crash:

, QNetworkAccessManager only one instance for per thread

no, from your code, you create 10 QNetworkAccessManager instances and all live inside the main(Gui) thread

[wantfat]

@j-hilk QMetaObject::invokeMethod(QAbstractEventDispatcher::instance(thr), ={

});
This code make sure lambda run on thr.

[J.Hilk]

@wantfat have you checked that ? by combining invokeMethod with a lambada the object reference pointer becomes a context pointer. I see no reason, why it should be called from the Thread instance, or I personally don't know, never tried threading in this unusual way.

[wantfat]

@j-hilk Yes, I have checked it, this is detail info, https://stackoverflow.com/a/21653558

[wantfat]

The test code work well on Qt 5.12.3, The problematic version is Qt 5.12.4 . I compared two versions of the relevant code

If method __res_init resolve fail dlsym be call, and it return a valid pointer, But it is not a thread safe function. Maybe so.

[wantfat]

I solved this problem by export thread safe __res_init

#if (QT_VERSION == QT_VERSION_CHECK(5,12,4))

#include "resolv.h"
#include "QMutex"

static QMutex mut;

int __res_init(void) {
QMutexLocker lck(&mut);
return res_init();
}

#endif

Thanks every one.