How to avoid repeated execution of loading Qlibrary?

[RogerBreton]

I wanted to try the changes in debug mode but I immediately ran into the following error message :

Time for a cup of coffee...

[Christian Ehrlicher]

@RogerBreton said in How to avoid repeated execution of loading Qlibrary?:

Time for a cup of coffee...

I would rather say - time for a debugging session :)

[JonB]

@RogerBreton
If, from what you have shown, you presently have:

   bool Result;
    Result = myLib.load();
RB_StartMeasurement = reinterpret_cast<Fn6>(myLib.resolve("FDX_StartMeasurement"));
sdkError = RB_StartMeasurement();

without checking the intermediate return result variables, RB_StartMeasurement may be nullptr. Then RB_StartMeasurement() would cause a SIGSEGV?

[RogerBreton]

@JonB I don't dare say RB_StartMeasurement may be a nullptr in ALL LIKELIHOOD, and that maybe the cause of the segmentation fault. That is exactly my hypothesis. So, if that is the case, this proves my intuition : where is the application getting the DLL from? If its name isn't specified anywhere? It is not in the PRO file.

I was thinking, perhaps, I should test whether the library is loaded before calling RB_StartMeasurement? And if it is not loaded, then load it? But that would not explain why I get the SIGSEV when the application tries to load? Or is it happening in the constructor?

Somehow, I must be missing some important piece of the puzzle -- I'll continue to look around but I am optimistic...

[JonB]

@RogerBreton

bool Result;
Result = myLib.load();
if (!Result)
    qDebug() << "This is bad...";
RB_StartMeasurement = reinterpret_cast<Fn6>(myLib.resolve("FDX_StartMeasurement"));
if (RB_StartMeasurement  == nullptr)
    qDebug() << "This is bad.  Get ready for SEGV if you call RB_StartMeasurement() now...";
sdkError = RB_StartMeasurement();

[RogerBreton]

I declared the RB_StartMeasurement as NULL in mainwindow.h :

class MainWindow : public QMainWindow
{
    Q_OBJECT
    QLibrary myLib;

    typedef DEVICE_ERROR_TYPES(__stdcall* Fn6)(void);
    Fn6 RB_StartMeasurement = NULL;

But I still get the Segmentation Fault...

[SGaist]

Hi,

Did you implement @JonB´s suggestion ?

Start in debug and you should see exactly where it fails.

[RogerBreton]

@SGaist That is exactly what I do :

I found the culprit...

DEVICE_ERROR_TYPES sdkError = RB_RegisterDeviceEventHandler(EventNotice);

The above function is a static member function declared in SomeClassName... which was working fine before ... The EventNotice function is also part of the same class.

[RogerBreton]

For some reason (?), the EventNotice "address" is garbage :

EventNotice 2372415452829272149 void (DEVICE_eEventCode, uint32_km, DEVICE_ERROR_TYPES)

It should be a proper address like 0x00007ff739a21970.
I tried restarting QT Creator many times to no avail.

[RogerBreton]

Thank you all for your patient help.
I'm putting QT on the backburner for now.
Too bad. Such a nice environment.