serial port in dll

chr_sch

In the dll i specified the following function:
-header
public:
void Test(int a);

-cpp
qDebug()<< a;

in the Test program:
int b=1;
MyLib c ;
c.test(b);

The exact error message is:
main.obj:-1: Error: LNK2019: unresolved symbol ""__declspec(dllimport) public: void __cdecl MyLib::Test(int)" (_imp?Test@MyLib@@QEAAXH@Z)" in function "main".

SGaist

You are not exporting Test properly

chr_sch

@SGaist
How to do so ?
Where is my fault ?

SGaist

You have a nice explanation in the Creating shared libraries chapter of Qt's documentation

chr_sch

@SGaist
I red this chapter already and my header files as well as the pro file are as specified in the explanation:
dll.h:

#ifndef MESSWERT_ZUORDNUNG_DLL_H
#define MESSWERT_ZUORDNUNG_DLL_H

#include "messwert_zuordnung_dll_global.h"

MESSWERT_ZUORDNUNG_DLLSHARED_EXPORT void Test(int a);

class MESSWERT_ZUORDNUNG_DLLSHARED_EXPORT Messwert_zuordnung_dll
{

public:
    Messwert_zuordnung_dll();

    void Test(int a);
};

#endif // MESSWERT_ZUORDNUNG_DLL_H

dll_global.h

#ifndef MESSWERT_ZUORDNUNG_DLL_GLOBAL_H
#define MESSWERT_ZUORDNUNG_DLL_GLOBAL_H

#include <QtCore/qglobal.h>

#if defined(MESSWERT_ZUORDNUNG_DLL_LIBRARY)
#  define MESSWERT_ZUORDNUNG_DLLSHARED_EXPORT Q_DECL_EXPORT
#else
#  define MESSWERT_ZUORDNUNG_DLLSHARED_EXPORT Q_DECL_IMPORT
#endif

#endif // MESSWERT_ZUORDNUNG_DLL_GLOBAL_H

I cant see a big difference.

SGaist

Following your various piece of code, you don't have any class called MyLib containing Test(int) nor any namespace containing such a function

chr_sch

@SGaist
I changed the name, because the actual is a bit long. My class is Messwert_zuordnung_dll.
The function for the export is Test.

SGaist

Ok so your

MyLib c;
c.test(b);

should rather be:

Messwert_zuordnung_dll mzd;
mzd.Test(b);

correct ?

So, when you are building your dll, do you get both the dll and corresponding lib file ?

chr_sch

@SGaist
Yes that´s correct. Sorry at this point for the confusion with the names.

Yes the build creates a .dll/.lib and .obj file.
At the beginning I had some trouble with the link I set as dependent path and libs in the pro file because there where a space in it. The error said "could not open .obj" so maybe it the program tries to open the .obj instead of the .dll ?

SGaist

No, you should link to the lib file. However having space in your path on Windows is generally a Bad Thing (™) so just avoid them altogether

chr_sch

@SGaist
Yes I realized that this is a problem and renamed the folder. But this was just at the beginning, now it has to be an other problem

SGaist

It still can't find it ? Did you implement Test(int a) ?

chr_sch

@SGaist
What exactly do you mean with implement ?
Under the exportet class in "public" I added "void Test(int a)" and right clicked refractor and added the function to the cpp file.

SGaist

Then it's been implemented

chr_sch

@SGaist
I created an other time a new project and did all step by step. After all the dll works. I wrote the dll and the test program exactly as in the files before. I don´t know where the difference is.

I am able to pass an integer through the function of my dll.
In the next step I would like to establish an serial port and send the passed integer to my mikrocontroller.
The code whrer i implement the serial port looks like this:

QSerialPort *serial;

void Messwert_zuordnung_dll::Test(int a){
    serial = new QSerialPort();


    //+++++++++++++++++++++++++++++++++++
    //+++++++++++++++++++++++++++++++++++
    // COM-Port, checked in device manager!

    serial->setPortName("COM12");

    //+++++++++++++++++++++++++++++++++++
    //+++++++++++++++++++++++++++++++++++


    serial->setBaudRate(QSerialPort::Baud115200);
    serial->setDataBits(QSerialPort::Data8);
    serial->setParity(QSerialPort::NoParity);
    serial->setStopBits(QSerialPort::OneStop);
    serial->setFlowControl(QSerialPort::SoftwareControl);

    serial->open(QIODevice::ReadWrite);
    serial -> write(c);
    serial->close();

The connection can´t be opened and in the console of the test program I get the following error:
"QObject::start timer: Timers can only be used with threads started with QThread"

What means this? In my GUI i did not start a Thread seperatly. How can I solve this error?

SGaist

Are you calling that function from your application main thread ?

Note that you have a memory leak since you don't delete serial

chr_sch

@SGaist
Ok I will delet the serial object.

I call the dll function in the main.cpp of my test program.
I tried to create the QSerialPort *serial and the object serial=new QSerialPort in the main.cpp of my test program and pass it to the dll function, so that in my dll the object created in the test program is used. But the connection can´t be opened.

SGaist

What do you mean by "connection can't be opened" ? What error did you get ?

chr_sch

@SGaist
If i pass the object(QSerialPort) through the function to the dll, the test program stuck and there is no error written in the console.

If i create the object (QSerialPort) in the dll the following error is shown:
"QObject::start timer: Timers can only be used with threads started with QThread"