QLibrary not working

IknowQT

#ifndef MYFIRST_LIB_H
#define MYFIRST_LIB_H

#include "Myfirst_Lib_global.h"
#include "QDebug"

extern "C" void TEST_FUNC_LIB();
extern "C" void TEST_FUNC_LIB_For()
{
    qDebug() << "Show Myfirst_Lib";
    for(int i=0; i<10; i++)
    {
        qDebug() << QString("Index: 1%\n").arg(i);
    }
}
class MYFIRST_LIB_EXPORT Myfirst_Lib
{
public:
    Myfirst_Lib();
    void TEST_FUNC();
};
#endif // MYFIRST_LIB_H

#include "myfirst_lib.h"

Myfirst_Lib::Myfirst_Lib()
{
    qDebug() << "Show Myfirst_Lib";
}

void Myfirst_Lib::TEST_FUNC()
{
    qDebug() << "Show Myfirst_Lib";
    for(int i=0; i<10; i++)
    {
        qDebug() << QString("Index: ").arg(i);
    }
}


void TEST_FUNC_LIB()
{
    qDebug() << "Show Myfirst_Lib";
    for(int i=0; i<10; i++)
    {
        qDebug() << QString("Index: 1%\n").arg(i);
    }
}


#include <QDebug>

MainWindow::MainWindow(QWidget *parent)
    : QMainWindow(parent)
    , ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    QLibrary_Test();
}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::QLibrary_Test()
{
    qDebug() << "QLibrary_Test\n";

    QLibrary g_testLibrary;
    g_testLibrary.setFileName("C:/Users/yhJeong/Documents/QT_Proj/Lib_TestProj/Depoly_Exec/debug/Myfirst_Lib.dll");

    if(g_testLibrary.isLoaded() == true)
        g_testLibrary.unload();

    if((g_testLibrary.load()) == false)
        qDebug() << "Test Library Load Error\n";

    typedef void (*p_libFunc)(void);
    p_libFunc libraryExe = NULL;


    libraryExe = (p_libFunc)g_testLibrary.resolve("TEST_FUNC_LIB");
    if(libraryExe)
        libraryExe();

    libraryExe = (p_libFunc)g_testLibrary.resolve("Myfirst_Lib");
    if(libraryExe)
        libraryExe();

    libraryExe = (p_libFunc)g_testLibrary.resolve("TEST_FUNC");
    if(libraryExe)
        libraryExe();

    libraryExe = (p_libFunc)g_testLibrary.resolve("TEST_FUNC_LIB_For");
    if(libraryExe)
        libraryExe();
}

I tried to load the library, but it didn't work. I succeeded in importing the dll file in that location, but libraryExe is 0. Please tell me what's wrong

IknowQT

@jsulm

There is something wrong with creating a dynamic library.

extern "C" MYFIRST_LIB_EXPORT void TEST_FUNC_LIB_For()

MYFIRST_LIB_EXPORT I added this and it worked fine.

jsulm

@IknowQT said in QLibrary not working:

Please tell me what's wrong

You did not export TEST_FUNC_LIB() function.
See https://doc.qt.io/qt-5/qlibrary.html#resolve

IknowQT

@jsulm

 libraryExe = (p_libFunc)g_testLibrary.resolve("TEST_FUNC_LIB");
    if(libraryExe)
        libraryExe();

    libraryExe = (p_libFunc)g_testLibrary.resolve("Myfirst_Lib");
    if(libraryExe)
        libraryExe();

    libraryExe = (p_libFunc)g_testLibrary.resolve("TEST_FUNC");
    if(libraryExe)
        libraryExe();

    libraryExe = (p_libFunc)g_testLibrary.resolve("TEST_FUNC_LIB_For");
    if(libraryExe)
        libraryExe();

Calls the dll function with resolve, but returns false in the conditional statement.
I don't understand why it returns false. Where did the problem come from?

jsulm

@IknowQT Which of the 4 functions?
Which conditional statement fails?
resolve() does not call any function.
Did you read what I wrote before and act accordingly (as reminder: on Windows you have to export symbols in a lib which you want to use outside of the lib).

IknowQT

@jsulm

There is something wrong with creating a dynamic library.

extern "C" MYFIRST_LIB_EXPORT void TEST_FUNC_LIB_For()

MYFIRST_LIB_EXPORT I added this and it worked fine.