use of STL causing LINK2019 linker error

jonah765

Hello, So I have the following function:

void StartWindow::newPOTWButtonClicked()
{
    std::cout << "creating new POTW" << std::endl;

    //generate new window
    POTWSetupWindow setupWindow;

    //generate questions
    QuestionBox* week = new QuestionBox("What week is it?");

    //add question elements and link to correct slot
    std::function<void(void)>func(std::bind(&POTWSetupWindow::weekFilled, &setupWindow));
    week->addDropDownItem(1,100, func);
    
    //push questions to POTW setup window
    setupWindow.addQuestion(week);

    emit setNewMainWindow(setupWindow);
}

However, this throws the following linker error:

startwindow.obj:-1: error: LNK2019: unresolved external symbol "public: void __cdecl POTWSetupWindow::weekFilled(void)" (?weekFilled@POTWSetupWindow@@QEAAXXZ) referenced in function "public: void __cdecl StartWindow::newPOTWButtonClicked(void)" (?newPOTWButtonClicked@StartWindow@@QEAAXXZ)

Now, the error goes away If I run the code without the use of std::function and std::bind , so it appears to me that they are causing the problems. My .pro file looks as follows, which likely needs to be changed to solve my problem:

QT       += core gui

greaterThan(QT_MAJOR_VERSION, 4): QT += widgets

CONFIG += c++14

DEFINES += QT_DEPRECATED_WARNINGS

SOURCES += \
    button.cpp \
    fancyslider.cpp \
    main.cpp \
    mainwindow.cpp \
    potwsetupwindow.cpp \
    startwindow.cpp \
    questionbox.cpp \

HEADERS += \
    button.h \
    fancyslider.h \
    mainwindow.h \
    potwsetupwindow.h \
    startwindow.h \
    questionbox.h \

# Default rules for deployment.
qnx: target.path = /tmp/$${TARGET}/bin
else: unix:!android: target.path = /opt/$${TARGET}/bin
!isEmpty(target.path): INSTALLS += target

Also, my project is using Desktop Qt 5.14.2 MSCV2017 64 Bit

fcarney

@jonah765 said in use of STL causing LINK2019 linker error:

std::function<void(void)>func(std::bind(&POTWSetupWindow::weekFilled, &setupWindow));

Why are you using std::function and std::bind? std::bind should return a function object.

You are also storing a pointer to an object that will be destroyed at the end of this function:

POTWSetupWindow setupWindow;

Is your setupWindow QObject based? Then you can create it with new and have the parent object in the constructor. This will handle destruction when the parent window/object gets deleted.

Edit:
How is weekFilled defined?

jonah765

Thanks a lot for your response, I appreciate the effort, but the error was in the end something trivial.

aha_1980

@jonah765 said in use of STL causing LINK2019 linker error:

Thanks a lot for your response, I appreciate the effort, but the error was in the end something trivial.

... and would you like to share the trivial solution? It might help later readers.

Thanks