Ld: symbol(s) not found collect2: ld returned 1 exit status

luca72

Hello it this case i have this error:

@
#ifndef CLASSE_SCARICO_H
#define CLASSE_SCARICO_H

#include "Classe_scarico_global.h"
#include <QTcpSocket>
#include <fstream>
#include <QHostAddress>
#include <QProgressDialog>

class CLASSE_SCARICOSHARED_EXPORT Classe_scarico : public QObject {
Q_OBJECT
public:
Classe_scarico();
~Classe_scarico();

private:
QTcpSocket socket_scarico;
int lung_file_scar, lung_scaricata;
std::ofstream file_scarico;
QProgressDialog pd;

public slots:
void connetto(QHostAddress indirizzo, QString porta, QString nome);

private slots:
void leggo_scarico(QString nome, QProgressDialog pd);
void vedo();
void socket_errore();
};

#endif // CLASSE_SCARICO_H
@

If i delete Q_OBJECT i never get the error why?

EDIT: Please wrap code by Q-tags, Gerolf

giesbert

Hi Luca,

first of all, which tool chain do you use? I suggest mingw if it is windows?

which OS?

a bit more info of the error would be good: which symbols?

do you compile the shared lib or the exe using the shared lib?

how is CLASSE_SCARICOSHARED_EXPORT defined?

florent.revelut

You might want to make sure that you actually reran qmake
=> your class derivates from QObject and it has slots/signals, to work, it actually needs to be moc'd up

=> check that you have MOC ran on your file (it should generate a moc_classe_scarico.cpp somewhere)

Note that qmake knows which objects needs to be moc'd by analyzing for presence of the Q_OBJECT macro : if you added it after generating your project / makefile, it can't know it has to be moc'd up

luca72

Hello and thanks for your reply:
the os is osx 10.6.6
i use qtcreator now the class seems to be ok and the .h file is this:

@
class Classe_scarico : public QObject {
Q_OBJECT

public:
Classe_scarico();
~Classe_scarico();

private:
QTcpSocket socket_scarico;
int lung_file_scar, lung_scaricata;
std::ofstream file_scarico;
QProgressDialog pd;
void leggo_scarico(QString nome, QProgressDialog pd);

public slots:
void connetto(QHostAddress indirizzo, QString porta, QString nome);

private slots:
void vedo();
void socket_errore();
};
@

But when i try to use it i get another error The .h of the other class is this:

@
namespace Ui {
class Widget;
}

class Widget : public QWidget
{
Q_OBJECT

public:
explicit Widget(QWidget *parent = 0);
~Widget();

private:
Ui::Widget *ui;
Classe_scarico *prova_scar;
@

but when in the cpp file i add this line in one function:

@
Widget::leggo_base() {
prova_scar = new Classe_scarico;
}
@

i get:
Undefined symbols:
"Classe_scarico::Classe_scarico()", referenced from:
Widget::leggo_base() in widget.o
ld: symbol(s) not found
collect2: ld returned 1 exit status
make: *** [Alex_rev_01.app/Contents/MacOS/Alex_rev_01] Error 1

EDIT: please use @-tags for code highlighting, Gerolf

giesbert

sounds like you have no cpp file with the implementation of Classe_scarico::Classe_scarico. Or the class is in a seperate dll and not exported. Or you don't link against the dll.

luca72

how i have to link?
this is the are the .pro file of the two class:
Classe_scarico.pro:
QT += network
TARGET = Classe_scarico
TEMPLATE = lib
DEFINES += CLASSE_SCARICO_LIBRARY
SOURCES += classe_scarico.cpp
HEADERS += classe_scarico.h
Classe_scarico_global.h
Alex_rev_1.pro:
QT += core gui network webkit

TARGET = Alex_rev_01
TEMPLATE = app
SOURCES += main.cpp
widget.cpp
HEADERS += widget.h
FORMS += widget.ui
INCLUDEPATH = /Users/lucabertolotti/Desktop/Qt/Progetti_C++/Classe_scarico/Classe_scarico
Thanks

Luca

florent.revelut

Currently, you're telling Qt to build

an application on one side
a library on another side

But you're not telling it that the application depends on your library
in your Alex_rev_1.pro, add some information for the linker:
@
#name of your other library
LIBS += -lClasse_scarico

folder where it's generated

LIBS += -L/Users/lucabertolotti/Desktop/Qt/Progetti_C++/Classe_scarico/Classe_scarico

@

Note that usually you don't have one class per library.

luca72

Many thanks
Now it works, i'm beginner thanks for your time

Luca

Shmuel6

[quote author="florent.revelut" date="1300986306"]Currently, you're telling Qt to build

an application on one side
a library on another side

But you're not telling it that the application depends on your library
in your Alex_rev_1.pro, add some information for the linker:
@
#name of your other library
LIBS += -lClasse_scarico

folder where it's generated

LIBS += -L/Users/lucabertolotti/Desktop/Qt/Progetti_C++/Classe_scarico/Classe_scarico

@

Note that usually you don't have one class per library.
[/quote]

Signed up just to say THANKS!!!
I am running Knoppix 7.05 and was trying to install imapfilter but for the life of me could not understand why after installing all its dependences it still would not compile. Turns out OpenSSL was the culprit.
Well thanks a TON.
IOU1!